Tuesday, September 04, 2007
Driving a stepper motor
I found a stepper motor in a scanner and decided to hook it up. They're dead easy to drive from the parallel port. All you have to do for normal stepping is pulse the pins in order. Each pin goes a transistor that hooks the motor coils to a 9v power supply. And that's it, very easy.
I tried to get the pulses as small as possible, but under 10ms per pulse it gets pretty flaky. This probably has more to do with the fact that I'm severely underpowering the coils. They should be getting more like 24v, not 9v. It works, but it has almost no torque.
I also did "high torque stepping" by powering not only the coil I want to move the motor to, but also the coil after that. I think I'm getting slightly more torque, but still not much. I did microstepping too, which powers the coil you want to move to, plus the coil after the next. This kind of gets the rotor stuck between two steps. It allows for finer control (moving in half steps) and smoother motion (stepper motors are "jerky").
I just got my Arduino and replicated the same stuff on it. I'll post picture of that later after more experimentation.
at 4:18 PM