Eight years old and still relevant. Absolutely awesome. Havn't seen anything like this anywhere else; not only talking through the circuit but walking through the whole design process with a master. Priceless.
Wow, Dave. It's really special to see this latest series of vids. Comparing where you started to where your at now, I can discern no less determination, charisma and honesty than that first vid... but without the distraction of that day job, well, what your doing here is really meaningful and helpful. As a father, I'm certain that Sagan will be proud of what your helping people everywhere learn to do (both in terms of EE, but more also generally: how to help other people and make ends meet too)
It's wonderful to see that you're doing so much work every day. This really is an example of "how it should be done". This will be the quality I'll start to want from everyone who even desires to make any tutorials about subject x :D Without people like you Dave, TH-cam wouldn't have any quality videos. Keep these coming :)
Wow - a must have Video not only for all electronics and digital oscilloscope beginners. Wonderful !!!!!!! What is so fantastic in this series ist that you not only say what is but also what one might think but in fact not is. Sometimes i think you just read my mind. Fantastic !
@Wilfredkazoks The light is not the same from all angles, so it constantly has to be changed, and my camera has a problem where it automatically jumps back out of manual exposure mode to auto after returning from playback mode. I do try and put it on manual exposure when possible, I forgot this time with the paper, sorry.
Dave, great stuff, as usual. You are the EE equivalent to khan academy. Very well set up, good explanations, give reasons why/why not, etc. You're a wonderful teacher, keep it up.
I only wish that there was someone with your knowledge and personality in the electronics repair indusry. I am familiar with Jestine from Malasia and Dave from Oregon, but apart from that no one seems to come near your standard. For a newbie like me 70% of this great video soared over my head.
@superdau You didn't miss anything, the fact that it was available led me to use it, and it was helpful to show show the issue with identical comparator inputs. You can certainly use another transistor, and that's a more accurate way to do it.
This series of videos has been well planned out and very informative. Thank you for posting these. I really do appreciate the effort you put into your videos. When you get around to doing the video for the final project I would hope that you also include some information on "the traps for young players" when designing the layout of the PCB. I will be looking forward to more of these educational videos from you. Thanks
@Microman171 The LT3080 is designed to be stable. If you roll your own, you have worry about stability over a wide range of loads. May or may not be a problem for you, but something to watch out and test for.
17:20 To make the LED indicator for the "current limiting" mode work correctly, you can use comparator to monitor the voltage at pin 7 (input voltage to the transistor) (to compare it against about 0.6V - this voltage can be derived with voltage divider from the 2.5V reference).
@randomgarfield @LeonValkenborg Yes, there are countless high current/high voltage linear and switchmode PSU's on the market, and they are cheap as chips. I'm doing something different, which will become clearer with time...
EEVblog I am learning so much from your channel please dont pay the haters any mind , keep on doing your thing . We need to design a circuit to slowly electrocute the haters ..
@horfittunge Thanks. Interesting in that it's not even supposed to be a tutorial, it's just me breadboarding a design and doing a few tests and yapping on while doing it :->
Tnx for beautiful TubeYou Psu-construction video-series. ..Big appreciation for 'all' your video-making and qualitative electronic lectures Dave. Also nice atmosphere with those crickets sounding now&then :) ..No such sounds here up north. (br, from norway to australia)
Hi Dave! Thanks you so much for the class. I am designing a voltage source with current limit, using a 2n3055 and 2n2219 as a darlington, because there are so many in the stock where I work and we need some voltage sources. In my simulations, when a put a capacitor of 22uF, the overshoot in the current flowing to the load is too big for me. In the simulation, I change the load from 24R (24V, so sucks 1A) to 1R, trying to mimic a short in the output. In this cenario, the current limt circuit start to act and the output voltage drops till the current finds the setpoint. When in continuous current mode, there is a small oscilation in output voltage of 33 mV and a current overshoot of 2A, when I use the 1uF capacitor in the darlington's base. Against a current overshoot of 15,5A and a voltage oscilation of 3,3mV when I use a 22uF capacitor. So I have decide to use a 1uF capacitor in there. The oscilation in the load voltage was not very big. For me was more important to limit the current overshoot than the oscilation present in the Continuous Current Mode. Because, I dont pretend to use the source as a Current Source. Just use this feature to limit the current and protect the transistors and the load. Do you think is a good way to do it? Thanks again!
