Build an Obstacle Avoiding Robot with Ultrasonic Sensor
Feb 1, 2026
8 min read
Obstacle Avoiding Robot: Build Your Own Autonomous Navigator
Want to build a robot that can "see" and avoid walls and furniture? This project uses an Ultrasonic Sensor (HC-SR04) to measure distance and change direction accordingly.
How Ultrasonic Sensors Work
The sensor sends out a pulse of high-frequency sound (ultrasonic, hence inaudible). When this pulse hits an object, it bounces back. The time taken for the echo to return tells us the distance.
Formula:Distance = (Time × Speed of Sound) / 2
Components
Arduino Uno
HC-SR04 Ultrasonic Sensor
Servo Motor (for sensor sweep)
L298N Motor Driver
2x BO Motors & Wheels
Chassis & Battery
The Algorithm
Move Forward continuously.
Measure Distance in front.
If distance < threshold (e.g., 20cm):
Stop.
Look Left (using servo to rotate sensor).
Measure distance.
Look Right.
Measure distance.
Turn towards the direction with more clearance.
Repeat.
Upgrade Ideas
Add a second sensor on the back for reversing.
Use an ESP32-CAM for visual object detection.
Implement SLAM (Simultaneous Localization and Mapping) for navigation.