Drive your robot from your phone

Remember those chunky plastic RC cars from childhood — the ones with a separate controller, a fat antenna, and batteries in both halves? You're building the modern version. Except your controller is the phone in your pocket, and your antenna is a $3 Bluetooth module.

Your Bluetooth RC Car uses an HC-05 module to receive commands from a free phone app called *Serial Bluetooth Terminal*. You send a single character — F for forward, B for back, L for left, R for right, S for stop — and the Arduino reads it and drives the motors accordingly.

No internet required. No server. No cloud. Just two devices talking directly to each other over Bluetooth — the same protocol your wireless headphones use, at roughly the same range: about 10 metres indoors.

Hardware: HC-05 Bluetooth module + Arduino Uno + L298N motor driver + 2 DC motors (or 4 for a 4WD build).

This project is intermediate — not because the hardware is harder, but because the software pitfalls are subtler. You'll discover the most dangerous one at the very end.

Let's start with the wireless link itself.