My fans have stopped working



  • Long story short, in doing some maintenance on my delta printer that uses a Duet WiFi, I accidentally shorted the wires going to my hotend's always-on fan. I caught a whiff of solder smell, and when I put everything back together correctly, I discovered that all of my fans had stopped working. Everything else is working fine – the hotend, the heated bed, the motors (although I've not tested the extruder motor), the Panel Due, but none of the fans. I measure approximately 0.1v when these fans are activated, rather than the 12v they should be receiving. Although I can wire the Duet board's cooling fan and the always-on hotend fan directly to my power supply's 12v output, the part-cooling fan poses more of a conundrum. So: Is there something I can do to get this working again, short of buying a new Duet? Please keep in mind that I'm far from an expert at electronics hardware -- I can use a multimeter and solder wires together, but extensive troubleshooting or wiring together a circuit with more than a handful of components will be beyond me. Thanks for any advice!



  • The fan mosfet is probaply burned out.
    See this link for the replacement: https://www.duet3d.com/wiki/Connector_and_spare_part_numbers#Fan_mosfet



  • The page you reference makes it sound like each fan has its own mosfet? Would all the mosfets burn out at once? Because none of them work. (I even tried the two fan circuits I'm not using.)


  • administrators

    Each fan does have its own mosfet, how were you powering them (5V or Vin?)



  • They were powered by VIN, AFAIK. (I wasn't aware there was any way to do it, and they're all 12v fans.)


  • administrators

    If all the fans have stopped working then you have fused the via in the trace between the VIN pin of the fan jumper selection block and the +VIN power input terminal. You can add a wire on the back of the Duet to connect them together again.



  • I've found a workaround. Discussion in a couple other threads here led me to move the fan's + line from the fan connector and instead connect it directly to the power supply's 12v + line, while leaving the fan's ground connected to the ground pin for the fan on the Duet. Connected in this way, the fan now works again, including software control of its speed. It's not exactly "good as new," but it's an acceptable workaround – unless of course somebody tells me that this configuration is a disaster waiting to happen.



  • That sounds good; AFIK the fan controller works by switching the fan ground pin on the connector to gnd, or leaving it open, controlled by a N-channel mosfet in the normal Arduino manner. In theory you can use this to drive a fan off any reasonable (0-24v) psu so long as that psu's OV (gnd) is common with the Duet.

    Similar to that other discussion, I'm doing exactly this on my cartesian's RAMPS board to control a 9v light rig powered off the 12v bus through a buck converter. Although the board is different, the principle and controller side circuitry is the same.


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