Print cooling fan not working properly



  • My print cooling fan does not respond to fan speed changes or being turned off. The fan is always on regardless of fan speed setting. When the fan is set to anything lower than 100% speed it plusses.

    The fan is a 50mm 2 wire 5V blower style fan connected to FAN0 on my Duet WiFi. Below is my fan configuration located in my config.g

    M106 P0 S0.0 I0 F100 B0.1 H-1

    I have tried a number of different values for F as I have read that lowering the PWM frequency from the default 250 is sometimes necessary. I have also read that some fans do not like PWM, but I'm pretty sure that the fan I am using should work.

    Any ideas what the problem could be.



  • I think the h-1 is not meant to be there.

    Kind Regards,

    Sam



  • H-1 is needed to disable thermostatic control



  • How high of an F value have you tried? I had a fan that needed to be very high (10000) to keep it from pulsing. I eventually just swapped out to a better fan.



  • Highest I went was 1000. I using Pelonis fans and they definitely make high-quality products. I will try higher values and see what happens. Thanks for the suggestion.



  • I guess when I said better I meant to say, better suited. Some fans are just not designed to work well with a PWM voltage like this.



  • @phaedrux I tried higher frequencies with no luck. I also tried another 50mm blower fan I had laying around with no luck.

    Not sure what is going on as these fans work just fine on my other Marlin/Rambo based printers.



  • Just keep trying values from very low to very high.

    I wonder if them being 5v has anything to do with it? Not sure.



  • @phaedrux

    On a side note, PWM seems to work reasonably well with a Noctua 40x10 fan.

    You mentioned you found a fan that worked better. Was it also a 50mm blower? If so any chance you could shoot me a link it?



  • @jckray I use 12v Sunon blowers. Not sure if they have 5v equivalents. If you're still interested I can dig up the digikey link.

    Or if you know what you're looking for with fans browsing digikey might find you some good options.



  • https://www.digikey.ca/product-detail/en/sunon-fans/MF50151VX-B00U-A99/259-1829-ND/7691033

    https://www.digikey.ca/product-detail/en/sunon-fans/MF50151V2-B00U-A99/259-1870-ND/7942633

    The first one is a bit more powerful and louder, the second is practically silent, but will probably need 100% speed for PLA.



  • Hi,

    If raising F doesn't work then I would conclude that it is the fan.

    You do have the fan outputs configured for 5 volts - correct?

    I have used a wide variety of fans and never had one not work though some worked better at low speeds than others.

    Frederick



  • I made a little progress. I tried sending the fan configuration line M106 P0 I0 F10 B0.1 H-1 as a console command. This works until I reset my printer at which point it goes back to have the same problem discussed before. I confused because I have this exact same fan configuration line in my config.g.

    Does anyone have any idea why the line in my config.g is getting ignored? I pasted my full fan configuration section located in config.g.

    ; Fans
    M106 P0 I0 F10 B0.1 H-1 ; Set fan 0 value, PWM signal inversion and frequency. Thermostatic control off
    M106 P1 S1 I0 F500 H1 T50 ; Set fan 1 value, PWM signal inversion and frequency. Thermostatic control is turned pn



  • Okay nevermind. I have solved it! Should have waited another minute before making that last post. I had a bad line of code in a separate file I have set up to run on startup. Everything is golden now.

    Thanks for everyone's help and ideas!



  • Hi @jckray,

    Glad you got it sorted out.

    Just thought I'd chip in about the issue of PWM frequencies for the benefit of anyone else struggling with pulsating fans and potentially reading this thread. 100Hz (or even 1000Hz for that matter) is way too low for PWM fan signals. Although there's no one frequency that's suitable for all PWM fans, conventional wisdom puts the number at 25,000Hz (or 25MHz), while some even opting for a little higher (around 30MHz). Often times, changing the frequency to that level makes a significant difference in terms of the fan's acoustics.



  • @snowcrash Not sure if I am understanding exactly how PWM affects the fans, but could setting a high frequency (as in the mHz range as you mentioned) damage the fans or the board at all?

    I'm running a 24v blower fan and any time I set it lower than 100% it emits a high pitched whine (at 500hz). Curious as to if changing the frequency to much higher will remove the whine without damaging anything



  • @red-sand-robot said in Print cooling fan not working properly:

    @snowcrash Not sure if I am understanding exactly how PWM affects the fans, but could setting a high frequency (as in the mHz range as you mentioned) damage the fans or the board at all?

    I'm running a 24v blower fan and any time I set it lower than 100% it emits a high pitched whine (at 500hz). Curious as to if changing the frequency to much higher will remove the whine without damaging anything

    Raising the PWM frequency to the levels I mentioned won't cause any damage to the fan or board (btw, I previously verified with @dc42 in another thread that the board can generate these frequencies and indeed it can). I'm not surprised your blower whines at 500Hz. Give 25MHz a go and see if it solves the problem (don't forget the value is entered in Herz, so 25000).



  • @SnowCrash so 25kHz is what you recommend for even a 2 wire fan that is pwm’d? The wife got sick of the whine so I ordered some 4 wire fans but in the mean time should I bump it up that high as it might be a few weeks before the others show up.

    Regards,
    Sam



  • @samlogan87 said in Print cooling fan not working properly:

    @SnowCrash so 25kHz is what you recommend for even a 2 wire fan that is pwm’d? The wife got sick of the whine so I ordered some 4 wire fans but in the mean time should I bump it up that high as it might be a few weeks before the others show up.

    Regards,
    Sam

    Hi Sam,

    No reason not to try and see. Though certainly not all 2-wire fans like to be PWM'd as they weren't designed for this kind of operation, still in many instances there will be a significant improvement with higher frequency in terms of noise (and functioning).

    Btw, if you're hooking up a PWM fan to the Duet by running the blue (=pwm signal) wire to the GND pin of the fan header and independent power lines to the fan, don't forget to add the protection diode on the signal line.

    For anyone interested, I dug up 2 previous discussions on this topic in which @dc42 took part (and also include instructions on the said protection diode):

    https://forum.duet3d.com/topic/6054/help-configuring-pwm-fan-in-thermostatic-mode-for-duet-drivers/4

    https://forum.duet3d.com/topic/5248/maximum-frequency-of-pwm-fans



  • @snowcrash Hey, thanks for the tip to turn the frequency up to 25kHz! completely fixed the electronic whine I was hearing from my blower fan, didn't even think it turned on when I set it to 30% speed!


 

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