Using heater two output for fan with thermostatic control



  • Greetings

    I have configured the heater two output with the required gcode M307 H2 A-1 C-1 D-1 to make it usable as a generic output via M42 P2 S(0-1) but I would like to be able to use this output as a thermostatically controlled fan like you can do via gcode M106 P2 S1 I0 F500 H1 T45.
    I have looked at the gcode reference and have not found a way to configure an M42 output to be used as a thermostatically controlled fan, is this currently possible and I have missed how to configure it?

    Another thing I did not see in the gcode reference material is how to change the pwm frequency of a M42 controlled output. I have found that when running the fan at anything other than full speed ie S1 that it buzzes in the most annoying way. It would be nice to not have to run the fan at full speed as it is kinda loud


  • administrators

    There is currently no facility for repurposing a heater output as a fan output controlled by M106.

    I can add an F parameter to the M42 command to set the PWM frequency if you need it, however there are some fans that just don't work with PWM at all because they have a long startup delay.



  • Having the F parameter would be very helpful. I used to have the fan paralleled with another fan on one of the PWM fan outputs and it seemed to work with out producing the buzzing with an F100.
    I changed this as I wanted to have more control over when specific fans turned on and at what speed they run at. These are compartment cooling fans for the power supply and Duet and I was hoping to have thermostatic control of them, I am really looking forward towards the proportional control in 1.19
    One thought I had was producing a small breakout board that would have the components needed for the additional fan channels on the expansion port and adding in the additional thermistor inputs as well. That would allow for the most flexibility in having more fans and temp inputs to monitor things in the future.


  • administrators

    I've added the F parameter to the M42 command in 1.19beta7, which I intend to release tonight or tomorrow. Like the I parameter, it isn't remembered for M42 (unlike in M106).


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