Remove Fan PWM Noise

Author: AETEK

The changes shown here require knowledge in the field of electrical engineering and can overwhelm normal users. Also, I would like to point out possible dangers that exist in certain interventions. All adjustments have been checked for function.

Difficulty: Advanced

What is this about?
PWM (Pulse-width-modulation) is a technique to control the performance of e.g. a fan (as in the A5). As a side effect, noises can be emitted through the fan due to the pulsating current. This refers to noises that cause the propeller to vibrate due to the electric coils. Noise can also have other causes. Worn bearings are often the cause. The PWM filter does not help against this kind of interference noise. If the fan is mechanically good and there is still noise, then it is the PWM frequency emitted by the fan. The Marlin firmware offers several options to reduce noise by software. I have checked all these options. Unfortunately, hardly anything has changed in the result. That's why I developed this hardware solution. It is specially tailored to the fans of the A5.

Just as the A5 is delivered from the factory, only the component cooler (A5 lower fan)
is PWM controlled. The Cold End Fan (A5 upper fan) is directly connected to 24V. 
There is no PWM. So the filter can not filter PWM noise. In another article, <add link> 
I show how to control the Cold End Fan (A5 upper fan) via PWM and thus gets quieter.       
Then the PWM filter helps to prevent PWM noise for the Cold End fan, too.

Required Electrical Parts

  • 1 x Diode 1N 4007
  • 1 x Resistor 100 Ohms 3 Watts
  • 1 x Electrolytic Capacitor 220uF 35V
  • Optional 2-Pin plug and socket for building a plug-in-adapter.
  • Some cable and heat shrink

The hobbyist will most likely have the parts in the tinker box.

Build The Circuit




Please note the polarity

Connection On MKS GEN_L Mainboard

The PWM-Filter is connected between the MKS GEN_L mainboard and the fan.

The speed and volume of the component cooler (lower A5 FAN) can be regulated via GCODES. The cooling duct supplied by the factory is not effective. DaHai has tested alternatives and found that fan speed can be reduced with a more effective cooling duct. This is very good because we want to reduce noise.

Printable Cooling Ducts on Thingiverse

Status 6. July 2018: Did Some Text updates

a5/remove-fan-pwm-noise.txt ยท Last modified: 2018/07/06 15:23 by aeket