Servo Motor Control Using 8051 Microcontroller

Introduction

Servo motors are widely used in robotics, industrial automation, and control systems due to their precise control over angular position. Controlling a servo motor involves generating precise pulse width modulation (PWM) signals. This article explores the design and implementation of a servo motor control system using the 8051 microcontroller, a versatile and widely-used microcontroller.

Components Required

1. 8051 Microcontroller

2. Servo Motor

3. Push Buttons

4. LCD Display (optional)

5. Power Supply Unit

6. Miscellaneous (Resistors, Capacitors, Diodes, etc.)

Circuit Diagram

The circuit diagram involves connecting the servo motor to the 8051 microcontroller, along with push buttons to control the position of the servo motor. Here is a brief overview of the connections:

1. 8051 Microcontroller: The core processing unit that generates PWM signals to control the servo motor.

2. Servo Motor: Connected to the microcontroller to receive PWM signals.

3. Push Buttons: Used to adjust the position of the servo motor.

4. LCD Display: Optional, used to display the current position of the servo motor.

Working Principle

The servo motor control system operates by generating PWM signals of varying duty cycles. Here's a step-by-step working principle:

1. Initialization: The 8051 microcontroller initializes all peripherals, including the servo motor and push buttons.

2. PWM Signal Generation: The microcontroller generates a PWM signal with a specific duty cycle to control the position of the servo motor.

3. Position Adjustment: Push buttons are used to increase or decrease the duty cycle of the PWM signal, thus adjusting the servo motor's position.

4. Display Position: The current position of the servo motor is optionally displayed on an LCD.

Software Implementation

The software for the 8051 microcontroller can be written in Embedded C. Below is a sample code snippet to illustrate the main functionalities:

#include <reg51.h>

#include <intrins.h>

// Define the pins for push buttons and servo motor

sbit Button1 = P3^0;  // Button to increase angle

sbit Button2 = P3^1;  // Button to decrease angle

sbit ServoPin = P2^0; // Servo motor control pin

void delay_us(unsigned int us) {

    while (us--) {

        _nop_();

    }

}

void delay_ms(unsigned int ms) {

    unsigned int i, j;

    for (i = 0; i < ms; i++)

        for (j = 0; j < 123; j++);

}

void servo_control(unsigned int angle) {

    unsigned int pulse_width;

    pulse_width = (angle * 1.5) + 500; // Convert angle to pulse width

    ServoPin = 1; // Set servo pin high

    delay_us(pulse_width); // Delay for the pulse width duration

    ServoPin = 0; // Set servo pin low

    delay_ms(20); // Delay for the rest of the 20 ms period

}

void main() {

    unsigned int angle = 90; // Initial angle of 90 degrees

    while (1) {

        if (Button1 == 0) { // If Button1 is pressed

            angle += 10; // Increase angle by 10 degrees

            if (angle > 180) angle = 180; // Limit angle to 180 degrees

            while (Button1 == 0); // Wait for button release

        }

        if (Button2 == 0) { // If Button2 is pressed

            angle -= 10; // Decrease angle by 10 degrees

            if (angle < 0) angle = 0; // Limit angle to 0 degrees

            while (Button2 == 0); // Wait for button release

        }

        servo_control(angle); // Control servo motor with the updated angle

    }

}

Detailed Explanation of Code

1. Initialization: The pins for the servo motor and push buttons are defined. The initial angle of the servo motor is set to 90 degrees.

2. Delay Functions: Two delay functions are defined, one for microseconds and another for milliseconds, to create the required pulse width and period for the PWM signal.

3. Servo Control Function: The servo_control function generates a PWM signal with a pulse width corresponding to the desired angle. The angle is converted to pulse width using the formula: pulse_width = (angle * 1.5) + 500.

4. Main Function: The main function continuously checks the status of the push buttons. If Button1 is pressed, the angle is increased by 10 degrees, and if Button2 is pressed, the angle is decreased by 10 degrees. The servo motor is then controlled using the updated angle.

Applications and Benefits

1. Robotics: Precise control of robotic arms and joints.

2. Automotive Systems: Used in steering control and throttle control.

3. Aerospace: Control of flaps and ailerons in aircraft.

4. Home Automation: Controlling window blinds, doors, and cameras.

Conclusion

A servo motor control system using the 8051 microcontroller provides an efficient and reliable solution for precise angular position control. By leveraging the capabilities of the 8051 microcontroller, such systems can be easily implemented and customized for various applications. As technology advances, servo motor control systems will continue to play a critical role in automation and control systems across different industries.

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