Electronic circuits - stepper motor driver controlled by Snowdrop OS
This board I built is a stepper motor driver. The motor to drive was the 2-phase KP35FM2-035 by Japan Servo Co. Ltd. I was unable to find a specification document for it, but it seemed OK with about 200mA per phase, and can probably go higher.

The driver connects to my parallel port isolation board. Each phase is driven by an H-bridge similar to the one in the diagram below. Of course, each NPN base had a series resistor (not shown in the diagram) to limit current.

I drove the circuit using four parallel port pins, via a Snowdrop OS BASIC program. It was nice to see both my OS and its BASIC put to work.