You should definitely continue to make these videos. I've watched all of them so far. You have a good way of explaining sometimes complex things in ways that people can understand.
Possibly the best walk-through video I've seen in a long time. You've got a talent for knowing how to explain things and you've helped me tremendously. Thank you
I’ve never run into a video that’s so perfectly matched my every need after so many hours of searching. Fantastic video can’t wait to watch all your videos. I’m euphoric.
Absolutely incredible instruction and teaching. Learned so much and definitely helped convince me to buy a linear power supply for my DAC. Thank you so much. You tube education rules!!!
Wow - Wonderful explanation of sinusoidal wave(AC voltage) conversion to smooth straight line (DC voltage) & devices used in the process. From one of the answers you gave in comments below, it is gathered that you a college student - I must say you hv brilliant teaching methods . Crystal clear explanation that is so easy for a person to understand and gainfully absorb ! 🙏 Complex things made easy - tons of thanks ! 🙏🙏🌹
WoW, i learnt and understood more in this video than i have in hours of others on the same subject, most take for granted that you understand everything else about electronics other than the subject at hand and end up talking well over my head, Very well done, Thanks. I'll now watch all your other videos and probably subscribe.
great , really great,,, your are the best so far , cause you are doing a detailed analysis and very good way demonstration, i will keep share your videos in my page.
Keep up the good work nice write up. Gave me some good ideas. I made a power supply but used alot of Capacitors after the Rectifier and my voltage went up a bit like 4 volts.
I'm glad you're posting videos again! I love your graphics. What software do you use to create them? Also how long does it take you to make a video? It looks like a lot of work. Keep up the great work!
I'm using PowerPoint 2013, but you can achieve the same quality graphics on 2007 or 2010. This video probably took me around 10 hours total to get all the graphics and animations right. Voicing it over takes a while too. Thanks.
P. Patil Electronics Symbols I made in PowerPoint. Not sure what you mean about pointers but it's all from PowerPoint. I would undoubtedly like to make more videos. I had more time last year when I was still in high school. Now, as a college student it is much more difficult to find time to make videos. I will try my best.
great video. can u show me how you can construct a 5v - 9v variable power supply using the LM 723 and an 18V CT 1A xfmr. I have problems coming with the right resistor values. Thanks
@9:20 ... VERY COOL animation! (I have no idea how people do stuff like that, but I know it's way harder and took WAY LONGER than the 2s the animation of wire wrapping around a transformer took to show!
The LM-723 is still widely used in power supplies as it also has a current limiting capability. It has a max voltage of 40V and cost almost nothing. The LM338 is 5A.
Thanks again for making these videos. I have a quick question. At 16:39 you say that the current can't flow through the bottom left diode because it is reverse biased, but it can flow through the diode in the bottom right. I don't see or understand why it can't go through the bottom left diode. Aren't both the bottom diodes oriented in the same way?
Current only flows across a thingy that has a voltage difference across it. If you have a chunk of wire connected to + of your power supply on one end and connected to nothing on the other end - no current will flow through it because if you put a voltmeter across this chunk of wire it will read 0V. Same thing if you put this same chunk of wire where both of it's ends are connected to + of your power supply: one end of it is at 12V (for example) and another end of it is at 12V too! Voltage difference across this wire will be 0V so no current will flow. Same thing applies to the diode in the presentation: no current will flow through it since there is no voltage difference across it - both of it's leads are connected to the same potential.
Sorry, I'm sure if this were a refresher instead of my first intro I'd get [ALL of this] but not the voltage regulator diagram. The Op Amp's job was unclear, as were the roles of the resistors. Particularly, the ROLE of the 2nd resistor and why we're making a SHORT to ground ? Or why we care to control the voltage of the short? V Ref seems like a "dead-end" that'd just get hot? What's the collector / emitter doing ...? And, what're the "necessary & sufficient" conditions for the "out" path we're meeting ...?
