Steppers As Rotary Encoders
Charles has some good stuff on his site (techlib), but still, he hasn't used a stepper as an INPUT device! If you hook an oscilloscope to one winding of a stepper (center tap common, CH1 to one side, CH2 to the other), you'll see that a stepper has a quadrature output. Using the tap as ground, send each output to a comparator to square up the signal, then use electronics to detect direction and speed and the final output can be used on 74LS193 counters to count up and down using a rotary control. It can be a very handy input device, cheap compared to buying a modern rotary encoder, and just a lot of fun to play with. Downside is that it takes a bigger stepper so that it can still put out a higher voltage with slow rotation -- the little steppers just won't get it, no matter how sensitive you make the comparators. And no matter what, really slow movement will be missed by the comparators. It is a lot of fun to play with, and regardless of how "unfeeling" everyone seems to want the digital world to be, there ain't nuthin' like the tactile feel of a stiff stepper motor with a knob attached to the shaft for input control, especially if it's a crank-type knob from the "old days", using it to control the frequency of an oscillator or receiver.
Dean