Using Duet 3Mainboard with external stepper drivers



  • Hi ,

    is it possible to use external stepper drivers with the duet3 mainboard ?
    For my axes (servo driven)I need the step and dir signals and want to know if it is possible to put the axes step and dir signal on the "9 IO headers for Endstops, probes, filament sensors and other low bandwidth sensors."

    Thanks
    Marc


  • administrators

    Currently that's not supported. We are planning an expansion board to drive external stepper drivers, with 5V outputs. In the longer term we may make a main board variant with buffers for external drivers instead of on-board drivers.



  • Thanks for your fast reply.
    Is there a timeframe when external steppers ,external or special mainboard, will be supported? 3/6/9/12 month?)

    Thanks
    Marc


  • administrators

    @mpentenr said in Using Duet 3Mainboard with external stepper drivers:

    Thanks for your fast reply.
    Is there a timeframe when external steppers ,external or special mainboard, will be supported? 3/6/9/12 month?)

    Thanks
    Marc

    It's quite high priority, so i think nearer 3 months than 12. We haven't decided how many external stepper drivers it will support yet, but probably 3, maybe 4. How many do you need?



  • Hi,

    at the moment I will need up to 4.
    The 3 main axes and an pellet extruder.
    I would be glad to do beta testing of the board, if you want me to.

    Thanks Marc



  • Oh, I forgot, I will also need support for up to 6 Thermocouples or PT100 thermo sensors for heated bed and pellet extruder


  • administrators

    @mpentenr said in Using Duet 3Mainboard with external stepper drivers:

    Oh, I forgot, I will also need support for up to 6 Thermocouples or PT100 thermo sensors for heated bed and pellet extruder

    To support 6 thermocouples/PT100s using standard hardware/firmware would require one main board and one expansion board. Each will support 2 of the temperature daughter boards, just like the Duet 2 and DueX boards.

    Don't forget that PT1000 sensors can be plugged into ordinary thermistor inputs too.



  • @mpentenr Hello, I am currently working on something similar with Duet2, I would like to know more about your work in this regard, I can share what I have.



  • Hi,

    one of the best things of the Duet2 is than is the best board working with external stepper drivers.
    In my opinion (and in my case) the next Duet3 (expansion or special board) never can have LESS external connections than the actual Duet2, the same number or more.

    Now have for 5 connections (if i don't remember wrong)...

    Thanks


  • administrators

    @fbg you can add a lot of expansion boards. If we decide to put 3 external driver connections on each then potentially up to 8 of those expansion boards = 24 drivers!



  • @t3p3tony No words.... incredible



  • @dc42 Are there any news on this topic ?


  • administrators

    @mpentenr said in Using Duet 3Mainboard with external stepper drivers:

    @dc42 Are there any news on this topic ?

    Not yet. Now that we have the prototype Tool Board, there are two ways we could support external drivers without needing a new main board:

    1. Do a version of the EXP3HC board with outputs for 3 or just possibly 4 external stepper drivers instead of on-board drivers. This would probably be best for those who are actually using external drivers, not step-servo motors. But we don't expect many people to need external drivers with Duet 3.

    2. Do a version of the Tool Board that has a single set of step/dir/enable outputs, to drive a single external driver or step-servo drive. I think this might be better for those using step-servo motors with built-in controllers.



  • @dc42 said in Using Duet 3Mainboard with external stepper drivers:

    @mpentenr said in Using Duet 3Mainboard with external stepper drivers:

    @dc42 Are there any news on this topic ?

    Not yet. Now that we have the prototype Tool Board, there are two ways we could support external drivers without needing a new main board:

    1. Do a version of the EXP3HC board with outputs for 3 or just possibly 4 external stepper drivers instead of on-board drivers. This would probably be best for those who are actually using external drivers, not step-servo motors. But we don't expect many people to need external drivers with Duet 3.

    That would be my favorite, because of my 2pt100(bed) and 3K-Type Thermocouple (Pellet Extruder) which I cant connect to the tool board or is it possible to use thermo connectors on one board and step/dir/ena on another board for one "axis/extruder"? I also would need 2 of these boards, because of the 3 (X/Y/Z)axis with external drivers and up to 3 external drivers for the (pellet)extruders.

    1. Do a version of the Tool Board that has a single set of step/dir/enable outputs, to drive a single external driver or step-servo drive. I think this might be better for those using step-servo motors with built-in controllers.

    Please take into account, that the Vin for example for my pellet extruder is 48V, when designing the driverless Tool Board with step/dir/ena output.

    Thanks
    Marc Pentenrieder


  • administrators

    @mpentenr, what motors and drivers do you plan to use on that machine? Although we don't support as much as 48V at present, we are considering making variations of main and/or expansion boards that support up to about 54V. The TMC5160 drivers can take 60V, it's just the voltage regulators we use that limit us to around 35V.



  • @dc42 Hi, on the 3 axis I am using 1KW 380V Servo Motors and on the pellet extruder, I am using the following:
    Motor Driver: https://us.nanotec.com/products/1768-c5-e-2-09-motor-controllerdrive-for-canopen-or-usb/

    Stepper motor: https://us.nanotec.com/products/574-st8918m6708-a/


  • administrators

    Thanks. Are you using the encoder input on the stepper driver for the pellet extruder? What is the maximum rotation speed needed by the pellet extruder motor? Have you established that you really do need 48V to drive it?



  • @dc42 said in Using Duet 3Mainboard with external stepper drivers:

    Thanks. Are you using the encoder input on the stepper driver for the pellet extruder? What is the maximum rotation speed needed by the pellet extruder motor?

    No, I am not using the encoder input (at the moment, perhaps I need to).
    The max rotational speed will be around 500 rpm, because of an 10:1 gearbox on the stepper, so up to 50 rpm at the pelletextruderspindle



  • @mpentenr said in Using Duet 3Mainboard with external stepper drivers:

    @dc42 said in Using Duet 3Mainboard with external stepper drivers:

    Thanks. Are you using the encoder input on the stepper driver for the pellet extruder? What is the maximum rotation speed needed by the pellet extruder motor?

    No, I am not using the encoder input (at the moment, perhaps I need to).
    The max rotational speed will be arounf 500 rpm, because of an 10:1 gearbox on the stepper, so up to 50 rpm at the pelletextruderspindle

    At the moment the pellet extruder is highly experimental, so I don't know the exact values. Time and experiments will show 😉


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