I just got two PC fans in the mail today, but I have a qustion.
These fans have 4 wires. Positive 12v, Negative 12v, PWN wire and a sense wire.
I've read a bit on the internet about PWM control a PC fan from an arduino, and it's a bit hard to use the PWM wire.
Is it possible to PWM control the fan using only the red (12v+) and black (12v-) wires. Can I just hook the yellow PWM wire to 12v+?
I'm thinking that you should power the fan normally thru the red and black wires and then PWM the PWM wire. That way the tach (sense) output wire will provide an accurate indication of RPM. Once you connect the red and black wires, the fan should run at full speed with the PWM wire floating. You should then be able to PWM the PWM wire.