Safe to use internal stepper driver for 2.0A?



  • Hi,

    I'm building a CoreXY printer and plan to use my old Duet 0.6 board (which I'm very pleased with). The motors (for XY and E) I've ordered are rated 2.0A (http://www.ebay.com/itm/331440962687). Is it safe to use these with the internal drivers on the Duet? I have read the Wiki but I'm still not sure what might happen if it's too much, since 2.0 seems to be the very upper limit for this board. Will I break anything or just realize I need external stepper drivers? If the latter, than I can just as well skip ordering external drivers for now and try using the Duet directly? Would prefer that ofc but I don't want to break things.

    Thanks,


  • administrators

    For the Duet 0.6 I recommend 1.5A maximum, and that's with a fan cooling the board. So you will be able to run your 2A motors at 75% current, which is likely to be high enough. Motors are typically run at 60 to 85% of their rated current in 3D printers.

    The Duet WiFi is comfortable at 2A and I intend to increase the maximum current in a future firmware release.



  • Thanks

    And what is the consequence of stretching the limits? I suppose the drivers or even worse the entire board would burn up?


  • administrators

    The driver have thermal thermal protection, that switches the current off until the cool down and then switches them back on. This effect is similar is some ways to skipping steps. It does not immediately damage the board, however your print will have layer shifts and other nasties so its not a useful way to run the drivers. Also constantly running electronics right at its thermal limits will reduce its life over time.

    Have a look at your motor data sheet, you may find that the 2.0A is @85C which is hot to run the motors at. At that temperature if you have your motors on printed mounts you may start to see softening of the plastic and the mounts will creep over time.

    That is why most people run their motors well under rated current.


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