Is there a way to power a fan at 50% power only when you're printing?



  • I just built a Kossel 250 Vslot BSE from Ultibots.com this weekend, it is a fantastic printer. For a delta it is SOLID has a bunch of awesome features but it uses a different style motor for the direct drive extruder, and they include a fan shroud and a 40mm fan to power it.

    Now I've used 40mm fans before on 12v and they are silent, but seeing this printer is 24v I don't know if it makes them louder or what, but it is LOUD. The printer on the Duet Wifi is DEAD SILENT but that fan, it's killing me.

    I know I have 1 more PWM fan slot open on the wifi, is there a way I can have it off when the printer is idle, and only have it come on at say 25-50% PWM power when it's printing, then shut off when the print is finished?

    This would be great for my sanity, and my fiance's. 😃

    Thank you!



  • My understanding is that it is not a good idea to run a 12v fan at 24v even with 50% PWM. So either get a 24v fan, or use two x 12v fans in series, or invest in a buck converter module (http://www.ebay.co.uk/itm/1-3-5-x-LM2596-DC-DC-Buck-Converter-Adjustable-Power-Supply-Step-Down-Module-UK-/161818793869?var=&hash=item25ad26d78dⓂmfnqbLbvaO6JOj7AXxfgPMQ) to get 12v output.

    If you want to be able to PWM control the fan using one of these converter modules you can:
    Connect the converter module positive input to the PWM fan header positive on Duetwifi.
    The converter negative input to your power supply negative.
    Then run the converter positive output to the fan, and then return the negative from the fan to the PWM fan header negative.
    The converter negative output is redundant as the ground is tied in the converter.
    This way the converter is only powered up when you want it on, and the duetwifi controls the PWM through the negative pin.

    If you want thermostatic fan i.e. fan on when one of your heaters is on then see the wiki here: https://duet3d.com/wiki/Connecting_and_configuring_fans
    Basically add M106 P1 T45 H1
    Where P1 is fan 1 and T is temperature and H1 is the heater to link it to.

    Whether you could use the thermostatic fan setting above with a command to set the fan to 50% pwm and still have it turn on/off triggered by the heater I do not know.



  • I believe the fan Ultibots provides to cool the "micro-extruder" stepper is indeed 24v as are the rest of the included electronics. It must just be a loud fan in general.

    Simply connecting that fan to your 3rd PWM fan channel and adding M106 P2 S.5 in your starting gcode would run it at half speed. Just make sure to keep an eye on the motor temperature to ensure the lower volume of air doesn't allow it to get too hot. Also keep in mind it's perfectly safe for most steppers to operate at temperatures that may be too hot to touch for extended periods, so it's not imperative that the motor be kept completely cool to the touch either. I imagine any small draft forced across the motor will be sufficient.

    I suppose you could even take this one step further and treat the extruder fan the same as an enclosure fan and control it thermostatically by attaching a thermistor to the stepper body. This way the fan would only cycle on when the motor needs to be cooled and cycle back off once it's temperature drops below whatever temperature threshold you set.


  • administrators

    @DjDemonD:

    If you want thermostatic fan i.e. fan on when one of your heaters is on then see the wiki here: https://duet3d.com/wiki/Connecting_and_configuring_fans
    Basically add M106 P1 T45 H1
    Where P1 is fan 1 and T is temperature and H1 is the heater to link it to.

    Whether you could use the thermostatic fan setting above with a command to set the fan to 50% pwm and still have it turn on/off triggered by the heater I do not know.

    Yes you can add the S parameter to that command to set the PWM, however the minimum PWM for thermostatic fans is 0.5 i.e. 50%.



  • Thanks for the help!!

    @DjDemonD:

    My understanding is that it is not a good idea to run a 12v fan at 24v even with 50% PWM

    Sorry, I should have been more clear. The printer came with all 24v fans, leds, psu etc. So it is fully 24v capable, i was saying the same size fan (12v variant) is SO much quieter by comparison.

    I ended up doing what W3DRK said to and it's worked perfectly..



  • Fair enough. I agree with W3DRK about steppers, if they are attached to metal, they can safely run quite hot, its when they're attached to printed parts its a problem if they're running hot.



  • @DjDemonD:

    Fair enough. I agree with W3DRK about steppers, if they are attached to metal, they can safely run quite hot, its when they're attached to printed parts its a problem if they're running hot.

    No worries man, it uses this motor

    http://www.ultibots.com/pg35l-048-geared-stepper-motor/

    and it is attached to printed parts, which is why I'm guessing it needs a fan. I can't see it getting too hot just extruding plastic at such a slow rate, but just to be safe I built it as I was instructed to.


  • administrators

    PG35Ls do get very hot in my experience although I have not used the Ultibots ones. Adding a fan or a good heatsink is a really good idea especially as the gears were plastic on the ones I had.


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