DWC - Set Fan max value

  • Hey so are using Duet Web Control (DWC) and we have our 3 PWM fans set to be visible.

    We would like to set the maximum value of each so certain fans can only go to a certain specific amount. So instead of Fan 0 going from 0-100% we want to limit it to 0-50%, but Fan 1 can go from 0-100% or whatever we tell it.

    This may not make sense to you, but the reason we want to do this is because one of these fan connections might be hooked up instead to interior LED's and we want to use the PWM slider to give a cool effect of dimming/brightening the interior lights.

    We have successfully done this already with no changes made, but when we went to 100% for the LED's there was noticeable smoke coming from the connection so we want to make sure not to burn anything and instead limit the current going to the Fan/LED connection.

    Here is a snippit of code from interface.js:

       // Fan Sliders
    setFanVisibility(0, settings.showFan1);
    setFanVisibility(1, settings.showFan2);
    setFanVisibility(2, settings.showFan3);
    numFans = undefined;						// let the next status response callback hide fans that are not available
    $('#slider_fan_print').slider("setValue", 35);
    $('#slider_speed').slider("setValue", 100);
    for(var extr = 1; extr <= maxExtruders; extr++) {
    	$("#slider_extr_" + extr).slider("setValue", 100);

    We are thinking that we can just change the 100 in this section to 50 and then the maximum can only be 50%...

    Is this correct?

    Thank you!

  • bump for visibility 🙂

  • Bump! Hope everyone had a good weekend! Still looking for a bit of help on this issue. Thanks!

  • Why don't you limit the PWM to the output in the firmware instead of DWC? I don't think either way is the correct way to go about doing this but I don't know enough about hardware to offer a better alternative.

  • administrators

    How much current do the LEDs draw? If it's more than the maximum recommended 1.5A, can you use lower powered LEDs?

  • This is addressed in https://github.com/dc42/RepRapFirmware/pull/179 but in firmware as @tjb1 suggested. Then it will be only a matter of adding the respective M106 ... commands to your config.g - though I am not sure how DWC will react to setting a fan slider to 100% but the output being limited to e.g. 50%. But since there already is a lower limit I guess it will just handle this out-of-the-box as well.

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