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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?
https://en.wikipedia.org/wiki/Pulse-width_modulation
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. If you're already there, then you can build the circuit twice. One for the Cold End fan (A5 upper) and one for the component cooling fan (A5 lower).
Note:
Just as the A5 is delivered from the factory, only the component cooler is PWM controlled. The Cold End Fan is directly connected to 24V. Here the filter can not filter PWM noise. In another post, I show how to regulate the cold end fan via PWM and thus gets quieter. Then the filter helps to prevent PWM noise for the Cold End fan.
Required Electrical Parts (for one fan)
- 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
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
More content is coming soonβ¦
Status 5. July 2018: Under construction