Duet 3 standard stepper motor wiring to thick wiring



  • Hey all,

    Recently switched to a Duet 3 from a Duet Ethernet and while the stepper motor molex connectors looked the same in showcasing videos they are indeed thicker for higher amperage use cases.

    I don't plan on running any stepper motor over 2A which all my wiring is already setup for however I'm unsure how to migrate over to these new larger molex connectors.

    Option 1: Solder 20-22AWG wire to the previous connectors and crimp on new connectors suitable for larger molex connectors.

    Option 2: Remove smaller molex connectors currently on stepper motor wires and directly connect the larger molex connectors.

    I would much rather just move forward with Option 2 but im wondering if others have gone that route successfully.

    Thanks!



  • Option 2 is the proper way of doing it.
    There is an option #3 if you want /need flexibility - make up a short adapter cable to go from one size connector to the other size. I would think that somebody must already be producing these but I have not searched for them.



  • This is what worries me from doing that:

    "The 4 wire motor and OUT1, OUT2 and OUT3 are JST VH series connectors. They require a minimum of 22AWG wire (20AWG or 0.5mm2 recommended. Most NEMA17 size stepper motor wire will will not be thick enough."

    From the duet wiring recommendations https://duet3d.dozuki.com/Wiki/Duet_3_Mainboard_6HC_Wiring_Diagram



  • I've been completely successful crimping those larger connectors onto old-style stepper motor wire. Just crimp REALLY well. I crimp with a PA-21. It is a little slower, MUCH cheaper, than specialized ratcheting crimpers, and does a better job for oddball things like big pins on little wire.

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  • I can also highly recommend crimpers from 'Engineer'. They make excellent crimps IF you take care (I guess that applies to all crimpers, never mind). On the other hand, a connector pin has a specification in regard to the wire it takes. If you put a 24 ga wire in a pin that requires a 20 ga wire, your success rate will take an enormous dive. To get around that, strip twice the length of wire you need and double it up. You MUST remove the insulation from the overlap. You can't just bend the stripped wire back over the insulation and crimp that.



  • I know it makes less sense when the stepper itself has a nylon connector that can be re-pinned, but I always add a disconnect about 100 mm or so away from the motor to connect to my cable runs. This allows be to transition to thicker gauge wire early, and in a controlled manner (ie by selecting a connector that can accommodate both wire sizes, etc.



  • I can confirm that with the correct tool, crimping stepper wires to the larger connectors works just fine. You need the correct tool though because all of those contacts have an outer crimp for the insulation and an inner one for the conductor and the crimp tool is stepped to match. I use the "el-cheapo" ratcheting iwiss SN-28B.



  • @bot said in Duet 3 standard stepper motor wiring to thick wiring:

    I know it makes less sense when the stepper itself has a nylon connector that can be re-pinned, but I always add a disconnect about 100 mm or so away from the motor to connect to my cable runs. This allows be to transition to thicker gauge wire early, and in a controlled manner (ie by selecting a connector that can accommodate both wire sizes, etc.

    Actually I do that as well for longer runs and use butt splices for the transition.



  • In this thread, I pointed to parts to make adapter cables.

    https://forum.duet3d.com/post/127732

    The housings I posted will accept 22 AWG wire at that end, then you can crimp the other end into the JST housings for the Duet 3


  • administrators

    @singhm29 said in Duet 3 standard stepper motor wiring to thick wiring:

    This is what worries me from doing that:

    "The 4 wire motor and OUT1, OUT2 and OUT3 are JST VH series connectors. They require a minimum of 22AWG wire (20AWG or 0.5mm2 recommended. Most NEMA17 size stepper motor wire will will not be thick enough."

    From the duet wiring recommendations https://duet3d.dozuki.com/Wiki/Duet_3_Mainboard_6HC_Wiring_Diagram

    When converting my tool changer to Duet3, I doubled the stripped part of the stepper motor wire back on itself to bulk that up, and I put a short piece of heatshrink sleeving over the insulation to bulk up the insulation. I then used a PA21 tool to crimp them. I've had no issues with bad connections.

    I have added this to the wiring recommendations that you linked to.


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