🤖 Obstacle Avoidance Robot

An Arduino-based autonomous robot that uses an HC-SR04 ultrasonic sensor mounted on a servo to scan its surroundings and navigate around obstacles in real time using an L293D motor driver.

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📖 Overview

The Obstacle Avoidance Robot is a fully autonomous wheeled robot built on an Arduino UNO. An HC-SR04 ultrasonic sensor continuously measures the distance to objects ahead. When an obstacle is detected within 20 cm, the robot stops, reverses slightly, then uses a servo to scan left and right — choosing the direction with more clearance to navigate around the obstacle. When the path is clear, it drives forward again.

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✨ Features

• 📡 Ultrasonic sensing — HC-SR04 measures front distance in real time using time-of-flight
• 🔄 Servo-mounted scanning — sensor sweeps left (160°) and right (20°) to compare clearance on both sides
• 🧠 Autonomous decision-making — robot selects the better direction based on distance comparison
• 🚗 Full motor control — forward, backward, turn left, turn right, and stop via L293D motor driver
• 🖥️ Serial monitoring — front, left, and right distances streamed via Serial Monitor (9600 baud)
• 🔋 External battery powered — 9V battery drives the motors independently of the Arduino

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🛠️ Hardware Components

Component	Quantity
Arduino UNO	1
HC-SR04 Ultrasonic Sensor	1
SG90 Servo Motor	1
L293D Motor Driver IC	1
DC Gear Motors	2
9V Battery	1
Breadboard	1
Jumper Wires	As needed

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🔌 Pin Connections

Component	Pin	Arduino Pin
HC-SR04	VCC	5V
HC-SR04	GND	GND
HC-SR04	TRIG	Digital 9
HC-SR04	ECHO	Digital 10
Servo Motor	Signal	Digital 3
Servo Motor	VCC	5V
Servo Motor	GND	GND
L293D	IN1	Digital 6
L293D	IN2	Digital 7
L293D	IN3	Digital 4
L293D	IN4	Digital 5
L293D	VCC1 (Logic)	5V
L293D	VCC2 (Motor)	9V Battery (+)
L293D	GND	GND

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🔌 Circuit Diagram

Built and simulated in Tinkercad

Breadboard View:

Schematic View:

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🚀 Getting Started

Prerequisites

• Arduino IDE (1.8.x or 2.x)
• Servo.h library — included with the Arduino IDE by default

Installation

1. Clone the repository

git clone https://github.com/deep-chatterjee/Obstacle-Avoidance-Robot.git
cd Obstacle-Avoidance-Robot

2. Open the sketch

   • Open Obstacle_Avoidance_Robot.ino in the Arduino IDE
   • Select your board: Arduino UNO
   • Select the correct COM port

3. Upload to your board

   • Click Upload
   • Open Serial Monitor (baud rate: 9600) to observe live distance readings

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💻 How It Works

HC-SR04 measures front distance
            ↓
     frontDistance > 20 cm?
        ↙              ↘
      YES               NO
       ↓                 ↓
  Move Forward        Stop Robot
                          ↓
                    Move Backward (400ms)
                          ↓
                    Servo scans LEFT → measure leftDistance
                          ↓
                    Servo scans RIGHT → measure rightDistance
                          ↓
               leftDistance > rightDistance?
                    ↙              ↘
                  YES               NO
                   ↓                 ↓
               Turn Left         Turn Right
                    ↓
               Resume Forward

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📁 Project Structure

Obstacle-Avoidance-Robot/
├── Obstacle_Avoidance_Robot.ino           # Arduino sketch
├── Obstacle_Avoidance_Robot_Circuit.png   # Tinkercad breadboard view
├── Obstacle_Avoidance_Robot_Schematic.png # Tinkercad schematic view
└── README.md

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🧠 What I Learned

• Using pulseIn() with the HC-SR04 for accurate distance measurement
• Controlling a servo motor to physically sweep a sensor for environmental scanning
• Driving dual DC motors in both directions using an L293D H-bridge motor driver
• Implementing autonomous decision-making logic based on real-time sensor comparisons
• Managing multiple delay()-based timing sequences for coordinated robot movement

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🔮 Future Improvements

• Replace delay()-based timing with a non-blocking approach using millis() for smoother movement
• Add PWM speed control via the L293D enable pins for variable motor speed
• Implement a continuous 180° servo sweep instead of fixed left/right snapshots
• Add IR sensors on the sides for faster edge and wall detection
• Enable Bluetooth control (HC-05) for a manual override mode
• Mount on a proper robot chassis for real-world testing beyond simulation

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👤 Author

Deep Chatterjee
GitHub

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📄 License

This project is licensed under the MIT License — see LICENSE for details.