Using Graphics Card fan in project

[Mike]

Yesterday was the tent sale at American Science and Surplus, a surplus store, and I purchased a fan there. It is made by 3dfx, so I am assuming it is a graphics processor fan, and I want to use it to cool a heatsink. The only problem I have is it has 3 wires, a black, red, and white. Which ones connect to the supply. My supply is of the split type, so I would connect it between the + and ground, right? I am running two of the fans on the heatsink. They each use 5V.<p>Thanks, Mike

[russlk]

Most likly the red is positive and black is negative power. The white is probably a tachometer output. Just to be safe, connect 10 ohms in series with the red or black wire and connect to 5 volts. If the fan turns, take the 10 ohms out of the circuit. If it doesn't turn, your guess is as good as any on which wire is which.

[dacflyer]

white whire could also be a speed control for the fan..being controlled by the computer etc...

[chessman]

<blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr>Originally posted by dacflyer:
white whire could also be a speed control for the fan..being controlled by the computer etc...<hr></blockquote><p>"A" for effort, but that's not how comp speed controls work for fans. The third wire is a tach output, so the comp knows how fast the fan is going. The comp supplies a PWM voltage to the +5/+12 and GND pins, thus varrying the speed.