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DIY Power Supply

Today we take a look at re-purposing computer power supplies.

If you’re anything like me you probably have a small stash of computer power supplies lying around in the corner of your room. You saved them just in case your computer’s supply dies but now they are turning into clutter and a magnet for dust bunnies.  Now I’ve finally found a use for at least one of them:  to use as a bench power supply.


Here is the end result. A small box that sits on top of my desk. It has 4 posts: Ground, 3.3volts, 5volts and 12volts. Hit the jump for more details.


Here is the power box again. It has a toggle switch to turn it on and off and a LED light that glows when it’s turned on.


If we follow the cable we see that it leads to the original computer power supply. Only it has been slightly modified. The cables have been cut off and instead the chassis has been fitted with a plug. The plug has 7 pins, which are used for 12v, 5v, 3.3v, Switch, and 3 pins for Ground. Each wire of the power supply has a specific voltage. Here are the wires I soldered to the plug:

RED wire – 12 volts

ORANGE wire – 5 volts

YELLOW wire - 3.3 volts

GREEN wire - Switch

BLACK wire - Ground

img_0154 img_0153

Some more pictures. Inside the box are just wires soldered to the binding posts, LED, and the Switch.


img_0179 Close up on the connector. It was bought from  The power supply wires used to come out of that hole, now there is a plug mounted there.  The hole turned out to be just the right size, I got really lucky.

7 pin jack7 pin plug


Here is what you’d find inside of the breakout box. The switch on the black box turns the main power supply on and off. The power supply has this feature built in already. All that was needed to be done was to wire the green wire to the Switch along with Ground. When the Green wire is connected to Ground, the power supply turns on. When the Green wire is left disconnected, the power supply turns off. Normally the motherboard does this, but by connecting the wire to the Switch I can turn the power supply on from the black breakout box without having to bend down and turn on the Switch on the power supply itself.

If you’re thinking about building your own power supply out of a computer supply I recommended this tutorial.