I found this circuit in my files. I don`t know where it came from, but it looks like I photocopied it from somewhere years ago. I have been told that it came from `The Robot Builder`s Bonanza`, by Gordan McComb. Anyway, I thought that it should be fairly useful, so I decided to post it here. The circuit is very simple and inexpensive. This is good thing because most commercial stepper motor controller ICs are quite expensive. This circuit is built from standard components and can easily be adapted to be controlled by a computer.