Build a Bluetooth Controlled Car with Arduino

A Bluetooth car is the most popular first robotics project for students in Bangladesh. You drive it from your Android phone using a free Bluetooth controller app — the phone sends letters like F, B, L, R and the Arduino turns the motors.

1. Wiring

L298N Motor Driver:

• IN1, IN2, IN3, IN4 → Pins 5, 6, 9, 10
• OUT1/OUT2 → left motor, OUT3/OUT4 → right motor
• 12V → battery +, GND → battery − and Arduino GND
• 5V → Arduino VIN (keep the 5V jumper on)

HC-05:

• VCC → 5V, GND → GND
• TXD → Arduino Pin 2
• RXD → Arduino Pin 3 through a voltage divider (1kΩ + 2kΩ from a resistor pack)

2. The Code

#include <SoftwareSerial.h>
SoftwareSerial bt(2, 3);
void drive(int a, int b, int c, int d) {
  digitalWrite(5, a); digitalWrite(6, b);
  digitalWrite(9, c); digitalWrite(10, d);
}
void forward() { drive(1,0,1,0); }
void back()    { drive(0,1,0,1); }
void left()    { drive(0,1,1,0); }
void right()   { drive(1,0,0,1); }
void stopCar() { drive(0,0,0,0); }

void setup() {
  for (int p : {5, 6, 9, 10}) pinMode(p, OUTPUT);
  bt.begin(9600);
}

void loop() {
  if (bt.available()) {
    char c = bt.read();
    if (c == 'F') forward();
    else if (c == 'B') back();
    else if (c == 'L') left();
    else if (c == 'R') right();
    else if (c == 'S') stopCar();
  }
}

3. Pairing

Pair your phone with HC-05 (default PIN 1234 or 0000), open any “Arduino Bluetooth RC Car” app from the Play Store and connect. Unplug the HC-05 TX/RX wires while uploading code.