Build Line Follower Robot using Arduino

Here’s a complete guide to build a Line Follower Robot using Arduino. This includes hardware requirements, circuit design, and Arduino code.

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Components Required

1. Arduino UNO (or Nano)
2. L298N Motor Driver Module
3. IR Sensor Module (2 or 3 recommended)
4. BO Motors with Wheels (2)
5. Swivel Castor Wheel (1)
6. Chassis (any basic robot car body)
7. Battery (Li-ion 7.4V or 9V with holder)
8. Jumper wires, screws, etc.

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Wiring Guide

IR Sensor (2-sensor configuration example):

• Left Sensor (IR1):
  • VCC → 5V (Arduino)
  • GND → GND
  • OUT → D2
• Right Sensor (IR2):
  • VCC → 5V
  • GND → GND
  • OUT → D3

L298N Motor Driver:

• IN1 → D4 (Motor A)
• IN2 → D5
• IN3 → D6 (Motor B)
• IN4 → D7
• ENA → 5V jumper enabled
• ENB → 5V jumper enabled
• OUT1 → Left Motor
• OUT2 → Left Motor
• OUT3 → Right Motor
• OUT4 → Right Motor
• VCC → Battery + (6V–12V)
• GND → Battery – and Arduino GND

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Logic

• Black line on white surface (black reflects less IR, white reflects more).
• IR sensor reads:
  • White = HIGH
  • Black = LOW

IR1 (Left)	IR2 (Right)	Action
LOW	LOW	Forward
LOW	HIGH	Turn Left
HIGH	LOW	Turn Right
HIGH	HIGH	Stop (off line or idle)

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Arduino Code:

// Motor Pins
#define IN1 4
#define IN2 5
#define IN3 6
#define IN4 7

// IR Sensors
#define LEFT_SENSOR 2
#define RIGHT_SENSOR 3

void setup() {
  // Motor pins
  pinMode(IN1, OUTPUT);
  pinMode(IN2, OUTPUT);
  pinMode(IN3, OUTPUT);
  pinMode(IN4, OUTPUT);

  // IR Sensor pins
  pinMode(LEFT_SENSOR, INPUT);
  pinMode(RIGHT_SENSOR, INPUT);

  Serial.begin(9600);
}

void loop() {
  int leftStatus = digitalRead(LEFT_SENSOR);
  int rightStatus = digitalRead(RIGHT_SENSOR);

  Serial.print("Left: ");
  Serial.print(leftStatus);
  Serial.print(" | Right: ");
  Serial.println(rightStatus);

  if (leftStatus == LOW && rightStatus == LOW) {
    // Move forward
    forward();
  } else if (leftStatus == LOW && rightStatus == HIGH) {
    // Turn left
    turnLeft();
  } else if (leftStatus == HIGH && rightStatus == LOW) {
    // Turn right
    turnRight();
  } else {
    // Stop
    stopMotors();
  }
}

void forward() {
  digitalWrite(IN1, HIGH);
  digitalWrite(IN2, LOW);
  digitalWrite(IN3, HIGH);
  digitalWrite(IN4, LOW);
}

void turnLeft() {
  digitalWrite(IN1, LOW);
  digitalWrite(IN2, HIGH);
  digitalWrite(IN3, HIGH);
  digitalWrite(IN4, LOW);
}

void turnRight() {
  digitalWrite(IN1, HIGH);
  digitalWrite(IN2, LOW);
  digitalWrite(IN3, LOW);
  digitalWrite(IN4, HIGH);
}

void stopMotors() {
  digitalWrite(IN1, LOW);
  digitalWrite(IN2, LOW);
  digitalWrite(IN3, LOW);
  digitalWrite(IN4, LOW);
}

Assembly Tips

• Place IR sensors in front of the car, close to the ground (~1cm gap).
• Test sensors individually before final wiring.
• Use a black electrical tape on a white surface as a test track.