Duet Wifi PWM Fan0/1 not working, Duex2 has no PWM support??



  • Two questions:

    1:
    Both my Fan0 and Fan1 outputs stopped driving fans (I think there were shorts on both, one wire for sure touched the heater block). Strangely both outputs are still outputting a measured 12v but no fan of any type will spin up, whats happening here?

    2:
    I didnt thinking this was a big problem as I have a Duex2 8a which has a load of PWM fan outputs... except I read here they are not PWM signal capable!? Is this true? From plugging in the hotend fan to Fan7 I can see for sure its either "on or off", M106 S1 or S0, nothing in below 0 drives any fan. This is a problem as at full tilt (ie on) the fan overpowers and clogs my E3D Cyclops (I think, its a new build).

    2b: - Bonus question, for now Ive jumpered Duex2 fan output to 5v to slow it down. I have a 15v PSU and the 12v jumper selection doesnt seem to work. Docs suggest this is for 24v setups, is it normal it wont drop 15v to 12v?
    EDIT: Found you need to enable two jumper positions (12v_en and the 12v three way jumper block) to get 12v output working. Still no PWM though.



  • In answer to your first question the positive pin of the fan connectors is connected to 12V and the ground is switched. Are you measuring across the fan while it is connected?



  • @nophead
    No I wasn’t, direct off wiring connected to the Duet.
    I haven’t changed the wiring around and I have a schematic of the wiring in front of me. It was working, one wire got heated off block, now it’s not.


  • administrators

    The fan outputs on the DueX are PWM capable, however the PWM frequency is fixed. Many fans are OK with the default PWM frequency, but some types of fan only work with very low or very high PWM frequencies, and some don't work at all with PWM.



  • @dc42
    Hmm, good to know. What is the fixed PWM frequency? Im ordering new fans so perhaps I can use them instead. I tried 5 different types here and none of them worked..



  • @dc42
    Any input on this mysterious PWM frequency on the Deux2. Ive got an ever increasing pile of fans that aren’t working on PWM. Makes me think either something else needs to be set on it OR perhaps you statement needs to be inverted, most PWM fans do not work.


  • administrators

    The nominal PWM frequency of the DueX fan outputs is 488Hz. Other choices would be possible with a firmware modification, but all outputs would be the same frequency. The possible frequencies are 7.81kHz divided by 2^N where N = 0 to 6.


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