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# Interfacing Stepper Motor with 8085

• Stepper motor is an electromechanical device that rotates through fixed angular steps when digital inputs are applied. It is suitable for precise position, speed and direction control which are required in automation system.

• The angle through which stepper motor rotates with a fixed angle for each digital data is called step angle.

• Different stepper motor has different step angle. The more frequently used stepper motor has step angle of 0.9 degrees and 1.8 degrees.

• Depending on the sequence applied to stepper motor, it can be classified in two category:

• 1. 4- Step sequence or full step sequence
2. 8- Step sequence or half step sequence

Calculations:
1. Total no. of steps=

Ex: = 200 steps are required to complete one rotation

2. Total no. of repeated steps=

Ex: = 50 repetition of sequence = (32) in Hexadecimal.

4-Step sequence:
• In this type of functioning, the following 4 binary sequence/code are used for rotation: (Considering step angle= 1.8 degrees)

• 8-Step Sequence:
• In this type of functioning, the following 8 binary sequence/code are used for rotation: (Considering step angle= 0.9degrees)

• Chips select Logic:

Control word Format:
=80H

Program:

• In the above program in look up table if the 4-step sequence for clock wise then stepper motor will rotate in clockwise direction and if the 4-step sequence for anti-clock wise then stepper motor will rotate in anti-clockwise direction.

• Speed control of stepper motor is achieved by writing program to rotate stepper motor continuously in delay program. We can change the delay between two steps and thus change the speed of stepper motor.

• ## Interfacing diagram of Stepper motor with 8085

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