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- เผยแพร่เมื่อ 16 พ.ค. 2024
- The 4th installment in the lab power supply design series. This time Dave shows you how to control the supply with a Pulse Width Modulation (PWM) signal, and chose the correct filter values.
- วิทยาศาสตร์และเทคโนโลยี
Wow, you explain everything really well. I especially like the way you're always comparing different options and explaining how the differences drive your design decisions. Thanks a lot!
Dave, I've been watching and re-watching your channel. EVERY time I find something I didn't spot before. Thank you for all the knowledge you are sharing with us and allowing us to see tests that otherwise we wouldn't be able to perform (lack of lab equipment). What you are doing is awesome. I wish you many successes! You can be sure, when I find a spare moment, I'll be building a PWM with RC low pass filter interface.
Amazing stuff. The impact from these series will reverberate throughout the EE community for many years to come.
Wow
An awesome tour of Power supply Pulse With Modulation and RC filtering with diagrams, LTSpice simulations, and a bunch of other cool stuff thrown in. I enjoyed the video very much, helpful and I will use the information. You can now say I got what PWM circuits are all about. Thank you very much! When you turn on your oscilloscope and apply it to a circuit you see so much, and.... you share what you see with all of us.
really great explanation - as always - thank you Dave !!
Wow Dave, this is an amazing series of videos. I don't even want to think about the time commitment here on your side, but WOW. THIS is the exact type of EE videos missing from the web. No one else dives this deep combining so many important aspects on anything. A simple project from the start, morphing into some serious experience sharing and teaching. This stuff is gold.
You are going to spoil me, I'll never be able to watch another "what is a linear reg" type video again!!
THANK YOU!
Dave, This series is terrific ... as others have said I am also learning a lot and very much enjoy seeing the design through prototyping. Can't wait for future installments and actual build!
Standing all that time, all that videos with that board on your shoulder is some kind of heroism! )))
Very good thank you. I have watched all the videos in this P.S. design series. Looking forward to the next video in the series.
AWESOME AWESOME AWESOME! Your way of explaining is very good! Thanks a million
Finally had a chance to catch up on the power supply vids! Keep up the good work, love learning from them!
Fantastic explanations... Bless u dave
Very nice video series. I really enjoyed the the first three (all of your videos really) videos on linear supply design but this video has taught me alot. I thought I understood filters pretty good from your other vids but this one has set me straight. Its a good thing im not your neighbor for your sake. you would probably have to get a restraining order to make me leave. Thanks Dave for all of your effort and time in making these videos. People like you sharing knowledge in an entertaining man
Can't wait for the next one. great work
simply the best explanation
I love the to be continued
@electrodacus DAMN sony vegas. Will have to re-render and re-upload :-(
I really like these tutorial like videos. Very informative. I'd definitely like to see more like this.
Dave, your video's are superb. Thanks.
Thanks; well done you are on a roll. That LT Spice is nice software.
Can't wait for the rest! :D
Thanks a lot, this is inspiring, fascinating !
Very cool Dave!! Can't wait for the rest of it. In terms of Op-Amps, you mentioned needing a rail-to-rail amp...I've recently sampled the MAX4040 and MAX4043 (single and quad versions) and they are really nice little amps that go really really close to the rails. The only draw back in the maximum supply being 6volts. I thought of them for your project however, since you are only dealing with 5volts or less in the MCU portion of the PSU.
I really like it!
Thanks for sharing your wealth of knowledge with us :) I've been in need for a CV supply for a while now and this will do nicely. I've drawn up a PCB layout with a tweak or two of my own. If interested I will share it with you. They are expresspcb files. I thought it turned out nice.
Ahhh.... I live in the wronf timzone. It's almost four in the morning here and there's a 40 minute EEVblog again. But .... can't ... resist.... (at least this time it's friday ;) )
@Kankki1 the good thing about going R-2R ladder would be that you could go have as much precision as IO pins your micro has, for example a atmega8 hase 22 io pins(23 if you use the reset one) say you use 2 for up/down, 2 for select/cancel, and 1 or 2 for the the lcd.
that lives you with 17/16 pins worth of resolution, aka 0,00076%/0,0015% and you wouldn't need a RC filter, hence wouldn't have extra noise, and with 17bits you could go high voltage, say 100V and still have 0,76mV steps!
@shiftplusone80 Thanks. Sony vegas screwed up again...
@SeanB88 In this exact case, only 0V input and output is required, not true rail-to-rail. There are countless opamps that'll do the job, buying almost based on price and availability.
