0-30 Vdc Stabilized Power Supply

[hansaship]

Xenobius,

First I have to say; It look very nice and tidy built, good job!
You can�t test it without some form of load. If you happen to have a 15Ohm 50W+ resistor this will put 2A on 30V. It�s possible to use bulbs but its not easy to find 30V bulbs.
Or maybe your next project could be a �dummy load�?

Ante : Since month i follow up this forum, but it's easy to find 32V light bulbs in US Fishermen's supplies, since they( Fishing Boats) use a 4x8V=32V battery system. Even 100Wx32V Bulbs can be easily purchased thru US suppliers.

rgfs,
manfred - hansaship

 

[hansaship]

Hehe thanks buddy for the compliments and sorry for the 50w resistor 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?

 

[audioguru2]

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

 

[SHOOTER1]

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

 

[audioguru2]

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.

 

[SHOOTER1]

Hi

Thanks! Now a question: By my shop there is no 10W 0,47Ohm resistor only a 5W. The Toleranz is 10% is this to much, or is this normal?

I will use the piower suplly not often at 3A Current, so can I use a 5W resistor, or would he to warm?

mfg
SHOOTER

 

[audioguru2]

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

 

[SHOOTER1]

OK thanks I will see who I would handle this.

But I think I will not even need 3A. I have no project that needs so much current.

mfg
SHOOTER

 

[audioguru2]

I think I will not even need 3A. I have no project that needs so much current.

If you use 1 ohm for R7 then its max current will be about 2A, use 2 ohms then its max current will be about 1A, etc. With reduced current then its parts won't get as hot as with high current.

 

[Smitjuh]

Shooter,

You can use 2x 0.22 Ohm 5W resistors in serie! Then you got a 0.44 ohm 10W resistor...

It's just a thought...

 

[SHOOTER1]

Hi

I thought I have to use a 0.47 Ohm couse I think ist must be exact that value that the current limmiter can work correct.

Is this not so? Well if not then I would find some right resistors.

mfg
SHOOTER

 

[Smitjuh]

NO it isn't. Like audioguru mentioned in one of it's earlier posts, you can change R7 to other value's. If you give it a higher value, the max. current will drop. 

 

[Smitjuh]

Audioguru,

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?

Greetz

 

[audioguru2]

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

 

[Smitjuh]

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

 

[audioguru2]

The output voltage is reduced by the current regulator when the current-setting pot is turned down, and the load's current tries to exceed the setting of the current-setting pot.

Maybe U3 is bad and causes heating. Try swapping it with another opamp.

 

[Smitjuh]

I already tried the swapping option.... The op-amp isn't the problem. Can't there be a problem with one of the transistors? I will check them for bad working of wrong placement later this day.

 

[audioguru2]

I already tried the swapping option.... The op-amp isn't the problem. Can't there be a problem with one of the transistors?

The output of U3 is miles away from any transistors. I think its output is shorted to the positive supply.
Pin 6 is close to pin7.

 

[Smitjuh]

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

 

[audioguru2]

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.

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