@aseglkj Stability across a wide range of loads is a major consideration with a roll-your-own solution. See a previous video I have done on exactly this solution. It is not a horrible design, I deliberately traded off extra cost for development simplicity and guaranteed stability.
i've had a little play around with an old school bench supply, used the original Xformer but gutted the late 60's era regulating circuits. i have managed to get reasonable results using a series pass transistor and the "jellybean" quad opamps. not current limited but i do have a constant current mode with preset current limits and voltages using the radio buttons and rotary switches the old supply had, 0 to near 15 volts with reasonable regulation and less than 2 amps
thanks Dave for the detailed tutorial but im still left with one question i would like to build this same thing but have it be capable of 30v 10amp i know i need a different current resistor and transistors to handle the output current but im concerned about the op amp, will it be ok with 30-35v input?? thanks!
Just stopped at 15:55 - why what would be against connecting opamp 2b to the output of 1b, thus as soon as the current limiter kicks in and there's > .65V on pin 7, we would have a clean indication the limiter is active, and just need to amplify that? Also of course, a simple npn transistor would also do that for us
Hey Dave, Im Loving this "Lab Power Supply" series more then any other. I have considered building it myself, and I came to the conclusion that the amperage and voltage that you have based this series on is a too low. If it was ~20A and ~35V, I would have built it by now. You are working with such a low voltage and amperage design that I just cant bother with taking the design to that stage. I wrote a WHOLE LOT! of massively positive things, but apparently I have a limit to how much i can write.
@EEVblog Limited by the reference. Up the unregulated rail to 12V and change the opamp gain to 3 and you will get 6V out, just change the one resistor from 22k to 27K will probably do it.
My first reaction on the current limiting mode LED: If you're using the spare OP-amp, why not compare the output of OP-amp 1b with a constant 0.4 V or so. Then you'll have an exact sensing without any fine tuned voltage divider (the 0.4 V voltage only need to be roughly in the ballpark).
@randomgarfield for higher current its better to use a switch mode design as you wont need a truck sized heatsink, further more you can control both voltage and current in the same stage if you use a micro or a dedicated ic.
The bounce at the beginning is due to the output current sink turning on. Nothing due to the LT part, just the dropout and fast turn on of that old current sink.
Question: For the CC limit LED. Could you not attach it to the positive rail via the 1k resistor and to the iset output (node 7) before the transistor? My logic is that it doesn't turn on until the transistor is turned on. Would that work? Or, is it going to be a problem in the lower mA range?
Just built it up. The LED turns on exactly when activated, "but" it is a gradual increase in voltage so the LED starts off dim and then increasingly gets brighter until it reaches 2 volts. Where as mirroring the opamp, the LED switches on instantly, albeit a smidge early. Once again, Dave is king...
One power-up test I'd be curious about is with the output voltage set to under 0.7V.. just because of that knee in the other power ups it makes me wonder if it can regulate down below 0.7v while it comes on. Learned lots though :)
Why did you use a second opamp for the limit LED (except for the fact that it comes free with one of the packages already in the design ;) ). Couldn't you just hook another transistor to the output of 1b to drive a LED against V+? The output of 1b seemed to jump to at least 1V as soon as current limit mode kicks in. If it's the part count I would not have hooked up the second opamp in parallel, but have it compare the output of 1b to lets say 0,5V. What did I miss?
@LeonValkenborg Dave already stated he has no interest in high voltage and high current PSUs. Seriously though how often do you require more than 12V and an amp when you're breadboarding something. However his design does scale (although expensive). If you want 20A, just use 18 LT3080s. :) They'll also go up to 30V without issue too, but you'd be really silly to scale it that large.
@laharl2k I wasn't being serious about scaling this up. Although you can make very large linear supplies that don't require huge heatsinks if low voltage output isn't a requirement.
It is nice (personally i would not use LM's but that's me) Whole OP-amp for current limit LED?! Just hook up LED in series with base of current limiting BJT, lower series base resistor, and add one resistor between base and emiter of current limiting BJT and voila. I've found i like 100microamps trough 5mm clear hi eff red led just fine, more then 3 mA is too bright for me, so choosing right resistors you can get it to work nice!
Dave, great tutorial. I was wondering if you would consider doing a short video showing how the PWM would replace the pots for the limit control voltages. Obviously PWM from the duty adjust on a signal generator. But then I was hoping you could show someone how to do the same thing with a simple opamp 4 bit DAC (r*2^n opamp adder) that is controlled by DIP switches or a shift register. Just to show what you can do for controls if someone wasn't using a PWM for the reference voltage.
