Max PWM Value for temp controlled chamber fan?



  • Hi,

    I would like to upgrade my current 12V System (Linear Kossel Plus with Duet Maestro) to 24V.
    Got everything prepared - good new 24V MeanWell PSU, new fans for the hotend, reminded myself of changing the smart effector jumper, switched heating capsule and edited my Lights makro to use S115 instead of S255 - should be roughly 12V for my LEDs connected to the heater pins.
    Last thing remaining is the temperature controlled chamber fan - is there any way to set a max pwm value of ~50% too ?
    It is currently set up with
    M106 P1 S0 I0 F20000 H103 H45:55 ; Set fan 0 value - chamber fan

    Thanks 😃 Oliver

    Edit says : As far as I understand this, hooking a buck down only for the chamber fan won`t be ideal for the temp controlled fan ?! Probably best solution is to just replace the fan with a 24V version too !?


  • administrators

    @p1ngb4ck said in Max PWM Value for temp controlled chamber fan?:

    Got everything prepared - good new 24V MeanWell PSU, new fans for the hotend, reminded myself of changing the smart effector jumper, switched heating capsule and edited my Lights makro to use S115 instead of S255 - should be roughly 12V for my LEDs connected to the heater pins.

    LED strings are very non-linear. If you power a 12V LED string form 24V, it won't just take twice the current, it will take around five times the current. So 20% PWM would be about right. However, that will still increase the power dissipation in the LED series resistors by a factor of 5, which will probably blow them. So don't do it. Use a 24V strip, or two equal 12V strips in series. Or use a 12V buck converter to feed the +ve input to the LED strip.

    @p1ngb4ck said in Max PWM Value for temp controlled chamber fan?:

    Edit says : As far as I understand this, hooking a buck down only for the chamber fan won`t be ideal for the temp controlled fan ?! Probably best solution is to just replace the fan with a 24V version too !?

    It's perfectly possible feed 12V from a buck converter to the positive side of a fan.



  • Hi dc42, thanks so much for wasting your time with such noob questions - I am sure it was discussed earlier and I apologize - tried to quickly look it up, but didnt find the exact answer - thanks so much for clearing this up to me.
    Yes, its clear to me that a buck converter would work in general - only question to me is - will this work with the temperature control too ? e.g. the temperature control only switches the fan on and off, but not with different fan speeds?


  • Moderator

    @p1ngb4ck said in Max PWM Value for temp controlled chamber fan?:

    e.g. the temperature control only switches the fan on and off, but not with different fan speeds?

    The PWM signal is switched on the negative side, so it should still work even with the positive side being fed by the buck converter.


Log in to reply