The two resistors form a voltage divider, with the voltage at the mid-point being the output voltage scaled by the ratio of the resistors. In the simplest form of a voltage regulator, the resistors are not needed, but in the vast majority of practical implementations, they are necessary. In the simplest form of a voltage regulator, Vref is chosen to be exactly the output voltage you require. The function of the op-amp is the compare the *actual* output voltage to the precise and known value of Vref. Vref is usually a band-gap voltage reference with excellent voltage accuracy and stability, but it cannot source any significant current. The op-amp finds the "error voltage", i.e. the difference between the actual output voltage and the set-point voltage (Vref) and then adjusts it's output (base drive current) to adjust the collector-emitter voltage drop. It adjusts the collector-emitter voltage drop such that the the op-amp inputs are exactly the same...that is to make Vout = Vref. Without the voltage divider, you need a separate Vref part for every output voltage you wish to create. So, if you wanted a 5V output, you need a 5V reference. If you want a 5.1V output, you'd need a 5.1V reference. It's not very flexible, among other things. So, the prevailing approach is to use a few standardized Vref value and an accompanying voltage divider to make any output voltage you desire (within practical limits). Popular band-gap reference values are 1.25V, 2.5V, and 5V. You set up the voltage divider such that the mid-point of the divider will equal the reference voltage (i.e. 2.5V) when the top of the divider (the output voltage) equals the desired value. For example, suppose you have a 2.5V reference, and desire a 5V output voltage. If we set the bottom resistor to 1K, then we need to set the top resistor to 1K in order to get 2.5V @ the mid-point when the output voltage is at 5V. 5V * [1K/(1K + 1K)] = 2.5V Or, let's suppose you have a 1.25V reference, and desire a 5V output voltage. If we again set the bottom resistor to 1K, then we need to set the top resistor to 3K to get 1.25V at the mid-point (the inverting terminal of the op-amp). 5V * [1K/(1K + 3K)] = 1.25V
@@SolidStateWorkshop Are you going to make anymore videos? They are much better explained than even my classes. I bet you could explain AC circuits and semiconductors super well. Thanks!!!
Is an Op Amp an Exclusive or Gate..? Or just in this circumstance..? (I'm familiar with XOR gates only because they're the foundation of RAID truth tables, not electronic knowledge. lol)
No, an op-amp is an amplifier. The output is proportional to the difference between the + (non-inverting) and - (inverting) terminals. When the difference between + and - is large, the output is large. The difference between + and - represents the "error signal". When the error (expected voltage - actual voltage) is large, then the op-amp provides a large correction signal to adjust the drive current of the transistor.
@@SolidStateWorkshop You're awesome man. Thank you SO MUCH for you actually answering my dumb questions. This is my first attempt at familiarizing with electricity and I'm pretty sure that my "electricity IQ" is about 20 points lower than every other field. I'm already watching your videos a 2nd time in hopes 'rote' will have some utility. I'm assuming you either have a Masters or you're an EE who works in the field ... either way, thank you a TON.
Great stuff. One thing though, about the theory of transformers. Is not that "the theory has been proven so it's not a theory anymore", a theory explains to you how something works, just like the theory of operation of pretty much everything. You need to understand the theory of something, if you want to understand how something works.
Gordon Freeman Ya! As if the remainder of the video, he spent time producing for the public to gain knowledge, wasn't enough..... We all appreciate and most definitely needed you to expand on "theory" Please be sure to keep us informed in the future. We wouldn't want to Miss any Technicalities caught in one's videos. Thanks!!!!🤐
My question of the day is regarding the 79XX series, such as the 7924. I see it's considered a negative voltage regulator versus a positive in terms of how it wires up. Can i construct a power supply using this versus the other? I can't seem to find clarity as to why 78XX is preferred since i always thought D.C flows from negative to positive why the 79XX isn't the more common. Any input is appreciated, thanks!
If your circuit has a positive voltage (with respect to that circuit's ground), you use a LM78xx regulator to reduce the voltage to a smaller positive voltage. For example, +12V --> +5V. If your circuit has a negative voltage (with respect to that circuit's ground), you'd use an LM79xx regulator to reduce the voltage to a smaller negative voltage. For example, -12V --> -5V. I suspect you might have some other misconceptions about "negative" and "positive" in this context. I'll try to explain further if the above does not make sense.
