Car Project 2 : Object Avoidance Robot Car
Overview
Have you ever wanted to build a robot car that can drive on its own and avoid obstacles like a mini self-driving car? 🚙✨ In this tutorial, you’ll learn how to build an object avoidance robot car using an ESP32, L298N motor driver, and an ultrasonic sensor.
This project is perfect for beginners who want to start exploring robotics and coding in a fun and hands-on way!
What you'll need
Techsage's Innovator Box Plus - its best AI & Robotics KitÂ
Components
- ESP32Â
- L298N motor driver
- Ultrasonic sensor (HC-SR04)
- 2 DC motors with wheels
- Robot chassis kit
- Jumper wires
- Battery pack (7.4V or 12V recommended) and holder
- Breadboard
How it works
The robot uses an ultrasonic sensor to detect obstacles in front. When it sees something too close (less than 20 cm), it stops and "looks" left and right to find the best path forward. If no clear path exists, it reverses and turns around.
Circuit connections
Diagram Representation:
Motors to L298N
- Motor A (left): Connect to OUT1 and OUT2 on L298N.
- Motor B (right): Connect to OUT3 and OUT4 on L298N.
L298N to ESP32
| L298N Pin | ESP32 GPIO | Function |
|---|---|---|
| IN1 | 27 | Left motor direction |
| IN2 | 26 | Left motor direction |
| IN3 | 25 | Right motor direction |
| IN4 | 33 | Right motor direction |
| ENA | 14 | Left motor speed (PWM) |
| ENB | 32 | Right motor speed (PWM) |
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Ultrasonic sensor to ESP32
| HC-SR04 Pin | ESP32 GPIO | Function |
|---|---|---|
| VCC | 5V | Power |
| GND | GND | Ground |
| Trig | 5 | Trigger |
| Echo | 18 | Echo |
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Power connections
- Connect battery + (positive) to L298N VCC terminal.
- Connect battery – (negative) to L298N GND, and also connect L298N GND to ESP32 GND.
- Use L298N 5V output (with jumper connected) to power ESP32 VIN pin (or use a separate 5V supply).
Uploading the code
Here’s the full code you can directly copy and paste into the Arduino IDE (make sure you select ESP32 board and correct COM port) :
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#define ENA 14
#define IN1 27
#define IN2 26
#define IN3 25
#define IN4 33
#define ENB 32
#define TRIG_PIN 5
#define ECHO_PIN 18
const int SAFE_DISTANCE = 20; // in cm
const int MOTOR_SPEED = 150;
const int TURN_TIME = 300;
const int SCAN_DELAY = 200;
void setup() {
 Serial.begin(115200);
 delay(1000);
 pinMode(ENA, OUTPUT);
 pinMode(IN1, OUTPUT);
 pinMode(IN2, OUTPUT);
 pinMode(IN3, OUTPUT);
 pinMode(IN4, OUTPUT);
 pinMode(ENB, OUTPUT);
 pinMode(TRIG_PIN, OUTPUT);
 pinMode(ECHO_PIN, INPUT);
 Serial.println("Object Avoidance Car Initialized!");
}
void loop() {
 int distance = getDistance();
 if (distance > SAFE_DISTANCE) {
  moveForward();
  Serial.println("Moving Forward - Distance: " + String(distance) + " cm");
 } else {
  Serial.println("Obstacle ahead! Distance: " + String(distance) + " cm");
  handleObstacle();
 }
 delay(50);
}
void handleObstacle() {
 stopMotors();
 delay(100);
 // Check left
 turnLeft();
 delay(TURN_TIME);
 stopMotors();
 delay(SCAN_DELAY);
