Build an obstacle-avoiding robot car

Build a two-wheel robot car that looks ahead with an ultrasonic sensor on a turning head, stops before it hits something, and turns towards the side with more room.

Time2 weekends

Parts₹1,580–1,890

Chassis built8 actions · read it below
Motors under control14 wires, 9 actions
The head looks around8 wires, 11 actions
Stops before it hits5 actions
Finds its own way5 actions

Start this build

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Before you start

Tools: Laptop with the Arduino IDE, Screwdriver, Double-sided foam tape or a glue gun, Soldering iron, only if your motors come without wires, Tape measure and a few cardboard boxes
Skills: A first robot. Basic wiring; steps 2–5 use code (or Get the code). Built the line follower? Steps 1–2 are the same chassis and motor wiring.
Safety: Li-ion cells: protected cells and a proper charger only, and never short them. Protected bare 18650s can be hard to find in Indian shops, so check they fit your holder before you buy. Keep fingers and hair away from the wheels while it's switched on. Run it on the floor, away from stairs and table edges: it can't see a drop.
Prices: Checked 2026-10, with a clone Uno, protected cells and a Li-ion charger; an original Uno adds about ₹1,950; the upper end includes a half-size breadboard (up to ₹200: the estimate the line-follower track uses, not checked separately)

Step 1 of 5

Chassis built

Motors, wheels, caster, battery holder and the servo for the sensor head are fixed to the chassis, and it rolls freely.

Build it

Task 01 of 08

Lay out every part from the kit and match it to the parts list. Keep the small screws in a cup.

Check: Nothing is missing before you start.

Steps

You need

2WD acrylic chassis kit (2 BO motors rated 3–6 V, 2 wheels, caster)
Arduino Uno R3
L298N motor driver module
2 × 18650 holder with an on/off switch
2 × protected 18650 Li-ion cells (check they fit your holder: protected cells are a few mm longer) and a Li-ion charger
SG90 micro servo, with its plastic horns and small screws
HC-SR04 ultrasonic sensor and an HC-SR04 mounting bracket (fitted in step 3)
Screwdriver, M3 screws and spacers, double-sided foam tape

Build an obstacle-avoiding robot car

Parts list

Chassis built

Build it