Buzzing sound from controller fan

General Discussion
1

Basic Information:

Printer Model: Custom
MCU / Printerboard: BTT SKR Mini E3 V3
klippy.log: klippy.zip (43.7 KB)

I have a 2 pin 24v fan for cooling a BTT SKR Mini E3 V3. The fan is connected to the FAN2 pins. The fan works as expected using controller_fan in Klipper, but if I run the fan at anything less than 100%, it makes a vibrating/buzzing noise. I have tried several fans, and they all behave the same. If the fans are removed and connected to a lower voltage (3v and 5v) they run whisper quiet. Is there a way to stop the fan from buzzing when run at lower speeds?

2

Sounds like the PWM humming.
If you would have attached the requested klippy.log one could check what frequency you maybe set for those printer port.

Long story short: always attach the klippy.log

For your issue: it is often a compromise between noise and range of control of the fan via PWM.
Read here:
https://www.klipper3d.org/Config_Reference.html#fans

As I do not think your MCU supports hardware PWM you should only play with

cycle_time: 0.010

It is the reciprocal value (in seconds) of the frequency for PWM control.
Default is 10 ms or 0.010 what equals 100 Hz.
Some fans might work better with 1000 Hz or even more.
Depending on the set cycle_time you might not be able to properly control the fan speed.
Meaning the fan might then already spin with 100% RPM although being set to only 60 %.

And of course the fans should support PWM control.

3

Thanks LifeOfBrian. I have attached the klippy.log - lesson learned.

I’ll experiment with the cycle_time setting tomorrow morning (NZ time)

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