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How to Build a Line Follower Robot (Step by Step Guide)

Introduction

A Line Follower Robot is one of the most popular beginner robotics projects. It’s a robot car that uses infrared (IR) sensors to detect and follow a path (usually a black line on a white surface).

This project teaches the core of robotics:

  • Sensing the environment (IR sensors).
  • Processing logic (Arduino brain).
  • Acting on decisions (DC motors moving left/right).

In this guide, we’ll build a simple Line Follower Robot step by step.

What You’ll Need (Components List)

  • Arduino Uno (or Nano)
  • L298N Motor Driver Module
  • 2x DC Motors + Wheels
  • IR Sensor Module (2 or 3 sensors for better accuracy)
  • Robot Chassis with battery (6V/9V)
  • Jumper wires + breadboard (optional)
  • Black tape/marker line on a white surface (track)

Kits are available online as “Arduino Car Kit with Line Sensors” — a good starting point for beginners.

How Does It Work?

  • White surface reflects IR light → Sensor = HIGH (logic 1).
  • Black line absorbs IR light → Sensor = LOW (logic 0).

The Arduino constantly reads the left & right sensor values:

  • If both read white → Move forward.
  • If left sensor sees black → Turn left.
  • If right sensor sees black → Turn right.
  • If both see black → Stop.

This simple logic lets it follow a line track automatically.

Circuit Wiring

Connections overview:

  • IR Sensor OUT pins → Arduino digital pins (e.g., D2 = Left, D3 = Right).
  • Motor driver IN pins → Arduino pins (D8–D11).
  • Motor driver OUT → Two DC motors.
  • Motor power supply → 6–12V battery.
  • Servo pins:
    • Arduino GND → IR & motor driver GND.
    • Arduino 5V → IR sensors’ VCC.

(Insert Wiring Diagram: Arduino + L298N + IR Sensors + Motors)

Arduino Code for Line Follower (2‑Sensors Version)

C++

// Pin setup

int leftSensor = 2;

int rightSensor = 3;

 

int motorA1 = 8;

int motorA2 = 9;

int motorB1 = 10;

int motorB2 = 11;

 

int leftValue, rightValue;

 

void setup() {

pinMode(leftSensor, INPUT);

pinMode(rightSensor, INPUT);

pinMode(motorA1, OUTPUT);

pinMode(motorA2, OUTPUT);

pinMode(motorB1, OUTPUT);

pinMode(motorB2, OUTPUT);

}

 

void forward() {

digitalWrite(motorA1, HIGH); digitalWrite(motorA2, LOW);

digitalWrite(motorB1, HIGH); digitalWrite(motorB2, LOW);

}

 

void left() {

digitalWrite(motorA1, LOW); digitalWrite(motorA2, HIGH);

digitalWrite(motorB1, HIGH); digitalWrite(motorB2, LOW);

}

 

void right() {

digitalWrite(motorA1, HIGH); digitalWrite(motorA2, LOW);

digitalWrite(motorB1, LOW);  digitalWrite(motorB2, HIGH);

}

 

void stopRobot() {

digitalWrite(motorA1, LOW); digitalWrite(motorA2, LOW);

digitalWrite(motorB1, LOW); digitalWrite(motorB2, LOW);

}

 

void loop() {

leftValue = digitalRead(leftSensor);

rightValue = digitalRead(rightSensor);

 

if (leftValue == HIGH && rightValue == HIGH) {

forward();           // On white → move forward

}

else if (leftValue == LOW && rightValue == HIGH) {

left();              // Left sensor on black → turn left

}

else if (leftValue == HIGH && rightValue == LOW) {

right();             // Right sensor on black → turn right

}

else {

stopRobot();         // Both on black → stop

}

}

Step‑by‑Step Build Process

  1. Assemble the robot chassis → mount motors + wheels.
  2. Attach IR sensors facing downward (1–2 cm above surface).
  3. Connect circuits (Arduino → Motor Driver → Motors → Sensors).
  4. Upload the given Arduino code.
  5. Place the robot on the track (black tape on white floor).
  6. Watch your robot automatically follow the line! 🎉

Troubleshooting Tips

  • Robot not following line? → Adjust sensor distance to ~1 cm.
  • Motors not responding? → Check motor driver wiring.
  • Moves in wrong direction? → Swap motor wires or adjust logic in code.
  • Wobbly path following? → Use 3 IR sensors (Left, Middle, Right) for smoother tracking.

Advanced Line Follower Ideas

Once the basic robot works, try:

  • Adding speed control via PWM.
  • Using 3+ sensors for smoother turning.
  • Making a maze solver robot with algorithms.
  • Adding Bluetooth/Wi‑Fi for manual override control.

FAQs

Q1: Can I use Raspberry Pi instead of Arduino?
Yes! With Python + GPIO, Pi can do more (like camera‑based line following). Arduino is just simpler for beginners.

Q2: Why does the robot need a motor driver?
Because Arduino pins can’t supply the high current motors need.

Q3: How can I make the track?
Use black electrical tape on white cardboard or floor.

Conclusion

Building a Line Follower Robot is one of the best ways to understand the pillars of robotics:

  • Sensors reading input.
  • Arduino brain making decisions.
  • Motors acting as output.

It looks fun, works practically, and sets the foundation for more advanced AI/robotics projects.

Start with the basic 2‑sensor version today — then upgrade with more sensors and smarter code tomorrow.

Downloade