Versatile Applications of Stepper Motors
Stepper motor find widespread applications in various fields of electro-mechanics, including model making, remote control devices, industrial equipment like picture scanners and printers, among many others. This simple 4-phase stepper motor driver circuit is an essential addition to this collection of circuits due to its practicality and versatility.
Clock Generation and Shift Register Operation
The circuit’s clock generator is constructed using two exclusive OR (XOR) gates IC2A and IC2B, along with components C1 and P1. The ENABLE input, when set to logic ‘0’, activates the clock generator, and the output frequency is determined by the relationship:
The output signal from the clock generator is then directed to the clock inputs of the two D-type flip-flops IC1.A and IC1.B. These flip-flops are interconnected to create a 2-bit shift register. The Q output of IC1.B is fed back to the D input of IC1.A, and the Q output of IC1.A is routed to the D input of IC1.B. This configuration generates the 4-phase impulses essential for motor rotation.
Direction Control and Phase Sequence Reversal
By altering the DIRECTION input to logic zero, IC2C and IC2D function as non-inverting gates. This reversal of the phase sequence in the output signals effectively changes the motor’s rotation direction. The specific rotation direction is contingent upon the arrangement of the motor windings.
Reversing the outer two coil connections on one of the windings can change the direction if needed. Using the specified components, the circuit oscillates at a frequency of 10 Hz. The clock frequency can be adjusted within the range of 0.2 to 100 Hz by replacing different values for P1 and C1. It’s crucial to ensure that the power drawn by the stepper motor remains within the handling capacity of the driver transistors T1 to T4. Diodes D1 to D4 are essential for dissipating the back-EMF generated whenever a drive impulse to each of the motor coils is turned off.