Transcript for:
Understanding Digital Circuits and Binary Systems

this brings us to section five of the book digital electronic circuits and um digital is very much unlike anything that we've studied to this point the original goal of digital was to simplify repetitive functions those same functions that we perform time and time again in electronic system and basically everything in digital is done with either a high voltage or a low voltage either an on state or an off state so all of the magic all of the money that bill gates has made simply boils down to a circuit that's either on or a circuit that's off it's that simple which also means if i'm doing my math correctly you all have a 50 50 shot at passing digital because all of the answers will either be a high voltage or a low voltage so you got a 50 50 shot at it actually it doesn't work out like that and i'm living proof it doesn't work out like that because i remember when i got went through my first digital course i was scratching my head like this doesn't make any sense digital i'm going to teach digital a little bit different for some of these chapters i'm going to use slides these slides for some of the chapters i'm going to deviate and not even use these slides to meet the objectives coordinating your quiz through the the class lead i basically don't want any of you taking any quizzes until i'm done with all the digital lectures so don't schedule the digital election quizzes for like this week schedule them for when i'm all done with digital i am also going to allow you to use some tools on your homework on your quiz and on your final exam those tools will include the use of these computers you can't use a web browser but you could use these computers the two things specifically that you can use is the windows calculator and there's a reason why i'm going to have you use that windows calculator so you could use your own calculator if you've got digital conversion on it but the windows calculators work really really well for manipulating some of these digital values and then the other thing i'm going to introduce you to is multi-sim in multi-sim we're going to use some very specific tools to help us solve these digital problems there's also going to be a deviation i'm just full of deviations tonight there also is going to be a deviation on the quiz all of you have come to know and love right my quizzes in digital you're going to be taking a quiz that is not multiple choice it's going to be a basically fill in the blank i give you a blank and you fill it in with all and everything and anything that you know about logic gates and if any part of the answer is wrong you get it wrong if there's 33 parts to the question and you get one wrong you don't get one thirty third you get that whole problem wrong because you either got it right or you got it wrong and digital is something that we really can't cut corners on because it's prevalent everywhere the world is digital right now we're in a digital world actually two years ago at the consumer electronics show in las vegas that i typically attend on an annual basis um that was basically their cl their claim that now on consumer electronics it's digital we're totally digital i mean there's still some analog applications out there but the predominance of circuitry out there now is digital so with that being said let's jump into it here chapter 32 which deals with the binary number system before we get started in this here who uh can you raise your hand who here has experience in digital have any of you taken any digital classes courses no couple okay if you did 116 you got some digital trust me you got some digital so you should find this a breeze if you haven't taken 116 there's some folks in this classroom that have a distinct advantage over you after completing this chapter you're going to be able to describe the binary number system identify the place value for each bit in a binary number convert binary numbers to decimal numbers convert decimal numbers to binary numbers convert decimal numbers to 8421bcd code and convert eight four two one bcd code to decimal numbers now they chose using binary numbers for a really important reason there's only two of them that was the reason the binary system is a base two system so if any of you struggle with this material i'm going to show no mercy on you because you've been using since birth a number system that is far more complex than the binary number system we use base 10. and that's actually one of the things that i find intriguing i enjoy travel i've traveled all over the world i've used money that i don't understand i've spoken to people people have spoken to me in languages that i don't understand but one of the things that's consistent around this planet is the numbering system a decimal based system and i think that probably has something to do with how many fingers and toes we have okay because again you're not going to find any other culture that i'm aware of that uses anything other than base 10 numbering system so the binary number system is a base 2 system it contains two digits this is where you got a 50 50 shot of passing this class either a zero or a one the position of the zero or one in the number indicates its value within the number the place value of the digits in a binary number increases by the powers of two and we could see that on this table here this is the decimal number base 10 and actually let's go through the decimal this is going to sound really infantile and stupid but let's go through it the first number in decimal is zero and it's kind of odd because we don't count that way we don't count zero one two three four the human computer does you ever hear that dude you ever see them like on leno or anything the human computer this this dude or the human calculator whatever they call that dude human calculator have you seen this guy i've heard him interviewed on the radio it's amazing i've seen him like on letterman and stuff they'll bring him out and they'll typically they'll bring out like some i don't know a cheerleader with a calculator and they'll like give numbers 4 million 276.34 times 43. and he he's got the answer faster than the cheerleader with a calculator he does so because he's trained his mind to think like a computer we're all a product of our upbringing in our traditional mathematics background so we think counting one two three four five he counts like a computer zero one two three four and zero has significance especially in machines so let's go through this 0 1 2 3 4 5 6 7 8 9 then we go to the number what we call the number 10 but the number 10 is actually 1 in the tens column and 0 in the ones column that's what makes up the number 10 base 10 do you agree with me the number is 11 is one in the tens column one in the ones column 10 plus 1 equals 11. 12 13 14 15 16 17 18 19 and again the ones column goes back to zero and the tens column increments by one so now two in the tens column and zero in the ones column we call that number twenty does that make sense i know it sounds kind of silly but you gotta understand where base ten really comes from and ten is not ten it's one in the tens column zero in the ones column so now binary well it's either gonna be a zero or a one or a zero and a one or a zero and a one so what we could look at here is the ones column it's zero one zero one zero one zero one we see it keeps repeating itself because those are the only two combinations it could have so the number zero the good news is the number zero in decimal is still the number zero in binary the number one in decimal is the number one in binary but the number two in decimal now is one in the twos column zero in the ones column so the answer to one plus one is not two the answer to one plus one in binary is one zero does that make sense so two plus one equals three two in the twos column one in the ones column now after we've gone through this sequence of course we have to go to zero here we have to go to zero here so now we increment one in the fourth column four plus zero plus zero equals four four four plus one equals five four plus two equals six four plus two plus one equals seven then we increment to our eights column does that make sense so make sure you could draw this on a piece of scratch paper because i guarantee you you will deceive me in the future i'll ask you some basic questions like this and it's easy to get tripped up with you end up getting tripped up strut down on your scratch paper it's no harm in that now in order for us to we we are a decimal people we are a decimal people we use base 10. so in order for us to use binary to count the numbers that we like to use how many places do i need to use in binary now i haven't defined bits and bytes yet how many places do i need in binary to represent the highest number that we count to in decimal before we increment to the tenths column how many places do i need four okay so the number nine here is one zero zero one one in the fourth column excuse me one in the eighths column one in the ones column eight plus one equals nine so this is what we call bcd binary coded decimal the highest number you will ever count up to in binary coded decimal is going to be the number nine because after the number nine what's next but do we call it 10 or do we call it one zero one in the tens column zero in the ones column decimal so we in binary coded decimal will never go past the number nine so this could be binary coded decimal this could be bcd this could be bcd bcd bcd bcd what i'm saying bcd i mean also what the book calls 8421 code because we use the eight columns the fours the twos and the ones not in bcd using four using four places you could go as high as 15. but in bcd we could only go as high as the number nine now you bring up a really outstanding point you're a smart guy you're like these computer engineers the past they said well you know we're already using this four digit system of binary counting all the way up to the number nine in decimal but we're not using this combination for 10 11 12 13 14 or 15. so we've got all of these different combinations that are going unused so what they came up with is another language called hexadecimal that's where this is where it gets really good folks instead of using numbers they start to use letters of the alphabet in hexadecimal instead of after the number 9 going to 10 they call this a they call this 11b c d e f f is as high as hexadecimal goes because after one one one one and we increment that then we go to one in the sixteens column so if you've ever heard of hexadecimal before and it's it's very common in coding to use hexadecimal because in the architecture of digital systems we've got four bits we might as well use the full size of those four bits if we're communicating if we're getting input or providing an output then let's keep it decimal because that's the human interface but inside the machine you've got all of these different combinations that are going unused so we use hexadecimal and i'll show you hex in a minute so it makes sense bcd code is an eight four two one code consists of four binary digits it's used to represent only the numbers zero through nine eight four two one designation refers to binary weight of four bits eight four two one but of course you caught it already you count all the way up to fifteen with four bits in summary the binary number system is the simplest number system so there's no excuses this is hard this is difficult contains two digits zero and one used to represent data for digital and computer systems binary data represented by binary digits called bits and bit the term bit is derived from binary digits so in defining bip the other term we should define since we're talking about it is byte b y t e and one byte is actually equal to four uh two nibbles true and a digital nibble is actually four bits so four bits equals a nibble two nibbles equals a byte or eight bits equals a byte so when you talk about your hard drive at home holding 500 gigabytes that's 500 gig times eight that's how many bits it can hold 500 times eight it's disturbing it's a lot of ones and zeros that can be held on those on those platters inside that hard drive the place value of each higher digits position and a binary number is increased by the power of two so ones column two four eight sixteen thirty two sixty four hundred twenty eight two fifty six 512 1024 any of these numbers sound familiar any computer geeks out there why do those numbers sound familiar if you play around with computers computer architecture and digital architecture is based on binary and the binary progression so you're never going to have you know a thousand different colors it's always going to be 1024 512 or memory it's always going to be in those increments because they're binary increments the largest value that can be represented by a given number of places is base 2 is 2 to the nth minus 1 where n represents the number of bits don't forget the zero place because now zero has significance in digital zero has significance before zero had no significance how much money do you have nothing okay if you've got no money in your bank of america checking account it doesn't mean there's no data it means that your account is at 0.00 okay and in the computers and the mainframe computers that keep track your accounts it's going to be 0.00 the value of a binary digit can be determined by adding the product of each digit to its place value fractional numbers are represented by negative powers of two to convert from a decimal number to a binary number divide the decimal number by two writing down the remainder after each division the remainder is taken in reverse order form the binary number do this on your homework to try it do it on your homework to try it but then correct yourself using a computer the four two one code a binary coded decimal code is used to represent zero through nine the advantage of bcd code is ease of converting between decimal and binary forms of a number human interface all the numbers we deal with at least i deal with are zero through nine any questions on anything that we covered in this chapter let me go ahead and show you now under accessories is the calculator this is your standard windows calculator if you have this when you call it up this isn't going to do much for you okay go to view you could select scientific which is a great scientific calculator if you're a scientific or you could go programmer this is the mode that you want to be in now you've got these options here right now the default for this was to come up in decimal so in decimal look at the numbers that are actually activated on my keypad 0 1 2 3 4 5 6 7 8 9 wow decimal zero through nine makes sense so here i could go one plus one equals two plus one equals three plus one equals four get the idea and look at what's happening on our screen at the same time you see that let me actually start subtracting one see how it's counting in binary for us there and it's counting in groups of four binary coded decimal so let me keep incrementing it now plus 1 5. what's gonna happen next 15 plus one very good so this is straight binary this is what we call straight binary so as an example let me um clear this out and let's uh you know nine million three hundred fifty six thousand eight hundred and seventy four well there it is in binary for us this is straight binary so if you start counting from the left zeros twos four eights sixteen thirty two sixty four get the drift so that's a nice thing about this it'll give you the display in straight binary in addition if you're doing bcd or eight four two one code you're gonna have to keep track of that you know that nine is as high as the number that you could go to the other nice thing about this let me clear that out is i could go to binary and when i select a binary look at the number two three four five six seven eight nine is disabled the only two keys on my keypad that are enabled are the zero and the one got a 50 50 shot at getting it right so what you could do is plug in the values one one one one what's that equal to in decimal so i could go to decimal and select decimal right here and it gives me my answer 15. i could go to binary let's clear that out one two three four five six seven eight nine ten eleven twelve thirty forty fifteen sixteen thirty two the neat thing about this see how high it could go how high going to go 64. 64 bits the reason i'm showing you this calculator is your calculator can't do that not that i'm aware of there may be a way of getting it to do it but it's not going to be very pleasant so this will allow you to simultaneously look at the contents of 64 bits now i'm going to convert this and we use 64-bit processing right we use 64-bit processing in computers now so how many different combinations are there in decimal of that crap i messed up i went one too many that's why i got the ding let me go back to binary ones are cheap slow down one all right 62 63 64. how many different decimal combinations why is it coming up with that why come it do that minus one i don't know why it's doing that i'm doing something wrong anyway let's go back to straight binary though and if you want to know the how many different combinations are in a bit system sixteen bit system decimal sixty five thousand five hundred and thirty six because zero has significance so that's how many different combinations there are so like what's the big one who who's like a computer fanatic here who doesn't like stuff with computers anybody do any color manipulation or any stuff like that what's the big one is it 24 bit color isn't that one of the options 32 okay 32-bit color oh i'm in decimal okay there's 32 bits how many different combinations color combinations will this give you and the human eye can only perce small perception of colors but yeah you could set your computer to give you this resolution of color so does everybody understand how this works the other nice thing about this is doing the conversions so remember that straight binary and hex let me go to hex right now and i'm going to count in hex and look at this when i enable hex now i've got the letters a b c d e and f enabled on my keyboard so i'm gonna go one plus one so i'm counting up what's going to come after the number nine in hex hey what's going to come after the letter f in hex 1-0 very good 1-0 oops added something wrong but see how we're counting up there so play around with this you want to get good at using this calculator because if i ask you questions on the quiz you could use this calculator to answer the questions i do want you to familiarize yourself with the division process that's outlined in the book just so you know how to do it longhand but quite frankly if i hired you as a technician you start you know you open up these scrolls and you're what the heck are you doing i'm doing these conversions use a calculator okay use the windows calculator it'll solve all your problems also there's another um format here it's called octal i used to work on a computer in the navy and ultimately went on i became an instructor at the school for a computer that communicated in octal so when i go to octal only the number 0 through 7 are highlighted so the way that this is going to work is let's count want to count an octal 1 plus 1 equals 2 plus 1 3 4 5 6. there's 7 what's going to come after seven we want to take a wild guess one zero one zero so the highest number that you count to is seven and then you go to zero one one zero makes sense why was it an octal system well it was obviously based on in three bits three bits per register it was an early computer robust computer a lot of i o channels built like a tank worked fine any questions on conversions okay let's go ahead and take a brief a 10-minute break at six uh at uh ten minutes after six we're gonna come back we're gonna talk about basic logic gates all right the long anticipated lecture chapter 10 inductance this is uh this is going to be an unusual property for us to discuss compared to what we've talked about up to this point what we've talked about up to this point really is conductance resistance period in discussing inductance you're going to see that things with inductance change over time okay the property actually changes the influence it has in a circuit changes over time so you're going to see that this is a very dynamic literally dynamic component and property chapter 10 inductance after completing this chapter you're going to be able to explain the principles of inductance identify the basic units of inductance identify different types of inductors determine the total inductance in series parallel circuits explain l r time constants and how they relate to inductance now the property of inductance is that characteristic of an electrical conductor that opposes a change in current flow opposes a change in current flow the symbol that we use is the capital letter l so in a circuit if you see on a schematic diagram l equals that means inductance is equal to whatever specific amount is identified now an inductor is a specific device designed to possess this property of inductance an inductor is a device that stores energy in a magnetic field and it's important for us to understand this property because we're going to counter this next chapter when we talk about capacitance right i'll let the cat out of the bag capacitance is an electro static field inductance is an electro magnetic field that's what's the magic behind an inductor now once current is moving through a conductor inductance helps to keep it moving as the magnetic flux lines build up they create an opposition to the flow of current in opposition to the flow of current lenses law talks about that lenses law states an induced emf in any circuit is always in a direction to oppose the effect that produced it the amount of counter emf is proportional to the rate of change the faster the rate of change the greater the counter emf so what this means let's go back last chapter that we talked about remember magnetism remember when we pass current through a conductor we create a magnetic field lenses law says if the current was going that away it's going to create an electromagnetic field like this makes sense if we shut the circuit off that electromagnetic field is going to collapse and it's going to produce a counter electromotive force that goes that way the opposite way of what created it so if the emf goes that way and it creates some magnetic field like this magnetic field collapses it creates a counter emf that goes in the opposite direction so the second part there talks about the rate of change the faster we turn that on and off on and off on and off expand collapse expand collapsing the more the faster we do it the more pronounced that effect is going to be if you connect one of these one of them their inductors to a dc circuit it's going to happen once when you close the circuit and energize it and when you de-energize it that field's going to collapse and create that counter current so it's only going to happen once it can expand once and it's going to collapse once now i'm going to let out a little secret because you guys have all read ahead ac what's one thing that's constant about ac it's constantly changing very good constantly changing so the higher the ac frequency is that we apply to one of these devices the more pronounced this effect is going to be does that make sense it goes back to lenz's law and again anytime that in class i i say anything about a law we should like ring a bell dim the lights hit some chimes hit a gong because laws you could take to the bank you answer a question on your quiz using a law on an exam using a law you approach a project or a lab assignment using a law you're going to get good results now inductance is measured by the henry and this was invented by a guy whose name was george a guy by the name of joe henry my main man henry ironically is abbreviated with the letter h and one henry is the amount of inductance required to induce an emf of one volt when the current in the conductor changes at a rate of one amp per second so one henry is equal to one volt of emf at one amp per second one is equal to one over one over one second now in electronics the typical values that we're going to see will be the millihenry times 10 to the negative third the micro henry times 10 to the negative sixth in some high power applications you may see henry's but generally speaking most of the stuff that we're working with in microelectronics miller henry's micro henries now inductors are those specific devices designed to possess the property of inductance so they're designed to have a specific inductance that's why come they be invented they consist of a conductor coiled around a core remember if we got like x amount of magnetism by creating one turn how much would we get if we make two turns twice as much it's that simple it's easy math of a conductor coiled around a core and it's classified by the type of core material whether it's magnetic or non-magnetic if we use a magnetic core material we're going to get a higher amount of inductance out of it if we use non-magnetic we'll get a little bit lower out of it so sometimes they'll use that core material to get it just not too much not too little but just right this is the schematic diagram for a fixed inductor and for those of you out there that want to go home and roll your own you could do that you just need magnetic wire magnetic wire is basically thin copper wire solid core that has a lacquer coating on it if you've ever looked into a transformer or motor and you see the windings that's magnetic wire it's all you need some cases you don't even need magnetic wire because you could you could roll a coil and as long as the wires aren't touching each other you're using air as an insulation you can roll your own i've been known to roll my own on a few times with mixed results i have no idea what i'm talking about actually i know exactly what i'm talking about this is a variable inductor created with an adjustable core material now the way they they come up with this is pretty fascinating what they'll do is they'll get a ferromagnetic core material typically like powdered iron and then they they basically uh form it into a material presidential material and then they thread it and then they thread the center of the core and what you could actually do with it right is righty tighty lefty loosey screw it in and as you screw it in what are you doing you're you're increasing the magnetic influence of the iron core so by simply adjusting that this is used for fine tuning in a lot of circuits that contain these very fine subtle tuning another thing that you could do and i used to see this old school not as much now they would use a brass insert and when you screw brass and what are you doing brass has a high level of reluctance so it's going to oppose that magnetic field so by screwing it in you're lowering the amount of inductance if it was iron core and you screwed it in you'd be increasing it so it's counterintuitive and it gets worse because what would happen is typically the questions that i used to be asked in a lot of my military navy equipment schools what we would have with circuit card extenders so you would do is take the circuit card out put it in the extender and then now the circuit card was was mounted above the rest so that you could get in there and adjust make adjustments a lot of times you'd have to make the adjustments from the back side they'd have a little hole physically in the in the board that you could put your adjustment alignment tool in so then they'd ask if approaching it from the back side which direction needs you turn the inductor to see a decrease in inductance so it's one of those things that you know you kind of let's see if i'm turning it clockwise from the top that's going to counterclockwise from the back side but it's it's brass core so as i'm turning it counterclockwise i'm really moving i mean it's just these questions that like you thought your head was going to explode but you know what you kind of hadn't well i don't see how that really ever helped me in life knowing that stuff because basically when you got out to the fleet you put a circuit you set up your test fixture basically as soon as you start turning it the wrong way you see needles go the wrong way and you turn it back and you get it to where it needs to be and you're done with it you don't sit there well let's see if i approach and if i'm using a mirror i'm actually seeing the inverse i mean just crazy stuff but think about that because these still and some of you may work on some legacy equipment it's fun to repair legacy equipment to retrofit to do things like that so you may end up finding some of this stuff this is my personal collection of inductors you guys actually believe me this is an air core inductor this is a fixed value inductor and that's all it is this wire wound around a magnetic core it's all it is all of these can type here are adjustable and actually if you could look here this almost looks like this takes a a hex head right like an allen an allen head whatever you do don't use an allen wrench to try to adjust this because typically the allen wrench in your tool kit is made out of iron steel ferromagnetic material so as soon as you get it in close proximity and you adjust it and get it just so you're going to remove part of the magnetic influence and your numbers are going to go cattywampus so all of these need to be adjusted with non-magnetic alignment tools i've got a i've got a role a tool roll at home from back in the day i should bring it in as an example this big tool roll it's like every alignment tool known to humankind and they're basically all plastic heads the other thing too is uh you know you stick your uh a hex head in there you stand a chance of damaging that and even if you break off a little bit of material that amount of material was designed engineered to be there to create x amount of magnetic field so you kind of gotta you kind of got to get it right so don't start if you don't have the right tool don't touch this stuff so it's typically called an alignment tool or actually a tweaker and a classical sense of the word a tweaker you could always tell who the technicians were you know because they'd always have the tweaker in their pockets and you knew it's kind of funny back in uniform submarine base in connecticut i'd be walking around i'd see you with tweaker in your pocket you know at the at the at the deli or whatever and i knew exactly what you did for a living the only guys running around only goofballs running around with tweakers in their freaking pocket or electronics techs that were regularly aligning equipment air core this is an inductor well not without core material because it has air in the core that's why it's called air core it's used for values up to five millihenries of inductance wrapped on ceramic or phenolic core in this case it was probably wrapped around a dowel or something and then removed and it has form in and of itself this is actually a really good photograph because you can see the magnetic wire here and you can see where the insulation has been stripped this is bare wire and then this is insulated a lot of times people see this and they think that it's bare wire it's not bare wire it's insulated one of the best ways of getting this insulation off if you're going to do a lot of this is with a chemical stripper chemical stripper and basically it's it's like a thinning agent you dip it in paint thinner and paint the uh remover and it removes that right down to the the metal and it makes it solderable you have to put a neutralizing agent on it but that's the best way of doing it other than that you know you're going to get your wire strippers and your wire strippers are just basically going to scratch the stuff off it's not going to really because this is a lacquer coating on it but that's this is an inductor believe it or not just a piece of wire making those five turns it's gonna give you x amount of inductance might be enough for you to get the job done question uh on the last air corps picture that you had there was a piece of metal going through it what's what's that this piece right here yeah i think somehow this is mounted this this serves as a a form somehow to keep that the shape of it i really don't know usually they're hollow though yeah oh yeah yeah this is not here to influence the magnetic or all it's either there for aesthetics or to help the way that's mounted or what have you it's a good observation some of these things are actually pretty cool looking again when you get into some of that older equipment they made it with a certain level of elegance you know and this would be an example of that if you opened up an old in a 1930s radio you'd probably find an inductor that looks like that in there it's 1970s radio no you're not going to find that in there iron core iron core could be either ferrite or powdered iron it's a typo not ion ion core captain the ion core is melting down damn damn you scotty that's why i'm not into drama right not a very dramatic kind of guy it's iron core used for values of 200 millihenries of inductance typically up to 200 ml henries of inductance schematic symbol shows these two parallel lines next to the coil that shows that there's an iron core next to the coil turret core these are donut shaped but do not try to eat them they offer a high inductance for a small size these are very prolific in a lot of contemporary electronic applications because the magnetic field is contained in the core offers a very high inductance for very small size if you opened up a computer power supply you'd find a bunch of these inside a lot of inductance for a relatively small package i've had graduates have gone to work for companies and they had to do this part of their job roll their own they're given the blank core spool of wire and you sit there and you thread it through and tighten it up thread it through tighten it up clean the leads solder it in the boards actually pretty good jobs most of the people that are playing around with this stuff are for rf applications radio frequency high energy radio frequency mr ground what's going on man got a question you're just back there waving man it's like [Laughter] what's up um magnetic field containing the core basically the significance of that is that it's not going to the inductance is not going to stray into things around it right it's just going to be contained in the course of like a normal transformer it's going to have a field around it yeah yep so it's not wasting that field going outside it's containing it basically increases the efficiency which makes it more better this is a shielded core shielded core have a shield of magnetic material to protect them from the influence of other magnetic fields because if you've got a a couple of these in close proximity to each other one field could influence another device now if you just saw this if you didn't know any better what would you think this device was it looks like a transformer and the only tell that there is on this is there's only two wires if you look on the other side you wouldn't find any other wires but it would look exactly like a transformer as a matter of fact you can use a transformer as an inductor if you don't connect the secondary leads the primer if you only use just the coil you could use a transformer as an inductor for some applications that's why i've got a garage full of junk because i won't throw a transformer away because someday i may want to use it as an inductor this is laminated core and again if you didn't know any better you'd think it was a transformer we know it's an inductor because it's only two wires coming out of it and the top is stamped 4.5 henry's 4.5 h and this was going to vary from point 1 henry's all the way up to 100 henries this is also sometimes referred to as a choke as a choke used as a choke in automotive applications noise filters meaning to choke off a change it's going to choke the change just like resistors inductors could be connected in series parallel or series parallel when you're dealing with inductors measured in henries in series you treat them exactly like resistors plain and simple if i've got two henries and i put it in series with four henries two plus four equals six and i now get six henry's worth of inductance in parallel you treat them like resistors in parallel so the total inductance will always be less than the value of least as long as you're dealing with the property measured in henry's now this is where things get interesting everything else i've been talking up to this point it's just been kind of hey he's trying to get to know you this the real deal this dis is what is all about it's a series circuit it's a series circuit i've got a switch that has two positions one is called the growth mode and the other is the decay mode okay so this switch i could toggle from either growth to decay when it's in the growth mode i have a simple series circuit do i not and the circuit contains an inductor actually what an iron core inductor because i see the parallel lines the inductor in series with a resistor makes sense when i close the switch as soon as i close the switch it's going to allow current to flow through this circuit do you agree with me what's going to happen is that current is going to come racing through the circuit negative to positive all of a sudden it's going to hit this curly piece of wire and that curly piece of wire it's hitting is an inductor an inductor is a specific device designed to possess the property of inductance inductance is that property which tries to oppose a change in current so current was at zero it wants to go to a hundred percent and this device is going to say uh-uh i want you to stay at zero why because you've been at zero and i like it like that but eventually as the current continues to come that magnetic field builds and current eventually goes to maximum it goes to a hundred percent for this circuit but the inductor because of its property of inductance is gonna fight the whole time to try to prevent that change from occurring but eventually it's going to lose so close the switch turn the circuit on the inductor is going to fight fight fight fight fight fight fight and eventually give up and current's going to be at 100 percent flowing through the circuit and by the way by the way when current is at 100 percent flowing through this inductor electrons are like what's up with that it's a piece of curly wire a period of time the electrons it's like why am i going through a piece of curly wire it just has no effect on them whatsoever and the circuit runs and runs and runs as soon as we get the switch and move the switch from the growth mode to the decay mode the magnetic field that was built up around inductor l1 is going to collapse and it's going to collapse into itself when it collapses into itself what is it going to do it's going to act like a what happens when a magnetic field passes through a conductor we induce we induce current if we move a conductor through a magnetic field we induce current if the if if the conductor is stationary in the magnetic field moves through a conductor we're going to generate current right so as soon as i move this to the decay mode this magnetic field is going to collapse into itself creating a counter current lenses law remember the opposite of the force that created it and then that current is basically going to flow through the circuit until it dissipates but if this was just a series circuit made up of a resistor a resistor and a switch you turn it on boom you go to 100 percent you turn it off pow you go to zero now with an inductor in here you turn it on it's going to come up and eventually get to 100 percent you turn it off that magnetic field's gonna collapse and eventually it's gonna get down to zero percent you follow what i'm talking about you guys know what i'm talking about i'm beating around the bush what am i talking about time constants time constants the time required for current through a conductor to increase to 63.2 percent so if i apply 100 to it and that first time constant it's going to rise 63.2 percent in the next time constant it's going to gain sixty three point two percent of that's what is what's remaining the next time constant sixty three point two percent of what's remaining the next time constant percent of what's remaining the next time constant basically after five time counts and we say enough is enough it's a hundred percent but is it really at a hundred percent no because it's non-linear so really it never reaches a hundred percent we say after five time constants it's reached 100 percent it's good enough for what we do to calculate out this time constant it's actually relatively easy l r is the symbol used for the time constant of an rl circuit and the formula is t is equal l divided by r period it's that simple take the amount of inductance divide it by the amount of resistance that's going to give you the time constant measured in seconds that's what we use as our base unit of measurement in electronics the second t is equal to l over r that would be for yes if i gave you four inductors you'd have to calculate out the total inductance and plug that in the circuit right there so i could give you some real nightmare circuits right now think about it it'd be fair game i could give you a circuit that's got you know 13 inductors and combination series parallel and 22 resistors combination the series parallel the bottom line is it's equivalent to the circuit here you've got to figure that out but you should be able to do so without a whole lot of fuss this is what a time