Disable Auto Restart on DC fans

Discussion in 'Overclocking & Cooling' started by MrPCB, Apr 19, 2019.

  1. MrPCB

    MrPCB n00b

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    Has anyone ever tried disabling or bypassing the feature on some DC fans that allow them to detect that they've stalled. I'm trying to run a custom built PWM controller for a small DC fan and the fans I've purchased dont seem to like anything that 100% duty cycle. I'm thinking it has to do with the onboard smarts on these fans.
     
  2. VanGoghComplex

    VanGoghComplex [H]ard|Gawd

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    Maybe I'm not very knowledgeable, but I'm... not sure I know what you're talking about. Any DC fan, assuming it's being supplied with more than it's startup voltage, will resume spinning after it's been physically stopped...

    Can you provide a little more detail on your custom PWM controller? And maybe what kind of fans you're wanting to control with it?
     
  3. Arcygenical

    Arcygenical Will Watercool for Crack

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    Some of the very high current fans could detect being spun down...

    You sure the controller works properly?
     
  4. MrPCB

    MrPCB n00b

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    Basically this is for a 3D printer cooling fan. Its a 40x40x20 Sunon fan rated at 24V. PWM is basically running off of a Rasperry Pi. I have a 24v mosfet in between. On cheaper fans it works no problem I can set duty cycles anywhere between 1 and 99 % without issue. I have the option of setting the frequency as well and I've tried lots of different frequencies and don't notice much difference. For some reason tho these Sunon fans might be too smart. Yes, they auto restart after stalled but the behaviour I'm getting is that they start to spin and then stop when setting any duty cycle except for 100. Lower values don't spin it at all but above 50% I get like a second of spinning and then it stops. Has to be related to the circuitry inside these things. I have no other way of explaining why it behaves this way. I know PWM works fine on other fans I have but I wanted something a little beefier. At first I thought it was maybe a current thing but even when stalled each of the fans pulls no more than 100ma of current. I think perhaps I need a super dumb fan without a fancy IC on board. Was wondering if I could somehow bypass all this intelligent stuff as I cannot find a dumb fan at this size.