Line Follower Robot Using PIC Microcontroller

Introduction

A Line Follower Robot is an autonomous robot that can detect and follow a line drawn on the floor. This project is widely popular among robotics enthusiasts and is a great way to learn about sensors, motor control, and the use of microcontrollers. In this article, we will design and build a simple Line Follower Robot using a PIC microcontroller.

System Overview

The Line Follower Robot works by using sensors to detect the line on the floor. Typically, infrared (IR) sensors are used to detect the contrast between the line (usually black) and the background (usually white). The microcontroller processes the sensor inputs and controls the motors to keep the robot following the line.

Components Required

1. PIC Microcontroller (e.g., PIC16F877A) - The main controller that processes sensor inputs and controls the motors.

2. IR Sensors (2 or more) - Used to detect the line on the floor.

3. Motor Driver IC (e.g., L298N) - Controls the speed and direction of the motors.

4. DC Motors (2) - To drive the robot's wheels.

5. Chassis - The base structure of the robot.

6. Wheels (2) - Attached to the motors.

7. Caster Wheel (1) - For balance.

8. Power Supply (Battery) - To power the robot.

9. Breadboard/PCB - For assembling the circuit.

10. Connecting Wires - For connections.

Circuit Diagram

Here’s a simplified circuit diagram for the Line Follower Robot:

[Insert a circuit diagram here showing connections:

- IR sensors connected to the analog or digital input pins of the PIC microcontroller.

- Motor driver IC connected to the output pins of the PIC to control the motors.

- Power supply connections to the PIC, motor driver, and sensors.]

Working Principle

The robot uses two IR sensors placed on the front left and right sides. These sensors detect the presence of the line by measuring the reflected IR light. When the sensor detects a black line, it sends a low signal to the microcontroller; otherwise, it sends a high signal. The microcontroller uses this input to decide the direction in which the motors should rotate to keep the robot on the line.

• Both sensors on the line (black): Move forward.

• Left sensor off the line (white): Turn right.

• Right sensor off the line (white): Turn left.

• Both sensors off the line: Stop or turn around.

Step-by-Step Implementation

Step 1: Setting Up the Development Environment

Before starting with the hardware, ensure you have the necessary software tools installed:

• MPLAB X IDE - Integrated Development Environment for writing and debugging code for PIC microcontrollers.

• XC8 Compiler - A compiler for converting C code into a hex file that the PIC microcontroller can understand.

Step 2: Writing the Code

Start by initializing the PIC microcontroller, setting up the IR sensor inputs, and configuring the motor control outputs.

Code Outline:

#include <xc.h>

#define _XTAL_FREQ 20000000  // Define the crystal frequency (20MHz)

#define LEFT_SENSOR RB0

#define RIGHT_SENSOR RB1

#define LEFT_MOTOR_FORWARD RC0

#define LEFT_MOTOR_BACKWARD RC1

#define RIGHT_MOTOR_FORWARD RC2

#define RIGHT_MOTOR_BACKWARD RC3

void main(void) {

    TRISB = 0xFF;  // Configure PORTB as input (for sensors)

    TRISC = 0x00;  // Configure PORTC as output (for motor control)

    while(1) {

        if (LEFT_SENSOR == 0 && RIGHT_SENSOR == 0) {

            // Move Forward

            LEFT_MOTOR_FORWARD = 1;

            LEFT_MOTOR_BACKWARD = 0;

            RIGHT_MOTOR_FORWARD = 1;

            RIGHT_MOTOR_BACKWARD = 0;

        }

        else if (LEFT_SENSOR == 0 && RIGHT_SENSOR == 1) {

            // Turn Right

            LEFT_MOTOR_FORWARD = 1;

            LEFT_MOTOR_BACKWARD = 0;

            RIGHT_MOTOR_FORWARD = 0;

            RIGHT_MOTOR_BACKWARD = 1;

        }

        else if (LEFT_SENSOR == 1 && RIGHT_SENSOR == 0) {

            // Turn Left

            LEFT_MOTOR_FORWARD = 0;

            LEFT_MOTOR_BACKWARD = 1;

            RIGHT_MOTOR_FORWARD = 1;

            RIGHT_MOTOR_BACKWARD = 0;

        }

        else {

            // Stop (or can be programmed to search for the line)

            LEFT_MOTOR_FORWARD = 0;

            LEFT_MOTOR_BACKWARD = 0;

            RIGHT_MOTOR_FORWARD = 0;

            RIGHT_MOTOR_BACKWARD = 0;

        }

    }

}

Step 3: Interfacing the IR Sensors

• Connect the IR sensors to the digital input pins of the PIC microcontroller (e.g., RB0 and RB1).

• Place the sensors at the front of the robot, ideally at a distance from each other to effectively detect the line.

Step 4: Motor Control

• Connect the motor driver IC’s input pins to the output pins of the PIC microcontroller (e.g., RC0 to RC3).

• Connect the motors to the output pins of the motor driver IC.

• Ensure the motors are connected in a way that they can rotate both forward and backward.

Step 5: Assembling the Robot

• Attach the DC motors to the chassis and connect the wheels.

• Mount the IR sensors at the front of the chassis.

• Connect the power supply to the motor driver and the PIC microcontroller.

• Assemble the circuit on a breadboard or PCB and fix it on the chassis.

Step 6: Compiling and Uploading the Code

• Write and compile the code in MPLAB X IDE using the XC8 compiler to generate a hex file.

• Upload the hex file to the PIC microcontroller using a programmer (e.g., PICkit 3).

Step 7: Testing and Calibration

• Place the robot on a surface with a defined line (usually black electrical tape on a white background).

• Power on the robot and observe its behavior. If necessary, adjust the sensor placement or code logic to improve line-following performance.

Applications

• Educational Robots: Ideal for learning about basic robotics, sensors, and microcontrollers.

• Warehouse Automation: Can be adapted for automated guided vehicles (AGVs) in warehouses to follow predefined paths.

• Line Following in Competitions: Commonly used in robotics competitions where the objective is to follow a line as quickly and accurately as possible.

Conclusion

Building a Line Follower Robot using a PIC microcontroller is an excellent way to get hands-on experience with embedded systems, motor control, and sensor integration. The project provides a foundational understanding of how to develop autonomous robots that can navigate their environment based on sensor input.

This project can be expanded with additional features like obstacle detection, speed control, or even wireless communication for remote monitoring and control. The knowledge gained from this project is applicable in a wide range of robotics and automation applications.

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