For those of you caught between stepper motors and the dredgery of
hand-cranking, try getting a 1 RPM motor out of a clock. I bought one from
American Science & Surplus in Chicago for $2.
Advantages: Cheap, universal, easy to retrofit manual barn doors, and no
confusing electronics.
Disadvantages: 120V AC, stuck to 1 RPM tracker models, but no altering
tracking.