Stepper motor is a simple way to make a motion control with high precision. A stepper motor control circuit is needed to make stepper motor works. A stepper motor controller usually use a microcontroller to make a complicated task. Some controller use stepper motor ic to simplify the circuit design. For simple task like just rotating with constant speed a simple controller circuit can be built using discrete components. Here is the schematic diagram of the circuit:
The final stepper motor driver uses transistors to drive the motor coils. Take a look at the table, you’ll find that you need a 2 bit free running counter if you want to make this stepper driver move the motor. If you have an up down counter circuit, the you’ll get an upward-backward stepper motor control. This stepper motor control circuit can serve up to 500 mA if you install a proper heat sink for each SL100 transistors. Higher current is possible by using 2N3055 transistors in Darlington configuration with the SL100 transistor.