Fan0 won't turn off



  • I have recently installed a Berdair with a flyback diode on the connector and it worked just fine until a couple of days ago I noticed that it turns on when the duet turns on.

    I have switched the fan out for another and it turns on as well.

    I noticed an older thread: https://forum.duet3d.com/topic/406/duet-wifi-fans-won-t-turn-off

    I am wondering if I might have fried something and if it is fixable.

    The only parts of my config related to fans:

    M106 P1 H1 T75 S0.4
    M106 P0 F25000
    

    I saw it mentioned by dc42 somewhere that the mosfet could run the thing (its at 24V) so I decided not to put it on the 'eswitch' or an SSR.

    I am running 1.0 or 1.01 of the duet wifi board (according to web interface), running on the latest stable (RTOS).0_1531835744782_config.g


  • administrators

    There is another thread on this subject, more recent than the one you linked to. In summary:

    Brushed DC motors (which is what air pumps normally use) draw a large surge current when they are powered up. I expect this surge current caused the fan output driver mosfet to fail. We recommend you either use a series thermistor to limit the surge, or else use an external mosfet switch that can handle the surge.


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