Question About Fans

[AMD Killa]

Hi, I will be running two fans in the project that I mentioned in the thread about the LEDs that I made. How can I get the fans to run at 9 volts or 7 volts so that they are quiet? At a guess, I think I need a resistor, but not sure what ohm resistor I need. 5 volts would be ok also, they are 80mm fans. I'm gonna use the fans to create airflow to cool a 250watt pc power supply. Would two 80mm fans on 5 volts be enough?

[FuzzyPlushroom]

Seven volts is easy, just plug the positive wire into the 12v line, as normal, on one of your Molex connectors (yellow), then plug the ground wire into the 5v line (red). 5v is even easier - just connect positive to red, ground to ground.

If the fans still have the four-pin Molex plugs on 'em, you can just take a pair of scissors or similar to the rounded edges of the plug and orient the plug upside-down; it'll run at 5v that way.

I couldn't tell you for sure whether they'd be enough - I don't know their airflow at 12v, I don't know whether they'd even spin up from 5v (many will not; most 12v fans have a minimum voltage of 6-7 volts to start) and I don't know the load this power supply will be expected to deliver.

[DonT-FeaR]

one of these should do the trick

http://www.pccasegear.com/index.php?main_page=product_info&cPath=40&products_id=885
http://www.pccasegear.com/index.php?main_page=product_info&cPath=40&products_id=3603

[AMD Killa]

cheers, I was only asking to confirm. I dont want to mess up the power supply.

[xmastree]

More about it here (http://www.thebestcasescenario.com/forum/showthread.php?t=9023)

Are the fans identical? You could connect them in series and they'd each get 6V. I'd put a 100µF capacitors across each one in this case, as they're a dynamic load.