| A 4017 decade counter/driver
driven from a low-frequency oscillator (U1-a and U1-b) is used to drive transistor
switches to sequence the windings, as is needed. MOT1 is a 12-V stepper motor. R9 and R10
are selected for the motor's current rating. A 3.3-Hz signal from U1 will cause the motor
to run at 1 rpm, a 33-Hz signal will result in 10 rpm, etc |