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0-30 Vdc Stabilized Power Supply


Sallala
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Hehe thanks buddy for the compliments :D and sorry for the 50w resistor :p because I don't have one.

Here is another picture of it so even the people who are going to build it will have an idea of the layout :) (sorry for the dirt on the table but I was just drilling a PCB lol)


Thi looks realy well built and profesional, so pls excuse my stupid question: WHAT IS THE GREEN CENTER- POST FOR? Do You get any negative Voltage out of Your PSU?
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Thi looks realy well built and profesional, so pls excuse my stupid question: WHAT IS THE GREEN CENTER- POST FOR? Do You get any negative Voltage out of Your PSU?

I betcha it is for the mains elecrical wiring's earth connection if needed. Then you connect the project's positive output to it and the 0V terminal becomes negative. ;D
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Hello all!

First I want to tell something about me. This is the first english forum who I registered because I'm German. So my English would not be perfect but I hope everyone knows at least the meaning. I'm 17 and learning a job as electronician and do electronic long times in my spare time for years ago.

So let me start... I wanted to build the Power Supply as I found the PCB and Schematic and I would use the parts that I found on the project page, but then I looked in the forum and there (it seemst to me) exists some problems.

I read that some peaple changed the 0.47 Ohm resistor in a 10W exemplar. The changes also some other resistors becouse the got very hot. Also some Opamps some people changed. Also the transformer seems a bit undersized (I read that, too).

My Problem is that I no a little confussed what change is good/bad necessary or bullshit. So I ask you what changes have I to make that the current limiter works perfect and all the other things works good?

Sorry to ask you but the treat is so long and haves about 52 pages and so I have no chance to read all the godd stuffs and read cfhanges that be made, but who worked not well. I'm not an english expert and I understnad not every post so I asked you here to help me.

So thanks for reading and thanks for posting in forward.

mfg
SHOOTER

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Hi Shooter,
Welcome to our forum. ;D
Your English is fine.
I recommend the parts list posted a few replies ago. Some people built it like that and it works perfectly and is much more reliable.
I am thinking about adding trimpots in series with the control pots so that the max voltage and current can be calibrated.

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Hi Shooter,
3A through a 0.47 ohm resistor will cause heating of 3 x 3 x 0.47= 4.23W. If it was 10% high at 0.517 ohms, it would heat with 4.65W. Sure it would be hot, enough to char the pcb or melt wire insulation since some power resistors are rated at 275 degrees C.
You might have the project's current set to max which might be much more than 3A without a calibration trimpot added. Then the output accidently shorts. A 5W resistor might desolder itself or catch fire!
10W, 0.47 ohm resistors are commonly available in a 5% tolerance. Maybe you should shop online. ;D

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I changed the op-amps to TLE2141CP one's. The supply regulates ok. At a full load, it won't exeed 24V. But with all the losts in the supply this seems ok. But my LED still won't light... U3 get's realy hot... maybe that rings a bell?

Hi Smit,
U3 doesn't do much work so shouldn't get hot. You already checked that R20 is 10k but maybe it is painted wrong, measure its resistance. Maybe your pcb has a short on it.
What is U3's output voltage?

Your project should give more than 24V at 3A even though your transformer's voltage is too low. You said its positive supply is 33.5V at 3A so maybe if R15 is 100 ohms, Q2 is a TIP31A and C1 has 12,000uF it will have more output voltage. ;D
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Output of U3 is 33,5 V. Values of R20 and R19 are like described in the project, 10k and 2,2k. So not wrongly painted, or got a alightly different color due to heat or something. I checked the PCB several times on shorts, but I can't find any.

The 24V can be al bit more, I read it quickly on a analoge needle voltmeter... But when the load is on, and the current pot is turned counterclockwise, I can see my voltage build up when I turn the voltage pot. until about 30V and then the voltage drops (realy quick) to say 25, 26V

Thanks again for the fast and good supply!!!

Greetz Tim

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YES!!!!  ;D ;D ;D ;D ;D ;D ;D

The thing works perfectly by now!!! It indeed was a short betwwen pin 6 and 7 a nasty one, but all short are nasty one's!  ;D ;D

I can't thank you enough audioguru!! I will place pictures when it is in it's housing!

one thing... what is the best place to add my amp, and voltage panel meters?

greetz Tim

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Hi Tim,
It's great to hear that you've fixed it. ;D

Connect your voltmeter directly to the output terminals because the internal wiring has some voltage loss.
A current meter in series with the load has a resistance that ruins the fabulous voltage regulation of this project.
Instead, I would use another voltmeter to read the voltage across R7 which is caused by load current. R7 is outside the voltage regulator so doesn't spoil the fabulous regulation.

post-1706-1427914256354_thumb.gif

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  • 2 weeks later...

Hi all.
I have just made this PSU. Everything works fine, but the current pot is regulating from about 0,02A to about 4,4A, but i want only 3A. Also when no load is connected and current pot is set to minimal current LED lights. I have some modifications on it. There are 2 paraller 2N3055 (0,33ohm resistor on each emmiter), increased power of resistors and digital meters. Ampermeter is coonected to the negative output of PCB. Can you help me? thanks

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The tolerance of the current-setting pot is probably 20%. It should have a trimpot in series with it to reduce its max to exactly 3.0A. Or simply temporarily use anothe pot in series to adjust the max current and replace it with a resistor of the same value.

The voltage-setting pot is the same. The voltage is too high when it is set to max. It should also have a resistor in series with it.

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Thanks for you fast answer, audioguru.
I have one more problem with my digital voltmeter. I think it is very sensitive. The range is 200mV and it is increased to 200V by a voltage divider. Sometimes it shows various numbers. For example when i touch with an unconected piece of wire on one output pin the display will show absurd values for a second and then will return to normal value, but somethimes it stay confused displaying absurd values or displaying a zero value still. But when i touch with my finger somewhere on the meter's PCB, it returns to "normal mode". I used exactly same voltmeter as an ammeter, but i didn't noticed this problem there. Can it be caused of using a transformator soldering gun?
thanks

Modified on 30th December 6:35 AM
I have also tryed to connect a DC motor, but when it starts to rotate, various numbers blink on both voltmeter and ammeter. I have tryed to add a 100n capacitor paraller to output pins. It is better, but when nuber of rotations increases it starts to do it again. Is there any way to supress disturbing?
thanks

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