@@SolidStateWorkshop Thanks for your response, it's always good to see publisher support interest in videos which were put out some time ago. I probably have more misconceptions than I should but try to move forward anyway. The crux of this was I have some 7924's and would like to make a supply from some 24vac transformers I also have, this would all just be driving output terminals which would then supply other outside equipment, so everything here is all just 24 volt with no steps up or down once I leave the main transformer. As a novice it seems that perhaps either 78XX or 79XX would work to regulate the overall current of my output but then again I'm limited to just wiring up low voltage access control systems in my occupation after a long separation from my childhood building radio shack kits. Therefore my component level understanding of these interactions is weak since as a kid I was just soldering what I was supposed to and as and adult it's been mostly "doorbell circuits" and terminal strip connections. Moving back into project box designs and (hopefully) electronic refurbishing I've been attempting to self learn and be less dangerous!
@@LockRocker Either 7824 and 7924 could be used to create a 24VDC supply. The key is: If you are only creating a single polarity supply (i.e you just want +24V *or* -24V), then either part would work fine. But, if you want to make a bipolar supply (a.k.a. a split supply) which simultaneously can supply +24V and -24V, then you need to use a 7824 for the positive supply and 7924 for the negative supply. A split supply usually uses a center tapped transformer (+ bridge rectifier). As mentioned, if you are making split supply with a center tapped transformer, you cannot use 7924 for both. This has to do with internal structure of the regulators, and how they are able to sink and source current. Current can only go *into* the OUT pin of a negative regulator (79xx) and current can only go *out of* the OUT pin of a positive voltage regulator (78xx). (Talking about conventional current.) Otherwise, if you only need a single supply, (i.e. just a single +24V or -24V supply), either types can be used. It may take some mental gymnastics to prove to yourself that the "negative voltage regulator" can produce a positive voltage. But remember that voltage is *relative*. It is the potential difference between two points in a circuit. For example, if you are measuring voltage with a multimeter, you can change whether you read a positive or negative voltage by flipping the red and black leads. Similarly, whether the output of the voltage regulator is negative or positive just depends on what circuit node you want to call "common" or "ground". According to the 78xx and 79xx datasheet, the center pin is called "GND", but that's only a name, based on the typical way it will be used. If you supply a negative voltage (w.r.t. to the GND pin) to 7924, the output will be negative with respect to the GND pin of 7924. But, if you decide to call the OUT pin "0V" or "common" instead, well now there is a positive voltage at the GND pin with respect to the OUT pin ("0V"). Keep in mind you still need to feed 7924 a voltage on it's IN pin which is negative with respect to its GND pin. That's the only way it works. But, the output can be considered as positive or negative, depending on what you want to call "0V". But remember, this arbitrary flipping of what's "0V" or "common" only works when you have a single polarity supply.
@@SolidStateWorkshop Fantastic, this all makes sense to me. I had previously seen the "bipolar" schematics and also have come to better understanding of the whole conventional current versus electron flow debacle. I'll just proceed and make a supply up with the 7924 version just for the experience of it all. I really appreciate your expertise and hope that those around you realize how blessed they are to have you around! Thanks again, you rock!
@@LockRocker Yeah basically you just wire up the bottom half (negative supply part) of those "bipolar schematics", and then just call it a positive supply. Thanks for your kind words! Appreciate it.
At about 21 minutes you discuss the current going through 4 discrete diodes as about 1 "amp", then the GBU-type bridge as about 3 to 5 "amps" and then mention the high power bridges if you need 25 to 30 "amps". Isn't this a slip of the tongue and you mean "volts"? Otherwise the presentation has been excellent!
Peter thanks for the feedback. However, "current" is indeed what I was talking about there. Just about all diodes, whether used individually, or in a diode bridge are safe to use with very high voltages. For example, a standard 1N1004 diode has a peak reverse voltage of 400V, meaning it can block current from passing if it is reversed biased with a voltage up to 400V. The current is physically the amount of charge the diode can pass, and not destroy itself due to overheating. The larger the package the more heat it can dissipate.
SolidStateWorkshop Keep up the good work! I've always liked the descriptive: "this board is fried". Your explanation makes sense. Bet you're a big Tesla fan. Edison moans.
Very thorough video thanks. I have a wall adapter which says 12V 500A, but measuring the voltage with a multimeter reveals it is 19V. Can anyone explain this? I bought a cheap replacement which was 12V 500A but it measures 12v and instead of charging it actually sucks the charge out!
