PWM Fan Testing Notes

Article based on the following videos/articles:
https://www.youtube.com/watch?v=4oCDdvxh5iQ
https://www.youtube.com/watch?v=gKHww3qJbs8
https://www.youtube.com/watch?v=Tzn9Rg9jIVQ

Quick test of controlling the speed of various brushless DC fans using PWM at various frequencies.  Speed control of brushless fans using a constant voltage is usually recommended.  However, PWM can be used in most cases. 

Wiring:
PWM signal into IRFZ44 N-CH MOSFET.  Fan +/- to DC power and MOSFET output.  Meter displays % duty cycle.  Osciloscope top trace (CH1) is input PWM signal.  Bottom trace is MOSFET output.  Operating frequency is 400-5000Hz.

The fan is still functional at various operating frequencies with little effect on speed.  The PWM % determines the speed.  At low PMW % (10%), the fan may not startup.  In most cases, 25% PWM is required. 

Audible switching noise is commom when using PWM at less than 20kHz.  Higher operating frequencies may lead to other noise problems.

Recommendation: Use a brushless DC fan with PWM input (4-wire) or constant voltage for speed control.  If using PWM, use a higher operating frequency with some noise filtering.

Arduino PWM Fan Controller: https://www.youtube.com/watch?v=Tzn9Rg9jIVQ

Another Arduino PWM Controller: https://www.youtube.com/watch?v=DAn4UguyzfE   MOSFET based along with Arduino

 

 

Support File(s):