EEVblog 1397 - DC Voltage & Current Source Theory

Electronics fundamentals video. Basic DC Voltage and Currenct Source theory.
Thevenin and Norton Theorms.
And compliance voltage demonstration on current sources.
Follow-up videos:
DC Fundamentals Playlist: • Electronics Tutorial -...
Mesh & Nodal Circuit Analysis • EEVblog #820 - Mesh & ...
Kirchhoff's Laws Tutorial: • EEVBlog #819 - Kirchho...
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[@treyistheway101]

I would have paid double for my electrical engineering degree to have this guy explain it instead. Great to refresh and relearn things!

[@lucvanhove9639]

Sure, here in Belgium, the minister of education skip electronics and replace it for electromechanica. In the high tech industry, they need electronics, so the new employees receice a one week powerpoint course from some idiote (copy paste from google) . They all receive a degree, but 🤦‍♂️🤦‍♂️🤦‍♂️🤦‍♂️🤦‍♂️

[@p_mouse8676]

I actually would have finished my degree. The morons back in the day were so much in their own theoretical bubble, absolutely no one understood anything from those courses, let alone the practicality of it. I figured it out myself on my own way. It's actually actually extremely powerful when you dive in equivalent circuits for mechanical analogies.

[@TeacherBrunoOneil]

Me too. My professors were really bad at teaching. They always wanted to approach circuit analysis mathematically first. That sucks. I guess I studied that in circuit analysis I.

[@TeacherBrunoOneil]

@Sean M more important than what you will teach is how you will teach it. The focus on teaching isn't the subject but how much of it the students will pick. That's how I see the situation. Today I am an engineer but at the beginning, if you have a teacher who has no good didatics to teach, chances are the most students will take longer to learn. My teachers' method were too conservative they focused on calculus nearly all the time. That's important but you choose when you will use it, especially with beginners.

[@ki4dbk]

@@lucvanhove9639 yeah. It sucks how the authoritarian classroom environment often takes the fire, joy and magic out of learning science and technology.

[@EEVblog]

Sorry, re-upload for extra clarification. Saves hundreds of comments over the next few years.

[@Ujwal5555]

what was the problem with the original video ? Sorry, I couldn't watch the original one.

[@power-max]

@@Ujwal5555 Here is the link to the original one: kzbin.info/www/bejne/g5eTf6B5i65labs but he made it private so oh well. I did watch the first half of the original one and I think he is mostly clarifying his erroneous claim that the solar panel is a constant voltage source. Most other people model it as a constant current source with a 'compliance voltage' although in the end it doesn't really matter.

[@chitlitlah]

I managed to see the original before it was taken down, so I wonder what's different so I don't have to rewatch it.

[@EEVblog]

@@Ujwal5555 Just some extra clarification on solar cells and their CV/CC characteristic curve.

[@Ujwal5555]

@@EEVblog Thanks for the clarification ! Dave you should make a video about explaining how micro inverter works and they sync with the grid. Maybe tear one down as well.

[@a1nelson]

Really pleased to see a new fundamentals video. They're great. Looking forward to more. Thanks

[@discontinuity7526]

Hey Dave, just graduated electrical engineering with distinction and got employed, very glad I had the support of you and your content for the ride, looking at this thumbnail made me think back to the recent past where I struggled with all of this, and I'd always turn to your channel for help, thank you for doing such great work Dave

[@EEVblog]

Glad to hear!

[@roseelectronics4582]

@@EEVblog You deleted my best comment, Dave.

[@EEVblog]

@@roseelectronics4582 If that was on the previous video, that's because I had to re-upload and all comments are lost. It's the way youtube works. I don't just delete comments.

[@TeacherBrunoOneil]

We all struggled. Lol and that's for sure.

[@ArcFlashWarning]

Please do more of these. We could all use the reinforcements just as footballs Vince Lombardi reinforced what a football was to his Super Bowl teams

[@AllElectronicsChannel]

A class by Davenin 😁

[@soniclab-cnc]

It doesn’t matter how many times you go over this stuff. You can always learn more and gather a better understanding of the fundamentals. I would have loved to have Dave as my instructor...

