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Author Topic: 0-30V Stabilized Power Supply  (Read 329247 times)
Masters2504
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« Reply #1386 on: October 29, 2012, 03:06:03 PM »

Thanks audioguru on the answer Smiley.

Yes you are right, my mistake, no one recommended the A version of the opamp.

I will use this MC34071PG opamp that I have.

Thanks for the suggestion to use two 2N3055 transistor to share the heat. I will use that modification.
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papuga
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« Reply #1387 on: October 31, 2012, 08:36:25 AM »

Hello everybody!
I wanted to build the first version of "0-30VDC Stabilized Power Supply with Current Control 0.002-3 A"
But now I saw this topic,and I have a few questions.
I tried to read this topic,but there is 100 pages, so i think that is better to ask.
I saw,that there are more versions of this PSU,but i don't have new transformer with 28-30V and 3+ A.
Can anyone help me,I'm new to this things.I don't want anybody to do my homework and if I must i will read the whole 100 pages if there are answers to my q.
My transformer is rated to 25.5VAC,3.6A.
My question is, will this version work with my transformer?


and this parts



if not, can anybody help me,to make changes to get this working.
I don't need for this PSU to give me 4+ Amp,just to give me 0-30VDC and 0.002-3A (3.6A)
Thanks in advance!
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audioguru
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« Reply #1388 on: October 31, 2012, 08:59:06 AM »

My transformer is rated to 25.5VAC,3.6A.
My question is, will this version work with my transformer?

I don't need for this PSU to give me 4+ Amp, just to give me 0-30VDC and 0.002-3A (3.6A)
Your transformer is rated for (25.5V x 3.6A)= 91.8VA.
The circuit works from rectified AC and the peak voltage is (25.5V x root of 2)= 36V. Then the transformer is overloaded if the output DC current from the project is (91.8VA/36V)= 2.55A.

The rectifier bridge reduces the output 2V and ripple reduces it further maybe 2V. The current-sensing resistor R7 reduces it (2.55A x 0.47 ohms)= 1.2V. The output transistors reduce it about 1.5V and the driver transistor reduces it about 0.8V. The saturation voltage of opamp U2 reduces it about 1.8V. Then the total reductions are 9.3V so the maximum output voltage at 2.55A will be about (36V - 9.3V)= 26.7V and will be less if your mains voltage drops.
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papuga
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« Reply #1389 on: October 31, 2012, 09:15:56 AM »

Thank you very much  Cheesy
So, if i understood right,it will work,but the maximum output of PSU would be 26.7V; 2.55Amps, without any damage to transformer or components..For my needs its good..
Anyhow i don't want to push it,but just one more thing,is there any way to modify PSU to give 30V?
It doesn't mater how many amps will give,i need the voltage.

Actually don't bother,if it will work,I will buy a new transformer one day.

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raresvintea
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« Reply #1390 on: November 20, 2012, 05:18:56 AM »

Hello. My power suplly work ok, till 2N2219 was blown.

Please recomand a replacement that can keep well hight currents without modifications or with minor ones. Please say what you tested and it works!

Thanks, Rares!
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redwire
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« Reply #1391 on: November 20, 2012, 10:56:47 AM »

Hi raresvintea,   It appears that you used the original design that has several parts that need to be upgraded.   Papuga posted the most recent sketch and parts list two or three threads above your post.   
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raresvintea
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« Reply #1392 on: November 20, 2012, 01:27:42 PM »

With the original design, using a lower voltage transformer (i will not obtain 30V but who cares!!!), i want to pus BD139, what modifications i need to do? What is the scope of Q1 in the original schematic? If i put BD139 and keep TL081, did i need to do modifications? What are those?

The recomanded opamps in the newer version is expensive in comparasion with TL081!

If i understand well, for 5A, i need 4 output transistors to keep up with the current, and a better rectfier!
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cpu123
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« Reply #1393 on: November 20, 2012, 10:26:33 PM »

I want to build this power supply. However, I am very confused about and how to start. There are several versions and proposed upgrades that I did not know what to do. I need the schematics and drawings of printed circuit board. The user "red baron" published schematics and pcb's desings, someone could confirm me if this is reliable? Apologies for repeating questions, I read a lot of stuff before, but I did not have my doubts resolved. Thank you.
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redwire
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« Reply #1394 on: November 21, 2012, 07:03:58 PM »

raresvintea,   check out http://www.electronics-lab.com/forum/index.php?topic=7317.msg1009204#msg1009204 or search for "inversion"  it will answer your questions about the Q1 and TL081.

I don't understand the concern that the new op-amps cost more.  They are about $1 more ($3 total) for the project.   The cost of boosting the power supply to 5 amps is probably at least $25 (beefier transformer, more 2N3055's, heat sinks etc).   Just building the original design and puting it in a case  is likely to run $80, so $3 more is insignificant.
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WinDTrek
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« Reply #1395 on: November 25, 2012, 06:07:53 PM »

i'm currently building the 5A version. i have all the components soldered already on the PCB. however just now i noticed that D10 is not in the schematic but it's on the part's list. i have check again the final schematic from red and audio and both has NO D10 but it's on their part's list.
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audioguru
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« Reply #1396 on: November 25, 2012, 06:47:49 PM »

The original schematic had a useless D10 from the base of the driver transistor to the output.
I deleted it from my schematic but it is still on the parts list by mistake.
The 10V/1W zener diode is on my latest 3A schematic (March 11/09) but it does not have a "D" number. It is D12 on my latest 3A parts list.

I didn't make a schematic for the 5A version because the changes are only a few.
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redwire
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« Reply #1397 on: November 25, 2012, 07:57:04 PM »

Audioguru,   Also note that the 10V, 1W Zener is listed as D12 on the parts list but on the schematic D12 is an led indicator for the current control.   If you make the changes I'll  post the revised parts list on the first thread.
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WinDTrek
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« Reply #1398 on: November 26, 2012, 01:35:10 AM »

red/audio.. thanks..   
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red baron
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« Reply #1399 on: November 26, 2012, 05:32:31 AM »

Hi AudioGuru
Finally the project is near completion - pics attached.  Thank you for the help getting to this stage.
I have two problems:
1) The current limiting circuit does not function correctly and I need some help with trouble shooting.  With P2 turned down to about 1kohm (near minimum) the LED comes on, but turns off one current limit is set higher.  Setting the maximums of 5A and 30V, the LED starts to turn on faintly and then gets brighter, but only at the max.  In between all works well.  Could Q3 have blown?
2) From the pics you will see that I have used Picmaster pcb, but I believe there is one mistake - the polarity of C10 (in your circuit C3) has the +ve on the pcb away from ground and -ve connected to ground.  Surely not correct?
Regards
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