Meet the obstacle avoider

You're building a robot that drives around a room on its own — and doesn't crash into anything.

Sounds simple. But this exact problem — detect obstacle, decide how to avoid, execute — is the same loop your Roomba runs hundreds of times per second. It's how parking sensors on every modern car work. It's how a Mars rover decides whether to drive forward or take a safer path.

Your version uses an HC-SR04 ultrasonic sensor (the two-eyed 'face' on the front), an Arduino Uno as the brain, an L298N motor driver, and two DC motors.

The robot drives forward continuously. The moment it detects something closer than 20 cm, it stops, reverses a little, turns, and tries a new direction.

Every concept — from how ultrasonic physics works to how you write the distance formula in code — you'll reason out yourself first. The quiz always comes before the answer. That's how real engineers learn.

Let's go.