Welcome! Log In Create A New Profile

Advanced

Lower PWM frequency on part cooling fans?

Posted by bowzee 
Lower PWM frequency on part cooling fans?
November 23, 2019 06:06PM
I am having a problem with my part cooling Sunon maglev fans, they will not rotate when the PWM is lower than 80% in default conditions and 60% when using the FAN_SOFT_PWM and SOFT_PWM_SCALE 0 directives. Is there any way to make them work with a lower value? Maybe lowering the frequency even more, as to get an occasional blip?
Re: Lower PWM frequency on part cooling fans?
November 23, 2019 07:48PM
This is an issue with your fans they just don't do PWM very well

Google putting a capacitor over the power wires
Re: Lower PWM frequency on part cooling fans?
November 23, 2019 08:29PM
Dust, thank you for your reply.

So a low-pass (or averaging etc.) filter solves it? Wow, that is the exact opposite of what I would expect, in fact, by experience, usually these fans will stop working below a given (usually high) DC voltage. But I will try you suggestion anyway.
Re: Lower PWM frequency on part cooling fans?
November 24, 2019 03:23AM
Let us know how it worked out! smiling smiley


http://www.marinusdebeer.nl/
Re: Lower PWM frequency on part cooling fans?
November 24, 2019 04:19AM
Quite a lot of fans that don't work at the standard PWM frequencies do work with 100Hz PWM. Some others, such as the heatsink fans supplied with E3D hot ends, don't even work at those low frequencies.

You could use a flyback diode and a series inductor as a low pass filter, but in order to keep the inductor reasonably small you need to increase the PWM frequency to several 10s of kHz.

Some people use a parallel capacitor to partly smooth the PWM, but this risks blowing the mosfet because of the high peak current when the mosfet turns on and the capacitor charges.



Large delta printer [miscsolutions.wordpress.com], Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].
Sorry, only registered users may post in this forum.

Click here to login