I want to use my CPU fan for cooling of other components outside of the computer. The problem is that when not connecting the PWM, the fan runs at minimum speed. How high voltage and ampere should I supply it with? Is it just a small pulse, or does it have to be a specific voltage?


You must provide a open-drain or open-collector PWM at 25Khz.

With maximum voltage of 5.25v / 8mA.

More information here

  • That document states that "If no control signal is present the fan shall operate at maximum RPM." (section 3.3). – Andrew Morton Feb 23 '14 at 18:45
  • Yeah @AndrewMorton that's the common, this is strange for me the fan operate at lowest speed without control signal. but him can try apply the pulse and see if the fan speed up. – Victor Aurélio Feb 23 '14 at 18:56
  • @AndrewMorton and Victor Aurélio: When trying it, the fan reached what I believe is the top speed. Then the speed turned down a lot. Maybe it has a very high speed when turning on? It is the i7 3770k stock fan. – Friend of Kim Feb 23 '14 at 19:07
  • @FriendofKim I don't know. have you see this fan working on the mobo ? if yes, the speed is higher than the fan without control signal ? – Victor Aurélio Feb 23 '14 at 20:22
  • No, I haven't tried it. I'll try, and just try with a PWM if it is faster on the mobo. – Friend of Kim Feb 23 '14 at 21:10

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