Found in a 90's EDN, this circuit controls both the speed and the direction of rotation of a stepper motor. Relays can be replaced by MOSFETs, with circuit adaptations.
The circuit in the figure trips with a negative transition of the input signal, its output...
The basic frequency of this circuit is determined by the capacitor of 470 nF and the adjustment of the...
The load current can be adjusted up to about 1 A. The transistor can be TIP32 or TIP42. The...