Wednesday, February 27, 2008
Steppers and couplings
My USB work has pretty much hit a plateau until my Jan Axelson book on USB programming arrives. That will be towards the end of next week. In the mean time I've spent a few hours hammering at the stepper instructions till they're all working right. I'm also getting used to all of the things that can come unstuck on my stepper board and how to diagnose them from how the stepper is behaving.
I slapped my multimeter on in amperage mode and discovered that one phase of the motor consumes a max of 220 milliamps with no load. That drops to about 190-195 as I crank the speed up. When I accidentally leave one of the phases charged it jumps to about 340-350. When that happens both the motor and the SN754410 heat up quite quickly. As a result of that I reprogrammed the firmware to turn off both phases 10 millisecond after the end of a run. That keeps the motor and the SN754410 quite cool. That's good, because the motor tends to skip when it heats up.
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