A desktop power supply is an extremely handy kit for electronics enthusiasts, but it can be expensive when bought new. If you have an old ATX PSU computer, you can give it new life as a desktop power supply. Here’s how.
Like most computer components, power supplies (PSUs) are outdated. When you upgrade, you may find that you no longer have the right connectors — or that your shiny new graphics card needs a lot more power than your little old PSU can handle — a dual GPU setup can easily draw up to 1000W. And, if you’re anything like me, you have a stash of old power supplies tucked away in a closet somewhere. Now is your chance to use one of them.
A desktop power supply is basically just a way to supply a variety of voltages for test purposes — perfect for those who constantly play with Arduinos and LED strips. Conveniently, that’s exactly what a computer power supply does too — just with a lot of different connectors and colored wires.
Today we’re going to strip the PSU down to its basic needs and then add some useful sockets in case we can plug projects into it.
Ordinarily you would never open a power supply. Even when the power is off, there are large capacitors that can hold deadly electrical current for weeks and sometimes months after being turned on. Be extremely careful when working with the power supply and make sure it hasn’t been used for at least three months before opening the case, or make sure you wear heavy gear gloves when poking around in there. Proceed with Caution .
Also note that this will permanently damage the power supply, so you will never be able to use it on your computer again.
- Two 2.1mm barrels and a connector — I will power the Arduino directly. Two plug connectors will be used to make a male-to-male power cable.
- Variety of 2mm colored sockets such as this one (can be used with banana plugs). You may prefer terminal messages.
- Heat shrink tubing, 13mm x 1m (less if you can afford to buy more).
- SPST (Single Pole Single Throw) rocker switch. I used illuminated to do double duty as a light source.
- 10 W 10 ohm wire wound resistor.
Unscrew and remove the top part of the power supply case. You may need to remove the plug from the main circuit to completely separate the caps.
These are nasty capacitors that contain a huge amount of electricity:
Remove the plugs and run the wires through the hole in the case.
Then tie them together with cable ties to match the color to keep things a little more organized. As a general rule:
- Black: ground
- Red: +5V
- Yellow: +12V
- Orange: +3.3V
- White: -5V
- Blue: -12V
- Purple: +5V standby (not used)
- Grey: power indicator
- Green: switch
The exact power lines you choose to connect are your choice, but I chose to work with only 3 positive lines — 3.3, 5, and 12V. I will also not use purple or gray wires, instead I will connect a 12V illuminated switch.
Use HSS drills to cut appropriately sized holes in the metal — 2mm plugs and DC cylinder required 8mm holes. Secure the body with a piece of wood underneath. Making the hole for the rocker switch was a lot harder, but you should be able to use a smaller drill to cut out as much as possible and then feed the rest with a hobby drill and grinder.