Moving printhead by hand - Generated voltage - Can i damage anything?



  • Hey Duet3D forum!
    This is a question regardning my DIY printer here: https://www.duet3d.com/forum/thread.php?pid=35122#p35122

    Now i am wondering how sensitive the stepper drivers (and the board in general) are to generated power from moving the effector by hand?

    I never really thought much of this with my old prusa, but now that i cannot just swap out the stepper drivers anymore i got a little worried.

    I noticed that if I move the effector around by hand when the printer is unpowered one blue LED on the board turns on (3V LED). This makes me wonder, can I damage my board by moving the effector by hand with the printer turned off?

    I have read a thread here regarding bed drop. There the answer was that the generated voltage must be below 29V. So moving the effector slowly to the point where the 3.3V LED turns on means that only 3-ish-V is generated or?



  • The Duet Wifi/Ethernet is pretty bulletproof. There's an entry in the Wiki on "How to destroy your Duet Wifi or Duet Ethernet" https://duet3d.com/wiki/How_to_destroy_your_Duet_WiFi_or_Duet_Ethernet, and I seem to remember a video showing these attempts to destroy it, with the bottom line being it's really hard to do any damage.

    I've moved my carriages by hand and you can see the board actually power up from the voltages generated, but the driver chips are pretty bulletproof so I haven't damaged anything (so far anyway). I think you're safe.


  • administrators

    When the motors are connected to the Duet, you should only move them SLOWLY. Otherwise there is a risk of generating too much voltage.



  • Okei so only slow moves when absolutely necesary.. That is noted!

    Thankyou!



  • I was thinking about installing these for the X,Y motors: https://www.ebay.de/itm/172980421084?var=471745181900

    The diodes will "eat" at least 0.5V, but that can be compensated.

    Any thoughts?


  • administrators

    Those are useful with DRV8825 drivers but probably not with most other types.


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