constant curve looks like there's that first time constant 63.2 percent 63.2 percent of what's remaining 63.2 percent of what's remaining 63.2 percent of what's remaining what's remaining and what is it that i'm actually looking at here what is this in blue is this voltage what is this the current current number one because the slide says so but number two most importantly because it's current that's going from zero the inductor is trying to prevent the change trying to prevent the change trying to prevent the change trying to prevent the change trying to prevent the change trying to prevent the change all right current winds then as soon as you shut that circuit off current's going to try to go from 100 to zero but because that magnetic field is collapsing ah i don't want to decrease i want to keep it a hundred percent but i can't i oh crap oh all the way down to zero but because that field is collapsing it's going to try to prevent that change that's why we use these that's why we use these can inductors affect voltage absolutely for affecting current definitely will have an effect on voltage in summary inductance is the ability to store energy in a magnetic field just remember the key word for inductance is magnetic that's how they do their magic the unit for measuring inductance is the henry measured by the capital letter h the letter l represents inductance inductors have specific inductances that's why they're designed the symbol for a fixed inductor it's down here at the bottom symbol for a variable inductor has an arrow going through it the arrow means it's adjustable types of inductors include iron core ferrite or powdered iron core toward core shielded core laminated core formula for adding them up in series is like the same formula for adding up resistors in series the only thing you need to be aware of your measure you're adding up inductance measured in henry's if it's not in henry's can't use this formula the formula for total conductance and inductors in parallel is the reciprocal formula use it same as you would for resistors in parallel time constant formula t is equal to l over r you run this calculation it shows you what one time constant is worth i need to multiply that by how many to figure out how long it's going to take to get to 100 percent five because it takes five time constants to reach 100 percent so understand that when you do this math you end only end up with one time constant takes five to get the job done or as it says here five time constants required to fully build up or collapse the magnetic field of an inductor any questions on anything that we discussed with the inductors yes yup and that's it we have inductors because they create inductance and inductance is that property which tries to oppose a change in current so we're going to have a lot of different components that are going to want to bring about a change in current in a circuit and if we put an inductor in there an inductor could help stabilize that current flow because of that electromagnetic property so it's going to help stabilize current levels in a circuit the majority of applications that we're going to use inductors for is really going to be filtration because once we're not there yet some of you may have read far enough ahead that when we apply an inductor to an ac circuit it starts doing some wacky stuff and by harnessing that wacky property called inductive reactants we can use that to filter we could use it in in audio applications where we want only certain frequencies to go to certain speakers heck i knew a guy that was getting some interference on one of his cable channels back in the day and because this friend of mine had extensive electronics background he didn't want to call the cable company and have them waste their time and come out and exactly so this friend of mine built a filter circuit to filter out the garbage signal that somebody was putting on this pay-per-view channel and by filtering out the garbage that got put on the channel the reception was enhanced and made the station viewable and the key component in that whole so i'm told project is an inductor and ironically it was an inductor that was like three turns of wire one two three turns a wire was adequate enough for the reception to be enhanced mind-boggling so i'm told question some of those old the fossils and kind of like you would do a garden hose or on the back of the ship just coil up a line that would gentle things out enough that you could strike an arc in that board oh really interesting yeah and a little did you realize what you were doing at the time yeah nobody knew why but it worked now you know all right let's go ahead and take a break and uh at about 6 20 we'll start up with chapter 17. all right this brings us to section 2 of the book for those of you that are keeping track of what section you're in it's never that important to me with those at home keeping track section two chapter 12 alternating current once we go down this path nothing will ever be the same you will you will look back at the days when you played around with dc and dc was your biggest challenge because ac is going to open up a whole bunch of new problems but ac is good stuff ac is like what our power is what's powering this building right now is ac okay ac is is what uh the signal from the the cable company to give you uh you know pay-per-view channels is ac uh you listen to the radio on the way home from school tonight you're listening to an ac signal so um you know the the dc world is it's worse than black and white i mean it'd be like nothing ac is what really makes stuff work so after completing this chapter you're going to be able to describe how an ac voltage is produced with an ac generator define alternation cycle hertz sine wave period and frequency identify the parts of an ac generator which ironically we already did two weeks ago in lecture to find peak peak to peak effective in rms explain the relationship between time and frequency identify and describe three basic non-sinusoidal waveforms describe how non-sinusoidal waveforms consist of the fundamental frequency and harmonics i like this one here this is the kind of stuff you learn while you come to college understand why ec is used in today's society you'll have that going for you describe how an ac distribution system works i could do that for you right now it works quite well thank you identify and use the math associated with ac now one of the big misconceptions is um you know and i kind of grew up hearing about thomas edison some of that may be from the fact that i'm from the the northeast and um i mean thomas edison basically was the uh the founding father if you will of electrical distribution uh commercialization in the u.s you go to new york and the utility company has consolidated edison con ed you know i mean it got its start from a guy named edison um he was in debate heavy debate with a guy nikola tesla and um nikola tesla was the father of alternating current and edison wanted dc distribution tesla wanted ac distribution who won tesla edison was wrong but yeah again growing up i knew the name edison i didn't know the name tesla why is that why is that i'm not a historian but why is that actually tesla well truth be told a lot of people think maybe he was not of this world okay because this guy had some brilliant ideas uh you know edison died and they uh you know opened up a memorial and museums and everything else tesla died the fbi came in and confiscated all of his materials and um you want to know what's going on behind the uh the walls at area 51 behind the fences at area 51 probably some of tesla's work i mean he was out there the dude really was out there brilliant whether or not he was not of this earth well who knows but anyway the world adopted his electrical distribution system tesla said ac is the way to go he was an american leader no um i don't know what his citizenship status i believe he you know he was a immigrant and he came here for a better life and to teach us about the ways of ac we got that going for us he was actually a tesla serbian i believe ac generator produces an alternating voltage using the principles of electromagnetic induction this is a review blast from the past a couple weeks ago we done talked about this stuff right here's our magnetic field north pole south pole we have a rotating armature that rotating armature maintains connection through 360 degrees rotation through these slip rings that means we harness the entire alternation of the armature through the magnetic field so we get that 360 degree waveform out of it and this is uh basically as we rotate this armature through we create the positive alternation and then the negative alternation and then we repeat the cycle so how we rotate this how we rotate the shaft right it's really up to us it could be water from a dam hydroelectric it could be a wind turbine that's turning the shaft it could be a gas turbine it could be a steam turbine we could be heating that water with nuclear with coal with diesel however we want to do it bottom line is we've got to get this shaft turning once we get the shaft turning get the armature turning through the magnetic field we're generating ac power ac power cycle each time the generator completes one revolution we call that a cycle its output voltage is referred to as one cycle of output voltage it produces one cycle of output current in a complete circuit keyword is in a complete circuit because if you don't have anything connected up to that nothing's just rotating through will the electrons have anywhere to move to no so if they don't have anywhere to move to you don't have current so it's just going to sit there stationary you have to complete it to a circuit but even if you connect it to your meter is your meter a load so if you connect your meter you just completed the circuit now you're going to measure now the electrons have a way to a place to shake back and forth to you've completed the circuit the two halves of the cycle are called alternations alternations two complete alternations make up a cycle one cycle per second is called the hertz hertz is also has the rental car company spokesperson used to be o.j simpson remember that how many of you remember that commercial all right o.j is like running through the airport go get his car police chasing him the hertz we're talking about here has nothing to do with the car rental company hurts the hertz we're talking about here was heinrich hertz heinrich hertz we used to actually call this cycles per second if you find any i don't know what the cutoff date was on that but if you find any older radios it'll say cycles per second cairo 710 710 000 cycles per second we now call that 710 000 kilohertz we named it after heinrich hurts um i think heinrich we had a problem calling it hertz because of heinrich's political affiliations in the late 1930s i think eventually science got caught up with that and let's give heine the credit he deserves and the rest of course is history we see here that these cycle and remember these degrees here are associated with the degrees of rotation of the armature through the magnetic field it's that simple it really is when you rotate it 180 degrees through you go from zero to a maximum of 90 now you're back to zero so you've put it under the influence the strongest influence in this first 180 degrees of the magnetic field then on the back side you're putting it under a negative influence of that same magnetic field you're cutting the lines of flux remember lenses law left hand rule what kind of a wave is this sine wave okay sine wave what is the sine how many of you got your scientific calculators handy break out your scientific calculators what is the sign of 180 degrees how can that be zero how can that be does that make sense 180 degrees the sine is zero what's a sine wave doing at 180 degrees it's at zero so your calculator just proved it let's try something extreme like what is the sign of 90 what is the sign of 90 degrees one what 100 percent one hundred percent the sign of ninety is one so it means a hundred percent what is the sign of i'm thinking of a number between ninety and 180 220 um no 120 what's the sign of 120 0.866 so 86.66 of 100 occurs at 120 degrees check this one out you want to do something really funky right what is the sine of 270 degrees negative 1. the calculator knows that we're operating during the negative alternation if you plug in 270 it knows that it's the negative alternation so for a lot of you that never had any use for trigonometric values on your calculator check that out now you got that sine key you could predict what is known as the instantaneous voltage present at any point of a sinusoidal waveform isn't that the bomb i could say what is what voltage is present at 337 degrees you could plug in sine of 337 and that gives you the percentage you're obviously going to have to know what this peak value is peak multiplied by the sine of that value will give you the multiplier any of you realize this prior to this lecture kind of cool elena sine key in the calculator you could predict any voltage present long and what exactly is going to be present as at what what's called a instantaneous voltage meaning what we're doing is a sine wave we're stopping it at a specific instant and saying what voltage is present okay remember that that's a powerful tool for you and by doing that you're doing like that they're trigonometry but keep it a secret armature is the rotating loop of wire sinusoidal waveform also called the sine wave but if you want to impress your wife your neighbor's wife your best girlfriend what we were studying in school tonight huh my professor was lecturing on the attributes of the sinusoidal waveform makes you sound like makes you sound like you're paying a lot for tuition can be produced by mechanical and electronic means mechanical means means rotate the shaft how we rotate the shaft it's up to you electronic methods mean we're going to have a electronic circuit called a function generator it's what we use in the lab next door to create different ac signals and it's a circuit that makes that sine wave but the best the purest way of doing it is really with a generator rotating a shaft there's also another way too some of you uh in mobile electronics may be familiar with it there's something in your car that you can plug an ac device into and give you ac and your car of course is a dc system low voltage system it's called an inverter very good any of you heard of an inverter any of you own an inverter and if you own two inverters three anyone here own any big ass inverters like a five you know 5000 watt inverter i had one for a while bought it on the used market i sold it to a guy i actually wanted to live off the grid i'm like what am i going to do with this thing i got a gen i got a backup generator at home i wasn't going to put in a solar system or anything but i do i got a nice backup generator you know started powering my whole house got it wired directly and stuff but then my buddy dropped a bomb on me about a couple months ago he's a pilot and he knows that i love aviation and stuff it's like joe i can't believe like out of all the people i know you don't have like an apu powering your house and a power outage and i'm like why didn't i think of that apu is an auxiliary power unit it's a small jet engine like for an airplane that's parked they'll run that to power all the electrical systems so i mean that would be the deal living next to me man the power goes out how long we gonna be listening to that until the power comes back and you'd get that kerosene smell and everything man wouldn't that be i think i'm gonna do that this summer head down a freaking desert and go to pick apart pick apart the aviation pick apart and get myself a good apu the only problem with the aviation apu's is they produce 400 hertz that produce 400 hertz they don't produce 60 hertz aviation uses 400 hertz systems why so high precision the old navigation systems the old navigation systems needed cleaner power and on board aircraft specifically they have what's known as an inertial navigation system and what that would do is take track of every motion the aircraft made and it would keep track of all of that in the computer so that an airplane could take off from seattle and then fly to hawaii with really no external navigation aids they still would use external navigation aids to check their plot and everything but the inertial navigation system should be able to get under my submarine had an inertial navigation system and and a submarine i know some of you may find the shocking doesn't have windows so literally when you go under water you keep track of how deep you dive every time you turn right every time you turn left every time you slow up and that inertial navigation system is keeping track of that um this is kind of like you know we all get up in the middle of the night to take care of business right no i'm not talking monkey business talking business right so how many of us turn the lights to go take care of our business how many of us could find our way to the to the bathroom in the dark okay that's because your mind has an internal inertial navigation system you know when you get out of bed you know and how many paces over and then you know you turn right and then the doorknob and you know you can find the bathroom in the dark yeah oh geez who put that there you know happened to my wife the other morning she gets her up early a lot and i don't know she hit something and oh geez what the heck's going on but it's an inertial navigation system it's really important for a submarine with nuclear weapons to know because basically underwater you're making all of those maneuvers right and then what you got to do is be able to pop up and then launch a nuclear weapon and have it hit its target and if you didn't know where it was maybe you're going to launch it in the wrong direction or whatever so it was very very important so by using a 400 hertz system gave you cleaner power which got better performance out of the inertial navigation system so aircraft would use the same same technology identical to the trigonometric sine function i ready to let the cat out of the bag with that you all could do it the sign of plug in the degrees the key is got to make sure your calculator is in the degree mode if your calculator is not in the degree mode don't ask me how you got out of the degree mode that is normally the default for the calculator but by hitting the wrong sequence of buttons the bottom line is if you are not because you could be in the radian mode or the gradient mode that's not going to work for sine function to work properly you have to be in the degree mode so hopefully you paid attention when we were during this lecture and you were getting the same numbers as everybody else was getting if not you may have to look up google data sheet instruction manual on your model calculator and i'll show you how to change modes and make sure you're in the degree mode ac values each point on a sine wave has two numbers associated with it the degree of rotation this is the angle to which the armature has turned and the amplitude the maximum departure of the value of an alternating current or wave from the average value peak value is the absolute value of the point on the waveform with the greatest amplitude so what we're looking at right here this is the positive peak this is the negative peak so this right here check this out and this is another one that i've seen on professional exams over the period of a cycle what is the average voltage of an ac sine wave thank you smart people i said zero because over the average this basically this counters this out and you end up with zero this here is like my this is my freaking finances okay i make i make the money i spend the money okay and in the end there's nothing literally nothing left over it's just paying my american express bill this month and literally there's like three dollars it's kind of funny i work they give me lake washington gives me money i give the money and hand it directly over to american express you know no middleman no middleman actually there is a middleman called bank of america all they do is is they take it and then they distribute it and there's supposed to be a mortgage somewhere in there that's ironic so that's what they're talking about here so the maximum departure from zero is the peak the maximum negative departure from zero would be your negative peak peak to peak value well that's the maximum departure between your positive peak and your negative peak and the thing of it is the reason that we're teaching this to you the reason we're presenting this to you is different tech manuals different pieces of equipment may reference some of these critical attributes for some applications they just may want to know what the peak voltage is for other applications they might want to know what the peak to peak value is so it really doesn't matter you know i mean i'm i'm a pretty quick study if i'm driving 55 miles an hour on i-5 in bellingham you know 55 miles an hour i'm driving probably at or below the posted speed limit okay i go into canada and i'm driving i'm driving 55 miles an hour well canada don't roll that way okay it's kilometers per hour up there so it's kind of the same thing whether i want to call this 12 volts peak or 24 volts peak to peak it depends on the application it could be both well yeah but it's 24 volts peak to peak well yeah you're right but the manufacturer doesn't think that's important they just want you to ensure that you're getting 12 volts positive peak out of this okay makes sense so you just got to be able to recognize the differences and articulate the differences now one of the big things here effective value this is the amount that produces the same degree of heat in a given resistance has an equal amount of direct current can be determined by the root mean square rms process also called the rms value the amount that produces the same degree of heat in a given resistance is to an equal amount of direct current this here is a blown landing light off my airplane this is a 13 volt light 12 volt system and this is a 100 watt bulb okay really nice polished glass on the inside this thing really reaches out and sees some stuff i mean because you know you're coming in on approach or whatever and you've got to be able to see the numbers and align with the center lines you know you've seen landing lights on aircraft before even though it's 100 watts it's a nice beam a nice clean clear beam now you want to modify this one glass that'd be the deal get faa pma approved could retire just sell them for an exorbitant amount of money this lamp if i applied 12 volts dc to this lamp it would be this bright it'd be this bright you understand what i'm saying it'd be 100 watts bright to be this bright if i applied how many volts did i apply to it 12 or 13 12. if i applied 12 volts the same value of ac rms or effective value you know how bright this bulb would be it'd be the exact same brightness so the effective value means it will have the same effect as the equivalent amount of dc being applied to a device so quite frankly with a bulb like this an incandescent bulb that's a really good example i'm so proud of my example it's a really good example this is an incandescent bulb there's a filament inside whether i apply 12 volts dc to this or 12 volts ac to this it's going to be equally as bright as long as i apply 12 volts ac rms or 12 volts effective to it does that make sense now the thing about it the thing about rms is rms is actually equal to 70.7 percent or 0.707 times voltage peak 0.707 times voltage peak so if i'm going to apply 12 volts rms to this what's the voltage peak going to be let me show you a little trick you see this .707 this is a number you gotta remember it's not remember isn't memorized it's a number you gotta know plug this in your calculator 0.707 and then on your calculator you've got a key that's one over x it's called your reciprocal key or x minus one on some of yours what is the reciprocal of 0.707 1.414 make sure you use that whole number don't round that number off so it's 1.414 okay what's 12 volts times 1.414 16.9 volts peak if i apply 16 volt 0.9 volts peak voltage to this it's going to be this bright if i apply 12 volts ac rms to it it's going to be this bright if i apply 12 volts dc to it it's going to be this bright if i moved it's the same what's that number 16 point multiply that times two 33.9 if i apply 33.9 volts peak to peak to this bulb it's going to be this bright see they're all the same but they're all different values does that make sense so the key is understanding what you're being given in a technical document and why they're referencing that that's one of the classic things in audio that used to make me used to crack me up 1000 watts peak well the thing basically is a a resistive load so basically rms is going to have the real effect on power but some marketing dude attended joe grennick's class and like wow a peak you know sounds more powerful we'll put that in our marketing literature and you know sell it 1000 watts peak a thousand watts peak peak peak output using cmos cmos cmos technology cmos since 1972 cmos but it sounds cool marketing you got to be careful with numbers because they all say right the bulb it's all the same number so that's a trick on how to get that 0.707 and then make that the multiplier so if you're at effective and you want to make the number peak you got to multiply it by a number larger than itself 1.414 if you're at peak and you want to make it rms you take 70.7 percent of that value and that gives you peak period is the time required to complete one cycle of a sine wave we're all familiar with different things in life that have period cycles right the tide the tide there's two high tides a day there's two low tides a day if any of you are into fishing or boating or anything like that it was kind of funny i'm ex-navy but i never understood it it's like we're on a nuclear submarine man i mean can't we just like plow through the freaking tide why do we have to be up at two o'clock in the morning to leave with the tide you know it just never made sense to me but you have to do that so you don't hit like rock submerged rocks when you're pulling out a port and stuff but so the tide has cycles to it the moon has cycles to it the earth has a cycle of rotation 24 hours in electronics the the period that we're talking about is always going to be measured in seconds the letter t is used to represent period so t equals means i want an answer in seconds unless i specify otherwise frequency is the number of cycles that occur in a specific period of time it's expressed in terms of cycles per second unit of frequency is called the hertz named after heinrich hertz one hertz equals one cycle per second so if you find any old radio gear it may say cycles per second world war ii era radio gear if you go and get a tour of a b-29 bomber b17 down at boeing field you'd look at it you'd see the radio gear and it would say cycles per second let me go back to that real quick there's an easy way to to switch between the two if you know the frequency take the reciprocal of the frequency and that will give you the period how many times does this fit into one second also by algebraic manipulation f measured in hertz is equal to one over time so what comes out of our wall here as far as frequency 60 hertz okay plug this in the formula right there one divided by 60. what do you come up with 0.0166 give it to me in proper terms please it's how i roll it's kind of my thing 16.67 milliseconds a sine wave that comes out of the wall repeats itself every 16.67 milliseconds okay so what that looks like would be this every 16.67 milliseconds repeats itself 16.67 milliseconds repeats itself that means that we could cram 60 of these cycles in one second 60 cycles per second 60 hertz 60 cycles per second 60 hertz synonymous same thing so if you divide that by two which gives you about 8.3 milliseconds that means that the lights are turning on and off every 8.3 milliseconds right when it goes from the positive to the negative technically but we just can't pick it up and in europe it's 50 hertz so that period of time is even more pronounced but for an incandescent bulb the filament doesn't cool down enough to for some of these bulbs you will notice and some people they don't dig it some people don't dig it there's a lot of studies it's a whole separate area of study be honest with your lighting and what power are you using do you have the condition of power you want to apply dc convert the ac into dc you know so you get a the right mood set the right mood if you have a graduate out of the program that he works in aerospace aircraft interior exterior lighting and he has sent me pictures and emails from around the world he'll be sitting on a uh in indian air 767 over in mumbai with a light meter measuring the frequency and the light and making sure it meets the customers requirements because all airplanes are boeing bit makes are not created equal different cultures have different requirements for lighting and in effect and mood and different airlines i mean they want people to put them to sleep and you know i don't know if you've ever flown you know like on a it's funny you're flying on a on a domestic flight and um you know people leave the windows open you know not the windows open but you know the shades the shades up and uh you know during the day if you're on an international flight or whatever people close them because again it's dark and you could it's easier to sleep you don't see the sun and it creates a different effect so the same thing can be said for lighting it creates different effects and there's people that study this stuff and spec it out so like yeah we want to keep our you know our passengers like calm we don't want them to be all riled up and they'll sell them a package for lighting and big deal years ago um has to do with single phase two phase three phase in uh wood shops and uh table saws was that um the table saw or the saw blade would act as it was standing still like it was not even in motion because of the reaction with the lighting so they chain and you could literally go to make an adjustment a strobe effect yeah and it would it would make the blade look it would make the blade look standing still and there were lots of accidents that happened and so they changed lighting to phase yeah fabrication industry many many many years ago does make a difference so make sure you know how to perform those calculations and it's easy once you measure this you're going to measure this on the oscilloscope once you do that it's easy converting it over to frequency non-sinusoidal waveforms are generated by specifically designed electronic circuits they're used to represent either current or voltage this is known as a square wave the thing i want you to remember about a square wave is half the time it's on half the time it's off okay and it looks square literally half of it's on half of it's off on and off on and off on and off square wave and also be able to articulate what this is this is holding a constant amplitude for a period of time and then it immediately drops almost instantaneously drops and then holds that off condition then instantaneously rises this is a triangular waveform a triangular waveform has a rise time and a fall time that are linear and equal you understand what i mean by linear straight line is linear curve is not linear curve is non-linear that's why it's called a curve so a long a a l a rise time and a fall time that are linear and equal if you describe that to me as a tech assist i'm looking at a waveform that is linear and the rise time and fall time are equal i'd say bingo you're looking at a triangular wave how would you articulate this how would you describe this to me over a satellite phone you're trying to fix something and you're looking at a wave pattern that you've never seen before not linear linear is a straight line so i have a long linear rise time and a relatively short linear fall time i'd say oh my golly you're looking at a sawtooth waveform and to be honest with you what a sawtooth waveform is used for is actually developing like a raster scan on a crt monitor it's what actually drags the electron beam across the screen this increasing voltage is dragging the beam left to right across your screen and then drastically it's pow it's resetting it back to the left side of the screen so that the naked eye can't even perceive it and then it paints the next line pow the next line pow the next line on and on and on that's how a sawtooth generator works sawtooth generator works that's because you got a dot in the middle of your screen you turn your tv on you got a dot on the screen that sawtooth generator probably has failed same thing with your oscilloscope that's how an oscilloscope works when you get a display up basically what that display is is that beam that getting pulled left to right across the face of the oscilloscope it's a soft tooth generator that's creating that low voltage to a high voltage and then rapidly resetting it faster than the naked eye could perceive it square waveform useful as an electronic signal because its characteristics are easily changed triangular waveform used primarily as an electronic signal signal is you know when i use this i use the term signal loosely i use the term signal loosely actually i don't i i probably hear more so than anybody use it accurately signal means intelligence is behind it signal means intelligence is behind it it's what my job classification in the military used to be signal intelligence elent electronic intelligence sig in signal intelligence and first of all if you have a signal it means intelligence is behind it if you saw the movie contact with jodie foster that's what she was looking for she's out there down in freaking new mexico those big dishes been down there it's phenomenal place magical like over a mile above sea level and you're out there in the plains and it's just lighting up a stogy and it's magical out there at night whole another ball of wax man there's stuff out there flying around at night jody foster was looking for a signal in outer space if she found a signal in outer space that basically would signify that she found intelligence extraterrestrial intelligence because signals just don't occur randomly in nature signal means something is behind it so that's what she was looking for and if you saw the movie she found it i think she either found her or she got a hold of some magic mushrooms i still still haven't figured it out she went to puerto rico and then thought she was on another fluorescent planet maybe she wasn't in puerto rico maybe she went on a flight to amsterdam i've been on that flight before if you know what i mean i don't even know what i mean don't even know what i mean wasn't scary until you shut the lights off and you can still see everything real clear i don't even know what that means sawtooth waveform used to sweep the electron beam across the screen creating an image such as television sets radar displays any of those cathode ray tubes fundamental frequency is a frequency that represents the repetition rate of the waveform this here would be the fundamental frequency for 60 hertz waveform fundamental frequency this is the period right 16.67 milliseconds reciprocal of that gives me frequency 60 hertz fundamental frequency harmonics are higher frequency sine waves that are exact multiples of the fundamental frequency harmonics are going to be odd multiples of the fundamental frequency even harmonics are going to be even multiples of the fundamental frequency so this means whenever you create a frequency a signal you're going to create these harmonics after it can't be avoided it could be mitigated but it can't be avoided necessarily now since these harmonics are all out there just waiting to be utilized square waves are actually made in an electronic circuit by taking the fundamental frequency and all the odd harmonics and adding them up when you do that algebraically you end up with a square wave if i put a square wave on a piece of test equipment called a spectrum analyzer you would see that fundamental frequency and then you'd see all of those harmonics lined up in lower amplitude but they'd still be present you'd see them someday in the lab will do that i'll call you all over i'll say hey look at this here spectrum analyzer i'm looking at a square wave and look at them they're harmonics and then you'll say i remember that 17th of may 2011 joe grenick talked about these harmonics now i'm seeing them my life is so much better now so do the harmonics have the same shape as whatever the waveform less of an amplitude but yeah the same the same shape but just the same frequency triangular waveform is made of the fundamental frequency and all odd harmonics 180 degrees out of phase fundamental frequency in all odd harmonics 180 out of phase sawtooth waveforms composed of odd and even harmonics with even harmonics 180 degrees out of phase with the odd harmonics the big thing about harmonics let me just say one more thing on harmonics um harmonics used to frustrate the dickens out of me earlier i was talking about my surveillance equipment manual controlled i hate to say it but i was really good i was trained very very well i was really good at what i did then this computer operated system well computer is only as good as how it's programmed so one of the problems that we had it was it was kind of funny because i could laugh at myself i was very very junior and it was on my first mission in the mediterranean and we used to go to what were known as soviet anchorages and the soviets because they didn't have any warm water ports they were in cadute in cahoots basically with muammar gaddafi and gaddafi would let the soviets anchor in these protected ports and they'd put their entire fossil fuel burning fleet in these ports and they position them in a warm water port ready and able to go if they decided to push the button and start world war three instead of coming out of her mask and all these cold water ports that were frozen so my first mission we went and we basically would creep up on this anchorage and every day with electronics they have to turn the electronics on and cycle them and run through and everything and we're so close that we're not only picking up the fundamental frequency i'm picking up all of the harmonics so like the first time that i went over there with a computer controlled system and as soon as our periscope broke the water in the morning when they're running the soviets were running the tests on their equipment all of a sudden my screen is just like just just bogged down with every hit known to man because the computer wasn't able to differentiate between the fundamental frequency and the harmonic it just was getting wow it's a really electronic noisy environment out there and i'm going to try to process everything and that was something that i had to get my learning curve up on is how do we mitigate this how do we filter this how do we attenuate this so that we could sort out the good from the bad and make this a valuable exercise a valuable mission on gathering the intelligence so um those those harmonics could be really bad news because they could lead you astray and you needed to be able to analyze that actually one of the techniques that i used to use and maybe in the fall we'll see who teaches you the test equipment class but one of the things the techniques that i used to use is i in my operator position i had a keyboard and two computer monitors and i had some equipment up here i mean it's just loaded with equipment anything i wanted to do i had gear arms reach away to be able to analyze stuff but one of the things that i had an oscilloscope up here set up for with a function generator is i would take if i if i question the computer i would take that signal and route it to the oscilloscope in oscilloscope just like we have here in the lab and then what i would do is i'd get a function generator just like what we have in the lab and i would feed the input into the function generator out of the function generator into the oscilloscope into what's known as my x-axis so my y-axis is the unknown frequency the x-axis is my known frequency and i could mix those two signals together on the face of my oscilloscope and does anybody know what i would come up with on my oscilloscope here's my oscilloscope face if i mix those two frequencies together anybody want to take a guess at what i'm going to end up with i get a circle i'd get a circle because the unknown on my vertical axis matches the known on my horizontal axis and a mix and if i got something that looked like this it's a harmonic if i'm at the perfect frequency it's going to be a circle if i'm at double that frequency it's going to give me one of these things so i could get all these different patterns on the oscilloscope but for me i had the equipment set up like that so that randomly i could you know if i was looking at something because i had to act really quick on analyzing stuff very very quick i mean we had a literally a matter of seconds to is this a safe environment for us even to be near the surface or somebody looking out there looking for a periscope that's going to target us boom sent a sub rock down and blows to kingdom come so i had to make a quick decision is it a threat or not and by having that connected like that and i look at the computer and then pow immediately hit patch it up to the oscilloscope look circle yeah the computer's not lying to me or now i'm getting one of these