Basically My PS3 has to be in a cupboard and it gets too hot and therefore I want to attach together and the to the cupboard some 120mm fans maybe 3 or 4 to keep it cool. And I plan to power it of the PS3s USB port. But which cable do I use for the power and I assume it is 5V , unlike the 12V the is the maximum for the fans. So the fans will just run slower.
So what is the best way to go about getting the power out of the USB, or should I just get a 12V AC adapter, and the rig up a relay to detect when the ps3 is on (How would i do the relay in this case???)
powering fans from the USB port will add to your heating issues. Specifically in the place you don't want the added heat (your PS3 PSU)...of course the fans help remove the heat, but, it would be better to power the fans from another source.