[@DarkMatterX1]

Facts. My electrical theory prof was a working engineer at Motorola. Smart guy, knew his stuff, but wasn't the best at getting information across.

[@mikemike7001]

A nice blend of theory and practice, where Dave goes the extra mile (as usual!) and takes us from the whiteboard to the bench, explained in the way I think an engineer thinks. Looking forward to more.

[@captiveimage]

Superb. Theory with a simple, well delivered explanation followed up with practical demonstration that reiterates the theory. Love these fundamentals vids.

[@stewartthompson72]

Love these kind of videos Dave. It has been a lot of years since I thought about those theorems. Keep it up!

[@laboratoriodeprojetos1351]

Ótimo vídeo sobre alguns fundamentos da eletricidade. Abraço Dave.

[@twobob]

Solid, and thorough. Articulate reiteration and passionate precis. Appreciated.

[@KevinNguyen1]

If you thought you have seen this video before, then you did see it before! This is a reupload of the video with some extra clarification as EEVblog has said.

[@Guineh76]

Yeah. He pulled the original video as I was watching it and I was really enjoying it, too. Lol

[@karpiewscy]

Thanks a lot for the clarification. I watched it around 1 am tonight (Europe) to fall asleep, and when I woke up and could not find it even in the YT history I thought I dreamed it all up! Just wasn't sure how I could make up the Norton's equivalent. I remembered only the Thevenin theorem from my high school :D

[@jeffm2787]

Always good to see a fundamentals video. 👍

[@amirmograbi]

I've never seen it explained so well, thank you !

[@johnmanzang7272]

Another well explained and great fundamentals video! Thank you very much!

[@Francesco-bu1hh]

Thank you Dave. Please do more of these!

[@jgurtz]

Funny thing about that guy is his name is a real tongue twister when trying to say it in English, but actually rolls right off like buttah when saying it in French. Thanks for the explainer Dave!

[@jaguarpaw1638]

love this tutorial so happy please do more. Although I submitted a piece of coursework about Thevenin's theorem but was marked down for using the term "good enough for Australia"

[@omniyambot9876]

I need to comment so Dave knows that these videos are useful especially for students like me. Electronics engineering for the win!

[@stevenspmd]

Yes more fundamentals please. I've been learning on my own using YT videos for the last year and just signed up for the edx self study electronics course. For me, I do find it is quite easy to gloss over terms like super position and linearity but taking the time to get familiar / explicit about the basics leaves me feeling much less confused when it comes to understanding theorems, etc.

[@topquark22]

Dear Dave, You are so enthusiastic. It is infectious. I could not imagine how you could make a channel about bits of silicon so exciting. And I love the little troll with green hair sitting on the ledge of your white board/

[@ondrejgratz4088]

Perfect, thanks. This made me remember my 1st grade at electrical high school which was looong time ago.

[@McTroyd]

Wow... an explanation of current and voltage sources without high-level algebra or obfuscated math constants! I love it. 👍

[@travisporco]

Really great to see this kind of content.

[@markusherrmann9681]

Hy Dave, please do more of these fundamental videos. Your explanations are so good. Thanks a lot.

[@andymouse]

I love the basics stuff, very well explained, personally can't get enough, I should have paid more attention at skhool !....cheers.

[@leogray1091]

Although I have masted the idea about this topic. I still love to see this kind of content being produce. Great job Dave! BTW, I love your enthusiasm when you make these videos, much more fun than lectures.

[@advanceringnewholder]

Great teacher goes a long way

[@lasersbee]

Interesting Dave... Well explained as usual. Been a while since your last Theory tutorial...

[@bensonwr]

Remembering stuff I learned 30 years ago. I thought had long gone. Thank you!

[@TomLeg]

Excellent intro to Thevenin & Norton

[@protocolfree]

now we're back on track. lovely!

