Controlling Fans

[plutoniumJoe]

I was looking for a way to control fans on my hood. The metal halide bulbs and ballast run on a simple 120v timer, however I am using an old pc power supply to run all my DC things like L.E.D.s and fans. I can't put my pc power supply on a timer because at some time during the day something is running off of it. I was wondering if anyone knows of a way to make my 12v or 5v fans kick in when the lights go on or for my moon lights to go on when my big lights go off. I am thinking there must be some type of relay that I could use or even a thermostat controlled relay for the fans.

[spreerider]

you could use a 120V controled relay to turn on your fans when the 120v for the lights turns on.
just connect the relay control wires to a standard cord end and plug it into your timmer like you would your lights, then connect the dc that you want to have switched to the relay switched terminals and when the lights turn on all the devices plugged into the relay will turn on.
make sure its a NO (normally open) relay or you use the NO contacts on that relay.

[BMW Rider]

I think the simplest solution would be to pick up another transformer and run the fans seperately. All that is needed to run the fans would be one of the wall-wart type transformers from an old piece of electronics gear. They are easy enough to come by and cheap.