8085 Microprocessor-Based Stepper Motor Control System

•    The motor is controlled by  ON/OFF the control winding.

•    The popular stepper motor used for demonstration in laboratories has a step size of 1.8° (i.e.,

200 steps per revolution).

•    This motor consists of four stator winding and require four switching sequence as shown.

•    The basic step size of the motor is called the full-step.

•    By altering the switching sequence, the motor can be made to run with the incremental motion of half the full-step value. The switching sequence for half-step rotation is shown.

The switching sequence for full-step rotation
The switching sequence for the half-step rotation

ding stepper motor is shown.   The system consists of an 8085 microprocessor as  CPU,  EPROM, and  RAM  memory for program  &  data storage and for the stack.

8085 microprocessor-based stepper m

•    Using  INTEL  8279,  a  keyboard and six 7-segment  LED displays have been interfaced in the system. Through the keyboard, the operator can issue commands to control the system. The LED display has been provided to display messages to the operator.

•    The windings of the stepper motor are connected to the collector of Darlington pair transistors.

•    The transistors are switched  ON/OFF  by the microprocessor through the ports  of8255  and buffer (74LS245).

•    A freewheeling diode is connected across each winding for fast switching.

•    The flowchart for the operational flow of the stepper motor control system is shown.

•    The processor has to output a  switching sequence and  wait for  I  to  5  mull-seconds before sending the next switching sequence. (The delay is necessary to allow the motor transients to die- out).

Flow chart for stepper motor speed control system

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