[@axelBr1]

Traditionally chemical plants use 4 to 20mA values to communicate measured values from the transmitter to the controllers and then from the controllers to the valves etc. Many years ago I somehow managed to build a variable current source to generate a current signal to simulate a transmitter for use with a PLC I had on loan. I spent ages worrying about what voltage it should use. I used a 9V battery, and no smoke. The box actually got used but the company project team to check out indicator loops at site in the end. But to this day, I still don't know what the loop voltage should be.

[@samuelbauer7646]

I really appreciate your videos. Keep up the great work 👍

[@jeffb.6470]

Thank you Dave Jones.

[@SnowRaptor]

14:08 Wow, Dave! With that simple graph you did a much better job at explaining the maximum power point in a solar cell than all "solar and battery" youtubers I see trying to do that! (At least to me, a physicist that can easily visualize the power as the area of that rectangle ;) )

[@hedleyfurio]

Super to see you back at the whiteboard 👍👍

[@Sal3600]

Your videos are used at Victoria University by our lecturers.

[@joeyjustin6895]

THANKS. DAVE. HOW'D You Know I NEEDED All This. You are EXELLENT. Thanks again For Another Educational Video. YOUR Great ! See ya next time.

[@mscir]

Great class, thank you.

[@DrJALAGHARI]

Thanks for sharing this valuable information.

[@fullmoon6661]

Reminds me of when I did an internship in a government agency. I was redirected to their electronic & instrumentation division, my mentor presumably is an 'expert' on this field and given a task for me to build what I know now as bench PSU with CV CC capability. He explained hell lot, it overwhelmed my still innocent uni student brain. It didn't make a lot of sense what he was explaining, about the circuit has to be sourcing constant in voltage AND in current........... I got back to him how does that make sense if the Ohms Law math doesn't even add up? And what happens if you unplug the port where does the current go? He just said that the Ohms Law doesn't apply in this application. I never felt so betrayed that I was unable to complete this task, mostly my fault because I was so dumb.

[@abdurrahmanyaman4373]

I just searched "current source eevblog" and this video came up. Same day that video uploaded :)

[@BoB4jjjjs]

You should do a complete series of these videos.

[@remontlive]

Ou yes, Dave! Fundamentals Thursday again!

[@DarkMatterX1]

Friday in Oz my man.

[@74LS_NE555]

I really like these videos please keep them coming

[@vdiallonort]

Love your videos, i learn so much with it. Just a head up ,in French we do not pronounce the h,so pronunciation of thévenin is pretty much "Tévenain". Cheers

[@duxforddude]

This was brilliant thank you!

[@JWH3]

This video was enjoyable just to hear you saying Thevenin that many times.

[@StefanSchlott]

Loved it, thank you!

[@wonderboy7768]

New eevblog, time to crank the low-pass filter.

[@clems6989]

Very good video and great udea.

[@AlmightyDemon]

Dave is teaching me electronics since freshman year in college

[@SpeedDeamon95]

Man, your probably one of the few people I would pay for a Circuits 1&2, video course! 😁

[@Reapzorian]

Thanks Dave

[@girishss5118]

Sir thanks, It was enlightening 💡

[@francismannion7075]

Ah, that was great. Thank you.

[@GlennHamblin]

Nice video, thanks.

[@georglinde3910]

That is funny, I teach customers about hydraulics and I find it extremly important to understand the difference of a 'constant pressure source' (e.g. accumulator) and a 'constant flow source' (e.g. gear pump) and there is no ideal source in real world... this is the perfect analogy to this stuff here. :-D

[@LambdaHalbe]

Thumbs up for the nice Casio Basic calculator from the mid 80ies. Unfortunately I can't read the typ label from the video but it seems to be a FX730P, which I have in my collection.

[@e74av]

OMG you threw me back 15 years back.

[@excavatoree]

Don't feel bad about "Theremin." Bob Pease once said "carbon compensation" resistor instead of "carbon composition."

