Here is the circuit diagram of a simple stepper motor controller using only elementary parts. The driver circuit uses, four transistor (SL100) to drive the motor windings, two NOT gates and one XOR gate to decode the two bit control logic to drive the four windings of the motor. The diodes D1 to D4 protects the corresponding transistors from transients generated during the switching of motor windings. d0 and d1 are the control logics which determines the direction of rotation as well as speed.
Circuit diagram with Parts list.
- The control logic for the circuit can be obtained from a 2 bit up/down counter clocked by a 555 astable multivibrator.The direction of count determines the direction of rotation and the frequency of astable multivibrator determines the speed of rotation.
- As shown in the schematic above, IC1a IC1b belongs to same IC 7404.
- Pin 14 and pin 7 of both IC1 and IC2 must be connected to +5 V and ground respectively, though it is not shown in circuit diagram.
- The 5V can be obtained from a 7805 based power supply circuit.
- 5V power supply using IC 7805.Click Here.
- Vcc is the voltage required for the stepper motor. It varies from motor to motor. Here we can use up to 24V stepper motors. For higher operating voltages and power the SL100 transistors must be replaced with higher power transistors like 2N3055.
Truth table for clockwise rotation.