the computer's lying to me this isn't even the freaking frequency that we're at flying to me i could discount that and then move on it's called elissa jewel pattern on the oscilloscope and i'll show you in the lab on some day on how to do that it's kind of cool it's kind of cool in summary ac is the most commonly used type of electricity so ac comes in two flavors power to power cities communities buildings power and signals and signals basically is anything that has intelligence behind it from dc to daylight cycle is that amount of time which it takes for a waveform to repeat itself alternations an ac sine wave has two one positive one negative hertz rental car company o.j simpson used to represent sinusoidal waveform or sine wave could be used is actually the most common form of power distribution peak value of the sine wave is the maximum deviation from average effective value of ac is the exact same effect as if you apply dc to a purely resistive load like a incandescent lamp how to determine effective value by the rms process it's simple 70.7 percent of peak i also showed you the technique on how to get the multiplier to go from p average excuse me rms to peak period measured in time frequency measured in f and the relationship f is equal to one over t we also talked about non-sinusoidal waveforms and where they come from it's kind of stuff i used to read my kids when they're growing up tonight we're going to read about non-sinusoidal wave forms and where they come from in the beginning there was what was known as the fundamental frequency tomorrow night we're going to talk about adolf hitler and what he tried to do yeah my wife man should run me out of there forget it i'll read to the kids all right you wanted me to read to them these are my books it's the stuff that i it's how i roll man square waves triangular waves and sawtooth waves all of these waveforms represent intelligence and all of these are made up of harmonics fundamental frequencies and harmonics added together and that's how we create those things that's how a function generator works internally it adds all of that stuff up and then gives us the circuit the the signal that we want any questions ever hit idea me 60 cycles um no it was actually that's a good question i can't answer it off the top of my head but it was it was really interesting a few years ago at the consumer electronics show i there was a display that was set up of all these worldwide adapters okay and there are some places that have some really goofy plugs and goofy voltages well and actually japan is interesting is there 120 volts like us 100 1520 but it's 50 hertz 50 hertz yeah so stuff like your electric shaver will work it's just going to work a little bit slower um but it'll still work but anyway this guy that was the the sales rep for the company he used to be a history teacher and it sounds like he got his job because he knew the history of all this stuff and it all goes back to politics like even in the caribbean i love the caribbean it's my favorite place in the whole freaking world okay the lesser antilles right the outer antilles beautiful beautiful area but it's funny my favorite place in the world of all places is saint martin half dutch small island okay smaller smaller than tacoma small island half dutch half french and they've lived harmoniously for hundreds of years on the dutch side it's pretty much us style plugs on the french side now and it's a small island and it's all because of history and and who ruled what and where the lines were drawn and that really is the governing factor specifically why 60 here why 50 there i don't know that'd make for an interesting uh i guess research project but a lot of it all played politics politics was was behind most of those decisions they want to be different 400 hertz specifically for industrial applications in aviation it was for the accuracy because ideally you know if you've got if you've got 60 alternations per second now you could cram 400 of those in there when you go to clean that up and convert that from ac into dc you're going to end up with much purer form of dc so that's why they do it absolutely it'll be just about null that was one of the i actually had a friend that i i served with in the military and he went to go to work for berkeley lab they have a particle accelerator down there and i went down there hung out in berkeley for a while hey now if you know what i mean i don't know what i mean we did some crazy stuff down there really the san francisco bay area is a hoot so anyway uh he gave me a tour of their particle accelerator and it was interesting what they were doing is they're buying energy from the power company and then literally what they would do is they would turn a giant motor and the motor would turn their own generator and what they were generating was 12 phase power at a higher frequency and what they would do with that is ultimately convert that into pure pure dc to power this particle accelerator and um i mean the power supply was it was like it was a cage and it had interlocked so like you could walk into the power supply and it's like these big huge rectifier tubes and it's fascinating i wish i had pictures i wish i had pictures not from the entire weekend but just from that part how do they determine uh that hurts you know say say you have 60 hertz and the power company also want to change to 100 hertz what what sense i guess that hurts kind of back to everett's question it's it's really government it's it's political it's it's the same thing even with us canada mexico you know we've got inner ties we're sharing electricity back and forth you know canadians want to be that freaking different a right uh why don't you guys change like different hertz rate and then like uh actually i think we're probably buying electricity from them they got those gas reserves and all that stuff up there i mean that's like freaking big time that's big time i drove the alcan last summer i had friends that moved up there and i was just kidding around hey you want somebody to ride shotgun it's like you'd be willing to do that it's like we don't want you to ride shotgun we got an extra vehicle that needs to be driven you want to want to go up with those in convoy yeah why not so i drove the alcan phenomenal and that whole area up in northern bc where all the oil exploration we paid more per gallon of gas or liter of gas up there our hotel costs more food cost more everything because of all the oil and gas exploration taking place up there in canada right now so they could probably kick our boat natural resources you know at this point right conventional means but it's political political we're friends with them stick with 60 hertz back and forth we have an intertie with mexico sell them our electricity if they were in a different standard then that'd be a bit of a hassle the only exception of that is actually down at the dallas on the columbia river they have a direct line this i shouldn't tell you about this it's too late in the night to tell you about this bonneville power administration has a direct tie with the city of los angeles and it starts in the dallas if we hopped in my airplane and we flew down there columbia river got there follow those power lines we'd end up in a place called los angeles and you know what they're doing they're generating ac at the dam they're converting it into dc and they're shipping dc to la supposedly i've asked bonneville power when they've been in here that exact same question and supposedly they're getting higher efficiency out of converting it into dc once it gets down to la what's the first thing they got to do with it convert it back to ac so they could you know power power the valley it'd be a great thing to study it'd be a great thing to study we could you know we have friends at bonneville power get them in here as a guest speaker we can actually plan a field trip a class trip um open it's one of the things that you you all you all students i'm going to rail on y'all students here for a second right as college students you can get yourself into places that the general public cannot get and i will help you get into those places because i as a teacher could get into places that the general public can't get one of the great tours that we did um years ago i haven't been back since is um the power generating plant snoqualmie falls not the one downstream the one underneath the freaking falls behind the falls it's like the bat cave i mean i'm hanging out there i expect like batman you know robin like looming in the shadows wearing tights it's the real deal we got their students it's not open to the general public we scheduled it ahead of time we all had hard hats we all rode the elevator down in if you've been a snow kwame falls before that the output if you're looking at the falls there's like this cave and water coming out of it and stuff we were down there we're standing there looking up at the falls like this is a freaking hoop wanna do stuff like that you know you could do that as projects we haven't been on tours and like eons because it's a pain i mean it really is we could do that kind of stuff go to freaking go down a columbia river gorge i mean charter a freaking bus do some fundraising get a freaking bus or kick in or whatever motor coach go down there get a tour see that i mean you're actually converting it to dc in this giant room and you mean that dc that that's that wires connected to the city of los angeles that's cool stuff i mean you watch stuff like that on discovery channel you can see stuff like that with your own eyes and this is the leverage that you could do because everybody loves helping out college students i was working with some old timers at psu and they were telling me the cool thing about that power plant so call me was when they built it they only had the one elevator shaft that went down so he was saying that anything and everything you see down there was deconstructed up top brought down the elevator shaft and then reconstruct it down below is that true it performed i understand yeah i thought i had to do it and that that was all too the neat thing about being down there that was all the late 1800s when that was built carved out by hand i mean it's phenomenal anyway hey we're handing out they take home here we go chapter 13 ac measurements we've talked about an introduction to meters earlier in elec 110 ac measurements are a little bit different and we're going to have to use some different equipment with that so this chapter is going to outline outline those differences after completing this chapter you're going to be able to identify the types of meters available for ac measurements identify the types of meter movements used to make ac measurements explain the function of an oscilloscope identify the basic parts of an oscilloscope and explain their functions demonstrate the proper setup of an oscilloscope describe how to use an oscilloscope to make a measurement explain how a counter works and then identify the basic parts of a counter ac meters the meters that we use for measuring ac are all based on the design of a moving coil meter movement and what i'm talking about here are the analog instruments you gotta understand the analog before you can understand how the digital work this type of meter movement is referred to as a d arsene wall meter movement and a diar's involved meter movement is designed to measure dc current designed to measure dc current so if you start talking about like the instruments on the dashboard of your car your gas gauge your engine coolant temperature gauge all of that stuff is typically based on this design so it's designed to measure dc current but we're going to want to measure what with it ac so therefore ac current must be converted to dc current to be measured so even if you're using an ac meter basically that ac is getting converted to dc and then it's going to show you the equivalency of what's present in the circuit this process of converting ac into dc is called rectification rectification the rectifiers are going to convert the sine wave into a pulsating dc current but the key word there is dc current it may be pulsating but it's not repeating itself ac goes back and forth remember two alternations now we're just gonna have one alternation positive positive positive positive positive because we're rectifying it okay um again so if you see one of these on sale or whatever it's well worth its weight but if you plan on doing a lot of ac stuff um this is actually very nice to have a digital meter like this or if you're also doing a lot with dc um and for any of you that want to get into alternative energy or anything like that having one that does dc or automotive applications i mean i find i find it real handy to be able to stick that across my my cable and see exactly what am i drawing out of my battery but typically these are higher values of current you're not gonna you know see the difference of 250 milliamps uh you know on something like this and of course this is analog the model that i've seen at harbor freight is an analog meter so as i saw that was my first indicator that you're on an analog meter there i couldn't see the face of that is that you're studying normally with a digital 1.26 volts you know i mean it's instant gratification here you got to look at this needle but it is still prevalent now the single most versatile piece of test equipment available for working on electronic equipment and circuits is the oscilloscope is the oscilloscope also the number one thing that i hear from students when they graduate you know i normally talk to students when they're going to graduate and you know what do you think what do you think you got you got to get did you get a good education here did you learn anything what would you like to learn more about and i always hear i wish i knew more about the oscilloscope uh the oscilloscope is such an important instrument and it's pretty intimidating there's a lot of knobs and buttons on it and the better you know how to operate the oscilloscope the more effective that you're going to be as a technician there's no question about it invariably in a job interview they're going to sit you down in front of an oscilloscope i did it to peter i hired peter when i brought peter in it was the first thing i had a little circuit that generates a signal and i actually have a uh a fluke scope meter so it's like a little handheld meter but it's got an oscilloscope on it and i've come to find out that peter actually hates those things which was good so i sat them down and the wires were all tangled up and everything and i'm like tell me what's coming out of test point 22. so he's got to set the oscilloscope up he's got to turn the thing on he's got to get it all calibrated and you know uh this is actually funny um because i asked him i said what's coming off test point 22 is tell me as much as you can about it and he said it was a square wave and then i said what's the duty cycle you know his duty cycle is a parameter that we measure and he looks at me like duh if it's a square wave the duty cycle's fifty and it was funny i had these phds that i had interviewed and they're like trying to calculate it out well do you have a calculator i could borrow let's say if it's a square wave the duty cycle's 50 if it's less than 50 it's a pulse wave if it's greater than 50 it's a rectangular wave so if it's a square wave just tell me it's a square wave and the duty cycle's at 50 so peter was the only person that got it right but that was one of the things i want i could tell so much about a person's background on how they approach using the test instruments so that being said every opportunity that you have in the lab try to use as many different models that's the other thing too i could have gotten better discount buying in bulk of multiple scopes i want different brands in there i want you to have the opportunity to play with different models how many of you here learned how to drive a ford how many of you here learned how to drive a chevy a toyota how many of you here learned how to drive a car you see my point learn how to operate the oscilloscope and i'm living proof tektronix had the contract with the military when i was on active duty in the military doing sophisticated electronics i believe the only company in the world that manufactured oscilloscopes was tektronix because that's all i was used to operating then i got out of the military and i'm like i don't even know how to turn this one on you know i was so used to that brand name so don't get used to the brand name make sure you try all of the different models and get proficient all the models because then you'll really learn what's going on now the nice thing about an oscilloscope is uh it's for those of you that like to watch if you know what i mean i don't even know what i mean it provides a visual display of what's occurring in the circuit a visual display of what's going on inside the circuit which is really cool this is a oscilloscope that at one point i was intimate with the tektronix 2440 and what this is is a digital storage scope and this is a combination of an analog scope and digital it'll actually provide us with some digital readouts uh the face of the oscilloscope what is this battery works we could see that it's actually processing some data and providing it to us in a digital display but yet we're getting an analog representation of the signal that we're evaluating so this is kind of a marriage between both oscilloscopes provide us with the frequency of the signal the frequency of the signal the duration or period of the signal the phase relationship between signal waveforms the shape of a signal's waveform and the amplitude of a signal now the basic parts of an oscilloscope are the cathode ray tube crt the sweep generator horizontal and vertical deflection amplifiers power supplies the first part we're going to talk about is the cathode ray tube this is a vacuum tube it's a vacuum tube inside the vacuum tube is a phosphor screen phosphorescence i don't know if any of you have been boating at night on a cruise ship or anything and you can see the wake of the ship and it's kind of like glows in the dark okay because all these microbes and stuff i remember once cape cod i was getting a bunch of blue crabs and one of the inlets capturing them and then you know we'd cook them up and eat them and uh the shells that were all left over they actually started glowing in the dark and there was no nuclear power plant anywhere near uh where i was getting these crabs so they weren't radioactive it was just the phosphorescent reaction of what was taking place also inside the cathode ray tube is an electron gun the electron gun shoots electrons the electrons come out and the position of the electron beam is controlled horizontally with these deflection plates and vertically through these deflection plates and when the electron beam hits the phosphor screen it causes the phosphor to glow in the dark for a brief moment in time that allows you the technician to take a reading as the image is painted on the scope face so let's turn this classroom here into a giant crt and i'm going to come to the back of the class here and i want you to use your imaginations here and looking at the screen let's imagine that the screen right now is coated with phosphorescence and i have an electron gun in the back of the back here and i'm pointing it at here does that make sense so the electron beam hits this if i turned it off right now it would glow in the dark for a brief moment in time and then gradually fade so the first thing that i'm going to do when i turn the oscilloscope on is these horizontal deflection plates are going to be driven by a time base inside the oscilloscope we're going to talk about that in a second and what's going to happen is this remember last week we talked about a sawtooth generator the sawtooth generator is going to create a voltage that has a long rise time linear and then a short linear fall time and we're going to couple that voltage to our horizontal deflection plates and when i turn it on with my electron gun what's going to happen is it's going to pull this across the screen along linear rise time and then gradually it's going to shoot back really fast faster than the naked eye could even see it does that make sense can you envision that and can you envision that if it glowed in the dark for just a brief moment in time we would begin to perceive it to be what nothing more than a a static image a straight line going across our oscilloscope face so the horizontal deflection amplifier is or the horizontal deflection plate is driven by the horizontal deflection amplifier the horizontal deflection amplifier is actually driven by the internal time base it's actually calibrated it's got more in common with a stop watch than it has with a volt meter because it's a calibrated time base to pull that beam across the screen in a in a predetermined amount of time now our vertical deflection plates are controlled by our vertical deflection amplifier our vertical deflection amplifier is fed by what you connect your probe to so when you connect your probe and touch your probe to an ac signal that signal is going to be amplified vertically and then it's going to control the voltage across these deflection amplifiers so remember before on how i was pulling my beam across the center of the screen now what's going to happen is as i'm pulling it left to right i'm also going to pull it up and down based on the signal that i'm looking at so can you envision i need your imagination here but can you envision of what this would actually look like if it glowed in the dark for a brief moment in time it looked like a sine wave very good gotta use your imagination i said use your imagination okay it would look like a sine wave okay i got a positive alternation i got a negative alternation and over a period of time it's changing the oscilloscope is functioning so that's how that's how an oscilloscope works at least the cathode ray two portion of it does that make sense the reason i'm beating this to death is if you understand if you understand how the oscilloscope works internally i could put you down in front of any oscilloscope and you're going to look for horizontal controls vertical controls you're going to you're going to look for these basic parts it's like learning how to drive a car if you know that a car has it's kind of funny i learned how to drive it was an automatic okay but i learned how to drive standard nobody taught me standard i was mechanically inclined i understood how a gearbox worked i understood the function of a clutch i basically got in a car and just okay clutch in first gear release the clutch like you know a little bit of finesse is required i figured it out nobody had to teach me how to do it you know i remember my son who's less mechanically inclined he's not afraid to get his hands dirty um that was a it's a pretty sore day teaching him how to drive standard and then jerking and he just did you know but once you get the feel you figure it out so that's what i want you to do i want you to understand these functional parts of the oscilloscope then i can put you down in front of any brand name and at least know what you're doing make sense okay the next part believe it or not this is a pretty important part of the oscilloscope is the face plate the face plate is marked in centimeters typically centimeters along the vertical and horizontal axis typically it's eight by ten eight squares high by ten squares across and each one is graduated so you end up with all these little squares now these squares can be calibrated with a known voltage before testing an unknown and that's how the oscilloscope is set up is every square and i saw you guys in there the other was yesterday today yesterday and you were looking at that and every square was worth 5 volts with what you were looking at so if you've got 5 10 15 and then 3 more 15 18 about 18 volts you were looking at peak value okay so that's why the graticule markings are calibrated for this known voltage and that's what they're called is graticule markings kind of like the cross hat the crosshairs on a scope or on a periscope it provides you with range information if you know how to read them it's mounted in front of the crt and all it is is a reference standard don't laugh but the power switch is usually on the front panel and actually for job interviews i've tried to find some oscilloscopes that had the on off position in a very unusual place and then i just want to see how people struggle with it you know they're trying to you know they know how to operate the oscilloscope they must because they're engineers and stuff but they don't even know how to turn it on because this particular model is a little switch you reach in the back and you depress it you turn it on and i know i find that entertaining you know so always make sure you know how to turn the oscilloscope on maybe a toggle switch push button or a rotary switch sometimes it's mounted separately or with another switch and what it's do it's used to apply line voltage ac to operate the oscilloscope provides voltage to power supply that brings the oscilloscope to life so make sure you know how to find that switch intensity switch also called brightness controls the electron beam within the crt it's usually a rotary switch you have to be careful because too much intensity for too long can burn a hole or etch a line in the phosphor screen if you just sit that electron beam just sitting here all day long it's going to burn a hole in it it's going to burn that phosphorus and coating this is one of the reasons i don't know if you realize like screen savers are called screen savers because originally computers used a crt and that image sitting there all day long is going to burn that image onto the screen so over a period of time you want it to switch to something that's going to move and change or just your screen to go black is fine so this is again one of the qualities that i look for in a technician if you're working for me as a technician if you're taking a reading you tune you you turn your intensity up you take your reading and you turn that intensity up so it's very very dim because the dimmer that it is the crisper and clearer your line will be on the oscilloscope and the more precise you are in taking your readings that make sense as soon as you're done taking that reading you just turn the intensity down and you go back to whatever else you're doing if i walk by you more than once twice three times and i see the image on the oscilloscope up i gotta beef with that you're putting additional wear and tear on the machine that you really don't need to just turn that intensity down oscilloscopes don't come with screen savers focus and astigmatism controls these are connected directly to the electron gun and they're used to adjust the electron beam size and shape and these are rotary controls okay focus and astigmatism deal with the focus of that electron beam on the oscilloscope face on the phosphor coating think of this as like a fire hose or like your garden hose you know sometimes you want to find mist other times you want a direct beam okay with the oscilloscope you always want the direct beam but you have to have the ability to control that so you end up with a pinpoint beam so focus and astigmatism controls will control that electron beam so you get a sharp focused clear point where it comes in contact with the phosphorus encoding horizontal and vertical position controls these are really self-explanatory horizontal position position it moves your image horizontally on your oscilloscope face vertical moves it vertically up and down don't be afraid to adjust those because you may want to align your image just so with the graticule markings so that you could take a measurement it's okay to move it horizontally and vertically that's why they have these controls so that you can align it with those graticule markings so that you can make an accurate measurement it's designed that way so it allows the electron beam to be positioned anywhere on the face of the crt this is a a typo this should say vertical block up here vertical not horizontal the vertical block and that's the section that we're talking about and by the way this is i'm going to give you a helpful hint here when you're talking about the oscilloscope i don't want you to remember the abcs of the oscilloscope i want you to remember the x y z's of the oscilloscope and the reason i say the x y z's is does anybody know what my x-axis is x-axis is horizontal what is my y-axis vertical what's my z-axis it's what's coming at you so you got to get those three things working for you you have to have a horizontal display and what data is it that we look at horizontally with the oscilloscope time very good what do we look at vertically amplitude or voltage very good and what do we look at in our z-axis what's that no i don't know you told me i'm not going to answer your questions these are my questions what is the z-axis what did we say the z-axis was what's what's coming at you what is coming at you electron beam so what do you think we control when we control our z-axis the electron beam so we're going to control things like brightness astigmatism focus it's what's coming at us and those are those controls so think of it break the oscilloscope down into that is i got my horizontal controls i got my vertical controls and i got my z access controls make sense so my my vertical block is going to consist of a vertical input jack this is where you connect your probe to an ac dc switch so you can listen to ac dc while you're operating your oscilloscope now actually this is so that are you looking at an ac signal purely where you want to discount the dc component or do you want to look at the dc component as well because sometimes we have ac that's writing on a dc level so as soon as you connect it to the circuit your signal may jump off the screen and you can't even see it if you're just concerned about the ac signal set it for ac and then it won't jump off your screen if you're concerned about ac and dc then put it to dc and then you'll see that ac signal jump up and then you could say okay yeah i've got a small signal writing on a 24 volt dc level so you got kind of got to make sure this is in the right position then we also have the volts per centimeter rotary switch this shows exactly what each graticule marking is worth the other day in the lab when i caught you working on labs it was 5 volts per centimeter if you change that position switch it'd be 2 volts per centimeter 1 volt per centimeter half a volt per centimeter or whatever you set it for make sense the oscilloscope probe is connected to the input jack and all probes are not created equal you can have an oscilloscope probe that's a one-to-one probe meaning whatever you measure in the circuit is going to be read by your oscilloscope you could also have a 10 to 1 probe that means whatever you touch in the circuit now is 10 times less going into the oscilloscope by you simply getting another probe what did you do to the oscilloscope you just extended the range of it by how many times it's pretty cool that's pretty cool by just getting in a ten to one probe you just extended the range of that scope by by ten times they also have hundred times probes we really don't need them here at lake washington for any of your stuff the ten times probes come in handy 100 times probes we we really don't recommend you get one of those but 10 times probe is definitely good to have the horizontal block is also called the time base right because this is our horizontal information our electron beam going left to right it's going to consist of a time per centimeter rotary switch a trigger control switch and a trigger level control remember when i said when you're operating the oscilloscope you got to pay attention to the what i call them the xyz i left out an important part you do have to pay attention to the xyz but you also have to pay attention to what's known as triggering have any of you here ever discharged a firearm before what do you got to do to discharge your firearm pull the trigger got to pull the trigger where these people get shot in accidents and all i e yeah i never understood it but then again i was classically trained in the military and handling firearms so i never saw anybody get shot by accident in the military so that's the people that were involved in training accidents that's another story now to discharge a firearm you gotta pull the trigger to get a display on your oscilloscope you have to anybody want to take a wild guess pull the trigger got to pull the trigger now you could either pull the trigger manually which i don't recommend you do because if you pull it manually you're only going to get one image on your oscilloscope face you want to get a regular image on your oscilloscope face so the best thing that you could do is set your oscilloscope to what's known as automatic internal triggering so what it's going to do is whenever it senses a waveform starting to either rise or fall depending on how you have it set up it's automatically as soon as that threshold is exceeded it's going to start to display so if you're looking at like current coming out of a wall outlet and you set that every time that waveform starts to go positive it's going to start to display so what you're going to get is a nice stable image on the oscilloscope every waveform is going to be nice and stable and you're going to see it and perceive it as a stable image the number one problem that students have operating the oscilloscopes is the image is jumping all over the screen and it looks just like an image jumping all over the screen that is because they don't have triggering set up properly so if you could opt for automatic triggering do it if you could opt for internal triggering do it all of those oscilloscopes have that feature if you don't have triggering set right and the threshold set right it's that you're just going to end up with nonsense on your screen that is not useful information so you have to have not only the xyz but you also don't need to have the triggering set properly the level control sets the amplitude that the triggering signal must exceed before the sweep generator starts this would be like again for some of you with firearms experience this would be like your ability to set a hair trigger what does it take for me to discharge this firearm a simple little bit of movement on the trigger or solid pull on the trigger and i i've never shot competition or whatever but i guess some people play with that you know so a little bit of pressure boom and it go you know discharge the firearm half of the stuff that i shot in the military was uh you had a pull on that trigger pretty good to get at the discharge so this level control allows you to set the threshold that will cause the oscilloscope to start triggering on now this next thing here is the initial oscilloscope control settings i'm big into uh checklists i'm big into checklists as a matter of fact my whole adult life has been revolved around checklists and standard operating procedure okay it's how i live my life as a pilot i wouldn't think of getting in an airplane and not using a checklist because it's so easy to miss something and let's face it an airplane cockpit it's pretty complex because there's a lot that you could miss some of it for me is ritual and muscle memory some of it you got to go through that checklist i highly recommend you make your own internal checklist on operating the test equipment and if you consistently follow that checklist you're going to end up with good results every time okay i've been doing this so long i've got the checklist for the oscilloscope really in my mind and you know what my checklist in my mind is going to consist of x-axis set y-axis set z-axis set triggering set if i know if i got those four things set properly you know what i'm gonna get a display on my oscilloscope if one of those four things isn't set properly i'm not gonna get a display so this will serve as a as a basic checklist for an oscilloscope intensity set center of range set center of range astigmatism set to center of range position set to center of range trigger triggering set for internal positive level set for auto time per centimeter set for one millisecond volts per centimeter 0.02 power to on and if you follow this checklist you're probably going to get a display on your oscilloscope make sense you'll probably get a display on your oscilloscope so be ritualistic about it that's one of the other things too that you'll see i'm going to do it to you in lab from time to time just to mess with you because you're here to learn you walk away from your lab especially if you leave the the signal the intensity turned on and you go take a coffee break and i walk by i'm going to come over and screw up all the knobs in your oscilloscope and i guarantee you right now you could put any oscilloscope in front of me and screw up all the knobs i'm going to get an image up on that scope probably in 60 seconds because i've got this committed to memory because i've done it enough so the moral of the story is the only way you guys are going to get that good at is hands-on keep challenging yourself one of the things that's not this is not an assigned lab per se but i highly recommend you guys pair up in groups of two or whatever in the lab and do that to each other one of you leave let the other one totally screw up all the positions of all the knobs also let me i want to show you one thing here let me go back a slide intensity set the center of range focus at the center of range astigmatism do you see a trend here what is that trend set to center anybody want to take a wild guess how this oscilloscope was set when it left the factory yeah set the center of range when a device is calibrated that's the first thing they do they put all those controls to the center then internally they make adjustments to align it so that when it leaves cal you set at the center of range you're going to get a good display now gradually over time things change and you might have to change the focus or whatever a little bit plus or minus that actually used to be a technique that the old tv repairman used to do what they used to do is get it to the edge of range and then make an adjustment internal so that eventually as you try to change your brightness you're going to have to call them and say i can't increase my brightness anymore they'd have to come back for a service call charge your money for it when that television set originally left the factory everything was set to center of range if you go through a calibration procedure and you get an instrument back and it's not calibrated center of range you don't been ripped off used to drive me nuts once i understood calibration and everything that's what you always go for you set the center of range then you make the internal adjustments a really cool device out there that's used for ac is called a frequency counter frequency counter this measures the frequency by comparing a known frequency against an input frequency consists of a time base an input signal conditioner a gate control circuit a main gate a decade counter and a display this is what the block diagram of a frequency counter looks like what you do is you connect your input here the input comes in it's processed by this input signal conditioner and sent here to this main gate and counter circuit the main gate and counter circuit compares a known existing time base to this gate control circuit and does a comparison of the two and then displays the unknown frequency to you on this display the electronic counter is used in and on electronic repair shops engineering departments ham radio shacks industrial production lines sounds like really exciting stuff right let me add something to this list if you want to sweep a room for bugs all you need to have is an electronic counter you could buy an electronic counter on the internet with an antenna on it and set up a counter surveillance business and you could go into a room and sweep that room and if you're finding a frequency first of all you got to understand the design of the room and what else is going on but you come in like in this room right here quite frankly um if everybody's supposed to leave their cell phones outside ah i can't imagine anything in here my computer is going to be sending out a frequency um in internal frequency so i'm going to get something out of a computer but other than that no if i'm walking up and down these benches here sweeping and i come up with something that's emitting i just found something that's broadcasting out of this room that doesn't belong to be uh is not supposed to be broadcasting out of this room so frequency counter is like the most fundamental piece of counter surveillance equipment that there is you go to a hotel room you're afraid somebody's got a hidden camera in a hotel room or something you know that your wife put or your best girlfriend put a camera in there to catch you with your neighbor's wife or whatever the heck you know what i don't even know i don't even know what i'm talking about when it comes to that stuff i'm so straight laced it's not even funny seriously but i mean if you're in some kind of a goofball hotel or just concerned or whatever boy you sweep that room and all of a sudden you know you're getting a 2.4 gigahertz hit the heck is this you're looking in the lamp and you find a little pinhole camera or something i think you'd be surprised how many people have cameras and are doing goofy stuff like that the other thing about the electronic