[@EEVblog]

The mouth is faster than the brain.

[@RiyadhElalami]

Thermin Mermin

[@thomasfowler2964]

Plus theremins are sick as.

[@MattyEngland]

Cheers Joe 👍

[@Saimoun82]

YYYEEEEESSS - I LOVE the videos with the white board!!

[@NicolasDeFilippoOK]

Aunque no conozca bien el idioma te deseo lo mejor del mundo amigo 👏👏👏👏👏😎 muy buenas explicaciones

[@ovalwingnut]

Rated #1 by Re-Volt magazine. Ben approved this video.

[@hrnekbezucha]

Woohoo! Thanks, Dave!

[@mikemike7001]

The prequel to EEVBlog #819 on Kirchoff's laws, more than 519 videos and 5 years later!

[@roseelectronics4582]

Colleges teach Kirchoff's laws before thevenens.

[@EEVblog]

Better late than never!

[@babeandbii6051]

That whiteboard is better than the other one you tested the other day

[@OttawaOldFart]

Let's see how long I last before this goes over my head. That was indeed basic I followed along no problem.:)

[@datnguyenp]

I have seen some power supply schematic with the output load being represented as a current source and not a typical resistor. Does this mean the output current is constant and not variable depending on the load resistance? You can find some of them on TI’s WEBENCH Power Designer tool

[@daspolemon]

Could you make an in-depth fundamentals video about inductors? How they behave in different circuits, how to calculate them, etc. Would be great!

[@PomTheFrog]

Thévenin : To be pronounced in two syllables : “Tey”+ “Vnin” to make it simple 👍

[@ajinkyamahajan5736]

New addon to my knowledge base. But yet I didn't understand the current sources shown in circuit diagrams of various datasheets and what is their physical circuit. The only description given is a current sources with symbol of two intersecting circles (like a Venn Diagram). Someone please explain

[@ziadfawzi]

Thank you.

[@TomLeg]

Excellent

[@user-om2ol9wf1n]

I wonder what was first on white board: black marker vertical line or blue marker word "current"?

[@kick1ass20]

Expected to see a DC power supply (typical bench type) in this video. All the ones we use can auto-switch from constant voltage to constant current based on the load. Follow-up video on the second channel perhaps?

[@unlost117]

You and Dave has exactly that. Here is an example for a constant current power supply: if you need 1 amp constant current into a 10 ohm load, You will need to set the current to 1Amp and the "constraint voltage' to (at least) 10v. This gives you 1 amp flow through your 10 ohm load. Now if you increase the constraint voltage to 20v, you will still only get 1 Amp flow through your load (because you are using constant current power supply in this case). If you drop the Constraint voltage below 10v, the power supply now can not deliver enough current through the load now and will be less than your required 1 Amp.

[@kick1ass20]

@@unlost117 Cheers for the thoughtful response, but I mean I would be interested to see him look into a power supply that does both constant current and constant voltage. In this video, he only looked a constant current supply.

[@silverywingsagain]

So we use both of these models because they represent the ideals. For the the ideal voltage source would need to supply infinite current, and the ideal current source would need to supply infinite voltage.

[@MonochromeWench]

Keep increasing the voltage of an open circuit to produce a current you're going to eventually cause arcing and you get your current flow

[@oliverthane2868]

This stuff really starts to become important the minute you get a smu to play with

[@ultraderek]

In the circuits analysis final we had to find the value of a resistor in a circuit (I know crazy, right?). The resistance needed up being negative.

[@deang5622]

A gyrator circuit, a Negative Impedance Circuit using an operational amplifier will provide a negative resistance.

[@micsky99]

Love the short. Where can I get one?

[@dominicgoodwin1147]

Thanks for another great video! Just one little piece of total pedantry I can't help adding though... "If you hear anyone talk about Thevenin equivalent circuits..." then they don't know that you pronounce it like "Tevenin", not "Thevenin".

[@ebarbie5016]

The two circuits are not exactly equivalent. The Norton circuit is lossy and the Thevenin is lossless...

