A Simple Bench Variable Power Supply

As I have started messing around with electronics more I had struggled a bit with a whole lot of different adapters for testing. After doing some research I came to a conclusion that building one from an old PC power supply would be more than adequate, being how it gives 12, -12, 5 and 3.3v available (some older ones have -5v also but mine being newer didn't) making it great for testing most electronic projects.

Tools and materials required:

• old (or new) working PC power supply to repurpose (mine was 300W)
• amplifier binding posts (got mine here cheap)
• on/off switch
• wood
• screws
• heat shrink tubing or electric tape
• wood glue

• hand saw
• jigsaw
• sandpaper
• soldering iron and helping hands
• drill and few bits
• pliers

First I cut the base for the bottom, then cut the holes in the back section for the fan, power plug and the indicator LED. I also made screw holes and screwed the panel to the back.

I cut off all except the 24 pin wire cable, leaving about 5 cm of each wire before wrapping them in electric tape. This is made so in case later I decide that for some reason I want to use those wires again.

Next I cut a piece of wood for the side, attached it to the bottom part and the back side. I also cut a smaller piece for the other side and attached it to bottom (not pictured here).

Cut a piece for the front and drilled the holes for binding jacks and on/off switch. Space between the holes is 2.5cm (1 inch). I also drilled the pilot holes and countersinks for the screws.

After that I put all the binding posts in and tested if all the cables would fit in the front when the panel is mounted.

I cut the wires to size and soldered them to the binding posts; isolated them with heat shrink tubing to make sure there would be no unwanted contacts. All the wires of the same color give out same voltage so some of them are bundled together. You don't have to do that, you can can just pull one of the appropriate color wires to the jack and cut off the rest. Green wire and ground is connected to the on/off switch; grounding the green wire will turn on the power. Colors have outputs as follows:

• Yellow +12v
• Blue -12v
• Red +5v
• White -5v (non existent on this PSU)
• Orange +3.3v
• Black Ground
• Green Power ON
• Gray Power on indicator (attach 330 ohm resistor and led to it and ground it if you want an indicator)
• Purple Standby (not used)
• Brown (older PSU) 3.3v check, must be connected to orange wires if you want 3.3v output

I cut some more wood for the top, bearing in mind to keep the ventilation holes open. I checked all the connections and finally plugged in the power.

After checking the voltages I wrote them down on the front panel. Hope you enjoy the project and good luck making your own.