Subject: yellow cooling fan connection
By: Lou Bricant (IP: 87.242.153.*)
Written on: 29-01-2007 17:36
I have observed that most cooling fans have 3 wires red black and yellow. The red and black can go to the cooling fan 3 pin connector, or to the 12 volt connections on what I will call a 4 pin hard drive connector, connecting to the yellow and black connections to give 12 volts.
The 3 pin connector has an additional lead , a yellow wire, this comes from a temperature controller on the chip I think and is to slow the fan down when the chip is cool.
What I am asking is this ....How does this speed control work? Is the yellow wire supplied with a variable voltage to control the speed? Alternatively I wondered if the speed might be controlled by a variable resistance onto the yellow wire , as the resistance to earth changes, the speed would change. I guess its probably one way or the other. Any advice or knowledge gratefully received