counter is um and this is not necessarily deeply it's not classified anymore used to be one of the holiest of holies the holiest of holies seriously when i was on active duty in the military and electronic intelligence gathering the russians the soviets used to in the design of their radar systems use crystal oscillators and these crystal oscillators were extremely stable very very very stable too stable i had equipment i had a frequency counter that could go many places past the decimal point when you turned your radar on and i intercepted that signal and i analyzed the specifics of your signal i could see many places past the decimal point and then i because you were crystal controlled it gave me a fingerprint of your radar so if we could get close and i could see the hull number of the ship the name of the ship the the uniform the ball cap that somebody was wearing whatever and we could correlate that to the name of the ship we had an electronic fingerprint of that ship do you realize how critical that is you could you could have a target that's over the horizon and as soon as they turn that radar on because a radar is designed to go out have enough signal and then come back the basic principle of my job was that we had to be able to pick up something one two three times the distance so all of a sudden we're sitting way over here over the horizon they don't even know we're there and their range their radar can't even pick us up and i know exactly who you are i know exactly who you are what vessel you are and what your capabilities are and then i could relay that information it's like hey skipper this isn't a problem these guys don't have anything they can reach out and touch us anyway or in the middle of a fog bank all hell breaks loose in war starts yeah that's the bad guy we know exactly who he is fire take them out they're gone and we know exactly who we killed so imagine if the police could track your car like that which with lojack and some of the other stuff yeah but imagine if by simply by you starting your car you had an electronic signature that the police could track now if you're a god-fearing uh you know tax-paying citizen it's not a problem if you're a criminal and they can track you like that you got a problem so it was simply an electronic counter that somebody stumbled upon this and it was really one of the best kept secrets of the cold war it was one of the reasons that the soviet union crumbled because all of their military infrastructure was based on that design of electronics and we could exploit the dickens out of it simply by them turning on their stuff we knew exactly who they are now we also assumed that they knew that we knew i know that sounds confusing i actually got in trouble for about that once because i it was like dealing with like the holiest of holies really top secret information i'm like hold on this this information is about like their stuff don't they know what they got you know petty officer gretak you have a bad attitude no but honestly don't they know what they got yes they know what they got but they don't know that we know what they got if you know what i mean no i still don't get them but never mind yeah i got myself a big trouble over that one it was just big briefing there's admirals there and stuff critic why don't you keep your mouth shut that was a legitimate question silly me for thinking the wide use of the electronics counter can be attributed to the integrated circuit which has reduced the size and price increased its accuracy increased its reliability increased its stability increased its frequency range so again you can look at that frequency counter handheld frequency counter do a google on it you'll probably come up with a number of different hits small handheld stick an antenna on it or you know if you're really going to the counter surveillance business some kind of a goofy pole with a little sensor on the end and you're like a divining rod okay except a lot more high and it does work that's all you need that's all you need and there's so much i tell you if you start paying attention and you own one of these devices and you start paying attention what's in a room what's not in a room you get an image you can you really learn a lot about what's going down and what sensors are available the bode plot named after hw bode i don't know why i got to use an accent when i just sounds like bode a big 10 gallon hat driving a big cadillac horns in the front this here is my plot it's used for studying amplifier feedback that's the good news the bad news that requires the use of semi-logarithmic graph paper have any of you here in the past ever used semi-logarithmic graph paper right the reason we use semi-logarithmic graph paper is what we're looking at here is actually audio and audio is non-linear so we have to use a semi-log paper two graphs are going to be plotted out one is going to be the gain in decibels gain and decibels the other is going to be the phase shift in degrees now at lake washington technical college we do not own a bode plot if you worked at harman kardon you'd have access to one if you worked for what's a big automotive uh audio post you'd work you'd have access to these for the type of stuff that we're doing here buying the semi-log graph paper would break our budget so we don't have one we do have computer simulations and that's good enough for what we're doing computer simulations make them easier to use which is good news for you they're used to measure voltage gain or phase shift of a signal produces a graph of the circuit's frequency response this is very useful for analyzing the effectiveness of filter circuits in summary measuring ac current with a moving coil meter everything gets converted to dc so even when you've got your meter set for ac it's set for ac but that means the ac is going to get converted to dc and you're going to get the equivalent c or the effective value of it the iron vein meter we talked about the clamp on meter we talked about the oscilloscope oscilloscope we talked about the frequency of a signal the duration of a signal phase relationship between signal waveform shape of the signal's waveform amplitude of the signal we talked about the inner workings of the oscilloscope the crt the sweep generator the horizontal deflection amp the vertical deflection amp the power supply we talked about frequency counters it's not your father's frequency counter anymore you buy these things handheld battery operated great devices we talked about the parts of the functional block diagram of a frequency counter time base input signal conditioner gate control main gate decade counter and finally the display and basically he who has the display that goes the most places past the decimal point wins the cold war and that's the truth and then bode plotters great for analyzing amplifier and filtration circuits we don't have one here but on multisim it is one of our icons you can drag that into your circuit and analyze your heart's content any questions on anything that we covered in this chapter ac yes um nobody's invented it yet for it no because you're because technicians are considered smart so they know just turn it down when it's not in use how does a screen saver work it's just a timing circuit a screen saver and a computer is nothing more than a timing circuit to initiate a program that's going to change the value of what's being displayed on on the so if if a keyboard is inactive that timer is counting from the last time you touch the key and it's just sitting there and it's waiting for how long and then once the 10 minutes 15 however you have it set then automatically it's going to put something on that changes the image on your screen you know one of the other things that was kind of interesting um during the cold war is that for everything that i worked on that was super classified if you had a computer monitor that displayed top secret information on it that computer monitor now had a designation of top secret even though it's unplugged and it's removed because part of the image could be burned in there and they found russians soviets that were going through our junk bins trying to get stuff and then trying to pull an image back up and be honest with you if they could figure out like this computer monitor is using the weapon system and look at they could go to hundredths of a degree or look at the resolution that they could go to in a speed control or whatever you gain intelligence from that and the more that they could learn then [Music] it was all useful information i have two questions the first can lcd or led monitors still be burned in since they aren't using crt tubes any image that sits there for an extended period of time could cause degradation led lcd is not as uh pronounced as like plasma one of the worst things you could do if you got a plasma tv is you know when you're playing tivo freeze frame and then walk away for the day and oh you come back that night you're gonna have an image probably burned on your plasma screen so um i recommend keeping fluid motion on any display um because it's gonna you could have some degradation and then when when ac is converted to dc for the measurement of the meter does the meter just measure the top peak of the positive sine wave of the ac it actually measures 70.7 percent of that top wave it measures the effective value when you're measuring when you get out when you get your meter and you measure coming out of the wall here it converts the ac to dc and then it it actually represents 70.7 percent of what's coming out of that wall and that's what we consider so right now how many volts are supposedly coming out of the wall 120 volts that's 120 volts which is the rms value and we did this last week right 120 volts rms is actually like 170 167 volts uh 1.414 i know that number 120 times 1.414 equals 169.68 volts times two 339.36 volts peak to peak divided by two 169.68 volts peak times 0.707 now i messed up 120 224 120 volts rms makes sense all right let me go ahead take a about a 10 minute break when we come back chapter four 14 14 will be the easiest chapter that we do okay chapter 14 this is probably the easiest chapter of the whole book i think probably what happened is the author was paid by how many chapters he wrote so he like added this chapter just so that he'd make some extra money because really everything that you studied before in dc resistive circuits is exactly the same in this chapter for ac resistive circuits the key word here is resistive resistive so as long as the circuit is purely resistive all of this holds true if we start adding some other properties then what i speak of is no longer true and we're going to get to that next chapter in chapter 15. so that being said let's take a look at chapter 14 this should be pretty easy after completing this chapter you're going to be able to describe the phase relationship between current and voltage in a resistive circuit apply ohm's law to an ac resistive circuit and solve for unknown quantities in series ac resistive circuits parallel ac resistive circuits and also solve for power in ac resistive circuits now basic ac resistive circuit consists of an ac source ac source right conductors that connect the source to the load and the key here is that the load is purely resistive now when i'm beating this to death what am i talking around what do we make sure that the circuit has nothing of inside it no phase shift know what components cause phase shift no inductors or capacitors so as long as there's only components in there that have resistive properties we're good to go as soon as there's a capacitor in the circuit all bets are off soon as there's an inductor inside the circuit all bets are off but if it's an ac circuit that's made up of nothing more than purely resistive loads we're good to go now what we see here and we've got to be careful about this because you on the oscilloscope what is that we look at on our horizontal axis is time and in our vertical axes amplitude voltage so what we're looking at here is a correlation between voltage and current can i see current on the oscilloscope no can i see the effective current on the oscilloscope yes so if you think you're going to call the oscilloscope up and say well look at this is current and this is voltage you can't all the oscilloscope will display for us as voltage over time so we can't see this display on the oscilloscope but we can look at this as an xy plot to show the relationship that voltage now what i'm looking at here is pure ohm's law when voltage increases what is current though increases when voltage decreases what does current do they keep up with each other so when voltage is at 90 degrees current's at 90 degrees when voltage is at 180 currents at 180 when when voltage is at 270 current at 270. make sense get my drift so we say that these are in phase with each other now an ac source could either be an ac generator we talked about that last week where we have a rotating shaft cutting a magnetic field that we're generating ac or it could also be a circuit that generates ac remember how we said ac we have these different generators function generator they're circuits that could actually generate these waveforms for us typically power is created by a generator signals are created by some type of a circuit now the load in an ac resistive circuit could be a resistor a heater a lamp any similar device as long as the only property that we're taking into consideration is resistance period when resistance is the only property that we're dealing with in an ac circuit we're going to have voltage and current are going to be considered in phase with each other meaning at 0 degrees they're in phase at 90 they're the same at 180 they're the same 270 360. if it could pass that litmus test we say that these voltage and current are in phase with each other one of the things that i'm going to want you to do when you're dealing with these types of circuits ac resistive circuits are use the effective values the effective values this is the amount of ac voltage that produces the same degree of heat as a dc voltage of the same value remember this when i apply 13 volts to this it's going to be this bright and this hot when i apply 13 volts ac rms to it it's going to be this bright and this hot the exact same this is an ideal example of an ac or excuse me a resistive load it'll behave the same dc and ac effective applied to it exactly the same so it could be considered the dc equivalent value when we use that dc equivalent value ohm's law can be used in the circuit straightforward equals i times r just like what you've been doing with no modification series ac circuit the most important thing about a series ac circuit current is constant current depends on the applied voltage current is always in phase with the voltage at any point the current has the same value as the voltage at 100 percent currents at 100 percent at zero percent currents at zero percent in phase parallel ac circuit just like a dc circuit the most important thing to remember is in parallel voltage remains constant across a parallel network another term for a parallel circuit is a current divider so total current divides among each branch the total current is in phase with the applied voltage the individual currents are in phase for the applied voltage because it's purely resistive all current and voltage values are the effective values if they're not what do you do if i give you a problem like this and i start giving you values what do you need to do convert convert to the effective always convert to the effective unless you're told otherwise if you're in a tech manual and it tells you to measure look for 17.4 volts peak then look for 174.4 volts peak but if not always assume you're going to have to convert to the effective value now let me go back a step to last chapter this isn't something i really shared with you at the time but it's very important with ac test instruments why do we use an oscilloscope see what's going on in the circuit that's a good answer because i did say it's for those of us that like to watch if that's your thing that's one reason what's another reason why don't we just use our digital multimeters it doesn't show the waveform what happens if seeing the waveform isn't important to you what's that maybe you don't care about the frequency can i use an ac digital multimeter for an ac signal to give me the voltage accurately [Music] that's why we have oscilloscopes basically the digital multimeter first measuring ac is used for measuring ac power ac power what flavors does ac power come in remember this is his review europe what's the flavor 50 hertz north america what's the flavor okay seatac airport of 757 i just took off what's the flavor 400 hertz beyond that a digital multimeter separation ac pretty much worthless not worthless you could accurately measure probably up to about a thousand hertz after a thousand hertz the numbers you get are garbage so if i give you a lab that says you need to have a signal at 20 kilohertz and you need to measure 12 volts peak do not get a dmm and try to measure if i if i tell you you need seven and a half volts rms do not try to use a digital multimeter because about above a thousand hertz the data just goes out to lunch it's not designed to measure that repetition it's designed to measure ac power that is the number one reason we really use the oscilloscope because the oscilloscope you're looking at time versus amplitude doesn't lie to us that's one of the reasons that we taught you the math from last last uh last week if you could see the peak value on your scope you could calculate out that rms value you calculate out that rms value that's the real deal so the fun experiment for you to do would be in the lab do something at 60 hertz with the function generate do 50 hertz measure on the on on your dmm ac and then measure on your oscilloscope face do 60 hertz measure it on your dmm measure under your oscilloscope uh go up to 400 hertz go to 500 hertz go to a thousand hertz go to two thousand go to five thousand go to ten thousand and what you're gonna see is that accuracy is just gonna you're looking at the oscilloscope at the effect of the peak to peak value and you know effective is seventy 70.7 percent of that and your dmm is saying that you're you know you're way out to lunch that's why we use the oscilloscope because above a thousand hertz most of them drop off some faster than others that's actually the fun thing what do you got there mr carter what what type of a metar is that the is that digital so the fun thing to do the fun thing to do would be to do a comparative analysis of that meter that meter one of our fluke meters and an oscilloscope and then just start gradually plotting it out and seeing what the and you'll probably be surprised that analog meter might give you the best above a thousand hertz excuse me but we don't use them above that we don't use digital multimeters or analog meters for looking at signals you have to stick it on a scope power for measuring power electrical power and electrical energy for consumption is typically we use a dmm for that a handheld meter if you work for seattle city light you really don't need to be climbing a power pole with an oscilloscope okay because that meter is good enough to give you if you're an industrial electrician that meter is good enough if you're a residential electrician that's good enough if you're going to play around in that lab all of a sudden that meter now it's really limited unless you're looking at the incoming power if you're looking at a signal you've got to look at that signal on the oscilloscope make sense they're synchronizing with short power yeah yeah you want to be able to synchronize your generator with short power so you can transition easy from short power to to internal power and that's kind of kind of critical the way boats are in aviation it's not that critical you plug into a ground unit and then the lights all go off and ding and then you know you're on you're on the the ground connection but for a ship like that it's got a big freaking generator you want to make sure that you synchronize everything and they actually have small meters that allow them to synchronize the phases so that when you switch over you synchronize and everything's still in phase because you could destroy motors and stuff by giving them a goofy phase relationship so that's why you do that in a parallel circuit this is actually uh what we would be looking at we couldn't see this though because what do you see on the oscilloscope if i put an oscilloscope across this right here what am i going to see i'm going to see voltage right i'm going to see volt i'm going to see the same voltage everywhere across this okay but in actuality what's taking place inside the circuit inside this circuit let me go back a slide again i've got current flowing through this resistor i've got current flowing through this resistor this current plus this current equals total current so there's my current through r1 here's my current through r2 here's my total current this plus this equals this makes sense power in ac circuits is dissipated in the same way as in a dc circuit it's measured in watts watts is what it's measured in that's not a question it's a statement okay watts it's equal to the current literally it's equal to the current times the voltage in a circuit voltage times current gives us power p is equal to i times v or e literally what what what what's up with this this is odd right okay voltage times current voltage times current equals power that makes sense right this times this equals voltage times current well that i like your style like your yeah it's dissipated as heat but literally isn't voltage times current equal to power so how come power isn't going to be i like the fact that you say there's no such thing as negative power but shouldn't this blue line be drawn down here do you believe that two negatives multiplied times each other creates a positive i used to hear that and i never believed that so let's see i got negative 200 in my checking account and i go out and buy two plasma screen tvs and i'm going to have plus ballots in my checking account it never made sense to me but you know what it is the truth a negative times a negative equals a positive and for those of you that are non-believers here's living proof a negative voltage times a negative current equals positive for power and the reason is as as mark said there's no such thing as negative power this would suck you turn on your like audio amplifier like furniture starts getting sucked into your speakers and you know no turn it down you know you're gonna get sucked in or something it just it doesn't work that way this is this is dissipative energy so it's always gonna be that heat energy that's given off so there's no such thing as negative power no such thing as negative power makes sense so for those of you that have swallowed the algebraic pill on that a negative times a negative equals a positive here's a living proof this is actually the first time in my life that i saw living proof other than that i never really believed it never made sense to me in an ac circuit the average power is the power consumed we multiply the effective voltage value by the effective current value so it's that effective value that rms value sometimes you see the audio manufacturers playing around with that 1000 watts peak well since your speaker is basically a resistive load it's only going to be only the effective value that gets out but it allows them to put you know 14.7 gigawatts on the box or whatever they for marketing ploy in summary a basic ac resistive circuit consists of a voltage source conductors a resistive load voltage and current will be in phase with each other the effective value of the ac circuits is what you're always going to want to work with which is 70.7 percent of peak so if you measure peak value on the oscilloscope multiply that times 0.707 and that's going to give you the effective value and unless you're unless it's specified otherwise always convert to that if i give you a peak value say why the heck is joe give me a peak value convert it to rms if i give you a peak to peak value convert it if you look on a radar manual a tech manual you're working on a radar and it gives you a peak value for something assume they want you to know the peak value some stuff that is important that you achieve a certain peak voltage that will be specified in the manual if the manual just says 14.2 volts ac what do you assume rms so if it doesn't if it's not labeled peak or peak to peak or anything else assume rms any questions good question good question if you've got a generator out there that says 5000 volts peak or typically i think mine at home is 65 it's 5 000 um it's a 5kw generator 5000 watt generator and it's a 6.5 kw peak what that means is for a brief period of time that the manufacturer knows it could actually you know it could sit there all day long to put out 5000 watts but for a brief moment in time it could peak out like as a compressor on a refrigerator starting it may try to consume up to that 1500 watts more and then come back down so the key on that is when they say peak how for how long can it operate at that peak value for two seconds five seconds 10 seconds 30 seconds you know um if for some for some applications it could be critical you know you could end up with uh you know basically popping a breaker or something or overloading the generator if you know you you hold it up there for too long a period of time but that's what they mean by that peak output very good very good question very good question you'd also need to know the peak of the application right right and then normally like i say it's measured in in a brief in seconds you know to see what loads but the big thing at home like with me would be if my compressor was getting tired and it's trying to start and it's holding that up there really long the pow could pop that main breaker and shut the whole operation down um and i mean yeah that's that that was a very valid concern when i put in a generator in my home you know to make sure i didn't exceed that and then i left a big enough margin but that is my generator at 6500 peak 5 000 um continual operation and it's always good whenever they give you anything like that i always like throttle in the back a little bit you know supposedly could run at 5 kw all day long let's under rate it let's run it at 4 500 all day long you know and i'll feel a little bit better not right up at its max because you are but you're right if you're right at the max and you know engineers have derated systems like that too when they give you those specs they assume worst case scenario and you know there's always they always build in a margin of error so that their example from prosecution absolutely absolutely my my incident my incident that i was sharing with some of you last um last week for me um basically that we landed it was 4 000 pounds overweight from what boeing said it was okay but if they say it's 4 000 pounds overweight then it's probably good 20 000 pounds overweight you know to get the job done before things start breaking so good question any other questions comments concerns trials tribulations grief english sorrow all right let's go ahead take another brief 10 minute break when i say brief i mean brief because then we come back we do have a bit of a challenge here chapter 15 capacitive ac circuits game changer all right chapter 15 capacitive ac circuits you already know about capacitive dc circuits what we're going to study this evening is capacitive ac circuits it's a real it's a real game changer okay but if you follow the recipe and there's an easy recipe for success as a matter of fact it's all tied up in one formula if you know the one formula makes the behavior of a capacitor in an ac circuit totally predictable after playing this chapter you're going to be able to describe the phase relationship between current and voltage in a capacitive ac circuit determine the capacitive reactants in an ac capacitive circuit describe how resistor capacitor networks can be used for filtering coupling and phase shifting and explain how low pass and high pass rc filters operate now capacitors in an ac circuit ac voltage applied to a capacitor gives the appearance that electrons are flowing in the circuit okay let me draw a quick circuit here what kind of a circuit is this the way you should always start off with is the power source this is a dc series rc circuit right a dc series rc circuit the fact that it's dc tells you what you're dealing with as far as power series tells you whether current's going to be constant or in a parallel circuit voltage is going to be constant our c circuit tells you that you've got resistance and you've got the property of capacitance right now you guys know a little bit about the circuit don't you i hope you know something about this i get the switch here i got the switch s w one switch one when i close switch one what happens inside this circuit what happens inside this circuit loss current flow where it is current flow okay so current just flows through the circuit like this let's take a look more here at that what's going on right here okay this component here is a capacitor what is a capacitor two plates separated by a dielectric material it's like a battery but this is this is a dielectric material a dielectric material is a fancy way of saying insulator so let's go back to the circuit here when i close the switch is current flow through an insulator so mr carter was accurate when he said the capacitor begins to charge right when let's talk more about that charging when i'm actually charging the capacitor the voltage is going from zero up to a hundred percent and it takes time to do that so as the voltage v sub c voltage of the capacitor is increasing what's the voltage of the resistor doing decreasing and where is it starting off at that 100 percent and it's going to zero percent so it's coming down like this resistor when we're charging the capacitor is current flowing in this circuit when we're charging this capacitor is current flowing in the circuit absolutely absolutely because all of those electrons are going basically to the negative charge is on the on this plate here and positive on this chip plate here so if i've got a voltage that's increasing here current is increasing current flow goes from zero to or actually it goes from 100 percent to zero percent while that capacitor is charging when i first close this switch current is at a hundred percent in the circuit and what kind of a circuit is this series so if i've got current flowing here in the circuit do i have that same amount of current flowing here why thank you and what's the most important thing you need to know about a series circuit current is constant in the series circuit so if i've got current flowing here in a circuit out of the negative terminal battery i've got current flowing here the same amount do i have that same amount making a 90 degree turn here at the speed of light absolutely do i have current the same amount of current flowing here here here here here here here here here everywhere because current is constant in the series circuit can you dig what i'm selling does that make sense to you okay so back to the statement here gives the appearance that electrons are flowing in the circuit back when we studied this last week did have the appearance that current was flowing in a circuit none of you questioned me on this last week i didn't bring it up because i thought i didn't want to bring it up last week but i kind of got to bring it up this week last week when we were charging this capacitor was current flowing in the circuit to charge this capacitor absolutely was current flowing in the series circuit yes it was can current flow through a dielectric material no it can't but can current flow to build up an electrostatic charge across two plates yes it can and that's the current that's flowing when this capacitor gets to a hundred percent current in this circuit goes to 0 does that make sense very very important concept and you got to believe me with this okay especially this this week with this chapter so it gives the appearance that electrons are flowing in the circuit are electrons really flowing in the circuit yes are they flowing through the capacitor no am i building up a difference in potential across the plates in electro in the form of an electrostatic field yes in order for me to do that there must have been current flow because what is the plate a giant parking lot for electrons now check this out this is funny i think it's funny current and voltage do not flow in phase with each other they're 90 degrees out of phase current leads voltage current leads voltage is this a new concept to you is this something that i'm just first presenting to you in this chapter i'm saying it like this for the first time in this chapter but actually last week you were looking at it the voltage across the capacitor is increasing the voltage across the reason i hate that i don't like that i'm going to erase that and redraw come on look at that freaking yeah i'm not going to like this one either voltage of the resistor voltage of the resistor starts out at 100 percent and then it decreases to zero current starts out at a hundred percent then it goes to zero how do why does current go to zero the capacitor gets fully charged so i've got colors up here this vr is blue id is in red total current is in red so the voltage of the capacitor the current through the circuit decreases were these two were these two things for lack of a better work term in phase last week were these in phase last week no weeks left this is what you were looking at so things were out of phase last week here this week in applying ac to it we're going to have phase shift perpetually now when you're dealing with capacitive circuits like this there's a word i want you to remember and i want you to put this word on your scrap paper anytime you take a quiz an examination anything like that the word is ice ice the reason this word is so important in a capacitive circuit letter c in a capacitive circuit current leads voltage by 90 degrees current leads voltage by 90 degrees by leading we mean goes to a hundred percent and then voltage is going to follow that by 90 degrees they're going to be offset by 90. check this out if i actually kind of drew fill this out made it like into a sine wave if i'm at the peak value right here this means that what i'm like at 90 degrees right here and this would be like zero degrees or 180 degrees degree with that and then get this here if this is at the start of a waveform this would be at 0 degrees and this would be at 90 degrees so when the voltage of the capacitor is at 0 degrees where is the voltage across the resistor at 90. when the voltage across the resistor is at 180 where's the voltage of the capacitor how many degrees 90 in a capacitive circuit the behavior of current current leads voltage does that make sense now if we were to plot this out with an ac sine wave applied to it this is what it would look like voltage because actually let's go back let's dissect this this is actually kind of cool it's feeling so crappy tonight because i love this freaking lecture man for this lecture okay voltage or current is at a hundred percent you see that right there isn't that like this right here and when this is right here voltage is right here that's like this right here when i go up from zero to maximum peak value zero to maximum peak value my current flow goes to zero here when the capacitor discharges it's going to discharge in the opposite direction of what originally charged it so my current now is going to flow backwards it's going to flow backwards here now my alternating current ac goes from 180 degrees to 270 that means current goes from 100 percent to 0 why because the capacitor gets fully charged here but in the opposite direction here the capacitor discharges back to zero inducing current flow back into the circuit in the opposite direction so the way that this works check this out i don't think anybody it's it's like this is what voltage is always 90 degrees behind current why is it always 90 degrees of fashion in a capacitive ac circuit it's an easy answer why is it always 90 degrees why is it 87 degrees why isn't it 113 degrees why is it 90 degrees of phase shift in a capacitive ac circuit and you're looking at the answer do i look left or you're looking at the answer why is it 90 why isn't it 87 so what can ac sinusoidal waveform doing every 90 degrees it's doing that every 180 degrees what's it doing every 90 degrees changing direction for the first 90 amazing for the second 90 it's falling for the next 90 it's increasing but in the opposite direction and then for the last 90 it's going back to zero so what is an ac waveform constantly doing constantly changing in every 90 degrees it changes and reverses itself well every 180 degrees it reverses itself but it changes the direction first it's decreasing that it's in negative alternation then it's decreasing back to zero and then in a pure circuit current leads voltage by 90 degrees period end of story always 90 degrees purely capacitive how much phase shift is there in a purely resistive circuit this is review question by the way last last chapter how much phase shift is there any resistive circuit zero how much phase shift is there in a purely capacitive circuit 90 and what what leads what current leads voltage and if you can't remember that and i can't remember it that's why i remember this crap get it on your scrap paper ice in a capacitive circuit current leads voltage by how much always 90 degrees makes sense now how many of you would dig calculating out time constants for something that's constantly changing any takers okay the forefathers of electronics basically figured this out that they would go insane if they had to calculate out time constants for something with ac so instead what they came up with is they wanted to come up with a value that would show how a capacitor reacted to a different frequency of ac so what they did is they put this capacitor into a category of components that's called a reactive component because it reacts differently it reacts differently because at a low frequency this capacitor is going to be able to drop quicker right at a low frequencies more time at a high frequency this capacitor is going to have a tough time getting up to that 100 percent because as soon as it's on its way up next thing you know it's reversing itself because the higher frequency means more alternations per second plain and simple so it's going to vary it's going to vary with frequency what they came up with is and this is solid gold man this is this is choice this is primo that they did this they came up with something that's called this is a typo here this should say capacitive reactants capacitive reactants capacitive reactants is the opposition that a capacitor offers to the applied ac voltage and we abbreviate it by what we call x sub c x sub c capacitive reactants you want the good news you want the really good news i'll give you the good news it's measured in ohms why is that such good news because all of you in this room are used to working with ohms can you add up ohms in series for me can you add up ohms in parallel for me can you add up ohms and complex circuits for me well this formula is all you freaking need it's all you need if you apply this formula to an ac capacitor in a circuit like this it's going to show you how much ohms of reactants it has and then you can use the same math that you used at the beginning of the quarter analyzing those simple series circuits that i gave you to analyze the exact same thing so quite frankly this whole lecture it's a waste of time there's only one thing in this lecture that has any value and it's this formula right here this formula right here the formula is x sub c capacitive reactant that's how you say capacitive reactants x sub c is equal to 1 over 2 pi f c i just changed the f and c oh literally i just changed the f and c red they were green change the f and ch gutters mine's in the gutters the reason i change the f and c is that the f and c are the only variables in this formula they're the only thing that's ever going to change let's dissect this formula this here number one is the first number on the number line it's number one it doesn't it means that two but one this line right here means one divided by the product of the number two which is the second number in the number line it means not one but two this is where we kind of get wacky bear with me though works out okay on the end this here is is pi pi pi is a mathematical constant that deals with what that's the number 3.14 don't go beyond that there's a reason for that 3.4 we used to do that in high school before before billy bullying used to be in vogue bowling used to be cool so we used to go around yeah you know the nerds it's okay what's pi you know the 3.1 for whoever knew it back the furthest past the decimal point would like work over you know it's kind of funny now because they own like you know these like fortune 500 companies and stuff back to my high school reunion remember me crap out of me i'm sorry dude seemed like the right thing to do what is pi what is pi pi is the radius of a circle so what this is saying is we not only want to deal with one pie we want to do with deal with two pie why are we dealing with two pie not one pie whole circle but what whole circle are we dealing with peak to peak so we're dealing with not one alternation we're dealing with two alternations the positive and the negative