Hi

I’m very much a newbie at this sort of thing, so please excuse any apparently stupid questions / assumptions.

We have a media pc that lives inside a cabinet.  Things have been heating up in there so I hooked up an 80mm fan, at the back of the cabinet, to push out the hot air.  At the moment the fan is powered by an old 12V power adapter that I had lying around, but everything seems to be working well.  Unfortunately with this setup, any time we want to use the media pc, we need to remember to turn the fan on and it would be really great if it could come on automatically.

I had considered powering the fan off the pc power supply but I’ve discounted this because it would mean having wires sticking out of the case and would be harder to disconnect in the event of pc maintenance.

I’m now playing around with the idea of triggering the fan by way a USB port.  This is where my ignorance comes in, but it seems to me that if I had a relay across the powered USB port, it could switch on the external fan.  It doesn’t need to be anything flash – just when the computer comes on, the fan comes on.

If this is viable, what components would I be looking at?  Is it as simple as finding a 5V relay (e.g. http://jaycar.co.nz/productView.asp?ID=SY4036) and bridging the USB with it, or do I need something a bit more complicated (e.g. http://jaycar.co.nz/productView.asp?ID=KG9142&), or am I looking at having to develop a full-on circuit to support the relay?

Thanks in advance.