Computer PSU Conversion

A computer power supply is a dedicated power supply. It may be for running a computer, but you can harness this and modify it to run your chargers and other items that need a 12v source to run. Also, because it has a 5v rail, you can use it to test out radio gear such as servos and receivers and use the 3.3v to run your motors in. (do not do this if you are not confident in the voltage produced by the psu/power supply. If unsure DO NOT ATTEMPT. This Blog is intended to help. Any damage to your equipment/self will be solely your fault and will not be the responsibility of this blog.)

Parts List:
Equal or Bigger than 300w Power Supply
1x Green Led
1x Red Led
5x 10ohm 5w resistor
SPST toggle Switch
1x 1/4w 510 ohm resistor
1x 1/4w 100 ohm resistor
3x Black Binding Post
3x Red Binding Post
Super Glue


Step One: Find a suitable p.s.u. It should have 10 amps or above on the 12v rail. Depending on the charger that you use, you might need more than this.

Step Two: Check the wiring on it. It should have a 20 Pin Connector that usually goes to the motherboard. Now check whether or not it has a brown wire connected to an orange. If it does remember which wire it is. If not, continue on to the next step.

Step Three: Make sure the 240v lead is unplugged and power supply has been sitting for a while Open the case up. Locate the PS On wire, usually green or grey. Cut this off at approx 5cm from pcb. Remove all unneeded
wires, except for the Standby power, usually Purple, 2x Red +5v wire, 4x Black/Gnd wires. Cutoff -12v (dark blue) -5v (white) All except one Yellow/+12v and all all except one +Orange/3.3v (if there was a brown wire connecting to a 3.3v wire before removing the 20pin plug, leave 3cm of another 3.3v wire connected and connect this to the brown wire.)

Step Four: Put heatshrink on to the green wire and solder one side of switch attach a black wire to the other side.


Step Five: Solder the Orange and Brown wires together if present.
Solder the 5w Resistors together in Parallel, and put heatshrink on One of the Red wires and One of the black wires. Attach wires to the the resistors and shrink heat shrink.

Step Six: Drill Holes for binding posts, the switch and LED's and bolt in binding posts and switch.

Step Seven: Solder remaining wires to the binding posts, black to black, yellow to red, red to red and orange to red. Slide in LED's and apply a drop of super glue to the base to hold it in. Leave for ten minutes to dry throughly. Also if you want you could put some epoxy around the base of the led to anchor it better. Solder the 510 ohm resistor to the negative leg of the Red LED and attach to one of the ground binding posts. Attach positive to the 12v binding post. Attach 100 ohm resistor to the negative leg of the green led. Attach to one of the ground binding posts. Attach the Purple wire to the positive leg.

Step Eight: Put it all back together. Make sure that the case is closed before trying to test as you can easily brush something and get a nasty zap. Switch it on, and if the secondary switch is off, the green led should only light, but if it is on, the red and green should both light and the fans should go. Test that you have got the correct voltages with a multimeter.