[@vincentnonnenmacher9352]

Could be interesting to talk about this LOW output on this keithley current source, for metrology nuts here

[@dustinsmous5413]

Also in the PLC world, voltage source versus voltage sink...

[@TrickyNekro]

I mean, it´s easier to calculate the Thevenin Equivalent and convert it to Norton. I guess you could do the opposite if you design with BJT but haven´t really seen it yet.

[@magnuswootton6181]

thanks helps alot!

[@jimomertz]

I guess the power line coming into my house is a voltage source. It didn’t like being shorted at all. 💥

[@DuroLabs85]

Hi there I am a college student from India I wanted to ask a question regarding my project. I want to build a dual supply converter for my USB audio amp and for that I was trying to make +/-12V from +5V so I want to use a boost converter IC "XL6009" and I want to use a 1:1 transformer for that purpose. So just wanted to know which transformer core do I use core with a air gap or no air gap in between? hope you will reply soon, Greetings from India.

[@n3r0z3r0]

So, inductance is a close to ideal constant current source on a short period of time, isn't it ? And capacitor is constant voltage source on a short period of time.

[@BenMitro]

Dave, Dave, Dave...how many times do you have to tell me? On a serious note, can you do an in-depth on solar panels - how to work out the curve given Isc and Voc - which is what we get on the label. Maybe a series - LiFePO4 cells, PWM chargers etc. - perhaps a practical series covering practical equivalent circuits for each source/sink. I think this will possibly be interesting to many people who are now toying with solar panels, batteries etc.?

[@BenMitro]

Oh, yes, please use DaveCad(C) liberally.

[@dennybarton9572]

I got an old Budgit 1 ton hoist , it's so old Budgit don't even have the right diagrams any more , not sure what motor it has , most of the writing on the tag is gone but it has 5 wires , 4 bigger wires , A 1 , A 2 , S 1 , L 2 , and , F 1 , being a black , smaller wire , not sure how to wire it up to a drum switch, nor even sure what voltage, any suggestions ?

[@tuttocrafting]

Is he the real Dave? Too many tutorials in those days! BTW, I love thoose videos,you're helping a lot of people!

[@ovalteen4404]

Dave's not here, man.

[@RaviKumar-xx7gi]

Hi I have made the circuit of LM317 on bread board. I am generating a constant current of 100mA. The input to the regulator is 3.3vdc. 100mA constant current is fed to a resistor of 100 ohms. I should measure a voltage across resistor of =10mA x 100= 1000mV=> 1V, but the voltage across the resistor I am measuring is 3.3vdc. why so? I want to use the constant current source to find the unknown resistor using current and voltage How can I do this?

[@CraigHollabaugh]

Here's a question my networks professor posed 40 years ago, let's see who knows the answer. "You have 2 sealed enclosures with 2 binding posts. One has an ideal Thevenin source, the other an ideal Norton source. How can you tell which is which without opening an enclosure?" Anyone?

[@tgfcujhb7583]

Short circuit them , first one to let out the magic smoke WINS.🤣👍

[@JohnBurgessMusic]

I'm guessing that the Norton source would dissipate power without anything being attached to the terminals due to the shunt resistor. BTW I always thought Rs in the Norton equivalent circuit meant shunt, not source resistor.

[@nisserot]

There would be no discernible difference.

[@oliverthane2868]

The constant current source would be arching between the terminals in the air

[@EEVblog]

@@tgfcujhb7583 Just measure the voltage, one of them will blow up your meter with infinite voltage :-D

[@DrFrank-xj9bc]

The measurement /demonstration of the effective internal resistance (Ri ~ mOhm) of a voltage source and the differential output resistance dU / dI ~ MOhm .. GOhm of a constant current source would have been instructive.

[@martinda7446]

Tevenin I think is close to correct and easy with a silent 'H'.

[@MiguelHernandez-pw3gp]

I believe Thevenin is a French name. So no Th sound.