 int leftDistance = getDistance();
 Serial.println("Left distance: " + String(leftDistance) + " cm");
 // Return center
 turnRight();
 delay(TURN_TIME);
 stopMotors();
 delay(SCAN_DELAY);
 // Check right
 turnRight();
 delay(TURN_TIME);
 stopMotors();
 delay(SCAN_DELAY);
 int rightDistance = getDistance();
 Serial.println("Right distance: " + String(rightDistance) + " cm");
 // Return center
 turnLeft();
 delay(TURN_TIME);
 stopMotors();
 delay(100);
 if (leftDistance > SAFE_DISTANCE && rightDistance > SAFE_DISTANCE) {
  if (leftDistance >= rightDistance) {
   Serial.println("Turning left (better clearance)");
   turnLeft();
   delay(TURN_TIME * 2);
  } else {
   Serial.println("Turning right (better clearance)");
   turnRight();
   delay(TURN_TIME * 2);
  }
 } else if (leftDistance > SAFE_DISTANCE) {
  Serial.println("Turning left");
  turnLeft();
  delay(TURN_TIME * 2);
 } else if (rightDistance > SAFE_DISTANCE) {
  Serial.println("Turning right");
  turnRight();
  delay(TURN_TIME * 2);
 } else {
  Serial.println("Both sides blocked. Reversing...");
  moveBackward();
  delay(800);
  stopMotors();
  delay(200);
  turnRight();
  delay(TURN_TIME * 4);
 }
 stopMotors();
 delay(200);
}
int getDistance() {
 digitalWrite(TRIG_PIN, LOW);
 delayMicroseconds(2);
 digitalWrite(TRIG_PIN, HIGH);
 delayMicroseconds(10);
 digitalWrite(TRIG_PIN, LOW);
 long duration = pulseIn(ECHO_PIN, HIGH, 30000);
 if (duration == 0) {
  return 0;
 }
 int distance = duration * 0.034 / 2;
 if (distance > 200) {
  return 200;
 }
 return distance;
}
void moveForward() {
 digitalWrite(IN1, HIGH);
 digitalWrite(IN2, LOW);
 digitalWrite(IN3, HIGH);
 digitalWrite(IN4, LOW);
 analogWrite(ENA, MOTOR_SPEED);
 analogWrite(ENB, MOTOR_SPEED);
}
void moveBackward() {
 digitalWrite(IN1, LOW);
 digitalWrite(IN2, HIGH);
 digitalWrite(IN3, LOW);
 digitalWrite(IN4, HIGH);
 analogWrite(ENA, MOTOR_SPEED);
 analogWrite(ENB, MOTOR_SPEED);
}
void turnLeft() {
 digitalWrite(IN1, LOW);
 digitalWrite(IN2, HIGH);
 digitalWrite(IN3, HIGH);
 digitalWrite(IN4, LOW);
 analogWrite(ENA, MOTOR_SPEED);
 analogWrite(ENB, MOTOR_SPEED);
}
void turnRight() {
 digitalWrite(IN1, HIGH);
 digitalWrite(IN2, LOW);
 digitalWrite(IN3, LOW);
 digitalWrite(IN4, HIGH);
 analogWrite(ENA, MOTOR_SPEED);
 analogWrite(ENB, MOTOR_SPEED);
}
void stopMotors() {
 digitalWrite(IN1, LOW);
 digitalWrite(IN2, LOW);
 digitalWrite(IN3, LOW);
 digitalWrite(IN4, LOW);
 analogWrite(ENA, 0);
 analogWrite(ENB, 0);
}
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Testing
✅ After uploading, place the car on a flat surface.
✅ Make sure no wheels are stuck and motors spin freely.
✅ Watch your car start moving forward and avoid obstacles by turning left or right!
Tips & troubleshooting
- If motors spin in the wrong direction, swap OUT1 & OUT2 or OUT3 & OUT4 motor wires on L298N.
- Always power your motors from a battery — USB alone won’t be enough!
- Adjust
SAFE_DISTANCEandMOTOR_SPEEDif your car is too fast or stops too late. - Use the Serial Monitor to see real-time distance and debug easily.
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