I have some thoughts about current limiting transistor. What can you say about the voltage on the base, when it's turning into the current limiting mode (opening transistor). From your video it is seen like a jump from not limiting, to limiting. Isn't it smooth? Because the volgate on the transistor base is quite slowly rising... Can you comment this?
shoot, thats pretty low noise, the one i rolled myself using spare parts, an LM324 and external series pass transistors does about 50 odd mV of noise, i didnt have my own Oscope but i used a PC based scope, it seemed to measure 50 - 100 mV above/below 0 (AC coupled), pretty horrible compared to the 3080 but not bad considering i cobbled it together
pls recommend,,, no change constant 5v,, no matter what load does,,,, while i control from 1 to 80 ma ,,, in this case,,, constant 5v,,, current limit not affecting voltage,,,
Having a strange issue where my differential amplifier is giving output values with about a gain of 6. No idea why all the resistors are the same and I'm using the tlc272.
I have a question. What if we exchange the LT3080 for a TIP122 and modify the voltage control loop like this: - the 1k that went to adjust goes to base - the 12k that also went to adjust goes to emiter (and emiter becomes the regulator output) - collector goes to VCC No other circuit changes. Would it still work? In my mind it seems like it should? Of course we are left with no thermal protection. But voltage and current adjust should work, right? The question is based on a problem with availability of LT3080 for me (or rather it's price is not friendly and in comparison I can fry TIP122's all day long).
Harald Sangvik Well, I do believe you are fundamentally wrong. The way I proposed to connect the transistor was a emitter follower, with a modification to the control loop. The regulator in it self also has some kind of transistor that is the pass element. Idea was to scrap the expensive part and exchange it for a cheap one. Reread my previous post. And if you can't understand it - try simulating it.
You would need to pay more attention to regulation, where a regulator will do everything for you. I will design this circuit using a LM338 and a NE555 negative voltage rail for going down to 0 volts. Should be good for 15V 3A using a laptop brick as a power supply
Just finished building it. Yes, it has current limit. Had to do some dicking around with the current limit cicruit. Had to drive both the current limit opamp and sinking the control pin to negative, otherwise it would current limit at 1.25 volts. It goes all the way down to 0 with a 300 ohm resistor attached. Haven't received the lm334 yet. Everything is made using jellybean parts, LM338, LM358 and NE555. Except for the voltage reference. Used a REF02 5v reference for that. I have also added an arduino Nano for reading the voltage and current, and maybe logging, wireless etc. To get the negative 1,25 volts, i fed the 5v reference into the inverting input of an opamp, and a 6,8k resistor to the pot. I have also ordered an AD620, to see if i can get even more accuracy out of it
alright i might have a go with this supply, i wont have the regulator or the opamps, (i have got 324's though) i might want to find a site that gives free samples or similar for some of the parts and i can probably scrounge some of the passives
your output voltage does not seem to stay stable as you increase the amount of current drawn. it drops from 3.145v to 3.114v. should the output voltage not be monitored by a voltage devider and used to control the pass device?
LT3080 is $31 in the little package, The bigger packages are $116 and $91. LT stuff is completely exorbitant. It's lazy to pay through the nose for a part to do all the work for you.
If you buy the expenisive equipment yourself you have all the right to tap it, learn to live with it. If you find it annoying than dont watch the video.
The theory is good but the circuit is not good as a general purpose lab power supply: LT3080 has just 1.1 Amp rating, too low even to powerup a small audio amplifier, of course can use pass transistor etc but then it's a different story. TLC2272 has total max supply at 16V , way too low, considering a common lab power supply runs from 0 or 1 volt up to 30volts usually, so needs, considering dropout, something like 33-35V dc before regulation. Better using e.g. LM338K (5Amp, 10Amp if 2 in parallel etc) on large heatsink, an LM358 and a relay to disconnect output.. as in some old reliable commercial units , cheap but effective.
Why should matter what happens with a load under 0,5 mA? I mean, if you have a power regulator its because you want to power something, and something under 0,5mA is really that common? I think is more common to have loads > 6V, TBH.
Eight years old and still relevant. Absolutely awesome. Havn't seen anything like this anywhere else; not only talking through the circuit but walking through the whole design process with a master. Priceless.
love these videos. Thanks
Thanks for the awesome video !
