I am planning to use an old computer power supply to power my fans, but how would you go about switching the power supply on (so the fans start moving)? Thanks for any help you can offer.

http://www.directron.com/2powersupplies.html

Thanks for the link!

if it is an atx power supply,turn the main conector upside down so that the retainer clip is facing up.from right to left count over to the fourth and fifth wires.they shouldbe in order form right to left brown,blue,black,green,black. short together the #4 position green and the #5 position black.then plug it in and it should power up. what this does is show a dummy load to the power supply thus swithing it on when you supply it ac power.hope this helps

ron
p.s. this only works for an atx type power supply

Here's the easy explanation.

Thanks [H]ardOcp