or the magnetic field the generator that originally created the sinusoidal waveform makes sense mr carter question that's a good question you could you we could do this two different ways very very good question here we let you use a scientific calculator and the true formula is pi when i was in school 3.18 because i had a memorized pi i didn't i was not able i had to use a calculator that was just like this when they let me use a calculator and actually before that it wouldn't even but what happens what happens if the battery dies um i don't do math that day you know you go see the priest you know mr and mrs grenick were there and it was an ugly situation i'm like seriously if my battery dies i'm not going to do math that day i'll get a new battery and i'll do the math the next day i mean what's the problem whacking me good thing because it's a good thing we went on a bedroom system the nun's been using meter sticks as opposed to yardsticks i probably wouldn't be here today because there are a couple times that you just use scientific calculators with that comes a burden of you using the most accurate number so use pi it's a mathematical constant that's programmed and you got a pi key you use it it's going to give you the most accurate answer so that's the fmc f stands for frequency measured in first f measurement c stands for capacitance measurement so when you take two times pi times the frequency times the capacitance and then take the reciprocal of that whatever it shows you what capacitive reactance is measured in ohms it's that simple so one of the things that i want to show you with this formula and i i want you to hopefully the way i'm presenting this to you appreciate the formula more than just the formula if you if you know the formula you know what it's doing it's a lot easier to follow along with frequency if i increase the frequency what am i going to do to my capacitive reactants it's always easier this here is sitting underneath this line so whatever i do down here and i'm not going to change the number two because that's like the second number on the number line it means not one but two pi safety deposit box at an undisclosed location i have a hollywood screenplay that i wrote the day pie changed you know it was like some scientist you know he's performing his calculation my god oh no you know wheels are no longer round and you know the earth has shifted off its access and you know hopefully this teaching gig continues because if not i'm gonna have to break out my screenplay and try to have it done into a full motion picture you know the day pie changed pi is not going to change its mathematical constant so these two numbers are not going to change if f increases x sub c is going to decrease if c increases x sub c is going to decrease if f or c decreases x sub c is going to increase we call this an inverse proportional relationship so if i ask you on a test frequency and capacitive reactance is a a direct proportional relationship b an inverse proportional relationship c none of the above d all of the above you're going to want to get this inverse proportional relationship answer b inverse proportional relationship does that make sense that's the formula once you do that and you implement this formula i could put these components in series and parallel whatever it's all good this formula drives this entire chapter pi is the mathematical constant 3.14 don't use that though use the pi key in your calculator f frequency and hurt c capacitance and fair rads so you got to be real careful how you enter these because typically with capacitors are we going to be dealing with fair ads what are we typically going to be dealing with microfarads picofarads millimicrofarads nanofarads so it's going to be many places past the decimal point that's why remember when i said the beginning of this chat beginning of this this quarter how important it was to deal with engineering notation because now let me check check out just this formula 2 times pi the mathematical constant times frequency probably going to be in kilohertz or megahertz or gigahertz times 10 to the third 10 to the six ten to the ninth times times ten to the negative six negative nine negative twelfth it's a huge number to input this you try using old school two times three point one four times three zero zero zero zero zero no i count the wrong um you know you're going to mess up so you want to be able to enter this in engineering notation this is this is where the rubber hits the road this is why it's so important that you develop the skills in entering those numbers in your calculator capacitive reactants is a function of the frequency of the applied ac voltage of the capacitor and the capacitance meaning when this changes these change it affects this directly or inversely applications of these circuits can be used alone or combined with resistors to form rc networks used for filtering phase shift circuits decoupling phase shift circuits dc blocking phase shift circuits and coupling phase shift circuits also used for what's called a filter a filter this is a good one you go home tonight would you learn over at that technical college tonight we spoke of discrimination because that's what we're talking about here a filter is a circuit that discriminates among frequencies your million dollar word for tonight is attenuating which is the opposite of amplifying you've all heard of amplifying before an amplifier you put in a small signal you get out a big signal sometimes we want to attenuate a signal put in a big get out a small signal discriminating a filter is like a coffee filter what's a coffee filter do you filters out the grounds and allows the coffee fluid to pass but it holds the grounds behind that's what electronic filter does it keeps the bad stuff out and it allows the good stuff the good frequencies to pass that would be using it as a blocking circuit if we're if we're using a capacitor to block the dc but allow the ac to pass here we're talk we're simply talking about allowing some frequencies to pass while others two most common types are the low pass filter high pass filter probably the easiest way of talking about these two let me show it change this power source here we're gonna keep the rest and i'm doing that for it as well okay what i'm going to do is i'm going to change my circle to an ac this is what kind of a circuit ac series rc circuit you agree now i've got really two different combinations of components that i could i could measure three different combinations i can measure across i could measure at point a i could measure at point b and i could measure at point c i could i could measure the voltage across the what would i be measuring here the resistor the capacitor which is total do you agree with me three different combinations here okay so since i'm applying ac to this circuit what i'm going to do and i'm going to start doing this from this point on for the rest of the quarter i'm going to start showing you these x y plots my x-axis i'm going to be depicting frequency okay so this is a low frequency and this is a high frequency and this is a frequency that's just right a medium frequency makes sense okay so i'm looking at frequency here this is going to be amplitude this is zero amplitude this is a hundred percent amplitude which is going to be a measurement of voltage okay so what i'm going to do to this input is i am going to put in a variety of different frequencies behaves itself if i put in a low frequency a low frequency at a hundred percent amplitude when i put a low frequency into the circuit what effect is that going to have on capacitive reactants it's going to increase it it's going to increase so the the value of reactants of this capacitor is going to be extremely high when i put a low frequency into this resistor what effect is a low frequency going to have on this resistor that daniel it's not gonna have any effect on it because the resistor is purely resistant so frequency is not going to have an effect on this when i put a low frequency this the value of what properties we measure here that's so important to us how do we abbreviate that x sub c is going to be extremely high and what's this measure ohms so this is going to be a huge value here at a low frequency this is just going to be whatever value it is so when i put in let's do a mini xy plot right here let's do a mini xy plot here this is frequency this is amplitude let's do the same thing across a and b this is frequency this is amplitude at a low frequency where am i going to get the biggest voltage drop capacitor because this has a high value of accuracy so how would i plot out at a low frequency does that make sense what kind of a circle never forget that never forget that this is still i got a big voltage drop here what's my voltage drop across my resistor going to be because the series circuit is also known as a voltage divider so if i got a big voltage here what's my voltage across my resistor going to be it's going to be low degree am i baffling any of you hopefully not it's all straightforward it's all stuff that we've studied if i put in a high frequency at that same amplitude low and if it's low it's measured in ohms so i'm going to have a low value low x sub c if this is a low value of x sub c am i going to get a big voltage drop across this or a high voltage low voltage drop so when i measure between points i'm going to see a very small voltage so if i pop that out it's going to look like that right there if i'm getting a small voltage drop across the capacitor what am i getting across the resistor i'm going to get a high voltage drop across resistor because it's a voltage divider it's a series circuit make sense okay let's put in a medium frequency medium frequency at that same amplitude this amplitude here is going to be kept constant i want to make sure that i put in the exact same voltage into the circuit and that i check for each low frequency medium frequency and high frequency so if i put in a medium frequency what value of x sub c am i going to get i'm going to get medium i'm going to get a medium value of x sub c which means measured in ohms i'm going to get some voltage drop across it okay so let's just say i get a medium amount of voltage drop across it if i get a medium voltage drop across my capacitor where is the remaining voltage drop going to be it's going to be across the resistor so that's going to be right here if i plotted this out if i actually swept this input by by hooking it up to a sweep generator where i put in low and then i go all the way high and i keep doing this what i would what i just did is i created not only a low low-pass filter but a high-pass filter and the difference between a low-pass filter and a high-pass filter is what where i connect my output it's that simple both low pass filter and high pass filter are both examples of series ac series rc circuits for a pass filter you see how i'm passing that high frequency excuse me low pass what am i saying low pass filter see i'm passing the low frequency where do i have my output connected to across my capacitor across my capacitor what's another way of saying across my capacitor in what configuration with my capacitor parallel thank you and that's that's key you want to pass this quiz remember that this is a parallel capacitor because what's constant in a parallel circuit voltage that's what we're trying to harness here so this is parallel is this yes it is but we're connecting in parallel to parallel capacitor to make sure we get the same voltage across it if you connect in parallel with the capacitor we call that a low pass filter if i connect in parallel with the resistor i call that a high pass filter so i put a low frequency into this circuit right here if i'm connected if i'm connected here to this circuit as a high pass filter i put in a low frequency that low frequency is not going to make it out only the high frequencies are some of you have probably heard of like crossovers before for speakers exactly what you do it's exactly what we do use a resistor and a capacitor and what you do is you what what would we be feeding here what would be connecting across the capacitor here what kind of a speaker what kind of a speaker would be connecting here across in parallel with our capacitor subwoofer subwoofer or a base speaker because what do we want to feed that subwoofer that bass speaker low frequency you feed it high frequency it doesn't even it can't even do anything with that stuff it's not designed to do anything with that stuff what would we be feeding to this here tweeter or high frequency and achieving this point this crossover point between the two because i could uh i've got color pins finding this point right here is critical having a a speaker that could handle and then have pairing it with a speaker that can handle these frequencies is key in some cases you have a subwoofer you have a bass speaker you have a mid range you have a tweeter but the key is like a traffic cop directing all the frequencies to the right speaker because if you give a subwoofer high frequency it's not you can't even do anything with it you're wasting energy this is where people that screw around with audio there should be a license that you got to get before you could screw around with audio i guess anybody could get a big amplifier and speakers and hook it up and make sound come out of it but i tell you what tell you what when you do it right stuff begins to pop stuff begins to happen it's like whoa this really sounds freaking impressive because they got it dialed in what you're studying right now is how you dial it in does that make sense this whole chapter is one formula and if you embrace that formula everything else that i showed you siri circuit series rc circuit ac series rc circuit you should be comfortable with that current's constant the series circuit series circuit is also known as a voltage divider if you want to harness the voltage that's being developed you need to connect it in parallel with the output or connect the load to the parallel component this is the parallel cap this is the parallel resistor do not deceive me or you'll get it wrong in the quiz and then you'll be challenging the man and the man will have no sympathy basically yep yep um what i done draw it on the board here this is my artist's depiction you kind of get the gist this is actually what it would look like not this this is the projector coming on got my main man back there taking notes on this trying to draw it srgb this is actually what it would look like and this is that 100 value and this is that zero percent value the critical cutoff frequency is going to be this right here 70.7 of the output so whatever this is when we get to 70.7 percent everything below this is going to get rejected everything above this is going to get passed so we could call this a low frequency pass filter or we could also call this a high frequency reject filter at the plan depends on what colored pill you're taking what way you want to look at it some companies refer to this as a low pass filter some refer to this as a high frequency reject filter they're both synonymous they both do the same thing and to figure out exactly what this cutoff frequency is is when you get to 70.7 percent right at this point and there's some ways we'll talk about in the future how to move this how to move this cutoff frequency high pass filter we talked about already high pass filter we're doing what we're connecting it to the parallel resistor it consists of a capacitor and a resistor in series with each other all of these circuits consist of capacitors and resistors in series with each other this is what's called a decoupling network what is this this is a good one what's the first thing i want you to pay attention to your sources this is an acdc series r c circuit yep absolutely absolutely because this is used that typically dc is used to turn on semiconductor devices inside circuits and ac represents the signal the intelligence of what you're trying to amplify so in most pieces of equipment you're going to have ac and dc together sometimes you want to pull that dc off and let the ac just go on its way this is where you're going to use a decoupling network and the way that this works is real simple you all agree that this is a dc ac series rc circuit right well this what's the dc going to do here the dc is going to do what in this circuit it's going to charge the capacitor and it's going to stop where's the capacitor going to stop charging at what value after five time constants where's this capacitor going to stop charging yeah it's going to basically equal the dc value here so if i connect an output in parallel to this capacitor what am i measuring at the output the dc value what's happening to the ac value the ac is just going to zip right through the circuit it's going to go right through that cap not an issue not an issue so a decoupling network is pulling off the dc and allowing the ac to pass why do you even need ac in there though ac is gonna be the signal there might be something further down the stream here this is just a simplified illustration of it we're gonna let the ac pass but we're gonna block that dc this is a coupling network this allows the ac signal to pass while attenuating or eliminating the dc signal what do we have here it's a series dc ac series rc circuit same exact circuit how are we connected here in the circuit how are we connected here we're connected where we're taking the output in to the parallel resistor because what's happening the dc here is getting what blocked by this capacitor what's the ac doing flowing through the capacitor and as it flows through does ac generate a voltage drop as it flows through a resistor what was the second chapter we did see you guys are deceiving me already what's the last chapter we did ac series circuits when ac voltage encounters a resistive circuit does it create a voltage drop absolutely what are we connecting to here the parallel resistor so we're going to measure the ac voltage drop establishment drop across this parallel resistor make sense this is called coupling pulling the ac off allowing the dc to be blocked another thing that we could do is phase shift how much phase shift do we get with a capacitor 90 degrees how much do we get with a resistor zero so what kind of a circuit is this and i'm glad this is drawn differently this is a series rc circuit it's a series rc circuit so what we say here is typically when we have a capacitor and a resistor 90 degrees of phase shift here zero degrees of phase shift here in this circuit and generally when the circuits can engineered properly we get about 90 degrees excuse me 60 degrees of phase shift out of this entire circuit 90 if it was a pure capacitor zero if it was a pure resistor when we put the two together we say about 60 degrees of phase shift here so i could i my output here will be shifted in phase by 60 degrees if it's shifted in phase and 60 degrees here 60 degrees here 60 here 60 here 60 here what if i just 180 degrees of phase shift 180 degrees of phase shift whatever i put in here is going to come out 180 degrees out of phase out of the circuit and it doesn't matter i could also get the 60 here 60 here and 60 here 60 plus 60 plus 60 gives me 180 degrees phase shift so that's how i also use a series rc circuit all of these circuits are nothing more than what series rc circuits filters decoupling coupling and phase shift how do i do that with a series rc circuit make sense kind of a cool circuit really are in summary ac voltage applied to a capacitor appearance of current flow current flow is represented by the charging and recharging of a capacitor giving the appearance of currents flowing through it current applied voltage 90 degrees out of phase capacitive reactants measured in x sub z represented in x sub c is measured in ohms the formula this whole chapter right there x sub c equals 1 over 2 pi fc rc circuits are used for filtering coupling decoupling and phase shift low pass filter we take our output across the parallel capacitor high pass filter we take our output across the parallel resistor we talked about coupling and decoupling circuits any questions is this good stuff are you guys understanding why the beginning of this quarter was so critical on these chapters took um what's a goofy class i took well english some some some high school english was kind of goofy i remember this one thing we had to write poems you know we had to write like sonnets and we had a light one of them was limericks i was really good at the limericks although that got me set to the principal's office as well but you know much to my wife's dismay that i wrote a poem wasn't freaking high school i don't like write poetry so you know what i took the hit in that class and said you know what i'm not going to do this because this sucks this is stupid i'm not going to write any poems well you're going to lose x percent of your grade okay and i kind of know it right and it didn't affect my life i think my life turned out okay right electronics is different if you did not pay attention to series circuits you're dead in the water right now if you didn't pay attention to how to add up resistance in series you're dead in the water if you didn't understand the importance of ohm's law kirchoff's law watts law you're dead in the water now because we keep all those pieces and my assumption is that you know all of those pieces and if you do know those pieces and i suspect most of you have a familiarity with what we're doing so practice is going to increase the level of perfection with these circuits but i'm going to be brutally honest with you the only thing i introduced tonight that you have not seen before is this formula right here this whole notion about phase shift i mean don't these look like the capacitive curves you just didn't look at it that way before now i want you to look at it that way so the only thing new tonight is this formula any questions all right that's all i got folks appreciate a good one all right we got a big we got a big night a really big night ahead i'm gonna display some slides i'm gonna read some slides gonna talk about some stuff this is where the rubber hits the road man this is uh this is where it all comes together you've been working elec 110 all to get up to this point before we jump into chapter 16 i want to review a little bit just very briefly what we talked about last chapter because it's very very critical if we understand that last chapter um well it's going to make this chapter go really really fast okay the big thing you got to remember about last chapter remember that ice in a capacitive circuit in an ac capacitive circuit current i leads e i know i start to sound like some kind of an english teacher or grammar or whatever i never understood what the heck they're talking about i before e unless after whatever the heck it was i have no idea what you're talking about you know um you understand what i'm talking about here though in the word ice the letter i comes before the letter e i in electronics we use the letter i to represent current and we use the letter e to represent voltage so what we what we're talking about here what am i talking about leading lagging what am i talking about here what's taking place in a capacitive ac circuit phase shift phase shift right how much phase shift do i get in a purely capacitive circuit 90 degrees why is it 90 why isn't it 87 why isn't it 102 90 perfectly 90 degrees well you always get 90 degrees of phase shift in a purely capacitive circuit but why is that you're right there at the answer you just got to give it to me why is it always 90 degrees 90 degrees what's happening every 90 degrees for the first 90 we're increasing the next 90 we're decreasing back to zero the next 90 we're increasing in the opposite direction the next 90 we're decreasing back to zero so with a sinusoidal waveform applied to a capacitor every 90 degrees things are changing that's why phase shift will always be in a purely capacitive circuit exactly 90 degrees period makes sense so when that sine wave is increasing 0 to 90 that capacitor is going to try to charge isn't it when it's going down from 100 percent down to 0 percent it's going to try to discharge when it's going from 180 to 270 it's going to try to charge but in the opposite direction then when it's between 270 360 it's going to be discharging so it's always going to be that lag the lag of voltage current currents going to be instantaneous alternating current instantaneous makes sense it's blank stairs out there kind of concerns me a little bit i know it's a three-day weekend and all but comprende okay we're not going to talk about time constants when we we apply ac to it because that would drive us insane and i don't want anybody to go insane what we're going to do is talk about the overall effect that this capacitor has inside an ac circuit we're going to call that property x sub c capacitive reactants x's reactancy is capacitive reactants okay real easy formula one over two pi fc one is the number one it's the first number in the alphabet right two is the number two it means not one but the second number in the alphabet pi mathematic mathematical constant for dealing with the circumference of a circle two pi because we're dealing with a two alternations positive alternation negative alternation two alternations of a sine wave times the frequency times the capacitance now the interesting thing here remember last week we talked about the f and c those are the only two variables we have here the one over two pi that's not going to change the f and c they could change frequency can increase frequency could decrease capacitance could increase capacitance could decrease so the interesting thing is no matter what we do to the f and c the opposite is going to be felt at x sub c so that we call this an inversely proportional relationship if frequency increases x sub c decreases the frequency decreases x sub c increases whatever takes place here the opposite's going to take place there remember that okay so this is the important stuff this is the important stuff the book has got a lot of words in it it's got pictures it's got diagrams right my slides have got a lot of words kind of use it as a guide to keep me on track and what we're talking about here and basically it follows the objectives of the book the stuff that i'm lecturing in these are absolutes these are absolutes you've got to be able to describe this action the same way that i'm describing this action you follow what i'm saying because it's the kind of stuff you're going to be asked in a job interview describe the attributes of a capacitive ac circuit this is what they're looking for current leads voltage 90 degrees of phase shift x sub c is 1 over 2 pi fc if frequency increases x sub c decreases the frequency decreases x sub c increases i mean just this just this you know how many quiz questions i could generate from just this on the board i'm probably good for about 75 or 80 questions that i could ask you just on what i put up on the board here real easy if you know this real easy if you forget this then you're in a pickle what's up all right no no you can have the same value it's a good question if you go to radio shack and buy a capacitor you can have that value of capacitor you apply a high frequency to it right a high frequency high frequency means low x sub c low x sub c means it's going to act like a short circuit you apply a high frequency to it high frequency low x sub c low frequency high except see it's going to act like an open so that same capacitor that exact same capacitor could act like an open in a circuit or it can act like a short the variable is frequency because let's face it out of these things here right typically one two three of these are going to be engraved in stone three of these are going to be engraved in stone one of them only is going to be that variable make sense it depends what you're working on if you're working on a radio transmitter that frequency is probably going to be locked in because the fcc says it's going to be locked in so you know if you work for cairo 7 10 am that frequency you broadcast at is kind of an absolute so they're the only thing that you can play with is going to be your value of c if you're tuning a radio then you want f to be able to vary you want f to be able to vary so you may need to have a capacitor that you could tune to create this value of f to be able to move make sense okay so those are those are our variables let's jump to chapter 16 now inductive ac circuits after completing this chapter you're going to be able to describe the phase relationship between current and voltage in an inductive ac circuit determine the inductive reactants in an ac circuit explain impedance and its effect on inductive circuits describe how an inductor resistor network can be used for filtering phase shift explain how a low pass and a high pass inductive circuit operate i can actually do that real quick they operate quite well thank you so we got that out of the way all right inductors in inductance in ac circuits inductors as you know offer opposition to current flow or change in current that's what inductor is all about it's what an inductor is all about it tries to prevent a change in current it tries to help keep current stable okay i believe in god and god has a sense of humor actually this weekend i had the opportunity to work on an inductor a friend of mine owns a coffee shop and in their display case for pastries i thought they needed help eating the pastries they just needed help illuminating the pastries there's a fluorescent tube and in the fluorescent tube the way that those things work is there's a starter circuit and then there's an inductor the inductor typically is what we call the ballast and what happens is you light that gas you ionize the gas and then that inductor tries to prevent a change in the value of current to keep that fluorescent tube ionized the gas ionized and keep that at a constant level anyway it wasn't working properly and make a long story short they actually my friend ordered from the company they sent a replacement and it was a new solid state ballast so that allowed me to remove the inductor that you know that little starter thing that you know you put on fluorescent lights all of that got cut out so it was just a matter of me wiring that in directly throw the switch pow let there be light on the pastries i was offered pastries i actually declined the pastries but that inductor i can't believe i left that behind because she she ended up just throwing in the garbage should have brought it in because it was perfect inductor that's all it is and in anyone in the industry would call it a ballast for fluorescent light but in essence it was just nothing more than an inductor now inductors offer opposition to current flow voltage placed across an inductor creates a magnetic field okay you put put current through that you create a magnetic field when ac voltage changes polarity causes the magnetic field to expand and then collapse voltage is induced in the inductor coil called a counter electromotive force or cemf remember lens lenses law right lenses loss is what goes up must come down right now what did lens's law say basically what lens says is current going in that direction creates a magnetic field like this when you shut that circuit off the magnetic field is going to collapse into the conductor of which it originally was created when current when magnetic field collapses into an a conductor what does it do it induces current it's like a generator action just like a generator just like what's going over going on over at grant coulee dam right now the magnetic field is moving collapsing into the conductor and then it creates a counter current opposite of the force that created it that's in essence lenses law not what goes up must come down but if current going that way create a magnetic field going like this a magnetic field going like this is going to create a current going that way we call that c e m f counter electromotive force back in the day nobody ever even asked me about this the letter e i don't know if you realize this but the letter e that you've been using and i say you could use an e or you could use a v i really don't care what you use in this class i know what you're talking about but you know originally old school the letter e was used because you know what the letter e stands for emf electromotive force cemf is like counter voltage if you will if voltage create a current going that way cemf is going to create a counter voltage going that way so i got 5 going in that direction i got 4 coming back in this direction 5 minus 4 equals 1 in that direction and it's that simple that's how that's how these inductors work now the big thing to remember about ac is ac is alternating current 60 hertz 60 hertz that's coming out of our wall here in north america goes positive alternations 60 times a second there are 60 negative alternations per second of what's coming out of that wall so you've got a magnetic field that's expanding and then collapsing pushing back in changing direction 60 positive alternations 60 negative alternations that's 120 changes per second ac in an inductor cemf makes sense now cemf will always be 180 degrees out of phase with the applied voltage not 90 degrees 180 degrees because we're talking about what the lens is law cmf is always opposite of the force that created it it opposes the applied voltage because again lens was right its lens is law it's not lenses notion it's not lenses idea lenses idea if you're from the northeast lindsay's idea have you talked to your students about lenses idea no i haven't lenz's law opposition is as effective in reducing current flow as a resistor does not make sense if i got voltage going this way and it creates that magnetic field when the magnetic field collapses it creates that counter current it reduces the flow of current is as effective as a resistor but there's something unique about using an inductor say that it does not consume power exactly does not consume power these are reactive components resistive components dissipated as heat on a cold day nothing like warming up by some resistors as they dissipate heat who's paying for that we're all paying for that if we're converting electric current into heat typically that's not what we have resistors and circuits for so by using an inductor we gain back all that efficiency and we prevent the change in current so an inductor makes a lot more sense in a lot of circuits it's one of the reasons we use inductors now this is what it would look like if you had an oscilloscope and you could look at the counter emf the counter voltage here we see in blue the applied voltage there's our applied voltage and if lenses law holds true then we should be getting an induced voltage the opposite of which created it now if i could like um can i like pick this up and like if i could fold this over somehow no that won't work you understand what i'm trying to do if i could fold this in half if i could actually fold this in half and algebraically cancel these two well i just kind of gave my answer away what would these two do to each other they'd cancel each other they'd algebraically cancel each other out this would hold true if an inductor was 100 percent efficient is anything we've talked about since the beginning of this of this program 100 efficient in electronics now so what do you suppose here what do you what do you reckon what do you reckon which line here is going to be a little bit more stout and which one's going to be a little bit less voltage yeah the applied voltage is going to be a little bit stronger if there was a 100 efficiency the induced voltage would equal this but it's not why is an inductor 100 efficient real easy answer you know the answer you just don't know you know the answer is material what material has resistance the coil yeah the coil's made out of wire wire has resistance so to make an inductor you've got resistance in the equation we don't want it there so in a class environment like this theoretically perfect world now the coil has no resistance the coil is you know it's 100 efficient and this is what's going to take place in the world of reality a coil is made of wire wire has resistance resistance is going to mean that this induced voltage the other thing too is coupling with that magnetic field i mean lens is right lenses law is right i'm not going to dispute lens he's not here to defend himself okay that'd be a that'd be a hoot huh battle of the knot heads 1995 at the lake washington technical college auditorium joe grunick vs lens i don't think i'd stand too i don't think i'd do too well against lens lot on the other hand maybe but because an inductor is not 100 efficient we're not going to get this where it's going to be totally cancel each other out so if we algebraically add it up we're going to see blue here a little thin blue line a little hump there right and then we're going to see a little thin blue line down here because it's not 100 efficient but dog on it this is pretty effective in opposing that change isn't it it's pretty effective again in a theory class like this how effective 100 effective in the world of reality in the lab no it's not effective now the overall effect that this is going to have between voltage and current when we apply ac to an inductor is going to be this when i first close a switch when i put an inductor in a series circuit and first close the switch voltage is going to go from zero to a hundred percent in the first 90 degrees can you dig it makes sense as soon as i get up to 100 percent with voltage what's current going to be at zero because current's going to be doing what the inductor is going to be fighting a change in current it's going to be fighting a change in current here what's happening i'm going from 90 degrees to zero what's happening in my magnetic field collapsing and when it collapses what's it creating counter current so actually what we're doing here is now we're inducing a current into the circuit that's what we're doing here now we're reversing direction i'm going from 180 to 270 i'm increasing negative what's current going to do try to stay the same try to stay the same try to stay the same and it can't eventually it's going to go down to zero so what we end up with is no longer ice with a circuit like this we have eli eli and actually the phrase that pays if you want to keep pay attention to these sorts of things eli the ice we used to call it eli the ice man that used to be the phrase that pays but of course this is politically incorrect eli the ice person need to be sexually gender neutral or whatever so eli the ice person remember that eli in an inductive circuit voltage leads current is this an inductive circuit yep what's voltage doing voltage is leading current by 90 degrees when voltage is at 90 currents at zero when voltage is at 180 currents at 90. when voltage is at 270 current is at 180 when voltage is at 360. current's at 270. so it's constantly constantly lagging current is constantly lagging or we could say voltage is leading anybody want to take a wild guess by how many degrees and why is it 90 degrees why isn't it 87 why isn't it 103. and the sine wave changes direction every 90 degrees that's the real reason when you play c to it the sine wave changes direction every 90 degrees makes sense now inductive reactants this is a good thing this is the opposition offered to current flow by an inductor the good news is it's measured in ohms you guys know everything there is you guys you persons know everything there is to know you guys you're all guys all y'all getting ready for cansat texas cancer all y'all um is measured in ohms you guys know about dealing with ohms right can you add ohms up in series can you add ohms up parallel can you add ohms up in complex yeah that's why we had you do that early in the quarter we didn't do it because i had nothing better to do with my time we had you do that so that now if we give you ohms you know you can slice them dice them do whatever you got to do with them now x this inductive reactance depends on its inductance and the frequency of the applied voltage it's going to be expressed by the symbol x sub l and this formula believe it or not is even easier than the last formula x of l is equal to 2 pi f l you don't even have to do a reciprocal on this one the number two it means not one it means two two what two pi which represents that we're dealing with not one alternation but we're dealing with both alternations or the entire cycle of a sinusoidal waveform the positive alternation would be one pi the second pi is the negative alternation so this tells me we're dealing with the whole enchilada the whole sinusoidal wave form 2 pi 2 times pi times f the frequency in hertz times l the inductance in henry's so again be careful when you're entering this in your scientific calculation device your calculator right two that's easy you can't mess up that one pi you got a key in your calculator f typically your frequency is going to be in hertz kilohertz megahertz maybe gigahertz inductance measured in henry's the typical values you're going to be using in electronics are going to be millihenry's times 10 to the negative third micro henry's times 10 to the negative sixth but in on a quiz on an exam i could give you anything here i could give you three henries you may not see three henry's typically in electronics microelectronics environment but i certainly may give you three henry's as a question to see if mathematically you can interpret that actually i'm pretty sure you could deal with the three henries that