I want to add some active cooling to my printer to help with my prints.

I recently printed the following file and found it will work on my printer:

http://www.thingiverse.com/thing:295317

I just have a lot of questions about the 3rd fan. I want my printer to control the speed of the fan and turn it off and on at different layers if I need to. This leaves me with trying to hook up the third fan to my machine. Something I have never done and since I am running a prototype printer there are really no notes about its hardware.

The other option I have is to run the third fan from a DC power supply preferably a small one that I can adjust myself.

Anyone have any comments or help on that? I am running a makerbot clone it looks like so is there a way to add a third fan? If not is it possible to run the third fan in parallel with the #1 fan as I really only use one extruder.

Finally if I should run a DC Power supply any suggestions on a small power supply?