If it is an unregulated supply (without a voltage regulator) then an open circuit reading might show something higher than the printed value. The more current drawn from it, the more voltage is dropped internally in the adapter..and thus under full load you might get down to like 12V.
Thanks. You were right. The manufacturer got back to me and said that the unregulated supply puts out higher voltage than regulated, so if I buy a regulated one I need to get 15V instead of 12V so it is powerful enough to trigger the charging circuitry.
@11:00 Anyone else who wonders how a transformer's in+out are both wrapped around a COMMON iron core without CONDUCTING electricity..? Each of the wires are INSULATED ... and thus, only the magnetic lines of flux are interacting. :-). (had to look it up). Of course, though the 'input wire with 120v ac' only transmits half it's voltage, the 'return line' of the circuit just retains a larger percent of it's input energy (however it happens) -- but consistent with thermodynamics 'laws of conservation' ...
Howdy. With all due respect. With the circuit you show the op. amp. must deliver 0,7 V over the output to the power transistor base. The supply to the op. amp. needs to be at least 2V higher than the output at all times. Change the power transistor to a PNP item and switch emitter and collector and you will have a working circuit. The op. amp. will need an output resistor and a zener diode too to prevent the output going too high destroying the op. amp. Your circuit is a base current "pusher" circuit. My suggestion is a base current "puller" circuit. Regards.
Thanks! I have a zener diode that failed on a hard drive I'm trying to fix right now in fact ... and was just told that manufactures like to mislead us when repairing them with mislabelled values!!?? lol. Either way, this is an intro for me -- and as I suspected, it seems like most of the viewers are reliving "learning" or verifying the creator did it correctly ... where as for me (ignorant of the topic) I have a TON of questions; where pronouns and slightly vague descriptions are fine amongst people who already have shared concepts they're confirming with each other, things are completely different for those of us to whom this is alien.
should nail home that the windings are in fact insulated with shellac as and insulator when the insulation overheats than whoops. you stress ferrous core but forgot insulation. the mutual inductance is cutting B fields during changes in direction.
Jim Simon Indeed. This is originally a presentation I did for a high school class when I perhaps didn’t know any better. I now work full time in switch-mode power supply design, so this video makes me cringe a bit too.
Well I've scanned through several comments over several years and agree you produce a good video but you make some mistakes . the first one transformer's can be used with pulsed dc as well as ac . Your pointer sucks its out of synch.
You should definitely continue to make these videos. I've watched all of them so far. You have a good way of explaining sometimes complex things in ways that people can understand.
Thank you. When I'm home from school with time to spare and my recording equipment, I will work on some content.
@@SolidStateWorkshop Could you please make a video of logic gates?
Possibly the best walk-through video I've seen in a long time. You've got a talent for knowing how to explain things and you've helped me tremendously. Thank you
I’ve never run into a video that’s so perfectly matched my every need after so many hours of searching. Fantastic video can’t wait to watch all your videos. I’m euphoric.
Absolutely incredible instruction and teaching. Learned so much and definitely helped convince me to buy a linear power supply for my DAC. Thank you so much. You tube education rules!!!
beautiful presentation! Simple and clear.
100% pure understand presentation.
thank you!
Dang, I wish you made more. Excellent!
Awesome. Great clarity. Thanks.
thanks for explaining power supplies in a detailed manner... :)
you've helped me out with my degree thesis. i really do appreciate it. thanks a lot.
Wow - Wonderful explanation of sinusoidal wave(AC voltage) conversion to smooth straight line (DC voltage) & devices used in the process.
From one of the answers you gave in comments below, it is gathered that you a college student - I must say you hv brilliant teaching methods . Crystal clear explanation that is so easy for a person to understand and gainfully absorb ! 🙏
Complex things made easy - tons of thanks ! 🙏🙏🌹
This is an amazing video! Thanks for taking the time to help us beginners.
Very nicely done... look forward to seeing more videos from you. Good luck with school too!
I thoroughly enjoyed this tutorial, it was nicely done. Big up to you mate.
Tim, it's lamenting we don't see anymore of your wonderful work. I hope you put out more videos in the near future again.
