Friday, July 25, 2008

Stepper circa 1983 details

Unfortunately it looks like the stepper I found can't be wired as a bipolar, it has five wires, four of them go to one end of the four coils, and the other one ties all the coils together. It was being driven from the transformer, then controlled through a Darlington array. This is a simple way to drive a stepper as long as you don't want to half-step, or micro-step. The Darlington was a ULN 2003A, which is rated to 500 mA, so the motor must be 500 mA or less per coil. Since you can't wire the motor bipolar, the Stepper Motor Driver 1.1 won't work to drive this stepper. Need to find or design a unipolar stepper driver I suppose. There's newer quad Darlington arrays available that can put out 1.5 A per channel for about $2, or you could run the common wire to ground I suppose. Maybe there's a way to get the motor casing open and re-wire it, though it looks spot welded.

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