Duet Board Fan Control

  • Hi Everyone,

    I hope everyone is having a good weekend.

    Is there anyway that you can get the board cooling fan to only turn on when the motors are powered up?

    Kind Regards,

  • @samlogan87 Not exactly (at least not that I can think of off hand) but do you really want to do that or do you want to turn on the fan when driver chips start to get hot? This makes more sense because when the motors are idle, they run at a lower holding current.

    For that latter case there area couple of ways to do it. The driver chips send a high temperature warning signal which can be used to tun on a fan. It's not a measure of temperature - just a flag. Another way to do is as I do with a bead thermistor stuck to a driver chip with dab of epoxy. More details here https://somei3deas.wordpress.com/2017/04/18/stepper-motor-and-electronics-cooling/ (this includes cooling motors as well but you don't have to do that). It's a bit out of date as you no longer have to define dummy tools and you can also give "virtual heaters" a name but it'll give you an idea of what's possible.

  • Thanks for your reply @deckingman

    Either would work. I will have a look at your post. Running it off the flag word would be quite a bit tidier I guess. Like you said, the fans main goal is to cool the drivers.

    Kind Regards

  • Hi @deckingman,

    Great article. Once I start with my bigger prints, I will probably be copying you with your motor heatsinks. They look the part. Has the driver heat flag implementation happened yet?

    Kind Regards,

  • I have found a post about it and how to do it. Should have searched a bit harder first. Will give it a go and see how I get on.

  • @samlogan87 Hi Sam. TBH I made a mistake and printed two of the motor mounts in PLA and these have still warped despite the fans and heat sinks. The other two that I printed with PETG are fine however. I think the ideal is to make motor mounts from metal if that's possible. Mine also act as belt tensioners so they can't be simple brackets. I don''t have access to metal fabrication facilities, bit I do have a 3D printer - hence the printed parts. But the thermistor stuck to a surface to thermostatically control a fan is still sound. I'm not sure what the high temperature warning flag on the drivers is set to but I think it's quite a high temperature so I prefer to have my fans coming on earlier.

    Having said all that, the very simplest solution is to use a large, slow, 100 or 120mm PC cooling fan and have it run all the time. They use next to no power and you get get virtually silent ones these days. But then where is the fun in doing that? ☺

  • @samlogan87 There is an open Pull Request from me that will implement a fourth condition on the driver's virtual heater that will indicate that they are powered. Once his has been merged you could do exactly what you asked for.

  • Hi @deckingman
    Upon further thoughts, I probably won't have to worry about the motor cooling as my mounts are aluminum and so is the frame. They do get warm but I can still touch it so it would be under 40 degree.

    @wilriker I saw you had comment about that in another post. I look forward to that.

    Kind Regards,

  • @samlogan87 No you'll be fine then. The mounts and frame will help to conduct heat away, whereas my plastic ones act as insulators. Most steppers are rated to 80deg C as well, so they can get really hot but still be fine.

  • Hi @deckingman ,

    Yeah I think I will leave them. I have another question for you now. This is what I have set up under heaters in my .config file:

    M305 P101 X2 S"Duet Drivers" ;
    M305 P102 X2 S"Duex2 Drivers" ;

    and under fans:

    M106 P3 F100 L0.6 B1 T20:40 H100:101:102 C"Duet Fan"

    When I did not have the M305 parameters there, the fan would work as it should based off lower temps that I put for the board temp just to make sure it works. As you can see the start temp is quite low (I will bump this up). However, since I have implemented the M305's, they are reading 2000 degrees and the fan is going full speed. I tried putting the standard thermistor parameters in as well as what I have above, and it has not helped.

    Can you shed any light on this?


  • Actually I worked it out. I need to map the correct thermistor to the heater.

    I now have under heaters;

    M305 P101 X1001 S"Duet Drivers"
    M305 P102 X1002 S"Duex2 Drivers"

    and under fans;

    M106 P3 F100 L0.6 B1 T20:40 H100:101:102 C"Duet Fan"

    Seems to work well and the wife will be happy once again as it is a bit quieter.

    Kind Regards,

  • @samlogan87 Glad you got it sorted.


Looks like your connection to Duet3D was lost, please wait while we try to reconnect.