Adjustable precision stepper motor control circuit

Working principle of the circuit: As can be seen from the figure, the original input
signal of the microcontroller or other numbers enters the 4059N division counter to form a pulse sequence . The counting pulses of this counter
are supplied by a clock generator composed of 4049 and 1M crystal oscillator. The 14516 up/down counter
also takes input from the above digital source and provides a binary code output. This binary
code is a forward sequence or a reverse sequence, which is determined by IC2 and the directional input (forward/reverse).
The binary code output of 14516 is decoded by the 4028 binary decoder to drive the output
transistor 2N3706. Eight 2N3706s supply the 200 mA current the stepper motor
and control eight transistors as shown in Figure a. For motors with phase windings, if a four-phase
motor is used, the circuit is as shown in Figure b.