Love the automatic subtitles generation (6:40) : "1 milliamp current source" -> "1,000,000 carrot sauce" :D
i got "1 milliamp car sauce"
sadly 8 years later its fixed. no more carrot or car sauce :-(
😂@@HarryFortyTwo ahah thanks for reporting, great times ❤
Excellent series so far. Love how it evolved from "tap, tap, tap-tap!" to "bang! bang! BANG!" Awesome energy you have.
@SuperEvilbug Yes, this will hopefully become a kit. The final design I have in mind will be more than what you see here, and rather novel I think.
Wow, Dave. It's really special to see this latest series of vids. Comparing where you started to where your at now, I can discern no less determination, charisma and honesty than that first vid... but without the distraction of that day job, well, what your doing here is really meaningful and helpful. As a father, I'm certain that Sagan will be proud of what your helping people everywhere learn to do (both in terms of EE, but more also generally: how to help other people and make ends meet too)
Wow, this must seriously be the best tutorial I've ever watched. Super great job Dave!
It's wonderful to see that you're doing so much work every day. This really is an example of "how it should be done". This will be the quality I'll start to want from everyone who even desires to make any tutorials about subject x :D
Without people like you Dave, TH-cam wouldn't have any quality videos. Keep these coming :)
Wow - a must have Video not only for all electronics and digital oscilloscope beginners. Wonderful !!!!!!! What is so fantastic in this series ist that you not only say what is but also what one might think but in fact not is. Sometimes i think you just read my mind. Fantastic !
@Wilfredkazoks The light is not the same from all angles, so it constantly has to be changed, and my camera has a problem where it automatically jumps back out of manual exposure mode to auto after returning from playback mode. I do try and put it on manual exposure when possible, I forgot this time with the paper, sorry.
Dave, great stuff, as usual. You are the EE equivalent to khan academy. Very well set up, good explanations, give reasons why/why not, etc. You're a wonderful teacher, keep it up.
I only wish that there was someone with your knowledge and personality in the electronics repair indusry. I am familiar with Jestine from Malasia and Dave from Oregon, but apart from that no one seems to come near your standard. For a newbie like me 70% of this great video soared over my head.
@superdau You didn't miss anything, the fact that it was available led me to use it, and it was helpful to show show the issue with identical comparator inputs. You can certainly use another transistor, and that's a more accurate way to do it.
@ZitroOgu You can, yes, but only if you have the package that has the pin separate. Keeping lowest common denominator here. Forgot to mention that.
This series of videos has been well planned out and very informative. Thank you for posting these. I really do appreciate the effort you put into your videos. When you get around to doing the video for the final project I would hope that you also include some information on "the traps for young players" when designing the layout of the PCB. I will be looking forward to more of these educational videos from you. Thanks
It's good to use regular diode in series with zener diode, to minimize the voltage-temperature changes
@Microman171 The LT3080 is designed to be stable. If you roll your own, you have worry about stability over a wide range of loads. May or may not be a problem for you, but something to watch out and test for.
17:20
To make the LED indicator for the "current limiting" mode work correctly, you can use comparator to monitor the voltage at pin 7 (input voltage to the transistor) (to compare it against about 0.6V - this voltage can be derived with voltage divider from the 2.5V reference).
@randomgarfield @LeonValkenborg Yes, there are countless high current/high voltage linear and switchmode PSU's on the market, and they are cheap as chips. I'm doing something different, which will become clearer with time...
EEVblog I am learning so much from your channel please dont pay the haters any mind , keep on doing your thing . We need to design a circuit to slowly electrocute the haters ..
@horfittunge Thanks. Interesting in that it's not even supposed to be a tutorial, it's just me breadboarding a design and doing a few tests and yapping on while doing it :->
@xng14 Yep, I have a nice, and I think kinda novel build coming up, will be a while though...
Tnx for beautiful TubeYou Psu-construction video-series.
..Big appreciation for 'all' your video-making and qualitative electronic lectures Dave.
Also nice atmosphere with those crickets sounding now&then :) ..No such sounds here up north.
