Beginner4–6 h (estimate)7 parts

Obstacle-avoiding car

An ultrasonic sensor on a servo looks around and picks the clearer side.

Overview

A two-wheel car drives forward until an ultrasonic distance sensor sees something close, then stops, turns the sensor left and right on a micro servo, and turns toward the side with more space.

You will measure distance from the echo time, filter noisy readings, and write the behaviour as a small state machine (drive → stop → look → turn).

You will learn

· Ultrasonic time-of-flight distance measurement
· Filtering noisy readings
· Servo control with the Servo library
· State machines for robot behaviour

Parts list

Part (generic)	Qty	Note
Arduino Uno-compatible board (5 V logic)	1
Ultrasonic distance sensor module (HC-SR04-type, 5 V)	1
Micro servo (SG90-class, 5 V)	1	Optional: without it the car turns on the spot to look.
Dual H-bridge DC motor driver module (L298N-type or TB6612FNG-type)	1
Small DC gear motor with wheel	2
Caster wheel, chassis plate, battery pack, switch	1 each
Jumper wires	as needed

Generic part names only. Pinouts and logic levels vary between modules of the same type, so check the documentation of the exact module you have.

Tools

· USB cable and the Arduino IDE
· Screwdrivers
· Multimeter
· Tape measure or ruler

Safety

· Test on the floor with space around it; keep it away from stairs.
· Power the servo and motors from a supply that can handle their current, not from the USB port.

Learn the ideas first

Full build

01Assemble the chassis and motor driver
02Measure distance with the ultrasonic sensor
03Add the servo "neck" and scan left/right
04Write the drive–stop–look–turn state machine
05Filter readings and tune turn timing

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