Skip to content

How to Build an Obstacle Avoidance Robot (Step by Step Arduino Guide)

Introduction

Robots that can see and dodge obstacles are the foundation of autonomous navigation — from self‑driving cars to warehouse robots.

An Obstacle Avoidance Robot is a mobile robot that uses an ultrasonic sensor to detect obstacles ahead, then automatically changes its path to avoid crashing.

This project is the perfect way to learn how to combine:

  • Motors & Wheels (movement)
  • Sensor Input (distance detection with HC‑SR04)
  • Arduino Code (the logic to avoid collisions)

By the end of this guide, you’ll have a robot car that can roam freely without bumping into walls.

Components Required

  • Arduino Uno (or Nano)
  • L298N Motor Driver Module
  • 2x DC Motors + Robot Car Chassis
  • HC‑SR04 Ultrasonic Sensor
  • Small Servo Motor (to rotate ultrasonic sensor for better “vision”)
  • Battery pack (6–12V)
  • Jumper wires

Optional but recommended: Robot chassis kit that includes motors, wheels, and driver board.

How It Works

  • The HC‑SR04 ultrasonic sensor sends out sound waves.
  • Sound bounces back from any obstacle.
  • Arduino calculates distance based on time taken.
  • If obstacle < safe distance (e.g., 15 cm) → Robot stops and turns. Otherwise → Moves forward.

👉 Simple feedback loop = a self‑navigating bot!

Wiring Overview

  1. Motor Driver (L298N)
    • IN1 → Arduino D8
    • IN2 → Arduino D9
    • IN3 → Arduino D10
    • IN4 → Arduino D11
    • Motor A & B → DC Motors (robot wheels)
    • ENA/ENB → 5V (or use PWM for speed control)
    • 12V battery → Motor power
  2. Ultrasonic Sensor HC‑SR04
    • Trig → Arduino D6
    • Echo → Arduino D7
    • VCC → 5V, GND → GND
  3. Servo Motor (Optional: for sensor rotation)
    • Signal → Arduino D3
    • VCC → 5V, GND → GND

(Insert diagram suggestion: Robot car chassis + ultrasonic sensor “mounted as eyes” on a servo)

Arduino Code (Obstacle Avoidance Robot)

C++

#include <Servo.h>

 

// Motor pins

int in1 = 8;

int in2 = 9;

int in3 = 10;

int in4 = 11;

 

// Ultrasonic pins

int trig = 6;

int echo = 7;

 

// Servo pin

Servo myservo;

int servoPin = 3;

 

long duration;

int distance;

 

void setup() {

pinMode(in1, OUTPUT);

pinMode(in2, OUTPUT);

pinMode(in3, OUTPUT);

pinMode(in4, OUTPUT);

 

pinMode(trig, OUTPUT);

pinMode(echo, INPUT);

 

myservo.attach(servoPin);

myservo.write(90); // look forward initially

 

Serial.begin(9600);

}

 

// Function to measure distance

int getDistance() {

digitalWrite(trig, LOW); delayMicroseconds(2);

digitalWrite(trig, HIGH); delayMicroseconds(10);

digitalWrite(trig, LOW);

 

duration = pulseIn(echo, HIGH);

distance = duration * 0.034 / 2; // in cm

return distance;

}

 

// Movement functions

void forward() {

digitalWrite(in1, HIGH); digitalWrite(in2, LOW);

digitalWrite(in3, HIGH); digitalWrite(in4, LOW);

}

 

void backward() {

digitalWrite(in1, LOW); digitalWrite(in2, HIGH);

digitalWrite(in3, LOW); digitalWrite(in4, HIGH);

}

 

void left() {

digitalWrite(in1, LOW); digitalWrite(in2, HIGH);

digitalWrite(in3, HIGH); digitalWrite(in4, LOW);

}

 

void right() {

digitalWrite(in1, HIGH); digitalWrite(in2, LOW);

digitalWrite(in3, LOW); digitalWrite(in4, HIGH);

}

 

void stopBot() {

digitalWrite(in1, LOW); digitalWrite(in2, LOW);

digitalWrite(in3, LOW); digitalWrite(in4, LOW);

}

 

void loop() {

int dist = getDistance();

Serial.print(“Distance = “);

Serial.println(dist);

 

if (dist < 15) {

stopBot();

delay(500);

backward();

delay(500);

stopBot();

 

// Scan left & right

myservo.write(0); delay(500);

int distLeft = getDistance();

 

myservo.write(180); delay(500);

int distRight = getDistance();

 

myservo.write(90); // Reset forward

 

if (distLeft > distRight) {

left();

delay(700);

} else {

right();

delay(700);

}

} else {

forward();

}

}

Step‑by‑Step Build Process

  1. Mount motors + wheels on chassis.
  2. Attach servo motor at front as “head.”
  3. Fix Ultrasonic sensor to servo bracket (so it can pan).
  4. Wire Arduino → L298N → Motors + Sensor.
  5. Upload Arduino Code.
  6. Power robot with battery → Place in open space.
  7. Watch as it navigates freely, avoiding obstacles.

Troubleshooting

  • Robot not moving? → Check L298N motor power supply (needs >7V for wheels).
  • Sensor always shows 0 cm? → Ensure Trig/Echo pins are wired correctly.
  • Bot spinning wildly? → Motors wired backward — swap left/right pairs.
  • Delayed response? → Reduce servo rotation angles for faster scanning.

Advanced Upgrades

  • Add IR sensors → Prevent falling off edges (like a table).
  • Add Bluetooth/Wi‑Fi → Override robot manually.
  • Add Camera + OpenCV → Vision‑based obstacle detection.
  • Turn into a maze‑navigation robot with mapping algorithms.

FAQs

Q1: Can I build this without servo motor?
Yes — mount ultrasonic sensor fixed forward. Robot will only move back + turn blindly.

Q2: Can Raspberry Pi control this robot?
Yes, with Python GPIO + ultrasonic library. Pi even adds computer vision.

Q3: What power source should I use?
A 9V battery may be too weak. Use 2x 18650 cells (7.4V) or a 6–12V battery pack.

Conclusion

The Obstacle Avoidance Robot is one of the best beginner projects to learn autonomous robotics.

  • Ultrasonic works as the eyes .
  • Arduino works as the brain .
  • DC motors are the muscles .

With just these, you built a robot that thinks and reacts on its own.

Next, you can add more sensors or even computer vision for advanced robotics.

Downloade