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.
This optically coupled circuit was found in the February 1968 Radio Electronics magazine. The...
We found this circuit in the April 1978 issue of Radio Electronics magazine. The power supply must...
This circuit supports several sets of coils and can oscillate from 1 to 44 MHz. The transistor is an old...