Introduction: Bench Power Supply Using PC Power Supply

This comes in handy for testing most DC circuits that use 1.2 VDC up to 20 VDC. Total cost was less the $20. I know that this doesn't have the best looking wiring on the inside but I rushed placing components because I really needed it do for testing components at work.

Warning: In this project you wont be inside the PSU but if you do open it make sure to give a day or to unplugged for the capacitors to discharge. The wires coming out of the PSU only have 3 Amps so besides a quick shock there wont issues.

Step 1: Supply's

1. Tape
2. Screw Driver
3. Computer PSU
4. Cable
5. Soldering Iron
6. Drill & Bits
7. Wire cutters
8. Wire strippers
9. Volt Meter
10. Test leads with patch banana clips (red & Black)

superglue or epoxy

Step 2:

Step 3: Circuit Components

• Switch
• 2 LEDs of any color (Red and Green)
• 2 Resistors 330 OHM
• Heat Shrink Tubing
• External Enclosure
• Drill and Bits
• LM317, LM338K, or LM350T Voltage regulator
• 100nF Capacitors (ceramic or tantalum)
• 1uF Capacitors Electrolytic
• 1N4001 or 1N4002 Power Diode
• 120 Ohm resistor
• 5k Ohm variable resistor
• Binding Posts

ATX Power Supply Extension Cable ( comes included with most PSU)

Step 4: Circuit

I tested the circuit on a bread board first.

note: the voltage regulator can have different pins from what is shown. make sure to look up the stats sheet.

Step 5: Future Improvements.

Add a USB port to it by connecting it to the 5 DCV.

Add a cigarette lighter to the 12 DCV if I can get it to fit inside case.

a built in voltage meter.

Step 6:


lhj734017 (author)2014-07-01

where in the schematic is the diode supposed to go? I only see the location of the LEDs. I see the diode attached to one of the legs of the regulator chip in the picture but im having trouble following your wiring

klilly1 (author)lhj7340172014-07-01

Thanks for noticing that it goes in between the output leg and + 12 VDC I'll edit that when I get a chance.

jedii72 (author)2014-05-31

Cool project. Question: I was told that when you combine the + and - 12V, yes you get a loss, but you should not sure any of the Outs (+5 or +3) at the same time because the phase difference the 12Vs are using simultaneously will mess up the Vout. Have you experienced any such problem? Note: it was an electrical engineer trying to explain that to me, but since I'm not an engineer I may have lost something in the translation so my understanding my be wrong.

klilly1 (author)jedii722014-05-31

thanks this is all DC voltage so the phase will be constant also you do get voltage loss because the regulator needs to use some of it to work. I hope that helps. I could also explain why I use a negative and a positive voltage to get double the voltage.

mstone25 (author)2014-05-14

Ah sorry ignore my comment, I see you are using + and - 12V. :)

klilly1 (author)mstone252014-05-15

yeah I'm using +12 and -12 the and the most voltage I get out of it is about 20.1 VDC because of the loss.

mstone25 (author)2014-05-14

You do know that you can't get higher Vout than Vin don't you? In fact you'll lose about 1.6V across the regulator so best you'll get is around 10.5V with a Vin of 12V

About This Instructable




Bio: US Army Veteran, Maker and Tinkerer- Makers make things without tinkering or following instructions on a worksheet to complete a project is less about tinkering ... More »
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