Duet2 Stepper Driver Current Limit
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I read on an old thread that the current limit for the stepper drivers was increased after implementing some changes in RRF to keep the driver cooler.
Purely out of curiosity I would like to know if there are any more changes planned/possible to further increase the driver's current limit.
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Probably not. In theory, if I could implement standstill current reduction then we could increase the current some more, perhaps to 2.8A. Unfortunately the TMC2660 doesn't handle it automatically, and implementing it in firmware in a way that is totally reliable is difficult. I guess it might be possible to increase the current just in the middle section of high-speed moves.
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@dc42 is the 2A driver limit (and config setting number) peak per coil at a full step position, or RMS?
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The limit is 2.4A (increased from 2.0A some time ago) and it is the peak value per coil.
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Hi,
just doing research on this "old" topic: With heatsinks on top/bottom of the driver and/or active-cooling it could be experimentally increased another 0,2-0,4A up to those 2,8? (Just thinking out loud here...) -
@lb said in Duet2 Stepper Driver Current Limit:
Hi,
just doing research on this "old" topic: With heatsinks on top/bottom of the driver and/or active-cooling it could be experimentally increased another 0,2-0,4A up to those 2,8? (Just thinking out loud here...)You could recompile the firmware to allow 2.8A, but it would be at your own risk.
The point to remember is that Trinamic allows a higher current when the stepper motors are moving above a certain minimum rate than it does at standstill, because when the motor is moving, the heat dissipation is shared between all 8 mosfets instead of being in just 2 of them. Also the mosfets are on separate dies from the controller chip in the TMC2660, so the over-temperature detection on the controller chip won't react instantly to an overheating mosfet.
I originally hoped to implement standstill current reduction in firmware, but that turns out to be very difficult to do in a way that is 100% reliable.
Duet 3 will allow higher currents, certainly over 3A and maybe as high as 4A.