Go Dave!!!
@laharl2k R-2R ladders depend greatly on the matching between resistors to achieve smooth output. With 1% resistors you can expect to get 5 to 7 bits before the output inaccuracies overwhelm your precision. The output response becomes "jaggy" and actually steps backwards for some (many) steps, depending on how many bits change.
To get your 0.0015% output resolution (not just accuracy), you'd also need 0.0015% tolerance resistors (you'd probably need better than 0.0005% in practice).
You're Awesome!
I wish Dave had been our university teacher.
at 30:53 all of a sudden the video blacks out ?????? ok, around 40 seconds later it is back on. (great relief)
Is that all you got from this 5 part video series?!
Sad.
Dave..Im impressed. Great videos and this one gives an impressive insight in the processes involved in designing electronics :) Thx a lot :)
Is the schematics available online ?
Dave, I have seen many of your tutorials/reviews . They have been really good. This PWM stuff however, blew my mind away! This was seriously impressive :O
I am going to build this PWM set up and test it out. Any recommendations on the op amp?
@quicknuclearscience Not yet, coming soon...
I see a (very) minor problem here. While an 8 bit binary number can represent 256 different values, there are really only 255 'steps', since you start at an initial point (0) and step up only 255 times (to 255) So each step would be 5v / 255, not 5v / 256. At 5v / 256, you'd always end up just short of 5v. For 10 bit, it would be 1023, and 12 bit would be 4095. It would only be important if you needed that level of precision, though.
Buffer is because the regulator is a current source, and the filter works better with a high impedance load, preferably a very high value resistor to ground. If direct connection there will be an offset that makes the output voltage rise above the set value, and this will vary according to the voltage set. The buffer sinks the current whilst providing a very high load to the filter. RC filters will always have ripple on the output, cascading them just gets it below the noise floor.
@EEVblog Cheaper than running the whole micro on a precision source is to just run a 4050 or 4049 with a single stage driving the other 5 in parallel. Cheap and only the PWM load on the regulator, which generally is pretty poor in current regulation. Isolates the noisy micro from the analogue, just use the 4049/50 ground to join digital and analogue grounds. Will give a nice square output with good and consistent rise and fall times to the filter, and is dirt cheap.
@Spoif You can't get easily or cheaply get even 10bit resolution with R2R. The resistor tolerances will kill it.
@Microman171 Yes, that's how all linear PSU work.
Great!!!
What about using dither in the timer? This way you can increase output resolution.
I mean with STM32's in 16 or 32 bit timer this is a very neat way to get fine tuning of the PWM output resolution.
Really informative as always!
Although feels like you could just make it a lot simpler by just spending 4 bucks on a couple DACs :D R2R ladder perhaps a cheap way out? Requires a ton of IO though..
Great video (even with the Sony Vegas censorship). The video returns after a few minutes, so you don't miss too much.
nice set of videos! what would you recommend using to power your power supply? ;)
@ultimatefang007
Hi moved the proabe from the rc filtered PWM-pulse to the outputpin of the constant power source. Hi also explains the may be unpredicted flat curve on the output as a resoult of the capacitance in the powersupplys output...
Mind blown
@slateraptor Those Oops moments happen fairly often. My brain did know what it was thinking :->
Hey is there a possible way to know how to program that microcontroller to drive the dac?
@Jprojects1 very true this guy is great , I learn a lot everyday. its better than college .
The esp32 only costs $1.50 in quantity and $2-2.50 in single chip qty. Even dev boards can be bought for about $4. 16 PWM Channels that can go up to 25 bits and if I followed the tech reference charts correctly they can be clocked up to 80Mhz and adjusted quite freely depending on clock source. Should be possible to make a touch screen and WIFI controlled multichannel PSU using it. It also has 2 DACs but they are only 8 bit. The interesting part is the 18 12bit ADC channels.
I'm noticing some wobble on the scoped signal when you added the second filter stage. Mains interference due to increased impedance?
@PesimisTosbaa No need for an active filter.
@marcan42 silly me, totally forgot about that, and dave just explained it some videos ago XD
though i didn't know those details about the accuracy beyond 7 bits, ill have to investigate a little further about that :-P
Hey guys, does anyone know about any techniques for addition of PWM signals before they go into an RC filter? I'm working on an FPGA implementation project for uni and we are required to scale and add different waveforms that are generated via PWM.