(br, from norway to australia)
Hi Dave! Thanks you so much for the class. I am designing a voltage source with current limit, using a 2n3055 and 2n2219 as a darlington, because there are so many in the stock where I work and we need some voltage sources. In my simulations, when a put a capacitor of 22uF, the overshoot in the current flowing to the load is too big for me. In the simulation, I change the load from 24R (24V, so sucks 1A) to 1R, trying to mimic a short in the output. In this cenario, the current limt circuit start to act and the output voltage drops till the current finds the setpoint. When in continuous current mode, there is a small oscilation in output voltage of 33 mV and a current overshoot of 2A, when I use the 1uF capacitor in the darlington's base. Against a current overshoot of 15,5A and a voltage oscilation of 3,3mV when I use a 22uF capacitor. So I have decide to use a 1uF capacitor in there. The oscilation in the load voltage was not very big. For me was more important to limit the current overshoot than the oscilation present in the Continuous Current Mode. Because, I dont pretend to use the source as a Current Source. Just use this feature to limit the current and protect the transistors and the load. Do you think is a good way to do it? Thanks again!
@Th3Su8 My videos are almost never "planned out", these ones included. They kinda "just happen" :->
Beauty!
@aseglkj Stability across a wide range of loads is a major consideration with a roll-your-own solution. See a previous video I have done on exactly this solution.
It is not a horrible design, I deliberately traded off extra cost for development simplicity and guaranteed stability.
i've had a little play around with an old school bench supply, used the original Xformer but gutted the late 60's era regulating circuits. i have managed to get reasonable results using a series pass transistor and the "jellybean" quad opamps. not current limited but i do have a constant current mode with preset current limits and voltages using the radio buttons and rotary switches the old supply had, 0 to near 15 volts with reasonable regulation and less than 2 amps
When the nerds finally take over the earth, truly thou shalt be crowned as their king......
HAHAHAHAHAHHAHAHAHAHAHAHAHHA, sure thing!
thanks Dave for the detailed tutorial but im still left with one question
i would like to build this same thing but have it be capable of 30v 10amp
i know i need a different current resistor and transistors to handle the output current but
im concerned about the op amp, will it be ok with 30-35v input??
thanks!
Just stopped at 15:55 - why what would be against connecting opamp 2b to the output of 1b, thus as soon as the current limiter kicks in and there's > .65V on pin 7, we would have a clean indication the limiter is active, and just need to amplify that? Also of course, a simple npn transistor would also do that for us
38:50 Can't remember if this series was before or after the videos about scope input microphonics, but that screen tap was a great unstaged example.
I've really enjoyed following this process.
Thanks.
what a fucking great vid series!!!! thanks for the course, dave. you're awesome!
@electrodacus Yeah. I thought it was a good example of how it can hide things, so quickly shot a separate video.
I love the LT3080 - great component with some surprising features. I use it a lot.
Really interesting to see the startup transient on the digital scope. You weren't able to see that on the old analog scopes!
Wow, that DaveCad-XL is impressive!
I've been binge watching these and my brain is turned to mush but it's soooooo cool
Hey Dave,
Im Loving this "Lab Power Supply" series more then any other.
I have considered building it myself, and I came to the conclusion that the amperage and voltage that you have based this series on is a too low.
If it was ~20A and ~35V, I would have built it by now.
You are working with such a low voltage and amperage design that I just cant bother with taking the design to that stage.
I wrote a WHOLE LOT! of massively positive things, but apparently I have a limit to how much i can write.
@EEVblog Limited by the reference. Up the unregulated rail to 12V and change the opamp gain to 3 and you will get 6V out, just change the one resistor from 22k to 27K will probably do it.
These videos are amazing . thanks to you .
Is there a Dave-CAD download for this or shall I just do a screen-grab?
I am learning a lot. Thank you....keep it up!
@Dysl3xicDog Not yet, patience!
My first reaction on the current limiting mode LED: If you're using the spare OP-amp, why not compare the output of OP-amp 1b with a constant 0.4 V or so. Then you'll have an exact sensing without any fine tuned voltage divider (the 0.4 V voltage only need to be roughly in the ballpark).
@EEVblog In either case, I love it!
Keep it up.
@randomgarfield for higher current its better to use a switch mode design as you wont need a truck sized heatsink, further more you can control both voltage and current in the same stage if you use a micro or a dedicated ic.
Love the vids...
Did anyone count how many times he says bang? Lol
Or 'I like it!'? I really love the videos.
The bounce at the beginning is due to the output current sink turning on. Nothing due to the LT part, just the dropout and fast turn on of that old current sink.