Please!! could you make more videos like these. I've subscribed and would love to watch some more. Thanks.
simple and easy to understand.Thank you. I will recommend this video to my friends
This was really informative! Thank you
Best explanation on internet till this day!!!
A very good video. I would like to see a similar one concerning Switched Mode Power Supplies.
Your presentation is very intuitive and clear, excellently work here
The explanation was too good...' would like to view more of ur vedios..👍
WoW, i learnt and understood more in this video than i have in hours of others on the same subject, most take for granted that you understand everything else about electronics other than the subject at hand and end up talking well over my head, Very well done, Thanks. I'll now watch all your other videos and probably subscribe.
Wow! Thank you!
P.S. You are a quite good explanator.
Amazing tutorials! You definitely must create more like these! Your explanations are quite understandable :) I hope you'll find time to make more :)
Thank you so much for this ..really i understand it so well... now i can go to the exam safely :D :D
Good job making this video! Thanks:)
Great video, thanks!
very educational, good job!
This is a great video. I'm working on a power supply for my linear class and this was a huge help. Thanks so much for posting it. :)
You're welcome. Glad it helped!
awesome explanation!!!
Wow good stuff!
great , really great,,, your are the best so far , cause you are doing a detailed analysis and very good way demonstration, i will keep share your videos in my page.
Great video.. very helpful. Thank you so much.
Thank you for this, you helped me a lot
I like when your clone walked in the recording booth at 43:02
great vids...very good explanations. tks
Excellent. Very clear explanation
Very nice. Please add more videos
You are too good....thanks a lot....
great videos.thanks
Great videos mate, where did you go? you should definitely make more of these.
Really good man. I'm a new comer and this was really helpful, str8 up
wow, thanks ...you are the best
what's special and brilliant about your lessons is that you suppose that we know nothing and explains every little detail
good stuff merci pour le partage.
Great, thank you very much :)
great job thanks
love it
Very useful 😊
Very good, Helpful for viewers at different skill and knowledge levels. +1sub
Thank you. I’m glad it helped!
Keep up the good work nice write up. Gave me some good ideas. I made a power supply but used alot of Capacitors after the Rectifier and my voltage went up a bit like 4 volts.
Love that the transformer has a shadow.
I'm glad you're posting videos again! I love your graphics. What software do you use to create them? Also how long does it take you to make a video? It looks like a lot of work. Keep up the great work!
I'm using PowerPoint 2013, but you can achieve the same quality graphics on 2007 or 2010. This video probably took me around 10 hours total to get all the graphics and animations right. Voicing it over takes a while too. Thanks.
SolidStateWorkshop
Where did you get all those electronics symbols? and fancy pointers?
And why have you stopped creating any more videos?
P. Patil Electronics Symbols I made in PowerPoint. Not sure what you mean about pointers but it's all from PowerPoint.
I would undoubtedly like to make more videos. I had more time last year when I was still in high school. Now, as a college student it is much more difficult to find time to make videos. I will try my best.
great video. can u show me how you can construct a 5v - 9v variable power supply using the LM 723 and an 18V CT 1A xfmr. I have problems coming with the right resistor values. Thanks
thenx on good educational video
@9:20 ... VERY COOL animation!
(I have no idea how people do stuff like that, but I know it's way harder and took WAY LONGER than the 2s the animation of wire wrapping around a transformer took to show!
The LM-723 is still widely used in power supplies as it also has a current limiting capability. It has a max voltage of 40V and cost almost nothing. The LM338 is 5A.
Nicely done bro,I agree with every one else's comments! I'm assuming their all positive.
Good stuff. I was better able to understand some of the ideas with the oscilloscope readings as a visual aid.
Thanks again for making these videos. I have a quick question. At 16:39 you say that the current can't flow through the bottom left diode because it is reverse biased, but it can flow through the diode in the bottom right. I don't see or understand why it can't go through the bottom left diode. Aren't both the bottom diodes oriented in the same way?
Current only flows across a thingy that has a voltage difference across it. If you have a chunk of wire connected to + of your power supply on one end and connected to nothing on the other end - no current will flow through it because if you put a voltmeter across this chunk of wire it will read 0V. Same thing if you put this same chunk of wire where both of it's ends are connected to + of your power supply: one end of it is at 12V (for example) and another end of it is at 12V too! Voltage difference across this wire will be 0V so no current will flow. Same thing applies to the diode in the presentation: no current will flow through it since there is no voltage difference across it - both of it's leads are connected to the same potential.
