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Old 05-17-2018, 05:20 PM
Charixfox Charixfox is offline
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Join Date: Oct 2015
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POST ID # = 955084
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PWM fans will not spin when only voltage is applied. They must have a PWM pull-up signal as well.

Steady 12v should be applied to the 12v line.

25khz PWM signal at 3.3 or 5V must be applied to the PWM line in order for the fan to spin. Notably, the signal can be "100% duty cycle", which means just a steady 3.3-5V applied, in which case the fan will spin at full speed.


For more information, see:
http://www.formfactors.org/developer...e_pwm_spec.pdf
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