DIY laptop cooler

bushmins · 13 Sep 2009 at 08:11

Im looking for a circuit diagram that uses USB to power 2 x 5V fans. Has anyone got a link to one? I had a search but didnt turn anything up.

Unless i just need to connect the USB +5V and - directly to the fan?

mattyfez · 13 Sep 2009 at 09:03

I guess in terms of wiring you just need pins 1 & 4 hooked up to the fan

http://www.riccibitti.com/pc_therm/USB_A_pinout.jpg

PhillyDee · 13 Sep 2009 at 12:08

Yes, thats all ou need to do.
But a USB port only supplies 500mA so make sure that the fan is within those specs.

bushmins · 13 Sep 2009 at 12:40

I think most fans run at about 0.17A, so ill have no trouble hooking two up. Its just finding one that states that it works from 5V.

bushmins · 13 Sep 2009 at 14:47

Would i be right in saying that all fans that have moles connections can run off 5V?

JonJ678 · 13 Sep 2009 at 17:57

Nope. Generally they have the 12 and 0 wired up, and not the 5.

The issue is that 5V is too low to start some fans, so when you apply 5V nothing happens. Annoyingly some will run at 5V but need 6.5V or so to start.

You want the fans in parallel of course, so wire both + wires to the same usb pin, don't string the fans along. An alternative approach is to run two in series from a 12V line, but laptops don't have this so easily available.

edit: include a switch to turn them off

bushmins · 13 Sep 2009 at 19:59

Guess ill have to buy cheap fans and hope they work off 5V.

JonJ678 · 13 Sep 2009 at 20:16

Or you can visit silentpcreview, where they're likely to know which fans can be run at 5V

mattyfez · 15 Sep 2009 at 11:25

Just a random thought, but if they struggle to spin, could you push-start them? would that work?

5abr3 · 15 Sep 2009 at 11:40

Yes but you might cause issues in the USB rail as you are to some extent using the fan as a generator, also on startup some DC motors can use more than their running current for a short period of time (if they are running at 0.17A most of the time then they shouldnt exceed 500mA)