Perfect answer. Thank you, I needed that
Just in case your question doesn't get answered (from my understanding) it's because there's two positive (hot) wires connected to it.
Can you please do a presentation for Dc-Dc converter, and Dc-Ac converter? Thank you
And AC-to-AC converters (cycloconverters).
Great, Ths
Thank you
Please!! could you make more videos like these
Sorry, I'm sure if this were a refresher instead of my first intro I'd get [ALL of this] but not the voltage regulator diagram.
The Op Amp's job was unclear, as were the roles of the resistors.
Particularly, the ROLE of the 2nd resistor and why we're making a SHORT to ground ?
Or why we care to control the voltage of the short?
V Ref seems like a "dead-end" that'd just get hot?
What's the collector / emitter doing ...?
And, what're the "necessary & sufficient" conditions for the "out" path we're meeting ...?
The two resistors form a voltage divider, with the voltage at the mid-point being the output voltage scaled by the ratio of the resistors. In the simplest form of a voltage regulator, the resistors are not needed, but in the vast majority of practical implementations, they are necessary. In the simplest form of a voltage regulator, Vref is chosen to be exactly the output voltage you require. The function of the op-amp is the compare the *actual* output voltage to the precise and known value of Vref. Vref is usually a band-gap voltage reference with excellent voltage accuracy and stability, but it cannot source any significant current. The op-amp finds the "error voltage", i.e. the difference between the actual output voltage and the set-point voltage (Vref) and then adjusts it's output (base drive current) to adjust the collector-emitter voltage drop. It adjusts the collector-emitter voltage drop such that the the op-amp inputs are exactly the same...that is to make Vout = Vref.
Without the voltage divider, you need a separate Vref part for every output voltage you wish to create. So, if you wanted a 5V output, you need a 5V reference. If you want a 5.1V output, you'd need a 5.1V reference. It's not very flexible, among other things. So, the prevailing approach is to use a few standardized Vref value and an accompanying voltage divider to make any output voltage you desire (within practical limits). Popular band-gap reference values are 1.25V, 2.5V, and 5V. You set up the voltage divider such that the mid-point of the divider will equal the reference voltage (i.e. 2.5V) when the top of the divider (the output voltage) equals the desired value.
For example, suppose you have a 2.5V reference, and desire a 5V output voltage. If we set the bottom resistor to 1K, then we need to set the top resistor to 1K in order to get 2.5V @ the mid-point when the output voltage is at 5V. 5V * [1K/(1K + 1K)] = 2.5V
Or, let's suppose you have a 1.25V reference, and desire a 5V output voltage. If we again set the bottom resistor to 1K, then we need to set the top resistor to 3K to get 1.25V at the mid-point (the inverting terminal of the op-amp). 5V * [1K/(1K + 3K)] = 1.25V
@@SolidStateWorkshop Are you going to make anymore videos? They are much better explained than even my classes. I bet you could explain AC circuits and semiconductors super well. Thanks!!!
Great video, make more please. That would make ma very happy.
Is an Op Amp an Exclusive or Gate..? Or just in this circumstance..?
(I'm familiar with XOR gates only because they're the foundation of RAID truth tables, not electronic knowledge. lol)
No, an op-amp is an amplifier. The output is proportional to the difference between the + (non-inverting) and - (inverting) terminals. When the difference between + and - is large, the output is large. The difference between + and - represents the "error signal". When the error (expected voltage - actual voltage) is large, then the op-amp provides a large correction signal to adjust the drive current of the transistor.
@@SolidStateWorkshop
You're awesome man. Thank you SO MUCH for you actually answering my dumb questions.
This is my first attempt at familiarizing with electricity and I'm pretty sure that my "electricity IQ" is about 20 points lower than every other field. I'm already watching your videos a 2nd time in hopes 'rote' will have some utility.
I'm assuming you either have a Masters or you're an EE who works in the field ... either way, thank you a TON.
Great stuff.
One thing though, about the theory of transformers.