I have a new drinking game: you have to drink every time Dave says BANG!
should have joined me on the other parts with the whiteboard and tapping
Question: For the CC limit LED. Could you not attach it to the positive rail via the 1k resistor and to the iset output (node 7) before the transistor? My logic is that it doesn't turn on until the transistor is turned on. Would that work? Or, is it going to be a problem in the lower mA range?
Just built it up. The LED turns on exactly when activated, "but" it is a gradual increase in voltage so the LED starts off dim and then increasingly gets brighter until it reaches 2 volts. Where as mirroring the opamp, the LED switches on instantly, albeit a smidge early. Once again, Dave is king...
One power-up test I'd be curious about is with the output voltage set to under 0.7V.. just because of that knee in the other power ups it makes me wonder if it can regulate down below 0.7v while it comes on. Learned lots though :)
Why did you use a second opamp for the limit LED (except for the fact that it comes free with one of the packages already in the design ;) ). Couldn't you just hook another transistor to the output of 1b to drive a LED against V+? The output of 1b seemed to jump to at least 1V as soon as current limit mode kicks in. If it's the part count I would not have hooked up the second opamp in parallel, but have it compare the output of 1b to lets say 0,5V.
What did I miss?
@LeonValkenborg Dave already stated he has no interest in high voltage and high current PSUs. Seriously though how often do you require more than 12V and an amp when you're breadboarding something. However his design does scale (although expensive). If you want 20A, just use 18 LT3080s. :) They'll also go up to 30V without issue too, but you'd be really silly to scale it that large.
with the added uc this design would be great hardware for a diy single cell lipo charger :)
Nice work yet again, Dave. I'm reading data sheets in your voice now. 8)
@laharl2k I wasn't being serious about scaling this up. Although you can make very large linear supplies that don't require huge heatsinks if low voltage output isn't a requirement.
Bang! Jk - Excellent vid Dave!!!
Hi Dave!
The design videos are great! Definitely keep them coming!
What's next? pcb and case design? panel meters?
Thanks Dave
It is nice (personally i would not use LM's but that's me)
Whole OP-amp for current limit LED?!
Just hook up LED in series with base of current limiting BJT, lower series base resistor, and add one resistor between base and emiter of current limiting BJT and voila.
I've found i like 100microamps trough 5mm clear hi eff red led just fine, more then 3 mA is too bright for me, so choosing right resistors you can get it to work nice!
What type of capacitors are those in red and blue? Thanks
Dave, great tutorial. I was wondering if you would consider doing a short video showing how the PWM would replace the pots for the limit control voltages. Obviously PWM from the duty adjust on a signal generator.
But then I was hoping you could show someone how to do the same thing with a simple opamp 4 bit DAC (r*2^n opamp adder) that is controlled by DIP switches or a shift register. Just to show what you can do for controls if someone wasn't using a PWM for the reference voltage.
Can you use a reversed biased LED as a voltage reference (given it will be shielded from light)? I have some junk hong kong cheapies.
I have some thoughts about current limiting transistor. What can you say about the voltage on the base, when it's turning into the current limiting mode (opening transistor). From your video it is seen like a jump from not limiting, to limiting. Isn't it smooth? Because the volgate on the transistor base is quite slowly rising... Can you comment this?
Would like to use Arduino parts. Maybe a Arduino Nano board?
Boom! And there it is!
Bad man, you made me longing for a decent oscilloscope now!
shoot, thats pretty low noise, the one i rolled myself using spare parts, an LM324 and external series pass transistors does about 50 odd mV of noise, i didnt have my own Oscope but i used a PC based scope, it seemed to measure 50 - 100 mV above/below 0 (AC coupled), pretty horrible compared to the 3080 but not bad considering i cobbled it together
Could make a parody of this video just with the amount of "bangs" that were said haha. But I really do love the videos. Only poking some fun.
pls recommend,,, no change constant 5v,, no matter what load does,,,, while i control from 1 to 80 ma ,,, in this case,,, constant 5v,,, current limit not affecting voltage,,,
I subscribed .... I love your channel
Having a strange issue where my differential amplifier is giving output values with about a gain of 6. No idea why all the resistors are the same and I'm using the tlc272.
Dave must be popular at work, saying bang all the time while he's working on stuff lol
I have a question.
What if we exchange the LT3080 for a TIP122 and modify the voltage control loop like this:
- the 1k that went to adjust goes to base
- the 12k that also went to adjust goes to emiter (and emiter becomes the regulator output)
- collector goes to VCC
No other circuit changes.
