Question over stepper motor current 2.4A / 2.8A
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Hi,
I'm going to be setting up a couple of Ox CNC's with new Duet wifi boards (1.04)
I was wondering about the max current limiting on the stepper drivers.The stepper drivers in question are basically 2.8A per Phase Nema 23's
https://ooznest.co.uk/product/nema23-stepper-motors/From the looks of things the max you can go within config.g is 2.4A
But the stepper driver ic's support 2.8A- Is it the case that you can do 2.8A if you add active cooling (fan's / heatsinks) to the stepper IC's?
- Also is there some special flag you need to switch over to allow for 2.8A (i.e. a recompile of the firmware)
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You shouldn't drive stepper motors at their rated current anyway, they get too hot. 2.4A is a great fit for those motors.
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okay thanks, in that case I'll run them at 2.4
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https://duet3d.dozuki.com/Wiki/Choosing_and_connecting_stepper_motors
Since the recommended current setting is 85% of the motors rated max, 2.4a should be perfect.
You'll need to use active cooling that blows across both sides of the board.
https://duet3d.dozuki.com/Wiki/Mounting_and_cooling_the_board#Section_Mounting
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@garlicbread I'm using 2.5 and it seems that the firmware doesn't limit this at least on GCode level (it reports back the values that I set). Maybe someone could clarify what happens if you configure more than 2.4A. I haven't tried measuring it either. From the heat produced by the steppers I can tell with certainty that it's giving at least 2A.
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If you configure more than 2.4A you will get 2.4A. This is the maximum safe current for the TMC2660 drivers at standstill, so to use more it would be necessary to implement standstill current reduction. Unfortunately the drivers don't implement standstill current reduction in hardware, and doing it in firmware in a way that would be 100% reliable and not affect print quality is difficult, perhaps impossible.
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It sounds like using 2.4A / 85% of the rated current for the motor is best anyways so I'll be using that.
