Running Duet2 on 5V only?



  • I have a rather unique situation that I'm working on. I have a system that will use only external drives and only external relays for the heated bed and extruder heaters.

    Can I run the Duet2 solely on 5V power?

    When using only PS power, I get the error that the steppers cannot be driven when VIN is below threshold, despite no steppers being connected to any smart drivers requiring VIN.

    In the firmware, I disabled smart drivers and left voltage monitoring enabled, which did not seem to work. Then I disabled both smart drivers and voltage monitoring with no change. Applying power to VIN yields an error about drives 0,1,2,3 & 4 being shorted to ground. Presumably due to smart drivers being disabled. I re-enabled them with no change though.

    When running on ONLY 5V power, I am reading 1-3 volts on the VIN rail.. which doesn't even seem like it should be possible given the Zener diode and buck converter in the path.

    This is on a V1.0.3 board.

    EDIT: Just realized my firmware wasn't being generated correctly, so I was still using an older version (with smart drivers enabled). I have a few more settings to test, so I'll do that and update this thread.

    EDIT2: I reassigned stepper to X,Y,Z,E0.. but I didn't re-assign the initial X,Y,Z,E0 to other unused axes. So that might be part of it. If it was trying to drive the smart drivers AND the dumb drivers without VIN.


  • administrators

    As you say, you will probably need to modify the firmware to ignore the power monitoring if you want to run with 5V only, and make sure that all axes and extruders are mapped to off-board drivers.

    The voltage you are reading on VIN may be caused by power back feeding from the 3.3V supply to VIN through the stepper driver chips.



  • Use a little step up-module from 5V to 12V/24V and feed that into VIN. Then you can even control some 12V/24V fans. 2A should be possible.



  • With the corrected (changed) firmware, I am back on the right path. Disabled both the smart drivers and the voltage monitoring. I also changed pinouts so that X,Y,Z,E are my external drives. I believe everything will be working as soon as I get everything else sorted.

    As for the VIN shorting to ground issue, that ended up being a faulty bench power supply, and no fault of the Duet or the rest of my setup.

    @andres said in Running Duet2 on 5V only?:

    Use a little step up-module from 5V to 12V/24V and feed that into VIN. Then you can even control some 12V/24V fans. 2A should be possible.

    No need. Everything is external to the Duet.


 

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