One stepper driver, two stepper motors

 

Wiring two stepper motors on one stepper driver

I've had a couple of questions about whether its possible to drive two stepper motors with one driver, for instance to control a printer such as Prusa I3 or similar which uses two stepper motors on the Z-axis. The answer to that is yes. Just make sure the two stepper motors are equal. If the stepper motors are the same, the coil resistance should also be more or less the same and the power should distribute equally among them. You will then have to program the peak current to be double what you want for a single stepper motor.

Controlling a solenoid with Replicape

I've also been asked if it's possible to control a solenoid with Replicape. And you can do that as well, using one of the free mosfets, either a high power mosfet or one of the low power ones. Solenoids are sometimes used on 3D-printers to extend a micro-switch below the print head nozzle for automatic bed leveling. Unfortunately I have thrown away my only solenoid, but a coil functions in much the same way by physically moving a piece of metal as a result of power being applied to the coil.

The low power mosfets have a maximum current of 1.3A  giving a max power coil of 15W @12V which is more than most people would need for a bed leveling solenoid, but if you do need more power, the big mosfets go up to 32A which is 384W @12V. That will blow the 20A fuse, though.

 


Elias Bakken

11 COMMENTS
  • Rares Vernica
    Reply

    Hi, Do you have any pointers on getting started with the stepper motors for Replicape using the PRU? Thanks!

  • Elias Bakken
    Reply

    Hi! If you don't mind flashing your BBB and just want something that works, download the latest Thing-image: http://wiki.thing-printer.com/index.php?title=Thing. Actually I uploaded a new image yesterday, so just change the date on the image name. If you want to learn how the inner workings, have a look at Redeem: https://bitbucket.org/intelligentagent/redeem

    1. Rares Vernica
      Reply

      Thank you! I have to use a Debian image, but I'm just trying to get a stepper motor moving. Nothing fancy. The cape is correctly detected and I tried your example here http://hipstercircuits.com/accelerated-stepper-motors-on-beaglebone/ but I got stuck. I left a comment there.

  • Rares Vernica
    Reply

    BTW, what Python SPI library are you using in the Stepper.py file: "from spi import SPI"?

    1. Elias Bakken
      Reply

      I dont remember exactly, but python-spi should work, no?

      1. Rares Vernica
        Reply

        Thanks! I tried these two:

        https://pypi.python.org/pypi/SPIlib/
        https://github.com/datacode-taavi/python-spi

        but neither worked. Finally the files linked here worked:

        http://www.gigamegablog.com/2012/09/09/beaglebone-coding-101-spi-output/

        BTW, I managed to get Redeem work on Debian. There were a couple of issues with your Python code that I had to patch. I can send you some quick bug reports, just let me know where.

  • C A Buster
    Reply

    Am considering using the Replicape and Beaglebone Black to use for 3D printing with a Shapeoko-2 frame. Will one Replicape controller support two Shapeoko NEMA23 motors wired in parallel, that have these specs: Rated Voltage: 2.3 V, Current/Phase: 2.8 A, Inductance/Phase: 2.2 mH, Resistance/Phase: 0.82 Ohm. And if so, what would the programmed peak current be for the one controller?
    Thank you for your consideration.

    1. Elias Bakken
      Reply

      Hi! Two NEMA23 motors in parallel sounds like it might be beyond what this controller can do. It might be an option to use one controller for each of the steppers as a sort of slave mode, but that has not been implemented in software yet.

  • MatijaZ
    Reply

    Hi Elias, I am having difficulties with ordering your product above through my Chrome. Is it possible to get into shop with chromebooks. Site doesn't open and I am not sure wheter is it fault on my side. Thx in advance. Regards, Matija

    1. Elias Bakken
      Reply

      Hi! That's unfortunate! I tried going through much of the process in a Chrome browser with no issues. I don't have a Chromebook, though. Where does it stop for you?

  • Eric
    Reply

    Elias, if I wanted to use a dedicated host controller, such as pronterface or something similar, instead of octoprint to run my printer, is it possible? If so, how can this be accomplished? I have the replicape rev A4A.

    Thanks

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