I'm looking at building a new system and most of the good cases come with several fans, but most of the motherboards I've looked at only have one 4 pin case fan header. I'm looking for a guide on hacking in an additional hwmon compatible controller to add a few more 4 pin PWM fan headers so I can have the fancontrol package slow and spin down all the fans when the system is cool and idle.
migrated from askubuntu.com Jan 12 '11 at 17:10
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After reading everything I could find on the subject, it seems that the 4th pin contains the raw PWM signal, and the fan is expected to contain the mosfet and bypass diode required to use the PWM signal to regulate the voltage down from the 12v supply. It seems that I can add another hwmon controller described here:
The motherboard I am thinking of buying has one 4 pin and two 3 pin fan headers, and the case has 3 fans, so what I think I will do is break the PWM pin out of the 4 pin and split it out to all 3 fans. The motherboard might not be able to sink the combined current, so I will probably add a transistor to boost the signal.
That should let me control the speed of multiple fans, just not independently of each other. Now I'm just having a hard time finding 4 pin fans.