one would be easy it'd be three micro henries that you got to make sure you're equipped and dealing with applications for inductive circuits inductors are widely used in electronics they compete with capacitors for filtering and phase shift applications engineers are always going to weigh which component they want to use can we use a capacitor to do this can we use an index inductor to use this unfortunately inductors have fewer applications than capacitors because they're larger typically they get the amount of effect we need we have to have a pretty big inductor they're heavier and obviously with microelectronics heavy is not really popular and they're really more expensive because they're going to be made out of wire they have to be wound capacitor two plates separated by a dielectric material you know dipping in ceramic hey look at this i got myself a capacitor an inductor i've had students that have graduated this program and gone gonna work in in audio type applications or rf applications they had to roll their own roll their own so obviously that's labor intensive a company would rather just an engineer would say hey boy you can get these capacitors you know 150 in a little baggie and you know install them in a circuit instead of paying you as a technician not an assembler as a technician to sit there and be rolling your own inductor to put it in an rf circuit it's still the cheapest way out for some some applications inductors provide a reactive effect while still completing a dc circuit path capacitors provide a reactive effect but block the dc elements you think about that if the frequency is really really low like how low can you go like dc x sub l is going to be really really really low like non-existent if you apply dc to an inductor if you were an electron a dc electron you'd be like what is the deal with this curly piece of wire on the other hand if you come in as a high frequency you're going to come in you're going to see holy cow i got to go through this curly piece of wire and build up this huge magnetic field and there's this opposition the cemf and oh oh this is undoomed for failure i'm never going to make it through the circuit and that's exactly what it's like an electron trying to make it through a circuit at a high frequency the higher the frequency the harder the journey even go higher in frequency it makes it even worse go lower in frequency an inductor becomes a piece of curly wire plain and simple um inductors and capacitors are sometimes combined to improve the performance of a circuit sometimes an engineer will combine use use capacitors because of certain attributes and inductors and use them both in a circuit because of their positive attributes series rl circuits are used as high and low pass filters what kind of a circuit is this in ac series r l circuit can you all see this this is really the circuit right here one of the things this book is not i i don't necessarily think this book is the greatest thing since sliced bread but it's better than the book that i wrote for this course i doubt that if you wrote a book for this course i'll miss you truth be told i actually was a consultant to him on this book really one of the early editions i actually had a segment that i was hired as a ghostwriter to write in the center of this book they they finally dropped it but they were they're actually i'll show you an old edition there's actually pictures of me in a bunny suit in this book we would like to see that they dropped it because they offended people oh man is that just a creepy looking dude man i'll try i i think i got an old version of that laying around um but anyway there's there's some aspects about this book that i that i really like one of the aspects that i do like is they do draw the circuits differently and the important thing is uh some some textbooks they use like the same graphic program for drawing all their circuits and then you begin to think that a series rc circuit looks a certain way and you get used to that and then you get out into industry and the first day on the job your boss is like what kind of a circuit is you don't even make it your first day on the job because you go through an interview they say what kind of circuit is this i don't know i've never seen this before okay now look and see if the circuit is a series circuit the first thing is the type of power source ac series r l circuit when i take my output across the what arrangement is this what am i taking my output across the what resistor parallel thank you you're taking the output in parallel not series this is in series with the inductor but you're taking the output parallel across the output of the resistor when you do that this is what we call a low pass filter remember last week let me draw that circuit again remember the circuit that i had drawn up on the board like the universal circuit yeah joe we remember this circuit changed our life i took a picture on my smartphone and i blew it up at walmart this weekend into a poster size that was such an impressive freaking diagram that you done drawn last week for us remember that ac series r l circuit if it's ac there's going to be two parts to ac what are the two parts voltage frequency absolutely have to have these two parts okay if it's a resistor it's measured in ohms if it's an inductor it's measured in henrys that we need to convert to ohms with what formula thank you f c f f l it's an inductor remember right formula wrong wrong formula right f and c f and c now you've got a couple different combinations here that we could take we could take output across our resistor we could take output across our inductor i've got a b c or i could go across a b a c if i go across a c i'm actually reading source if i go across a b i'm measuring across the parallel resistor if i measure across bc i'm measuring across the parallel inductance makes sense okay now i do this on scrap paper when i take a quiz like this or an exam i do this on scratch paper because i i get twisting around easy i really do okay frequency [Music] amplitude if i put in a low frequency amplitude at 100 percent okay low frequency means low reactance very good okay that means that in ohms this is measured in ohms right x sub l and this is r which is also measured in ohms x sub l is going to be low which means my entire voltage drop is going to be across what why is my entire voltage drop going to be across the resistor because this is a what kind of a circuit voltage divider thank you it's a series circuit series circuit is also known as aka i like you like watching those crime shows aka also known as i want an alias maybe i don't want an alias so if this is low ohms is there going to be any voltage drop across my inductor very little is there going to be a voltage drop across my resistor yeah so at a high frequency or a low frequency i'm going to draw that same plot here frequency amplitude okay same thing here frequency amplitude i'm going to get a very low voltage drop here and i'm going to get a very high voltage drop here as a matter of fact 100 of my voltage drops can be across this resistor at a low frequency because at a low frequency this is going to look like a piece of curly wire not twisted wire curly wire curly fries want regular fries or curly fries he's got to upgrade to the curly fries it's a different there is a difference okay so this is going to be low that's going to be high makes sense now let's put in a high frequency when i put in a high frequency x sub l is going to be high measured in ohms that means i'm going to get what kind of a voltage drop across my inductor a big voltage drop across it if i got a big voltage drop here what kind of a voltage drop am i going to have across my resistor why because this is a series circuit and a series circuit is also known as a voltage divider makes sense let's put in a frequency that's not too high not too low that's just right medium you put in a medium frequency medium frequency means medium x sub l medium x sub l means medium voltage drop if i got a medium voltage drop here the remaining voltage is also going to be medium here okay you plot all of these out and you kind of end up with something that kind of looks like this so when i take the output across my parallel resistor what am i passing here what group of frequencies am i passing very good i could call this a low frequency pass filter also known as a high frequency reject filter same thing same thing what kind of a filter is this high frequency reject filter that's answer a answer b is a low pass filter answer c is both a and b above answer d is none of the above read the questions read all the answers these two things are the same and i've seen them listed the same it just depends on who's whose book you're reading whose manual you're reading makes sense if i take the output across the inductor what's going on here this is actually what a high pass frequency aka reject very good low frequency reject filter same thing makes sense so no matter how the they draw on an on a diagram or on a schematic don't get freaked out about it just look at what components are in series where's the output taken across and then figure it out on your own you can't memorize this stuff if you try memorizing this you're not going to do well on this program you got to learn it and if learning it means scrub scribbling the stuff down on a piece of scratch paper to answer the question that's cool it really is i've interviewed a lot of faculty potential faculty members here and if i ask them a question like this and they got to scribble this down and they come up with the right answer that's cool there's no harm in that start asking people and they can answer the stuff off the top of their head then it's kind of like well let's see if you could real if you really know your stuff you know get them in the lab they don't know what to do so it's okay the frequency above or below the frequencies passed or attenuated that's your million dollar word attenuated right attenuate is the opposite of amplify it's called the cutoff frequency and the symbol that we use is fco frequency of cutoff this can be determined by the formula this program doesn't like these fonts all these fonts sometimes it gives me goofy this should be fcl right here frequency of cutoff is the amount of resistance of the circuit divided by 2 pi fl and that cutoff frequency that we're talking about remember this 100 right here frequency of cutoff is actually going to occur where very good right there at 70.7 percent so if for an application you want to move this you want to move this left you want to move it right the way you're really going to be able to do that with this application here is going to be with that value of r and in later classes in the more advanced classes you're going to learn that actually that value of r factors in with something that's called quality don't take notes on this it's beyond the scope what you're learning right now and it's quality factor and it's how much resistance is there in the component as compared to how much reactance is there inside the component and engineers have to trade that off to get that zeroed in on just the right value this is a problem i have this is a problem that a friend of mine had several years ago while trying to get enhanced reception on his her cable television that to get that cutoff frequency just right that that quality factor needed to be just so and replicating that in a garage selecting the right gauge of wire the right amount of resistance to get the right amount of inductance there were trade trade-offs that needed to be made and eventually from what i understand is it only took like three turns of wire to get enough reactants to be able to help clarify an image a twisted image on the screen this individual was only trying to help out the cable company realizing how overburdened they were with service calls instead of having them come out and fix the reception this person because he she had an extended background in electronics just decided to take it upon himself to rectify the situation i would not ever endorse this because again if you get caught it's a serious freaking legal battle whoever told you a story about about me and the charges that were levied against me i'll tell you the story some day not a fun not a pleasant i was actually accused by the united states government of satellite piracy satellite piracy real serious and it was basically direct tv that was coming after me and i went to the government and it became a real ugly situation and i'll never forget that day you know like everybody knows like where they were when like kennedy was assassinated and everybody knows where they were on 9 11. i knew exactly where i was i was at my mailbox and there was a big freaking envelope in there you know it was like i open that up and it's kind of like whoa this is serious then the certified letters started coming we got to start going to the post office and signing for stuff not a pleasant experience so i had to just i had to defend my um my innocence and it cost thousands of dollars thousands upon thousands of dollars to do it do i know how to do it absolutely the navy made it a point to train me how to do it okay was i doing it if i was doing it why was i a paid subscriber to directv so anyway it was findings were in my favor but if you think you're innocent until proven guilty in this country wrong answer if you're accused of something you got to prove your innocence and that's going to cost some money it's going to cost some money and it's not your every uh you know you don't go get vern fern funk as your as your attorney okay you got to get a high-tech attorney that knows what the deal is and i actually had an attorney at the time that was was uh that i was working with with my airplane crash and i thought that my attorney could just like write a letter and make the whole thing go away when i when i showed her a copy she said well i gotta look into this you know you just wait here i was waiting in a conference room she disappeared for like 45 minutes she came back and she's all wide-eyed she's like this is beyond the scope of what i could deal with you need a different attorney i'm like oh yeah they had all kinds of stuff digital millennium copyright accurate levying against me the patriot act i was i was anti-patriotic because i was trying to commandeer our satellites for my own personal uh use and the use of al qaeda can't even spell al qaeda i don't know what the heck you're talking about stealing satellite signals which isn't all that difficult well i was paying for directv and you know what i'm still a subscriber to directv even though even though they came after me it's like it's a superior signal it's the real deal man why do i want to go to dish when i'm happy with that even though you all sued me you know it's it's typically one hand not knowing what the other is doing you know it's a good product and all and just as a matter of principle actually my my attorney thought i was freaking nuts she's like so have you dumped directv no it's a good quality signal it's i like their product you gotta be kidding better than this network as far as programming now as far as programming now but directv infrastructure i'm very familiar with they're satellite orbits i'm very familiar i have a friend i don't know it's just i don't know it's kind of my thing i better shut up on my head [Music] you got to beep all of this out of my recordings beep all of this out hey the bottom line though is we kid around about that kind of stuff and integrity issues when you learn more about electronics the more you learn about electronics you're going to learn there's a lot of hacks that are available and stuff you really got to look at the ethics about it and although i kind of with a you know tongue-in-cheek i kid around about it serious business very very very serious business you know if i wanted to go out and jam police radar you know i'd know how to do it if i wanted a jam police laser actually a guy out of this program came through this program graduated he went to go to work for a company that made laser jammers they were located up by payne field and uh for him it was a dream job because he was a gear head and he got he was getting sent to all these car shows all over the nation representing their laser jammer and i used to go i got him in as an intern so i'd go up there and visit him as an intern and it was cool on the shelf they had they'd go out and they'd buy the police laser units the exact same models and then go on their back parking lot and try to defeat it and try to you know this is the xj 12 you know f model f and you know this is how we got it the the funny thing about laser jamming is one of the owners of the company was actually an attorney and laser radar is controlled by the federal communications commission fcc laser is controlled by the fda the food and drug administration because it's light and they had there's nothing wrong with jamming a laser signal absolutely nothing wrong with it i mean the police might not dig it you know if you're driving by and actually they're really good too they would only give you i think like four three four seconds of jamming so if you're like flying down a freaking back road and you know there's a bunch of kids that just got off a school bus and you know the cop is there and he pulls the trigger that they're only going to jam you for like three seconds allow you time to slow down and give you fair warning and they did that for liability purposes you know they want you to slow down you know you're being painted with laser slow down modify your behavior and don't get the ticket not defeat the police and keep going you know that's not what it was all about so it's kind of interesting but like i say there's ethics side of it that we'll talk about in the future especially as you get more proficient in these things so we talked about these components of the formula fco r pi f and l in summary in a pure inductive circuit the current lags the applied voltage by 90 degrees inductive reactance is the opposition to current flow offered by an inductor in an ac circuit the symbol we use is x sub l it's measured in ohms and the formula is x sub l equals 2 pi f l impedance we're going to talk about impedance next chapter it's more appropriate that we talk about impedance next chapter and what impedance is is the combination what's resistance measured end what's reactants measured in all ohms are not created equal impedance is measured in ohms and it's a combination of resistance and reactive ohms makes sense we'll talk about that next chapter and then finally we talked about rl circuits used for high pass filters low pass filters if you can't remember it don't remember it just know how to do this and really what does this whole chapter boil down to eli and x sub l equals 2 pi f l if you know eli and you know 2 pi f l what can i ask you i could put them in circuits that are in series i could take the output in parallel what else can i do there's really not a whole lot more i could do to you because i know you think i'm up here trying to do stuff to you give your wicked you know crazy quiz questions and make you suffer before three day weekends and any questions on this chapter okay let's go ahead take a about a 10-12 minute break and when we come back chapter 17 quickly um and then i want to divert into my schtick because i don't think this chapter does a good job at all of of hitting the significant high points of what it needs to hit the first problem i have with this chapter is the title resonant circuits resonance only occurs at a unique set of circumstances are met period so in essence this is about rcl circuits below resonant frequency rcl circuits above resonant frequency and rcl circuits at resonance if this was just about resonance if this was just about resonance this lecture would be over ready okay because at resonance x sub l cancels out x sub c and there's only r and do all of you know how to add up r in series are in parallel can you deal with r do you know everything there is to know about r then that's the end of the lecture if this was about resonance period okay it's a lot a little bit more than resonance so we're gonna have to we'll spend a little bit of time with this here after completing this chapter you're to be able to identify the formulas for determining capacitive and inductive reactants identify how ac current and voltage reacting capacitors and inductors determine the reactants of a series circuit and identify whether it's capacitive or inductive determine define the term impedance solve problems for impedance that contain both resistance and capacitance or inductance discuss how ohm's law must be modified prior to using it in ac circuits solve for x sub c x sub l we're not going to solve for s because i don't even know what the heck that is siemens i don't know z and i t and rcl series circuits and solve for i c i l i x i r i z and rcl parallel circuits okay reactants in series circuits when an ac voltage source is applied the instantaneous value of current flowing through the resistor varies with the alternating output voltage applied ohm's law applies peak current is calculated from source peak voltage rms current is calculated from rms voltage meaning we can't compare apples and oranges if we're dealing with a peak value peak voltage we deal with pre-current if we're dealing with rms voltage we deal with rms current okay so first slide any any heartache makes sense right hopefully nobody's got a heartache with this two simple series circuits on the left we got a dc circuit okay direct current current flows negative to positive i got counterclockwise current flow through this circuit through r1 ac resistor ac is alternating current so this current's going back and forth back and forth back and forth all day long because that's what ac does the math associated with this if this was 10 volts and a 1k resistor and this is 10 volts rms and a 1k resistor exact same amount of current for both they're both going to behave identical make sense okay when a circuit contains pure resistance and no reactive components both voltage and current are in phase remember that chapter ac resistive circuits i made fun of that chapter too now the effects of pure inductance or capacitance cause the voltage and current to be 90 degrees out of phase well the best thing in dealing with this is remembering the phrase that pays which is dude okay in an inductive circuit voltage leads current by 90 degrees in a capacitive circuit currently its voltage by 90 degrees makes sense an ac circuit typically combines both reactive and resistive components voltage and current are in phase of the resistive portion of the circuit why it's pure resistance they're going to be in phase the pure resistance portion of the circuit voltage leads current by 90 degrees in the inductive portion of the circuit voltage leads current by 90 degrees in the inductive portion of the circuit why that was last chapter make sense that's where it gets fun it's where it gets fun we'll take it easy though we use vectors we use vectors everybody put down your pens don't don't take notes on this because this is going to be a dirty word we're going to use trigonometry as soon as i say trigonometry a lot of people get their freak on i don't want to do that math and i can't do that and i suck that trigonometry in school you know what when i was in school i sucked at trigonometry too but you know what now i do it and now i can look at this in my head and almost do it and i'm not bragging it's just that i see the direct application for trigonometry with ac when i was in school and they were teaching me this stuff you know calculating out the height of a church steeple i'm like i am never going to do that why would i be out trying to calculate out the height of a freaking church steeple i mean that is stupid i'm not going to do that you know for for math for electronics this makes sense so we're going to use vectors used to show the relationship between voltages in a reactive circuit now the type of circuit that we're looking at here just by me seeing this vector diagram i know what kind of circuit we're looking at do you know what kind of circuit that we're looking at here we're looking at a circuit that contains a resistor and we're looking at a circuit that contains a inductor this is the voltage across the inductor and this is the voltage across the resistor what kind of a circuit are we looking at what kind of a circuit is going to have two voltage drops series circuit because the series circuit is also known as voltage divider so just by looking at this i could tell what kind of circuit that we're looking at okay if you can't you may want to draw the circuit right so this is going to be an ac series rl circuit does that make sense ac we're going to have to have two pieces here one is going to be the voltage the other is going to be the frequency in a series rc circuit we're going to have resistance which is going to be measured in ohms and we're going to have inductive reactance which is going to be measured in ohms to calculate out this value i'm going to need to use the formula x sub l equals 2 pi f l i get the value of f from here i get the value of l from whatever l equals on my schematic diagram or bill of materials or wherever i'm getting my my most accurate data from does that make sense so this is the circuit that we're dealing with if to analyze this circuit we have to use these vector diagrams now some of the stuff in this book i kind of dig some of the stuff i don't dig one of the things i don't dig is this illustration right here because this is not accurate and if you're going to do trigonometry we probably want to do it right so we can recognize what's really going on this is not to scale this is not the scale they're showing this here let's round up this line this vector right here they're showing it at a magnitude of approximately 90 volts 89.5 90 volts makes sense this vector here they're showing at a magnitude of approximately 45 volts now when i was in school 45 is half of 90. does this look like this is the scale okay so what i'm going to do here everybody got this what the circuit looks like everybody knows a serious circuit that we're dealing with here let me erase this when you're doing this when you're doing these problems i highly recommend you use a a straight edge a ruler um where the heck is that that thing was around did somebody abscond with that we had the engineers rule is that a round small straight edge does that work out okay somebody somebody needed it more than we needed it i've got i've got a uh i got a yardstick here but i'm talking about the engineering rule that was up here yeah i don't know somebody else kind of everybody know what i'm talking about with an engineering rule it just has different graduations on it and they use it for for for drawing um you could use a yardstick you could use a ruler you could use as long as it has a specific uh um gradients marked so what i'm gonna do here is i'm gonna draw this again accurately so you see what we're doing er is gonna be um 90 volts so um what i'm going to do for the case of illustration here is since e l is one half of e r what i'm going to do here is i am going to make er 24 inches i'm going to make it 24 inches so this is going to be my reference point and then i'm going to draw this and i'm going to label that e r equals we might as well use the right number 80 i know let me use my numbers 90 volts everybody see that so now i'm going to draw e l e l what does voltage do in an inductive circuit it leads current okay so what we have to do is show a 90 degree phase difference of the voltage of the resistor and the voltage of the inductor because there is a 90 degrees phase difference between the two remember that 90 degrees difference er was 24 inches to represent 90 volts so el is going to be how many inches to represent half of that 12 inches so i'm going to go ahead and draw this 12 inches at 90 degrees exactly this angle here has to be 90 degrees because in our resistive portion of the of of our vector here how much phase shift is there through the resistor how much phase shift does a resistor have it's not a trick question zero zero degrees of phase shift with it through the resistor how much phase shift is there through the inductor 90. so this is this is what i'm drawing right here makes sense okay so this is going to be what do i label this e l and this is going to be equal to 45 we're rounding off just to make this easy okay so now i've got my two sides of a right triangle i have my two sides of the right triangle any uh trig experts here does anybody know we call these different sides jason opposite okay which is which who's on first depends on which angle you're figuring out no no no you're bs on me well depends on which angle you're figuring out which day of the week it is and come on man this would be the er yeah i got it backwards okay this is going to be our reference this is so this is going to be our adjacent side this is our adjacent side so this is going to be our reference this here is going to be what we call our opposite side okay um and then does anybody know that what we call the combined adjacent opposite and the the hypotenuse and mathematically what we're really doing is this opposite side we call it the opposite side because we're going to move it to the opposite side literally mathematically over here and then what i'm going to do is i'm actually going to draw a line from my reference to complete this right triangle and this line that i'm drawing here oh come on man this line that i'm drawing here is going to be my hypotenuse and the combination of the voltage across my resistor and the voltage across my inductor is going to be my voltage total or my hypotenuse does that make sense so do you see how does my drawing differ from their illustration it's in proportion thank you who's isn't proportional there's our mind all right that's the right answer that's the right answer okay the big thing though the big thing is this angle right here between my adjacent side and my hypotenuse this is a critical angle we call this theta we call this theta and this shows me how much overall phase shift there is inside this entire circuit how much phase shift is there in the resistive portion of the circuit zero how much is there in the inductive portion 90. how much is there overall how much is there overall who's good with angles and dangles give me a guess on this what do you think this is how much 35 degrees what was that 35 you said um question 35 degrees what's another one 45 why why is 45 a bad answer i don't want to pick on you but you threw 45 out there if if both sides were equal distance it would be 45. if this was 90 and this was 90 it would be 45. so ultimately just to play a safe what's the answer going to be here it's going to be less than 45 degrees you agree with that and for those of you that made the wild guess 35 33.8 degrees whatever you're on the right track that's one of the reasons that i want you to draw it like this on a piece of scratch paper because when you see i could look at this angle i see this less than 45 degrees that's actually around 33 degrees 35 degrees okay that tells me that this is predominantly a what kind of a circuit resistive circuit but i do have some reactive elements to it but it is more resistive than it is reactive why i'm looking at it i got 90 volts voltage drop across my resistor i got 45 volts across my inductor i got half of this half my voltage is across the inductor now what is the total voltage in this circuit give me a guess on what the total voltage is in this circuit vt a guess put the calculators away you can do the calculators use calculators on your homework and on a quiz i want you all to think in here 100 volts 100 volts you think this is 100 volts is if this is if this is if this is 90 volts how did that get to be 25 inches it was 24 there it is if this was 90 volts this mark right here would be 90 volts so going out to this point here approximately 100 volts do you agree with that does that make sense freaking hilarious it's freaking hilarious on professional examinations they will say in a series ac circuit that contains a resistor and an inductor you have 10 volts voltage drop across your resistor you have 10 volts voltage drop across your inductor what is total voltage answer a will be 20. and you'd be surprised the number of people filling it in answer a because 10 plus 10 is 20 in a series circuit is what series circuit is what it's a voltage divider right the answer is not 10 plus 10 does not equal 20 in a series ac circuit 10 plus 10 is going to be what it's going to be something more than 10 but it's going to be something less than 20. and i guarantee you on a multiple choice test only one answer will be correct so don't get suckered in that one so does this make sense now i'm not going to have you just guess that at this stuff i'm going to have you use a scientific method i'm going to have you use a a proven method called the pythagorean theorem the pythagorean theorem does anybody know the original pythagorean theorem like squared a squared plus b squared is equal to qe lewis right it's hip to be square right in the 1970s he had hair down to his butt in the 1980s all of a sudden attempt to be square that's the pythagorean theorem now we know that what we can actually do is is replace these values with electrical values and that's what we're going to do and in using algebra and reorganizing this formula what we're going to do is calculate out voltage total is going to be equal to the square root of the voltage of the resistor squared plus the voltage of the inductor squared does anybody know what we call this when i want to add up these two voltages what do we call it we call it the vectorial sum the vectorial sum so total voltage in this circuit will be the vectorial sum so once you go ahead in your calculator use my numbers don't use their numbers on the board use my numbers what do you come up with 180 180 no 100.62 volts 100.62 volts peak rms peak thank you and if it's not rms convert it into rms and then perform the math because you should always be dealing with rms when you're dealing with this make sense everybody get that number this 90 volt is occurring at a different moment in time than this 45 volts so if we with with asking for vt we're looking at what's the cumulative overall effect in the circuit does that make sense okay we could also do impedance this way and in doing impedance this through this method it's going to be the same thing well if we're getting a bigger voltage drop across the resistor than we are across the inductor what does that tell us right off the bat and not necessarily a high pass filter but if we're getting a bigger voltage drop here there's more ohms of resistance than there are ohms of reactants and as a matter of fact the exact same vectorial plot is going to work the exact same so what you're literally looking at right here is r here you're looking at if we're if i'm looking at r on my adjacent side what am i looking at my opposite side i'm going to compare r to x x what xl very good and what's the combination of resistance in reactants inside a circuit z so if you want the formula for z z t if you like is going to be equal to the square root of r squared plus x sub l squared if you don't have the value of x sub l you need to get it execute this formula but the vectors are going to be exactly the same exactly the same they have to be exactly the same because resistance is what creates a voltage drop reactance is what causes a voltage drop so you're going to plot this out exactly the same what's something else that we could plot out this way what else is additive in a series circuit what else is additive in a series circuit power isn't power additive in a series circuit that's actually a safe answer because power is also additive in a parallel circuit so i could do the power of my resistor here because obviously the bigger resistor the bigger voltage drop it's going to dissipate more power i could do the power of my resistor and here i could do the power of what power of my inductor and then here this would be what my power total what's the problem with what i just put up on the board there's a problem thank you so this is what we would call the apparent power a parent to a who apparent to who a parent to one of joe grunnick's students had dropped out of this program and thought they knew everything about electronics and went on with their life because power is additive i have power across the resistor i have power across the inductor that's going to equal power total right now this will equal apparent power inductors really don't dissipate energy in the form of of heat so actually i could do that same pythagorean theorem though this would be power total app apparent power total is going to be equal to square root of power of the reason power of the resistor squared plus power of the inductor squared there's another thing that we we deal with with these types of circuit it's called true power you know what true power is equal to the true amount of power being consumed in the circuit how much is the true amount of power being consumed in the circuit the power being consumed by the by the resistor so a true power is going to equal this vector period there is going to be no power total power total is going to be pr that's going to be true power in the circuit but mathematically the same vectors would work it's just apparent power is kind of irrelevant it's not it's not the truth that's why we have true power true power gives us the truth does that make sense the only other thing that you could work with here is or the only other thing that you need to solve be able to solve for this in a series circuit is angle theta angle theta and if you know any two sides of the right triangle you could solve for angle theta and um one of the phrase the phrase that pays the one that i always remember it's silly don't laugh got me this far in life right some old horse came uh hopping through our alley some old horse came a hopping through our alley sine function opposite over hypotenuse cosine function adjacent over hypotenuse tangent opposite over adjacent so let's go back to the original numbers that we had here i had the opposite and i had the adjacent opposite and adjacent so why don't you go opposite 45 divided by 90 0.5 and what's the tangent of 0.5 or inverse tangent put that into degrees that's tangent with a little negative one up above it inverse tangent key on your calculator 26.6 26.6 does anyone else concur who else got that mark to get that 26.5 26.5 got to make sure your calculator is in the degree mode on these if there if your calculator is not there to remote if it's in radians or gradients you're going to get goofy numbers so all you have to do is take this opposite divide it by adjacent 45 divided by 90 then take the inverse tangent of it that's tangent typically in your calculator it's second function tangent negative one everybody get that everett did you get that i could tell man i got the best seat in the house up here man i see dudes like all of a sudden like getting shifty squirming in their seats and stuff divided by 90. 