Build a Smart Obstacle-Avoiding Robot: A Hands-On Tutorial from AI Valley Zirakpur

A close-up wiring diagram showing the connections between the Arduino digital pins 4-7 and the L298N IN1-IN4 pins, alongside motor connections.

// Motor A connections (Right Motor)
const int IN1 = 4;
const int IN2 = 5;

// Motor B connections (Left Motor)
const int IN3 = 6;
const int IN4 = 7;

void setup() {
  // Configure all motor control pins as outputs
  pinMode(IN1, OUTPUT);
  pinMode(IN2, OUTPUT);
  pinMode(IN3, OUTPUT);
  pinMode(IN4, OUTPUT);
}

void loop() {
  // Move Forward: One pin HIGH and the other LOW sets the rotation direction
  digitalWrite(IN1, HIGH);
  digitalWrite(IN2, LOW);
  digitalWrite(IN3, HIGH);
  digitalWrite(IN4, LOW);
  delay(2000); // Drive forward for 2 seconds

  // Stop Motors: Setting all pins LOW cuts power to the H-Bridge
  digitalWrite(IN1, LOW);
  digitalWrite(IN2, LOW);
  digitalWrite(IN3, LOW);
  digitalWrite(IN4, LOW);
  delay(2000); // Stop for 2 seconds
}

A graphical flowchart showing the logic: Start -> Go Forward -> Stop -> Turn Right.

const int IN1 = 4; const int IN2 = 5;
const int IN3 = 6; const int IN4 = 7;

void setup() {
  pinMode(IN1, OUTPUT); pinMode(IN2, OUTPUT);
  pinMode(IN3, OUTPUT); pinMode(IN4, OUTPUT);
}

void loop() {
  moveForward();
  delay(1000);
  turnRight();
  delay(500);
  stopRobot();
  delay(2000);
}

// Custom Function: Move Forward
void moveForward() {
  digitalWrite(IN1, HIGH); digitalWrite(IN2, LOW);
  digitalWrite(IN3, HIGH); digitalWrite(IN4, LOW);
}

// Custom Function: Reverse
void moveBackward() {
  digitalWrite(IN1, LOW); digitalWrite(IN2, HIGH);
  digitalWrite(IN3, LOW); digitalWrite(IN4, HIGH);
}

// Custom Function: Turn Right (Differential Steering)
void turnRight() {
  digitalWrite(IN1, LOW); digitalWrite(IN2, HIGH); // Right wheel spins backward
  digitalWrite(IN3, HIGH); digitalWrite(IN4, LOW); // Left wheel spins forward
}

// Custom Function: Emergency Stop
void stopRobot() {
  digitalWrite(IN1, LOW); digitalWrite(IN2, LOW);
  digitalWrite(IN3, LOW); digitalWrite(IN4, LOW);
}

A photo of the fully assembled robot on a floor, facing a cardboard box or wall obstacle.

// --- SENSOR PINS ---
const int trigPin = 9;
const int echoPin = 10;

// --- MOTOR PINS ---
const int IN1 = 4;
const int IN2 = 5;
const int IN3 = 6;
const int IN4 = 7;

// --- VARIABLES ---
long duration;
int distance;

void setup() {
  // Initialize Sensor
  pinMode(trigPin, OUTPUT);
  pinMode(echoPin, INPUT);
  
  // Initialize Motors
  pinMode(IN1, OUTPUT); pinMode(IN2, OUTPUT);
  pinMode(IN3, OUTPUT); pinMode(IN4, OUTPUT);
  
  // Safety Delay: Give yourself 3 seconds to put the robot on the floor!
  delay(3000);
}

void loop() {
  // 1. Fire the ultrasonic ping and measure distance
  digitalWrite(trigPin, LOW);
  delayMicroseconds(2);
  digitalWrite(trigPin, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigPin, LOW);
  
  duration = pulseIn(echoPin, HIGH, 30000); // 30ms timeout prevents freezing
  distance = duration * 0.0343 / 2;
  
  // 2. Logic Controller: Make a decision based on the distance data
  // We check if distance > 0 to filter out sensor timeouts/errors
  if (distance > 0 && distance < 25) {  
    // WARNING: Obstacle detected within 25 cm!
    
    stopRobot();
    delay(300); // Pause to kill forward momentum
    
    moveBackward();
    delay(400); // Back up to create clearance
    
    stopRobot();
    delay(300); // Pause before changing direction
    
    turnRight();
    delay(500); // Spin 90 degrees to find a new, clear path
    
  } else {
    // Path is completely clear, full speed ahead!
    moveForward();
  }
  
  // Small loop delay for hardware stability
  delay(50);
}

// --- MODULAR MOVEMENT FUNCTIONS ---
void moveForward() {
  digitalWrite(IN1, HIGH); digitalWrite(IN2, LOW);
  digitalWrite(IN3, HIGH); digitalWrite(IN4, LOW);
}

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

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

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