Stepper Motor Interfacing with AT89C51

interfacing stepper

The Stepper Motor is a Digital Electromechanical Device which converts electrical pulse energy into equivalent mechanical energy for that digital data. As the name indicates that stepper motor rotates step-wise as per the given digital data.

It has main three types: Permanent Magnet, Variable Reluctance and Hybrid Synchronous. Stepper Motors comes up with 4-wires (Bipolar), 5-wires (Unipolar) and 6-wires (Unipolar). Bipolar stepper motor does not require the separate biasing supply but only the two coil end points are used to drive the stepper motor. The Unipolar Stepper Motors do have the common pin to provide biasing supply and coil ends are used to drive the stepper motor.

We can control three parameters of the Stepper Motor. The first parameter is Speed, second is Angle of Rotation and third is Direction which can be controlled using speed of sending digital data, number of digital values and sequence of digital data respectively.

Basically Stepper motor can be driven in two modes:

  1. Full Angle Mode (1.8ᵒ)
  2. Half Angle Mode (0.9ᵒ)

To complete the single rotation in Full Angle Mode we need to send 360/1.8ᵒ = 200 digital data values and in Half Angle Mode 360/0.9ᵒ = 400 digital data values.

Table 1-Digital Data Value for Full Angle Mode (Set 1)

Sr. No.D3 (MSB)D2D1D0 (LSB)Hexadecimal Value
11010A
210019
301015
401106

Table 2-Digital Data Value for Full Angle Mode (Set 2)

Sr. No.D3 (MSB)D2D1D0 (LSB)Hexadecimal Value
11100C
210019
300113
401106

Table 3-Digital Data Value for Half Angle Mode (Set 1)

Sr. No.D3 (MSB)D2D1D0 (LSB)Hexadecimal Value
11010A
210008
310019
400011
501015
601004
701106
800102

Table 4-Digital Data Value for Half Angle Mode (Set 2)

Sr. No.D3 (MSB)D2D1D0 (LSB)Hexadecimal Value
11100C
210008
310019
400011
500113
600102
701106
801004

Small size Stepper motor needs more than 100mA current in each coil to operate. As we know that 8051 microcontroller can sink/source maximum 10mA of current on any port pin. So to boost the current level to meet the requirement of the stepper motor, we need to use motor driver ICs such as ULN2803, L293D etc.

Applications of Stepper Motor:

– Automation

– Robotics

– Solar System for facing towards the Sun

– CCTV Surveillance System

– 3D Printer

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