45 over 90. yeah look at that 26.56 so we were all wrong well no i was right i said it was less than 45. we had a 35 that was in the ballpark that was in the ballpark definitely not 45 and we knew it was less than 45 so 26.6 degrees i said percent here degrees degrees that's how many degrees we are so if you told me there's so much but by this illustration or so much that i could tell by just looking at this i could tell this is a series r l circuit i could tell that this is predominantly a resistive circuit but it has some reactive components by me seeing that it's 26.6 degrees angle theta that tells me that it's predominantly resistive and it's not reactive if i wanted to make this more reactive if i wanted to increase the length of my opposite side how can i do it how could i do it make it longer with my pen he gets an a for the day you fill the quarter but you get an a for the day if i want to make this line longer and by making this line longer what effect is that going to have on angle theta it's going to increase angle theta how could i do this how can i make my opposite side longer across voltage you would bring your frequency down if i lower my frequency i lower my x a bell if i lower my x decrease if i increase my frequency so for the same inductor i increase my frequency if i increase my frequency i increase my x sub l if i increase my x about my opposite side gets longer my voltage drop across the inductor gets longer my power across the inductor increases angle theta increases you see how many questions i could ask you from just this problem alone i mean it's mind-boggling it's a big chapter this is the biggest chapter it really is because everything comes together if you don't believe that series circuits pow and a voltage is additive then we got problems you know but if you buy does everybody buy everything that i've sold them up to this point is this beyond your comprehension or is this right in the zone for what you've been studying kind of makes sense doesn't it what else can i do with this circuit really nothing what's current in this circuit first of all what kind of circuit is this what's the most important thing about a series circuit current's constant so what is current going to be for the circuit how would we calculate out current in the circuit how would i calculate out total current for the circuit i t equals e over r in an ac series circuit like this do i have r anymore and what do we call a combination of that z well you need to find xl first absolutely that goes without saying but this formula i t is going to work as long as it's e t over z t how do i calculate out z t with this formula right here how do i calculate out this formula here r and x sub l i got to calculate out x sub l 2 pi f l equals x sub l once i have x sub l i plug it into this formula the vectorial sum of r plus x sub l once i have that then i could solve for i t i t is equal to e over z t and where would i plot that out on this here on my vectorial plot where would i get plotted down the bottom where on the same vector as what absolutely why is and total current is total current whatever's happening at one point is happening at the other point there's no phase shift of current in the circuit i mean from any point in a series circuit so this is also going to be i is going to get plotted out on this vector i t does that make sense it's a lot going on here a lot going on here so to calculate out any vector use the pythagorean theorem which states e is equal to the square root of e r squared plus e l squared we call this the vectorial sum the vectoral sum can be used when two legs are known vector representation allows the use of trigonometric functions to determine voltage when only one voltage and phase angle is known the two voltages are known sine theta is equal to voltage of the inductor over voltage total cosine theta e r over e t tangent theta e l over e r i remembered that over here by sine opposite over hypotenuse cosine adjacent over hypotenuse tangent opposite over adjacent if you can't remember that remember some old horse came hopping through our alley get that on your scrap paper because i'll tell you what when i start hitting you on a quiz with these questions you're going to forget this stuff i give you any two of those sides you're going to be able to calculate out what angle theta is if angle theta is greater than 45 degrees it's going to show you that it's predominantly a reactive circuit if it's less than 45 degrees it's predominantly a resistive circuit if it's zero degree degrees it's purely resistive if it's 90 degrees it's purely reactive if it's 45 degrees it's perfect half resistive half reactive make sense impedance the combined effect of resistance and reactants must be used to calculate out current in a reactive circuit when the supply voltage is known represented by the capital letter z reactants in parallel circuits parallel circuits parallel circuits containing inductors and capacitors may be analyzed with vector diagrams what kind of vector diagrams are we going to want to use in parallel circuits a parallel circuit is also known as what current divider so what kind of vectors are we going to have to use current can i use voltage vectors in a parallel circuit why not voltage is constant very good there is no phase shift of voltage in a parallel circuit what the voltage is is the voltage do i need to draw a parallel circuit on the board do you remember what it looks like the tops of all the components are holding hands the bottoms all the components are holding hands so whatever voltages at the compared to the top of the bottom that is a constant value period and a story makes sense so in a parallel circuit we have to use vector diagrams voltage across each component must be equal and in phase must be whose law is that kirchhoff's law parallel circuit voltage is constant across a parallel leg see i don't have to draw it it's already done been drawn for me here's our parallel circuit voltage across the resistor is the exact same voltage across the inductor the current through the resistor what angle is this what side of the right triangle is this oh oh jason which side is my inducted um current through the inductor opposite my hypotenuse is going to be the total current through the circuit the combination of this and this classic example on a professional exam you take your ct exam or your fcc exam they'll give you the circuit here and say you've got two amps flowing through your resistor and two amps flowing through your inductor what's total circuit current answer a will be four amps answer a is wrong you know it's going to be more than 2 but less than 4 because it's the vectorial sum that you're actually calculating out does that make sense in a parallel circuit the book shows you this technique here the reciprocal of reactants the reciprocal of resistance equals the reciprocal of impedance my recommendation is you don't do this my recommendation is you don't use this formula because the reciprocal of inductance and the reciproc the xml the reciprocal of there's a lot of moving parts to this you're probably going to slip a finger on a calculator and get a wrong answer if that's the case how can you calculate out impedance in a parallel circuit how can i calculate out impedance in a parallel circuit how do i calculate out resistance in a simple dc circuit r is equal to what ohm's law again if you mess yourself up right e i r r e over i e over i does that make sense so if i'm dealing with an ac circuit impedance is going to be equal to what e over i the good news is this should be an easy one to get because it's the same voltage across the parallel network this is kind of engraved in stone in a parallel circuit how am i going to get this number you have to find reactants it now you don't have to find out reactants that's the whole thing i don't recommend you do that you can find out reactants this is where i went sideways good good question right if this is what has got an inductor in it x sub l equals 2 pi f l you just calculated out your reactants and a story if you want to calculate out your total current in the circuit square root of current through the resistor squared plus current through the inductor squared how do you calculate out current through the inductor how do you calculate out current through the inductor how do you calculate out current through a resistor r is equal to or i is equal to e over r so i is going to be equal to e l over over what xl x l that gives you this number once you have this number you plug it into this formula once you get this you get this once you get this you can plug it in here and get this it's a heck of a lot easier than the reciprocal of the reactants and i mean how would you this would be like help me out with this one guys this is uh so then is is one over t the i t is the vector is the absolutely vectorial sum right has to be has to be for this kind of circuit so this would be like i z is equal to the square root of 1 over r squared plus one over x sub l squared don't it's a lot of keys you gotta hit for a simple question okay you wanna calculate out your total impedance z is equal to e over i i you get from i t i is the vectorial sum of current through the resistor current through the inductor you calculate current through the inductor by calculating out voltage of the inductor over inductive reactants a lot easier so don't do what the book tells you to do if you want to play with this and just see if you can do it and hey look mom look what i did no hands you know cool do it but beyond that i'd stay clear of that formula actually there's a cool formula i want to show you a cool formula or you guys had enough cool formulas i want to see a cool formula remember when i had two resistors in parallel with each other just two what was that formula rt is equal to r1 times r2 divided by r1 plus r2 so product over sum so we could substitute this and turn this into an ac formula instead of rt what we call rt we no longer have rt we have what z z t so it'll be r one times r one is measured in ohms what am i multiplying that times l divided by be careful with this now have we been dealing with the sum what have we been dealing with what did i call that the vectorial sum so this will be the product over the vectorial sum x sub l squared square root of r one plus x sub l squared the product over vectorial sum this is another way that you could solve that zt and you already know how to do it because in dc you all remember this formula product over sum right so no longer are we dealing with the product over so we're dealing with the product over sum but we have to now deal with the product over the vectorial sum so if you really want to have fun with z calculate it out this way and if you don't do it this quarter that's fine we'll get to you when you get to third quarter and we'll have you do the formula in third quadrant either way before you graduate we're gonna have you do this formula might as well use it now it's another tool in your box makes sense here's a parallel circuit with a resistor and a capacitor same thing voltage is going to be constant i've got current flowing through the resistor i got current throwing through the giving the appearance is flowing through the capacitor so i have i i sub r and i sub c the impedance of a parallel rl and rc circuit is smaller than both the individual resistance or reactants right because we know that zt has to be less than the value of least use the reciprocal values of our x and z i don't recommend you do this you try it just a lot of moving parts mathematically it will work but all trigonometric functions previously mentioned are applicable to figure inductive circuits i is equal to square what kind of circuit are we looking at here what kind of a circuit is this i square root of i r squared plus i l squared what kind of a circuit are we looking at here series is it a series circuit or parallel circuit parallel how do we know it's parallel circuit because you're taking the reciprocal what's constant in the series circuit saying it backwards what's what's constant in a series circuit current so is there going to be any vectorial sum of current in the series circuit yeah so this is going to be what kind of a circuit in ac come on help me out guys first thing is we talk about what kind of our voltage source an ac is a series or parallel parallel circuit that contains a resistor and an inductor how do i know that i'm taking the vectoral sum of the current through the inductor and the current through the resistor does that make sense what kind of a circuit is this ac parallel rc circuit how do i know that because i'm taking the vectorial sum of the current through the resistor and the current through the capacitor if this were a series circuit they're the same current's constant necessary circuit make sense to determine the power consumption of a purely resistive ac circuit obtain the average power calculate the product of the rms current and rms voltage it's average power voltage times current it's average power power factor the ratio of true power in watts to apparent power in volt amps true power is measured in watts because true power is the only power that's actually being consumed in the purely resistive element of the circuit is the reactive element the circuit consuming any power no okay now remember how this chapter is titled resonance we haven't even talked about resonance yet now we're going to talk about resonance resonance a resonant device produces a broadening and dampening effect resonant circuits past desired frequencies and reject others an example would be a television tuning circuit an example of resonance is plucking a guitar string when you pluck a guitar string it vibrates at a unique frequency it is resonating if you get a piece of china and you ding ding the china the frequency it resonates at ironically is called its resonant frequency the biggest example of a man-made device resonating took place here in washington state an arrows bridge the wind blew across the original narrows bridge where i think on version number three 3.0 right now the original tacoma narrows bridge the wind was blowing and it began to resonate at its unique frequency which meant basically would break itself apart that was mechanical resonance in electronics resonance is when take notes on this in electronic resonance is when x sub l equals x sub c in a circuit another xy plot okay this is x this is actually amplitude reactants reactants and this is actually my x axis is frequency okay when i have x sub l equals 2 pi f l when i'm at a low frequency my x sub l is going to be at a that looks like a c low so at a low frequency x of l is low at high frequency exile is high at a medium frequency it's medium makes sense x sub c is equal to 1 over 2 pi f c do you agree with that so when i'm at a low frequency my x sub c is going to be high when i'm at a high frequency my x sub c is going to be low when i'm at a medium frequency it's going to be medium so when i plot these out this is xml and this is x sub c this is what i'm going to get because at low frequencies x sub c is high at high frequencies x of c is low and the opposite is with the inductor so when i combine both of these circuits both an inductor and a capacitor in a circuit together and i apply the frequency that hits this sweet spot right here the point at which x sub c equals x sub l this point right here is called resonance how much phase shift does capacitive reactants give me pure capacitive reactants how much does it give me 90. how much does pure inductive reactants give me 90 in the opposite direction how many degrees of phase shift is there now between the capacitive reactants of the inductive reactants 180 and they're both now at the exact same value so what are they doing canceling each other out what's the only property that you're left with in the circuit if x sub l cancels x sub c out what's the only property we have to deal with that's left it's the first thing you learned about here resistance at resonance x sub c cancels x sub l out the only thing you're left with is is a resistance that's a good thing that makes it easy because remember like several chapters ago it was a resistive ac circuit that was easy wasn't it i thought it was easy so it occurs when the circuits inductive and capacitive reactants are balanced or equal we use this inside tuning circuits inside televisions inside radios in a resonant circuit both the inductive and capacitive components are at the same frequency the frequency of resonance reactances are equal but opposite used with radio frequencies and tuning receivers and transmitters these are not used in audio bands of frequencies because in audio we're specifically talking about what what type of resonance acoustic resonance an acoustic resonance believe it or not this room this space has an acoustic resonance to it and if you find that so sweet spot and you put your speakers in just the right location pow music is going to pop things are going to happen that's acoustic resonance here we're talking about electromagnetic resonance of a signal in summary ohm's law applies to ac circuits the same way as it does dc circuits the ac current lags the voltage by 90 degrees in the inductor the ac current leads the voltage by 90 degrees in a capacitor we use vector representation to depict this through vector representation we could determine impedance apparent power power factor and ultimately identify a resonant frequency resonant frequency is where x sub c equals x sub l and they cancel each other out anybody have any questions on anything we discussed in this chapter there's a lot going on in this chapter but really this chapter is nothing more than x sub l equals 2 pi f l x sub c equals 1 over 2 pi fc when they're equal to each other you're at resonance check this out check this out if i'm below resonant frequency if i have a circuit a series circuit that contains a resistor an inductor and a capacitor and i am below resonant frequency what kind of a circuit am i dealing with you're looking at the answer if i'm below resonant frequency what kind of a circuit am i dealing with predominantly capacitive circuit if i'm above resonant frequency what's the predominant value that i'm going to be dealing with inductive the blue cancels out the red the blue winds if i'm above resonant frequency if i'm below resonant frequency the capacitor wins so you're either going to be dealing with an x sub c circuit an x sub l circuit or purely r circuit at resonance makes sense don't expect you to all be experts on this chapter i mean we want you to be familiar with phase shift we want you to understand the trigonometric functions that are taking place here and obviously we expect you to be able to solve some of these basic problems but i think you guys you guys did that for me i saw you do it in a simple series circuit that i had calculating out angle theta calculating out the length of my hypotenuse kind of funny you guys all calculated out the length of my hypotenuse tonight it's pretty entertaining and you got it right any questions on this chapter okay we're gonna do a brief seven minute break okay because then we come back we're gonna do chapter 18. other than that we're gonna have to defer okay chapter 18 transformers and i got to start this lecture off with a little story as you know in my past life i was a nuclear submariner and it's kind of a drag i mean it was some of the stuff i saw was kind of neat it was interesting but i would be gone for very very long periods of time isolated totally out of tune with what was going on in the world and pop culture and there was one year that i was going to be home for the holidays and i was pretty excited about it because i can't even tell you how many holidays that i was underwater submerged and how many memorial days i remember one memorial day i was actually going to the mediterranean we surfaced off the streets gibraltar we had a barbecue in the back of our submarine we're kind of showing off to the soviets uh yeah we're putting another nuclear submarine in the mediterranean so there so anyway back to my uh uh with me being home for the holidays you know i got back and i had some time off and my wife and i were going we had two kids at the time we're going christmas shopping and um i asked my wife so you know what do the kids want what are they you know what are they interested in my wife said [Laughter] my wife my wife said they'd really like some transformers you know what i'm like when did they first when they first became intrigued with electricity and electronics what do they want step up transformers step down transformers impedance mat i had no freaking clue you talking about a car that turns into a man that i don't understand so anyway we went out we found them some transformers and of course my kids are grown now or whatever um they wish that they had taken better care of their original transformers as they'd be able to sell them now on ebay and make a ton of money instead they were hey dad look at this you know i'm i'm i'm lighting my transformer on fire which i don't i don't blame them that was kind of the same thing when i was growing up actually believe it or not i still have my original lionel train um it's in a state of disrepair it still works but i mean i used to have that thing i used to get the track like put it in an s and then a straight away and then it would just like go right over the stairs if i only take care of that i probably could have sold that on ebay and retired now you know in mint condition but no no such luck anyway we're going to talk about chapter 18 which is our final chapter in the lec 110 transformers after completing this chapter we're going to be able to describe how a transformer operates explain how transformers are rated explain how transformers operate in a circuit describe the differences between step up step down and isolation transformers describe how the ratio of voltage current and number of turns are related with a transformer describe applications of a transformer and identify different types of transformers first of all electromagnetic induction this is nothing new the action caused when two electrically isolated coils are placed next to each other the ac voltage is put across one coil resulting in a changing magnetic field that induces a voltage into the second coil so what this is like is having an inductor remember how we build up that magnetic field the only thing is we're going to put that magnetic field in close proximity to another inductor so the magnetic field collapses it collapses into the second inductor or secondary winding the device they use to create this action is called a transformer transformers the coil containing the ac voltage is the primary winding the coil on which the voltage is induced is called the secondary winding now transformers have what's known as a coefficient of coupling and it's going to be a number anywhere from zero to the number one one indicating that all primary flux lines cut the secondary windings one as in one hundred percent make sense a zero indicates that none of the primary flux lines cut the windings if you have bought a transformer with a coefficient coupling of zero you've done been ripped off okay it's not gonna do anything for you because none of the uh none of the primary flux lines are gonna induce any current the design of a transformer is going to be determined by the frequency at which it will be used low frequency like for power applications 50 hertz 60 hertz 400 hertz we'll use iron core transformers and by using an iron core that helps increase its level of efficiency because remember using a ferromagnetic core will enhance the electromagnetic effect high frequency applications will use air cores because if you use a metal core sometimes bad stuff will happen with that expanding collapsing field you're going to get a lot of molecular shift and you're going to get heating and you're going to get losses 80 current losses and a variety of different things so somebody's high frequency transformers they'll just use air as a core a transformer is also designed and determined by the power that it must handle how much power can it handle and that's going to be measured in volt amps it's not going to be measured in watts don't go to vetco identify yourself as one of my students and ask for a 60 watt transformer the transformers are not measured in watts they're measured in volt amps also the voltage it must handle voltage is going to be a factor because of the dielectrics that are used if you put too high of a voltage across two points that are too close to each other you could end up with arcing so all transformers are not created equal high voltage transformers are used for high voltage applications transformers again are rated in volt amperes one of the things that you need to be pay attention to is what's called the dot convention the dot convention if we're looking at a schematic diagram here and there's a dot here and a dot here that means that whatever you put into the primary will be in phase with the secondary typically the output at the secondary will be 180 degrees out of phase with the primary this was what i suspect the original transformer did because the original transformer in the secondary you're inducing a voltage based on the collapsing magnetic field created by the primary so it's automatically going to be 180 degrees out of phase so say if lens is law right but what they could do is they could actually put this winding in backwards wind it backwards and account for that phase shift so in a schematic diagram just look and see if you see the dots if the dots are side by side there might not be any dots because it might not be critical but if there are dots like this it shows no phase shift dot like this 180 degrees out of phase on a schematic transformers are wound with tapped secondaries what are called tapped secondaries center tap secondary is equal to two secondary windings basically what they do is they get a hundred percent of the secondary winding and then what they'll do is they'll put a connection into the center so you got half 50 percent of your winding between here and here and then 50 percent of your winding between here and here some transformers have multiple taps and the reason that they did this in the past was so that you could create multiple voltages out of your secondary so a lot of older legacy equipment was like that where you'd have a transformer with a primary and then like eight or nine secondaries i remember the last thing that i really remember working on was uh it was an a hi-fi high fidelity stereo hi-fi for it belonged to my sister and this was i was this is like back in 1983 or something and it just stopped working it was a nice unit for for the day am fm stereo you know the phonograph player the whole thing was dead i get in there i started looking transformer had failed so it's kind of like i think that transformer cost like 72 bucks this is pretty expensive back in you know but still it was an expensive you know 500 stereo back then it's like you put a fifth into it uh you know but i troubleshot it i was pretty sure it was a secondary so i ordered it was fisher brand and i ordered directly from fisher replacement um transformer put it in good to go the funny thing about it is they had no protective device on it so when a malfunction occurred it took the transformer out pretty expensive piece to take out so i retrofit a fuse in there to prevent this from happening again in the future so i don't think she's still using it so it's kind of old school would have been nice if she kept it transformers around with that top secondary is also used for power supply to convert ac voltages to cc voltages transformer doesn't do the conversion but a transformer will get a high voltage and then make it a lower voltage so that it can be converted to a dc voltage the principle that all this operates on is what's called mutual inductance the primary induces a voltage into the secondary and the secondary induces a voltage back into the primary so one of the things in order for this to take place and this is not a trick question and but you will see this on some professional exams this is your source connected directly to the primary the secondary has to be connected to the load if the secondary is not connected to the load it's not going to induce any current because current's got to have a place to move so if this was just an open circuit right here where's the current go it's got no place to shake back and forth to in essence so you've got to connect a load up to the secondary in order for you to get this mutual inductance the primary having influence on the secondary turns ratio determines whether a transformer is used to step up step down or pass a voltage unchanged and this is by the way what transformers are used for step up step down or pass the voltage unchanged by passing a voltage unchanged we call that an isolation transformer an isolation transformer isolation is really the number one reason to use transformers keep us isolated from the source electron good thing it promotes electrical equipment and personnel safety the number turns in a secondary winding divided by the number turned to the primary winding this is how we would calculate outer turns ratio real simple ns over np and is going to be the number of turns physically the number of turns how many turns of wire are there in the primary how many turns are there in the secondary a step up transformer is going to be a transformer with a secondary voltage greater than its primary voltage and this is going to be expressed as in voltage of the secondary over voltage to the primary or number of secondary turns over a number of primary turns for this type of a transformer the turns ratio is always going to be greater than one it's always going to be greater than one which means one turn in the primary two turns in the secondary one turn in the primary two turns in the secondary meaning the secondary is going to have how much voltage as compared to the primary twice as much this is a typo this should say step down transformer step down transformer it's a transformer that produces a secondary voltage less than its primary voltage this will always have a turns ratio less than one this might be two turns in the primary one turn of the secondary two turns of the primary one turn in the secondary meaning we put in a high voltage and we get out a proportionally lower voltage when a transformer steps up the voltage it steps down the current now this here works great in the world of theoretical electronics fantasy electronics this is showing that power of the primary is equal to power to the secondary power of the primary is equal to current of the primary times voltage of the primary everybody understand this math straight watts law is going to be equal to power the secondary current the secondary times voltage is secondary what's the only flaw with this this assumes a 100 percent efficiency and no resistance you think we get 100 efficiency out of a transformer most of the transformers you screw around within the lab they may be 60 percent efficient had a student in my class in the past he worked in aerospace for a supplier for actually satellites they supplied components for satellites outer space satellites and they had a couple transformers really really expensive tens of thousands of dollars and um those were like in the low 90 efficiency but they were like you know precision wound and special you know cores and you don't want to have to buy stuff like that you don't want to buy replacement parts like that the current is inversely proportional to the turns ratio this is expressed as i p over is equal number of turns in the secondary divided by number turns the primary so all this is really straightforward impedance ratio one of the big things that we want to do with transformers is what's called impedance matching impedance matching is essential so that we get the maximum power transfer from our source to our load this is my mark in your past life right you got eight ohm speakers right you got to make sure that you're matching that to your output if you're not you're not going to get maximum power transfer have all of you heard of that before like 8 ohm speakers okay you don't want to hook 4 ohm speakers up to an 8 ohm output you can and it's going to work but it's not going to work efficiently you're not going to get maximum power transfer in order for you to get maximum power transfer you have to match the impedance one of the simple ways of matching the impedance is using what's known as an impedance matching transformer and an impedance matching transformer real simple impedance of the primary impedance of the secondary is going to be equal to the number of turns of the primary squared over the number turns the secondary squared applications for transformers include stepping up voltage and current stepping down voltage and current impedance matching phase shifting the big one this is the one they're looking for on the examinations folk the professional examinations isolation number one reason we use blocking dc while passing ac can dc make it through a transformer a dc dc could make it through your primary but how is it going to be coupled to the secondary it's the expanding and collapsing field so when you turn the dc on it's going to expand the field when you shut it off it's going to collapse the field so you're not going to be able to couple that dc so it's great keeps the dc on one side allows the ac to get coupled to the secondary side and also producing several signals at various voltage levels this is what i was talking about with a multi-tapped secondary multi-tap secondary transformers are used for transmitting and yes the term transmitting electrical power to homes and industry over at the grand coulee dam on the columbia river they generate the electricity then at the substation they run it through a transformer so that the generators are not connected directly to the power grid that way if the power line gets struck by lightning it doesn't take out the freaking generators they're electrically isolated one of the reasons they do that is at the power generating plant they get the electricity and what do they do do they increase the voltage of the current at the substation over at grand coulee dam whatever way you answer the next question is going to be why what do they do they generate the electricity over a grand coulee dam and what do they do do they increase the voltage or they increase the current a 50 50 shot at that one they increased the voltage why it's good answer but lower current passes you can pass you can pass over distance lower turrets yeah it's easier to step down no it's it's about it's it's really the same but the big thing that they're trying to do over at grant cooley dam is what they're trying to do is increase the voltage at the substation so they could transmit high voltage from that side of the mountains to this side of the mountains by increasing the voltage what do they do to the size of the conductor it gets smaller you need a big conductor to handle a high amount of what voltage or current current so by going to a higher voltage now they could make the wire physically smaller higher voltage and all they have to do is just keep it far enough separated from the other wire so it doesn't short out and they could bump that thing up to you know thousands tens of thousands of volts increase the voltage while they're increasing the voltage what are they doing to the current decreasing it so they could go with a smaller conductor then they bring it to the substation here on the west side of the mountains in your neighborhood what do they do to it they bring it back down lower the voltage what do they what does that do the current increases the current they do that so good they do it again they do it out on your street with the transformers right on your street they got high voltage going from power pole to power pole power pole but then what they do is they lower the voltage going to your home lower the voltage but increase the current and a typical household utility connection is 200 amps 240 volts ac at 200 amps you're isolated multiple times hit by light your house gets hit by lightning it may take out a couple other homes in your neighborhood period but it doesn't take out that entire circuit doesn't take out the substation doesn't take out the generator at grand coulee dam because everything is electrically isolated the electrons traveling in one loop are simply being shaken back and forth by the electrons traveling in the other loop you can create a power surge that happens power line gets hit over you know coming over the mountains it may send a spike through the line that could get to your home because an increase in voltage is going to create create an increased magnetic field which is going to influence the secondary but it's not going to have be the same amount of current traveling through that secondary loop it's going to provide you with isolation make sense auto transformers is a device used to step up or step down applied voltage uh there's we have examples the sencore units in here are considered auto transformers and what they do is they allow you to vary i saw a couple of you using doing some labs in there the other day with that that variable transformer that's what that is an auto transformer an auto transformer in and of itself does not provide electrical isolation both the primary and secondary windings are part of the same core but those cent core units also have power isolation and the reason we have those is so that when you do ac experiments you're not doing ac experiments plugged directly into the wall that's a safety violation it will not plug anything directly into those outlets if you got to do an ac experiment plug it into that centcor power isolation transformer what about coils on cars are coils on cars like transformers no what does a coil do on a car certainly a single coil yeah but what is what does a coil do what is the ultimate purpose of a coil you have a coil what is a coil feed distributor exactly and what kind of voltages are you talking about on your spark plug 5 volts 8 volts 10 volts 120 volts thousands of volts tens of thousands of volts so how are you going to create tens of thousands of volts under the hood of your car last time i checked there's a 12 volt battery underneath it and that that battery is 12 volts dc so how do you get 12 volts dc converted into 20 000 volts across your spark plug coils like a transformer the way a car coil works is you send a low voltage pulse to it and it's that basically it's that pulse it's that expanding and collapsing field that creates that high voltage spark so it's not ac per se but it's a pulse of dc that you're sending into the coil you have an expanding field then you have that field that collapses back into the the coil winding and that induces that 10 10 1 000 volt spark that gets sent to your spark plug but it's dc that originally created it so i don't know if there's any gear heads here or anybody that's ever thought about it that way but you know how do you get a 12 volt dc system in a car to create tens of thousands of volts that go to your spark plug now it's the coil the coil that does it my great coil story yeah and when you think about it you kind of go crazy because it is dc and joe said dc doesn't work with transformers but it's dc but it's put into a pulse actually if any of your old gear heads and worked on anything like setting the points on your distributor that point that contact that it makes and breaks that basically is what is sending that pulse to the coil to create that now it's all done electronically you've got solid state circuits in there that are you know actually want to hear the ultimate design the ultimate design is on my ford taurus that i have i've got the the taurus sho super high output v8 ford had a better idea what they did with mine is i have coil on plug so every spark plug has its own coil right over the top of it is that the distributor list yeah it's all fed directly from the computer that's great i mean it sounds like a great concept so i have low voltage going to my coil and my coil fits right over my plug right except when it comes time to replace these things anybody want to take a wild guess at how much my coil costs thank you thank you for adding that thank you for adding that there are eight of them there are eight of them no my wife is ready to freaking kill me it's one of the things that's special about my car um the retail if you go to the dealer and get it's 250 bucks a coil and my car takes eight of them so the maximum and a lot of you're gonna grunt grown at this it takes me working on my car eight hours to get to my rear coils because the engine is shoehorned in there and then even with that i'm bleeding i'm like oh you know it takes me eight hours to get back there so whenever i do a hundred thousand mile tune-up and i basically put in new plugs in the back i buy four coils and because the coils in the back are prone to a lot more heat and failure but i figure since i'm back there so you're talking a thousand dollars worth of coils a spark plug this one's not very reliable not with all the heat in the back of the engine but that's another story you know i mean that's it's so i actually got a pretty good price i bought some last i got some last year there's some of that stuff's not even available now because they don't make that car anymore they have a new version of it but they're not even supporting i've got the active suspension on mine where they got the magnetic fluid inside the struts so it sends a voltage and within one millisecond it stiffens my struts as i drive i had one of those fail okay that's a 328 dollar strut before it doesn't make them anymore so i need one right now i have failure of that strut so through a secondary market somebody in minnesota no wisconsin has one and they're gonna like sell it to me and my wife's like why don't you get a normal car it is kind of normal in an abnormal way but yeah i get some but that's and also this is a coil coil on plug all it is is a piece of wire that you that's that that low voltage comes in creates a magnetic field and when it collapses and induces that spark so i'm sure there's probably some retrofits that i could do but it'll make you feel good that one for a porsche is like only 50 bucks are you serious early coil plug only 50 bucks we did some research on our fuel injection stuff and [Music] some cayenne cayenne coil on plugs are cheap super cheap for new stuff i wonder if we could modify that to yeah to make that help keep my marriage intact [Music] you spent 1800 bucks on some plugs and some anyway um in summary transformers consist of two coils a primary winding and a secondary winding transformers allow an ac signal to be transferred from one circuit to another transformers allow stepping up a signal stepping down a signal or passing a signal unchanged transformers are designed to operate at certain frequencies transformers are rated in what are called volt amperes not watts it is power but we call it volt amperes turns ratio determines whether transformer is used for stepping up a voltage stepping down a voltage or passing a voltage unchanged and even if you pass a voltage unchanged are you still going to have losses yeah because transformers are made out of wire and wire is made out of copper and copper has resistance associated with it and you're still going to have a phase shift right and you're still going to have phase shift unless you wind it unless it's manufactured to account for that step up transformer produces a secondary winder voltage greater than its primary voltage that's why it's called step up has a turns ratio that's always greater than one step down transformer produces a secondary voltage less than its primary voltage as a turns ratio that's always less than one the turns ratio determines the amount of voltage that is stepped up or step down transformer applications include impedance matching that's a big