Controlling a 24VDC contactor via duet 3?



  • Hi everyone.

    I would like to know if its possible to control 110VAC / 24VDC (Coil voltage) contactor via duet 3 fan outputs (OUT7 thru OUT9 with flyback diodes). Does it damage the board during on/off sequence?

    I measured the coil power draw and its around 6-8W total (About 0.3 amps) when its active.

    This is the contactor that I would like to turn on/off.
    https://www.automationdirect.com/adc/shopping/catalog/motor_controls/iec_contactors_-z-starters-z-overloads/fuji_contactors-z-_overloads/9_to_25_amp/sc-e05g-24vdc



  • 2-pin KK connectors labelled OUT7 thru OUT9: these are intended for fans. Maximum recommended current 2.5A each. Flyback diodes are built-in to these outputs.

    Should be fine. Just select V_FUSED with jumper. I would use SSR instead.



  • Sorry for my noob question but I am no electronics/electrical engineer. I checked the specs and it should be fine on the paper. What concerns me if there will be a sudden current spike that flyback diodes cannot handle (I dont know if flyback diodes has max current limit?) when contactor turns on/off. I cannot measure it since it happens too fast. I dont know if anyone tried a similar thing before.



  • The contactor is actually going to power the heatbed SSR. I added the contactor as a safety measure if SSR gets break and start heating the bed as it is own. Duet 3 is supposed to turn on/off contactor when its printing only.



  • Not sure what kind of "sudden current spike" You have in mind.

    In general mentioned diode is to block negative voltage when switching inductive loads off (like contactor coil), and the contactor current (110VAC) is not flowing through them.



  • Got it. I probably misunderstood the whole flyback diode concept wrong :). I will go ahead and try it. Thanks. Still learning 🙂



  • Connected it and it works fine. Thanks!


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