Monday, February 17, 2020

Longs Motor DM542A idle current bug

Stepper motor drivers like this one usually have a jumper (that's usually SW4) that sets idle current.  So if you haven't sent any pulses in a while, rather than cooking your stepper by holding full current, it'll cut it down to half current:
Image result for dm542a
But I just noticed a bug on my Longs Motor DM542A: when it first powers on, it comes on at full current (the whole unit drawing about 1.3A at 32V) and stays there.  But if I move that axis (send the driver some pulses), then after I'm done it drops down to about 630mA.

So to work around this issue, make sure you move your steppers a little after powerup so that the half-current mode kicks in.

Also, I discovered that the half-current mode seems to actually be "half power" mode -- the current only goes down to about 70% of full, rather than 50%.

BTW, I checked this behavior against a stpperonline DM556S, and it does the opposite: it draws very little power until it gets its first step pulses, then moves up to half current.

1 comment:

Ratraco Solutions said...
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