one just with a little transformer you can match impedance and that's very very important especially if any of you get into any audio applications or anything like that it's it's extremely critical to get impedance matching correct microphones have different impedance mat you know associated with them and then the boards that you're plugging into are different got to get that impedance right to ensure what maximum power transfer tell you what you guys got to remember that when you get to peter's class he's going to ask you about what you know about maximum power transfer and usually students are like i don't know then peter gets pissed man they come sees me aren't you teaching about that yeah i teach them about it they're just not freaking listening okay maximum power transfer takes place when the internal resistance impedance of the source equals internal impedance of the load just always remember that's why you want to hook up 8 ohm speakers to an 8 ohm source or you don't want to hook up 4 ohm speakers transformer applications include impedance matching phase shifting isolation that's the big one for whatever reason i like asking that on professional exams blocking dc while passing ac and producing several signals at different voltage levels isolation transformers pass the signal unchanged used to prevent electric shocks you'll still get zapped but how many of you here would like to be connected directly to all the power of the grand coulee dam now so through the use of transformers you could be isolated from that still gonna hurt still going to hurt but you're not connected how many of you would like to be connected directly to the 200 amp source coming into your home but through the use of a power isolation transformer you can keep yourself isolated from that auto transformers used to step up or step down a voltage and this is like a variable a lot of people call them rio stats yeah connected to that real stat right they're not a real it's an auto transformer auto transformers do not provide us with isolation however our models here the cencor is not only an auto transformer but it also provides us with isolation that's the whole purpose of that unit any questions no because again with dc there's no way it's that on and off if it was a pulse hdc there would be a way like a car coil but other than that no there's no equivalent you know you could use a coil you got to be real careful though because again if it's dc and you're creating a pulsating dc then conceivably you can use a transformer to couple that expanding and collapsing field from the primary winding of the secondary but dc and the pearson dc voltage multipliers and we're going to cover that um next in the lec 120 and in essence what we're using believe it or not is um see how smart you guys are what component do we use to temporarily store voltage in capacitor in the form of electrostatic field so if you could charge up capacitors right and then you could take and then connect those temporarily in series with each other then you could get this voltage plus this voltage plus in essentially you're getting that dc voltage and you're multiplying it that basically use capacitive capacitors as their active component to give you a higher dc voltage out because yeah that is a big challenge um in some applications where you want to get a higher level of dc out um what's up fires you're opening one up there's lots of big capacitors question the first step was just one led with one capacitor and then it added two leds but it had a second capacitor in between the first led [Music] with an led i don't think you're you have to multiply the voltage necessarily different voltage yeah yeah does anybody have any final questions this concludes the lectures associated with the lac 110 so um it's up to your class lead i guess you're on track this this week to finish up your um your final quiz and then after this is just going to be a matter of matter of scheduling the final exam for elec 110. um don't forget got to get all your labs knocked out um projects are going to be due next week um the eighth i believe is the day and i've got a lot going on so we're we're tomorrow is june it may feel like january or february outside but tomorrow is officially going to be june this is the lec 120 and this is the class that comes after elec 110. anybody want to take a wild guess what comes after elec 120 lec 130 and most likely in the fall you'll have when you take that class will be taught by my esteemed colleague mr peter welty and uh when you get there it's a whole new ball of wax the neat thing about elec 120 it's the second half of the elysee 110 as far as the book goes so between elec 110 and elec 120 you're going to have experienced a journey from the fundamental physics of electricity all the way through how micro computers are basically put together from a functional block diagram which is actually pretty exciting to reiterate elec 110 and elec 120 are survey classes so this is not designed to make you an expert electronics technician it's not even designed to make you really an electronics technician it's to give you a survey an overview of the entire field that you're embarking on and all the parts that make that up one of the things to keep in mind is electronics is very much like an onion it's like an onion you pull one layer off and what's below that next layer another layer of onion it's not like a cucumber or an apple if you peel an apple outside the peel the center is the apple and as you dig deeper deeper deeper it's all apple and onion it's different layers very much like electronics so what this is is the first layer in overview okay you could dig in any in elec 130 peter's class and dig deeper you could attend the university of washington take theoretical classes get deeper you can become your p a phd and get deeper and deeper and deeper and deeper the only problem with this industry is as we dig deeper it continues to grow so i think if you dedicated your life to getting to the core you'd never be successful so with that being said let's go ahead and get started here for those of you at home following along in the text book this brings us to section three of the book semiconductor devices and to give you a little bit of background on this stuff this is uh actually kind of a cool kind of a cool area i look back um my dad is 87 years old he's a world war ii veteran he's still alive lives in connecticut it's quite healthy when he was a young boy when he was a soldier in world war ii this stuff hadn't even been invented yet it didn't even exist back in the day the way it was all done and some of you may be familiar with this it was all done with tubes vacuum tubes and the catalyst for this development really was world war ii to kind of refresh some of you there was a guy by the name of adolf hitler right and he basically wanted to wipe out a whole bunch of people and do some crazy stuff so we didn't think it was really cool so we went over there to bomb him and his people into oblivion him and his people didn't think that was cool so they shot back so when they shot back these bombers that contained sophisticated electronic equipment but it was made of vacuum tubes didn't react well to explosions outside the aircraft the tubes would break the electronics gear wouldn't work so there was a high demand a high demand for the development of something that could control current control electricity that was in a solid state a solid state so goes the development of semiconductor materials and semiconductor devices that's a whole section that we're embarking on so for old timers for grandmas and grandpas great great grandmas and grandpas this stuff didn't even exist didn't even exist back in the day once the stuff was developed the growth has been exponential and it continues to this day chapter 19 semi-conductor fundamentals after completing this chapter you the student are going to be able to identify materials that act as semiconductors you're going to be able to define covalent bonding you're going to be able to describe the doping process this is different than the doping process that some of you may already be aware of describe the doping process for creating n and p type semiconductor materials explain how doping supports current flow in a semiconductor material identify the advantages of semiconductors advise it identify the disadvantages because there are some disadvantages of semiconductors first of all this is refresher for those of you that took elec 110 which should be everybody in here because it's a prerequisite for elec 120 right was everybody successful in passing that i'll go check my grade books kaelin are you passed i don't think so anyway you all remember in our first lecture in elec 110 we talked about materials and we've got really three different actually four different materials that i mentioned the primary three materials we talked about are conductors insulators semiconductors what was the fourth i talked about superconductors very good so we've really got those four materials that are used in industry right now well superconductors really aren't used in industry that much they are used in some applications but they're not really prevalent because it's very difficult to work with those materials anyway back to the basics three electrons or fewer in the valence shell makes it a good conductor five or more makes it a good insulator what number i'm thinking of a number between three and five four that was it's amazing it's uncanny mathematician four electrons of the valence shell makes it a good semi conductor and i i think that um don't you wish that you lived back in world war ii and we're like a scientist because you could have drawn that same conclusion you know we're looking for a number between three and five four let's look at those materials and that's what they looked at were those materials and what we came up with what we what they came up with was carbon germanium and silicon those three materials they say they have four electrons in a valence shell we'll see if we could play with them so that they begin to act like a semi semi-conductor the first material that we're going to discuss is germanium this is germanium not geranium geraniums grow in flower boxes i think they like lots of sun and water sure a lot of you are shocked that i even know that actually i kind of made it up but i think it's the truth discovered in 1886 recovered from the ashes of certain types of coal don't ask me how they discovered it in 1886 and like well you know they're going through ashes of coal oh wow look at this it looks like germanium geranium germanium germanium not geranium when it's reduced to a solid form you end up with pure germanium silicon discovered in 1823 found in the earth's crust as silicon dioxide it's white or sometimes colorless abundantly found in sand quartz agate and flint chemically reduced to a pure silicon in solid form and it is the most commonly used semiconductor material where does most of our silicon come from what region of the world anybody know anybody anybody here heard of silicon valley have any of you been to silicon valley what's there vast mountains sand dunes of silicon what's there if you went to silicon valley what would you see today lots of buildings lots of high-tech buildings the reason silicon valley is called silicon valley it's where a lot of the developmental work did in harnessing the material silicon for electronic use and it's located basically down in the san jose area of california just south of san francisco silicon valley one of my favorite james bond movies of all time a view to a kill remember that one zorn industries with the with the with the zeppelin the blimp christopher walken is the madman i mean it doesn't get any better than christopher walken as a madman and what he was gonna do is i don't know create an earthquake in the san andreas fault and flood silicon valley because he held you know all of the world's microchips and anyway great movie highly recommend it they talk about silicon valley the big thing that we got to look at here is the subatomic structure you're all familiar with the valence shell the outermost shell here are our four electrons orbiting the nucleus of the valance shell that's what makes this a good choice to use as a solid-state semiconductor material now in this particular case we're talking about silicon silicon atoms now we need to grow these silicon crystals have anybody any of you here ever grown crystals before what kind of crystals did you grow in a box you know what kind they were i heard somebody say rock candy rock candy which is nothing more than basically melting sugar and water and then as the water evaporates the sugar starts to crystallize you put a string in there the crystals cling to the string and then you have rock candy that's nothing more than pure sugar but it's sugar crystals you do the same thing with salt they do the same thing with silicon they have a seed which is a a perfect perfectly pure form of silicon and then what they do in molten silicon is basically it's almost like dipping uh dipping a wick for creating a candle it's very similar that it crystallizes on it and as long as this is done in a perfectly clean environment you end up with pure silicon intrinsic silicon and when you grow it together as a crystal you develop what's called this covalent bonding covalent bonding it's the process of sharing valence electrons resulting in the formation of crystals so those of you in the back of the room have the best view of this if you actually look at this you see how it's all laid out in like a geometric pattern here that's because that outer valance shell is sharing the orbit with the one next to it and you create this covalent bond so the manufacturing process is very very critical all this has to be done in a clean room a speck of dandruff a speck of dirt a speck of dust means it's going to be embedded in this material and you won't have that covalent bond so you want to get this as pure as pure can be one of the things that you need to understand about these semiconductor materials is their behavior as it relates to temperature those of you that completed elec 110 shouldn't be surprised temperature does affect resistance does it not and with a conductor how does that work when the temperature increases the resistance goes up which is if you're an extension cord that's starting to get warm is a bad thing right because the hotter the extension cord gets the more resistance the more resistance the hotter it gets the hotter it gets the more resistance next thing you know what's that that's burning holy crap my extension cord's on fire so that's that's a problem negative temperature coefficient is the opposite as the temperature increases resistance decreases so we could say there's an inverse proportional relationship that means it's a negative temperature coefficient this is going to be the behavior of semiconductor materials now for silicon which is again the most popular semiconductor material resistance is caught in half every six degrees celsius of rise and temperature so you rise six degrees in temperature whatever resistance you're at is now cut in half for germanium resistance is cut in half for every 10 degrees celsius of rise and temperature so it takes a bigger change in temperature to bring that about in germanium does temperature affect semiconductor materials what's the most important thing to remember then when working with semiconductor materials maintaining the proper temperature you folks have all heard about my background right i've shared with you my background my military background you know the most important job i ever had other than teaching all of you fine people probably the most important job i ever had was when i was a very junior technician on board a nuclear submarine and one of the things that i had to do on a weekly basis was pull out air filters out of our equipment racks and vacuum those air filters then reinstall them once a month i had to put it in a ultrasonic cleaner vacuum and put it in an ultrasonic cleaner and then put it back in there were weekly maintenance procedures or monthly maintenance procedures why was that such an important job what effect would it have had if i decided to blow off my responsibilities it was an air filter going to electronic equipment racks just a simple air filter like the air filter in your furnace at home absolutely if i blew off my job and didn't vacuum them out there wouldn't be sufficient air flow if there wasn't sufficient air flow it would have overheated the equipment and the equipment would have failed so literally a multi-billion dollar submarine on a mission somewhere on the other side of the world could have been compromised because i decided i wasn't in the mood of vacuuming out the air filters and i'm not over exaggerating it's that critical one of the things that i do at home is twice a year i typically take my computer my pc i take the cover off i bring it outside at home i have an air compressor i make sure that the case is grounded because those of you that are embarking on on static understanding of static electricity air flowing past a circuit could generate static electricity so i make sure the case is grounded and then i blow it out with high pressure air and i'll be honest with you it's kind of embarrassing when i do it it's like a cloud of freaking you know what was it peanuts there pig pen where we walked around was like a cloud following them so my neighbors go by what the heck's he doing there's all this dust that's all dust in my house but it likes to collect on the circuit board when it gets into the circuit board on the computer what does it form it forms like a blanket over the electronic components so the heat can't be dissipated and the computer is going to be much more prone to failure the same thing with all your electronic equipment amplifiers i just did that with my directv my tivo unit about a month ago i was in there opened it up brought it outside blasted it all out it looks as good as it as it does uh the the day it was manufactured okay so you want to get dust out because this stuff the semiconductor materials are affected greatly by a change in temperature silicon has 1 000 times more resistance than germanium at room temperature thus making it more stable germanium is used where heat sensitive applications are necessary and today silicon is used for the for most solid state applications silicon is really the big the big material that's used out there that's why there's silicon valley have any of you ever heard of germanium valley or carbon carbon valley carbon auto down by mount rainier that's a little bit different though conduction in pure german germanium and silicon let's talk about conduction in these two pure pure materials electrical activity is highly dependent on temperature let me say that again this time real slow electrical activity is highly dependent on temperature germanium and silicon crystals function as insulators at low temperatures so at an extremely low temperature they're like insulators as the temperature rises they begin to acquire the characteristics of a conductor so if you've got pure germanium and silicon inside a box that you can control the temperature of just by you changing the temperature is going to change the amount of resistance in the material that's what's key does that make sense now here's something that i didn't want you to talk about in the elysee 110. now we're going to talk about it in the lec 120. hole hole an all-female progressive rock band from seattle washington whole was it beavis and butthead do america there's reference to that isn't it because they were talking about going to washington any of you see that movie right what was what was the whole premise of that sound like stole their tv or something or they stole the tv from the school and we're going to find a tv or they're trying to get a tv so they're going to go to washington right and they were talking about washington dc this bus is going to washington cool is it seattle and washington we could go see hull has nothing to do with this but it's actually somewhat entertaining anyway that's not the hole we're talking about here we're not talking about the female progressive rock band from seattle we're talking about the absence of an electron now how do we create an absence of an electron the process is called well here it's called doping but up to this point wasn't it ionization if we apply energy in a matter we can knock an electron off off what off the valence shell if we knock an electron off the valence shell that means we're left with a positive ion positive ion means there's an absence of an electron the absence of an electron here in our discussion will be signified as a hole so what it does is it represents the loss of a negative charge therefore has the characteristic of a positively charged particle now each corresponding electron and hole are referred to as an electron hole pair because you remember my lectures in the past in the beginning everything was in a neutral natural state that means there's an equal number of electrons and an equal number of protons so all atoms are in a neutral natural state and it will remain so until we impart energy on matter question yeah if an electron is a particle that actually has some mass even though it's you know very very minuscule yes um uh a whole is a whole actually considered to be something that has a mass since it's defined as a particle like an electron or is it more of a complementary state more of a complementary state because that absence of the electron mass wise is pretty insignificant now holes constantly drift toward the negative terminal of a voltage source why would a hole constantly drift towards the negative terminal of a voltage source opposites tracked it's that simple because opposites attract if you're a whole you want to be filled by what an electron where the electrons hang out the negative terminal of the voltage source if you're an electron what do you want to do fill a hole what are your best chances of filling a hole by hanging out on the negative terminal as the holes are attracted to you does that make sense so this is just it's a fundamental physics property of this this drift that's going to take place now electrons flow towards the positive terminal because they want to fill the holes now current flow in a semiconductor consists of the movement of both electrons and holes everything you studied up to this point in the lec 110 we were only really concerned about current i one amp is equal to one coulomb per second remember that now to be totally honest with you whether 6.24 times 10 to the 18 electrons go this way per second or 6.24 times 10 to the 18th holes go this way per second either will equal one amp does that make sense so don't be confused by holes we didn't want to beat it to death in elec 110 but i want you to you have to understand the concept of a hole the absence of the electron make sense can you dig it so as i just stated the amount of current flow is determined by the number of electron hole pairs six point two four times 10 to 18 electrons this way per second one amp six point two four times 10 to the 18th holes per second one amp it's the same electron hole pairs the ability to support current flow increases with the temperature of the material because as the temperature rises the resistance drops that's actually a problem for some electronic systems right because as the temperature increases all of a sudden current wants to flow more maybe more than should be flowing and that's what may cause a solid state component to fail direct result of a change in temperature fail now just having the solid state pure solid state materials really don't do a whole lot for us so what we need to do is we need to increase the conductivity of the semiconductors this is done through a process called doping so you all get to go home tonight what are you learning over there at that college my teacher is teaching us about doping you know that's part of the whole college experience right actually what we're talking about is a little bit different but still doping doping is the process of adding impurities to a semiconductor material not just adding impurities for the sake of adding impurities but adding specific impurities to change their behavior now we're going to really use two different classes of materials as dopants one of the classes is going to be called a pentavalent dopant and the other is going to be called a trivalent dopant now pentavalene penta means five like a pentagram penta meaning five you got a pentagram on your hand yeah there you go permanently yeah you thinking about it you're just doing a dry run all right i think i got one for my forehead your shocking experience now pentavalent made of atoms with five valence electrons the two primary materials that are used in the industry are arsenic that's fun stuff to you know break out at parties all right arsenic and antimony arsenic and antimony the trivalent dopants have three electrons in the valence shell and this includes indium and gallium indium and gallium what we did here is we got pure silicon pure silicon in a molten state got one of those ladles stirring the soup and then what we got is a pinch of arsenic and we added a pinch of arsenic to our silicon and then what we did is we grew it into a crystalline structure no longer pure now we have a dopant arsenic introduced into it when we begin to grow the crystals the arsenic atom will develop a covalent bond with the silicon atoms thus growing it into the material so it becomes part of the permanent material grown right in part of the crystalline structure does that make sense it's pretty crazy how they thought this stuff up it works in doing so we have just created what is known as an n type material an n-type material it has more electrons than holes why does it have more electrons than holes it has more electrons and holes let me go back a slide here because arsenic is a pentavalent material and we grew it in here so we grew in an atom that's got an extra electron in its valence shell now it's sharing the orbiting orbit if you will with the adjoining silicon atoms and it's grown right into the crystalline structure so we're going to say that it has more electrons than holes negative charge is going to be the what we call the majority carrier now this slide alone is probably about 15 different ways i could ask you questions from this slide if negative charge is the majority carrier what's going to be the minority carrier positive thank you positive i always used to get these questions wrong when i was a student you know negative charge is the majority carrier what is the minority carrier um arsenic it's like no we're talking about charge characteristics how many charge characteristics do you know about honestly honestly what are they but we could consider a characteristic can't we a neutral charge that means there's an equal number of positives and negatives so we could stretch it to that yeah so again look for look for look for stuff like that on my quizzes and i'm not trying to trip you up i'm just trying to prepare you for industry exams that are going to really make sure you got a grasp of this stuff because no longer are we no longer are studying the history of electronics you know who plays with this stuff on a daily basis a company called intel because this is how they make their microprocessors these are the materials that they use company called motorola right the microprocessors they manufacture this is what they manufacture them out of so this is no longer the history of electronics is what's really going down so in an n-type material what we're looking at here is a series circuit here's our voltage source this is n-type material and what's going to happen is electrons are going to want to flow through this material and the majority carriers are going to be these electrons why there's more grown in where did they come from we grew them in in the doping process by adding a pinch of a pentavalent dopamine make sense can you dig it you have a question what is the question no and to be honest with you but yeah knowing yes when when scientists beat their head against the wall trying to figure this stuff these are the materials that they came up with and quite frankly i don't know and i really don't want to know because it never helped me fix a piece of electronic equipment and knowing what the process is i'm sure you could do some additional reading on the subject but i don't know what drew the scientist specifically to those materials and what some of the other materials that had you know uh pentavalent materials that did not lend themselves well for that use good question but i don't know the answer hey check this out indium indium that was what type of a dopant trivalent meaning three electrons of the valence shell same thing you get your vat of pure silicon you stir it with your wooden spoon or your ladle or whatever you're doing with it in a clean room somehow i don't think you're gonna be using a wooden spoon but then you add a pinch a pinch of indium i've got some of that in my spice cabinet right indium a pinch of indium saffron rice with a pinch of indium i don't think you want to be adding indium to your rice when you grow it into a crystalline structure you grow in a hole what's that what's the definition of hole absence of electron you folks are like my best elec 120 students this quarter by far so we grow in an extra hole into the crystalline structure and create this covalent bond in doing so we create what's known as a p-type material p-type material has more holes than electrons positive charge is what we call the majority carrier if positive charge is the majority carrier what is my minority carrier indium no what's what's my what is my minority carrier it's going to be the electron right it's always going to be the opposite if one is majority the other is minority it's that simple you've only got two things electrons and holes there's nothing else no other moving parts and those parts aren't even really moving i guess maybe they are i guess in a solid state they are the holes move towards the negative terminal why does this happen they want to get filled holes want to get filled electrons want to fill the holes so in this particular case that's why they're going to migrate in summary semiconductor materials are materials with characteristics that fall between those of insulators and conductors literally right three electrons or fewer makes it a good conductor five or more makes it a good insulator i'm thinking of the number between three and five four five three point two that'll be a distractor on my quiz 3.2 i don't know i don't know how half the stuff works pure semiconductor materials include the use of germanium which you'll see out in industry silicon absolutely it's number one the most popular and carbon i don't even know if in my life my entire adult life i've ever even seen carbon i don't know don't know couldn't tell you beyond the scope silicon is used in most semiconductor devices valance indicates an atom's ability to gain or lose the electrons semiconductor materials have valance shells that are half full literally that way you could add to them or subtract from them by the use of dopings covalent bonding occurs when atoms share their valence electrons and that's how we grow crystals heat creates problems by allowing electrons to break their covalent bonds a hole is the absence of an electron in the valance shell current flow consists of both electron flow right and hole flow doping adds impurities to the mind no excuse me doping adds impurities to a semiconductor material the dopants that we use trivalent materials have atoms with three valence electrons they're used to make p-type material holes are the majority carrier that makes electrons the minority carrier pentavalent materials have five valence electrons they're used to make n-type material electrons the majority carrier holes therefore are the minority carrier nnp type sum n and p type semiconductor materials have a higher conductivity than pure semiconductor material remember that's how we increase the conductivity by inc by adding that dopant either trivalent or pentavalent anybody have any questions on anything in our first chapter okay let's go ahead and take a uh about a 10 minute 10 minute break and shortly after 20 after we will start up with chapter 73 pn junction diodes i get emotional it's your first real component absolutely why not absolutely we'll even do four or five all right let's rock and roll here chapter 20 which is the chapter that comes after 19 the chapter that comes before chapter 21. this is pn junction diodes and i get emotional because this is your first your first real component solid-state component that is it's your first real electronic component because when you figure everything you've studied up to this point capacitors inductors are they are they truly electronic are they electrical but this is truly electronic because this is made of solid-state stuff after completing this chapter you're going to be able to describe what a junction diode is and how it's made define the term depletion region and barrier voltage explain the difference between forward bias and reverse bias of a diode draw and label the schematic symbol for a diode describe three diode construction techniques identify the most common diode packages test diodes using an ohm meter now pn junctions pn junctions mobile charges remember how electrons and holes that drift from last chapter those are considered are mobile charges positive ions an atom that has more protons than electrons negative ions are an atom that has more electrons than protons remembering that again in the beginning everything was in a neutral natural state when we apply energy to matter we ionize it now there are always an equal number of mobile and ionic charges within n-type and p-type semiconductor materials diodes are created by joining n and p type materials together when these materials come in contact with each other they form a junction called a junction diode this is what it would kind of sort of look like if you were an artist trying to depict it you've got end material butted right up against p material pnn material we're going to create what's known as a depletion region the depletion region is near the junction where electrons and holes are depleted and extends only a short distance on either side of the junction so what's going to happen here is remember these electrons in the end material free electrons where a free electron is going to want to go to the p material to try to fill the hole but can they fill the holes not necessarily we've got p material holds where the hole is going to migrate to the end why they want to be filled by electrons so this is going to create this depletion region we call it sounds like something out of some sci-fi movie do not enter the depletion region also associated with the depletion region is what's going to be called the barrier voltage again it sounds like something out of a sci-fi thriller the barrier voltage we have opposite charges that build up on either side of the junction this is because of those mobile charges it can be represented as an external voltage source now when i say can be represented as an external voltage source don't try to get a volt meter a volt meter and measure the voltage of a diode can't measure this voltage this is a barrier voltage this is a voltage that must be overcome before you could get current to flow through this device you get it that's why it's called barrier voltage here's a new term for you it's called bias voltage bias means operating point so operating point voltage when a voltage is applied to a diode it is referred to as a bias voltage now in this particular case what we see here is our voltage source with a negative on the right current flows negative to positive so current is going to want to flow at an end material through to the p material and then complete the circuit path this is a series circuit right here is it not when we put a negative on the end material in a positive on the p material we are going to do what is known as forward biasing the diode forward biasing the diode that's why this is a new symbol i'm going to introduce to you i sub f current forward i sub f current forward when we do this when we apply forward bias to a diode this is where the diode kind of does its magic for those of you that come from a mechanical background some of you may be familiar with what's known as a one-way check valve a one-way check valve would be envision a a straw if you will with a little ball sitting on top of the straw as long as you're blowing through the straw that ball is going to become unseated and air will be allowed to pass but as soon as you suck on the straw what's going to happen to the ball it's going to seal it so that will only allow the air to flow one way but it won't be able to allow the air to flow the other way to check valve what's commonly known as a check valve a diode is the electrical equivalent of a check valve it's going to allow current to flow in this direction in this direction only so when we forward bias a diode current flows through it now forward bias when the current flows from an n-type to a p-type material the diodes forward biased germanium diodes require a minimum bias flow of this is a typo this should be 0.3 volts not .03 volts what i'm talking about is three you said it 300 millivolts or 0.3 this is actually an approximation so it might be a little less than that this is not gospel don't get in a circuit and say wow joe grenick over at their technical college or actually we just found out yesterday they changed the name they're going to change the name of this place not care about that it can be technical institute got that going for us maybe i'll get a new different colored lab coat so for germanium it's going to be 0.3 volts for silicon it's going to be 0.7 volts approximation and to be honest with you this that approximation could be anywhere 0.2.3 volts for germanium 0.6.7 volts for silicon what's that yeah some of it's the manufacturing the design what specific um what specifically the diode was designed to do so there's going to be some variance in that number so that's why we say this is just an approximation so if you know the 0.7 or the 0.3 for this class you'll pass okay when you get to the world of reality in the lab all bets are wrong you'll be close to these but it won't be exactly don't come banging on my door if you don't get point seven volts well joe you said in class or no i didn't say in class it's gonna be exactly point seven the forward voltage drop once a diode starts conducting a voltage drop known as a forward voltage drop occurs again for germanium it should be 0.3 volts for silicon 0.7 volts that means that voltage drop it's kind of the voltage that is going to be the price of doing business with a diode follow what i'm saying you're always going to get that voltage drop across the diode when you forward biasing because that's what i'm talking about right now you know what i'm talking about right what's up mr graham it's it still is it still is that's why these components are going to get hot yeah and there's going to be a maximum amount of power that can be dissipated that's why you raise a really good question basically he or she who has the largest diode physically the largest diode wins has the highest power because all diodes a little tiny diode is going to silicon diode is going to drop 0.7 volts across it a really big huge diode is going to drop 0.7 volts across that what's the difference between the two the amount of power they could handle yeah and you could always generally speaking go bigger but you can't go smaller so if you've got a big diode that explodes and you're going to replace it you need to replace it with a dial that is at least as equal to the original size or larger physically if you go smaller the smaller one will probably explode rapidly next thing we're talking about is reverse bias again the magic of diode when you reverse bias a diode the terminals are going to be reversed meaning we're going to put a positive on the end material and a negative on the p material when we do so what's going to happen is we end up where the diode will not conduct because we build a larger what did we call this remember from the sci-fi thriller do not enter the depletion zone the depletion region so when we reverse bias the diode we physically increase the depletion region so there's no way an electron trying to complete this circuit path is going to be able to make it through the depletion region so therefore the diode will be shut off in this condition i sub r current reverse it's going to act like an open it's going to act like an open there is going to be a small amount of a current that flows and what we're going to call that is leakage current but it's going to be really really really small you'll also see a little bit of current flowing because what are we doing here what's happening to the size of the depletion region it's getting bigger so if it's getting bigger how could it be possibly getting bigger something must be flowing and if something's flowing at any part in this circuit it's going to be flowing in every other part of the circuit because it is a what kind of circuit series circuit very good and remember the law with a series circuit whatever happens in one part is current's constant all that stuff that you learned about last quarter is really dependent you understand it now diode characteristics they can be damaged by excessive heat they can be damaged by ex