Computer Power Supply and Switch Wiring Questions

[BrianG]

Any fan should have the operating voltage and current on the center hub sticker. Current draws for normal speed fans is around 0.25A or less. Those really loud and fast "vacuum cleaner" fans can take ~0.5A. Either way, any switch capable of 1A is more than enough to control 1 fan. RadioShack has a micro switch which is rated for 6A; I use these because I like the stiffness of the lever actuation (no comments linc!).

If you want a rudimentary speed control, simply use a SPDT "center off" (3 position) switch. Then use 2 or 3 diodes in series when the switch is thrown one way (reduces the voltage to the fan by 0.7v per diode), and direct power when thrown the other way. When in the middle, the fan is off. The "circuit" is really simple, but I can throw together a schematic if you need...

And to answer your question; yes, a 125v switch will work fine. The volt rating just tells you that the voltage will not "arc" between the contacts.