Is not that "the theory has been proven so it's not a theory anymore", a theory explains to you how something works, just like the theory of operation of pretty much everything.
You need to understand the theory of something, if you want to understand how something works.
Gordon Freeman
Ya! As if the remainder of the video, he spent time producing for the public to gain knowledge, wasn't enough..... We all appreciate and most definitely needed you to expand on "theory"
Please be sure to keep us informed in the future. We wouldn't want to Miss any Technicalities caught in one's videos.
Thanks!!!!🤐
My question of the day is regarding the 79XX series, such as the 7924. I see it's considered a negative voltage regulator versus a positive in terms of how it wires up. Can i construct a power supply using this versus the other? I can't seem to find clarity as to why 78XX is preferred since i always thought D.C flows from negative to positive why the 79XX isn't the more common. Any input is appreciated, thanks!
If your circuit has a positive voltage (with respect to that circuit's ground), you use a LM78xx regulator to reduce the voltage to a smaller positive voltage. For example, +12V --> +5V. If your circuit has a negative voltage (with respect to that circuit's ground), you'd use an LM79xx regulator to reduce the voltage to a smaller negative voltage. For example, -12V --> -5V.
I suspect you might have some other misconceptions about "negative" and "positive" in this context. I'll try to explain further if the above does not make sense.
@@SolidStateWorkshop Thanks for your response, it's always good to see publisher support interest in videos which were put out some time ago. I probably have more misconceptions than I should but try to move forward anyway. The crux of this was I have some 7924's and would like to make a supply from some 24vac transformers I also have, this would all just be driving output terminals which would then supply other outside equipment, so everything here is all just 24 volt with no steps up or down once I leave the main transformer. As a novice it seems that perhaps either 78XX or 79XX would work to regulate the overall current of my output but then again I'm limited to just wiring up low voltage access control systems in my occupation after a long separation from my childhood building radio shack kits. Therefore my component level understanding of these interactions is weak since as a kid I was just soldering what I was supposed to and as and adult it's been mostly "doorbell circuits" and terminal strip connections. Moving back into project box designs and (hopefully) electronic refurbishing I've been attempting to self learn and be less dangerous!
@@LockRocker Either 7824 and 7924 could be used to create a 24VDC supply. The key is: If you are only creating a single polarity supply (i.e you just want +24V *or* -24V), then either part would work fine. But, if you want to make a bipolar supply (a.k.a. a split supply) which simultaneously can supply +24V and -24V, then you need to use a 7824 for the positive supply and 7924 for the negative supply. A split supply usually uses a center tapped transformer (+ bridge rectifier). As mentioned, if you are making split supply with a center tapped transformer, you cannot use 7924 for both. This has to do with internal structure of the regulators, and how they are able to sink and source current. Current can only go *into* the OUT pin of a negative regulator (79xx) and current can only go *out of* the OUT pin of a positive voltage regulator (78xx). (Talking about conventional current.)
Otherwise, if you only need a single supply, (i.e. just a single +24V or -24V supply), either types can be used. It may take some mental gymnastics to prove to yourself that the "negative voltage regulator" can produce a positive voltage. But remember that voltage is *relative*. It is the potential difference between two points in a circuit. For example, if you are measuring voltage with a multimeter, you can change whether you read a positive or negative voltage by flipping the red and black leads. Similarly, whether the output of the voltage regulator is negative or positive just depends on what circuit node you want to call "common" or "ground". According to the 78xx and 79xx datasheet, the center pin is called "GND", but that's only a name, based on the typical way it will be used. If you supply a negative voltage (w.r.t. to the GND pin) to 7924, the output will be negative with respect to the GND pin of 7924. But, if you decide to call the OUT pin "0V" or "common" instead, well now there is a positive voltage at the GND pin with respect to the OUT pin ("0V").
Keep in mind you still need to feed 7924 a voltage on it's IN pin which is negative with respect to its GND pin. That's the only way it works. But, the output can be considered as positive or negative, depending on what you want to call "0V". But remember, this arbitrary flipping of what's "0V" or "common" only works when you have a single polarity supply.
@@SolidStateWorkshop Fantastic, this all makes sense to me. I had previously seen the "bipolar" schematics and also have come to better understanding of the whole conventional current versus electron flow debacle. I'll just proceed and make a supply up with the 7924 version just for the experience of it all. I really appreciate your expertise and hope that those around you realize how blessed they are to have you around! Thanks again, you rock!