Would it still work? In my mind it seems like it should? Of course we are left with no thermal protection. But voltage and current adjust should work, right?
The question is based on a problem with availability of LT3080 for me (or rather it's price is not friendly and in comparison I can fry TIP122's all day long).
The TIP122 is a transistor, not a voltage regulator. It doesn't operate like the LT3080
Harald Sangvik Well, I do believe you are fundamentally wrong. The way I proposed to connect the transistor was a emitter follower, with a modification to the control loop. The regulator in it self also has some kind of transistor that is the pass element.
Idea was to scrap the expensive part and exchange it for a cheap one.
Reread my previous post. And if you can't understand it - try simulating it.
You would need to pay more attention to regulation, where a regulator will do everything for you.
I will design this circuit using a LM338 and a NE555 negative voltage rail for going down to 0 volts.
Should be good for 15V 3A using a laptop brick as a power supply
Harald Sangvik Nice hack idea. But no current limit?
Just finished building it.
Yes, it has current limit. Had to do some dicking around with the current limit cicruit.
Had to drive both the current limit opamp and sinking the control pin to negative, otherwise it would current limit at 1.25 volts.
It goes all the way down to 0 with a 300 ohm resistor attached. Haven't received the lm334 yet.
Everything is made using jellybean parts, LM338, LM358 and NE555. Except for the voltage reference. Used a REF02 5v reference for that.
I have also added an arduino Nano for reading the voltage and current, and maybe logging, wireless etc.
To get the negative 1,25 volts, i fed the 5v reference into the inverting input of an opamp, and a 6,8k resistor to the pot.
I have also ordered an AD620, to see if i can get even more accuracy out of it
Amazing Video, Merry Christmas Dave!!! (in Advance)
The EEVBlog drinking game. Dave says "Bang", take a swig. You'll be drunk in the first 10 minutes and in hospital before the end of the video. :)
alright i might have a go with this supply, i wont have the regulator or the opamps, (i have got 324's though) i might want to find a site that gives free samples or similar for some of the parts and i can probably scrounge some of the passives
@EEVblog does it have a flux capacitor by chance? :)
Dave I love your blog & will to "like" it. I am dying to get some of your T-shirts! Please, where do u get them?!?!
your output voltage does not seem to stay stable as you increase the amount of current drawn. it drops from 3.145v to 3.114v. should the output voltage not be monitored by a voltage devider and used to control the pass device?
awesome
Dave do you have a BOM and a official schematic to work from?
Do you often draw schematics on paper? :)
LT3080 is $31 in the little package, The bigger packages are $116 and $91. LT stuff is completely exorbitant. It's lazy to pay through the nose for a part to do all the work for you.
You should connect the unused op amps properly.
What about making a power supply with digital thumbnail switches? I have some mini-lever digital switches from Digitran Company, Pasadena California.
@4833504F You can already buy those for $5 :->
how can I get the maximum output voltage up to 30V?
@bswain9999 Depreciation, the global economy is tanking, didn't you hear. Gotta save all the volts we can :->
If you buy the expenisive equipment yourself you have all the right to tap it, learn to live with it. If you find it annoying than dont watch the video.
Is that really an 11500€ oscilloscope? :O
The original spec was for 6V but now we seem to be maxing at 5.5V... :/
Bang! subscribed.
@EEVblog lab power supplies as well ;)
i'd like to combine power supply and charger for all kinds of accumulators
The theory is good but the circuit is not good as a general purpose lab power supply: LT3080 has just 1.1 Amp rating, too low even to powerup a small audio amplifier, of course can use pass transistor etc but then it's a different story. TLC2272 has total max supply at 16V , way too low, considering a common lab power supply runs from 0 or 1 volt up to 30volts usually, so needs, considering dropout, something like 33-35V dc before regulation. Better using e.g. LM338K (5Amp, 10Amp if 2 in parallel etc) on large heatsink, an LM358 and a relay to disconnect output.. as in some old reliable commercial units , cheap but effective.
Why should matter what happens with a load under 0,5 mA? I mean, if you have a power regulator its because you want to power something, and something under 0,5mA is really that common? I think is more common to have loads > 6V, TBH.
What is IC1 and IC2 ?
and BANG!
Nah mate the gain in the non-inverting configuration is (1 + 12K/10K), don't take my word for it though, do the calculation.