Shouldn't the resolution be Vref / ((2^n)-1)?
Nice
@Kankki1 Even an R2R is more expensive, and more board space than a PWM solution.
@EEVBlog Can u explain me what a buffer does :)?
unitary KRC low-pass second order filters, that was my grave in my school last cycle. What progam you use to simulate?
12bit PWM resolution is quite nice. Just worth notice, that atmega8 has 16bit PWM controller, so you can have really beautiful resolution there. The question is, does one need such a great resolution? Maybe it's better to stay with attiny budget chip in some designs. Cheers!
ATmega328P also has 6 PWMs, and you could use 2 PWMs to increase resolution as well.
I have a servo motor call q40 use igbt I need to control the igbt with a TL 494
whats the highest voltage it can handle
how to get a 40A constant current output
Hello Dave, can you make a video about controlling methods the dc-dc converters?
Error amplifiers and comparator stages etc, i would like to learn more about them but couldn't find any resources which i can understand :/
Some PICs have 4.096V voltage reference out :D
Why rc filter? You could propably use lc or is there something that i cant understand?
Holy shi*t, uC-controlled PSU is very tricky.
I'm trying to controll by this way a SMPS PSU, it will be very hard :O
PID with a micro would be much slower to respond so it wouldn't be that good for a general-purpose bench supply. Look a the scope trace at 39:30 in part 3, see how steeply the voltage rises when the load suddenly drops - the trace is almost vertical. The analog circuit reacts in a couple of microseconds and limits the overshoot to 50mV. I don't think you could make a PID loop in an 8-bit micro react anything like that fast.
Couldn't you also just power a fet from a voltage reference forgoing the need to power the whole micro this way?
should have got some 555 pwm love in there
Can someone on here maybe help me explain whats wrong with my Advance / Gould os2200 Oscilloscope. It has a _really_ highpitched noise. Is it the supply or crt? Cant use it even though it works fine excluding the noise.. the noie is 10 to 17khz
@EEVblog Have you tried Adobe Premiere? If not, they've got a free trial version for download. IMO much better than Vegas!
@SajjadBro Haven't seen it, sorry. Too many books, I can only recommend The Art of Electronics.
@laharl2k Yep, although you'd need to halve it if you want current control :)
Use dividers, I think it should work.
All that fancy stuff. For a hobbyist, what's wrong with a transformer, full bridge rectifier, filtering and a pass transistor regulator circuit? Keep it simple.
hello, i set frequency at 30KHz, could attiny85 handle it, im following your source code. thanks you
do you have any photos or schematics of this on your websites
why not power your uc with a generic supply voltage then drive the pwm output with a transistor connected to the voltage source
You are the holy Bible of electronics
Can you explain how the PW to voktage filter works
Google low-pass filter or RC filter
Think he already covered that in video #392
HOW efficient is this unit ??? Thanks
How do I contact you to ask a question not related to this video? I want to use dc motors from treadmills to power machines.
Join the eevblog forum.
Man! That was quite a lumb of knowledge right there! I just wanted to know something about driving a mosfet gate with a PWM signal...:( Way too complicated
Good luck trying to build something without understanding what you're doing
It's been a few years, do you name your nets yet? :)
Nice. Which PWM frequency you use ? And what RC filter you use, simple, or 2-nd order ?
Hmm... this vid makes me want to change my power / energy saver settings. I kept wiggling my mouse... hitting the shift keys... maybe it's a full-screen mode bug... sigh.
so where's the pcb share
11 years later, I am wondering how we could modify the project using an ESP32 and it's DAC - worth an investigation.
Yes. Blue and Red high contrast does not compress well so please stay away from those if possible
oops! PWM is from 0 to 255, 256 is just a zero with sometimes a carry flag...
the video goes blank at 30 minutes and 55 seconds.
Hi I'm new to this so I might need a bit of help. I'm making a pitching machine for a baseball team and I have a 2.5 hp elec DC motor out of a treadmill. It puts out 180V at 5700rpm. I'm also in Australia and I want to be able to control the speed of the motor. Can you please help me out so I can make a control box for it. Thanks Randy
Your motor *puts out* voltage????
+TheHue's SciTech Didn't you read his comment? He's from Australia, everything's upside down there.
30:53 , no video?
1dB is 2^0.33
3dB is 2
10dB is 10
20dB is 100
30dB is 1K
60dB is 1M
Only for power. for voltage, it's double that. 10log() or 20log().
@Afrotechmods Afrotechmods sighting =)