@@LockRocker Yeah basically you just wire up the bottom half (negative supply part) of those "bipolar schematics", and then just call it a positive supply.
Thanks for your kind words! Appreciate it.
At about 21 minutes you discuss the current going through 4 discrete diodes as about 1 "amp", then the GBU-type bridge as about 3 to 5 "amps" and then mention the high power bridges if you need 25 to 30 "amps". Isn't this a slip of the tongue and you mean "volts"? Otherwise the presentation has been excellent!
Peter thanks for the feedback. However, "current" is indeed what I was talking about there. Just about all diodes, whether used individually, or in a diode bridge are safe to use with very high voltages. For example, a standard 1N1004 diode has a peak reverse voltage of 400V, meaning it can block current from passing if it is reversed biased with a voltage up to 400V. The current is physically the amount of charge the diode can pass, and not destroy itself due to overheating. The larger the package the more heat it can dissipate.
SolidStateWorkshop Keep up the good work! I've always liked the descriptive: "this board is fried". Your explanation makes sense. Bet you're
a big Tesla fan. Edison moans.
god bless
Very thorough video thanks.
I have a wall adapter which says 12V 500A, but measuring the voltage with a multimeter reveals it is 19V. Can anyone explain this?
I bought a cheap replacement which was 12V 500A but it measures 12v and instead of charging it actually sucks the charge out!
If it is an unregulated supply (without a voltage regulator) then an open circuit reading might show something higher than the printed value. The more current drawn from it, the more voltage is dropped internally in the adapter..and thus under full load you might get down to like 12V.
Thanks. You were right. The manufacturer got back to me and said that the unregulated supply puts out higher voltage than regulated, so if I buy a regulated one I need to get 15V instead of 12V so it is powerful enough to trigger the charging circuitry.
@11:00 Anyone else who wonders how a transformer's in+out are both wrapped around a COMMON iron core without CONDUCTING electricity..? Each of the wires are INSULATED ... and thus, only the magnetic lines of flux are interacting. :-). (had to look it up).
Of course, though the 'input wire with 120v ac' only transmits half it's voltage, the 'return line' of the circuit just retains a larger percent of it's input energy (however it happens) -- but consistent with thermodynamics 'laws of conservation' ...
Just noticed,this is 5 years ago lol ,so I better check your recent stuff,I bet u are going great guns now.
Until the cows come home :)))
Howdy. With all due respect.
With the circuit you show the op. amp. must deliver 0,7 V over the output to the power transistor base. The supply to the op. amp. needs to be at least 2V higher than the output at all times.
Change the power transistor to a PNP item and switch emitter and collector and you will have a working circuit. The op. amp. will need an output resistor and a zener diode too to prevent the output going too high destroying the op. amp.
Your circuit is a base current "pusher" circuit.
My suggestion is a base current "puller" circuit.
Regards.
Thanks! I have a zener diode that failed on a hard drive I'm trying to fix right now in fact ... and was just told that manufactures like to mislead us when repairing them with mislabelled values!!?? lol.
Either way, this is an intro for me -- and as I suspected, it seems like most of the viewers are reliving "learning" or verifying the creator did it correctly ... where as for me (ignorant of the topic) I have a TON of questions; where pronouns and slightly vague descriptions are fine amongst people who already have shared concepts they're confirming with each other, things are completely different for those of us to whom this is alien.
@@trumanhw Howdy.
Yes.
Regards.
should nail home that the windings are in fact insulated with shellac as and insulator when the insulation overheats than whoops. you stress ferrous core but forgot insulation. the mutual inductance is cutting B fields during changes in direction.
Jim Simon Indeed. This is originally a presentation I did for a high school class when I perhaps didn’t know any better. I now work full time in switch-mode power supply design, so this video makes me cringe a bit too.
Where the hell was youtube when I was doing engineering??
Well I've scanned through several comments over several years and agree you produce a good video but you make some mistakes . the first one transformer's can be used with pulsed dc as well as ac .
Your pointer sucks its out of synch.
Way too many commercials. I’ll make sure not watch any more videos.