PWM Fan Frequency / Duty Cycle Question vs. 100%

  • I've got a question about how the Duet handles PWM fans set to operate at 100%. I want to make sure I've optimized a thermostatically controlled fan that is intended to run at full speed.

    Is the fan output more or less just left ON when set to 100% or is PWM still in play?

    If PWM is still being used and the fan can handle low and high PWM frequencies, is it best to operate at higher or lower frequencies at that point to get the most RPM out of the fan?


  • administrators

    100% PWM is fully on.

    For 2 wire fans I recommend using the default 500Hz PWM frequency if it works, but drop to 100Hz if necessary. For 4-wire fans with a separate PWM input wire, the PWM frequency should be 25000Hz.

  • Thank you!

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