Voice-Controlled Robot Car Using Bluetooth (Arduino + HC-05)

Transform your robot car into a voice-controlled vehicle using Arduino, an HC-05 Bluetooth module, and a smartphone app. This method is simple, cost-effective, and perfect for beginners!

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1. Components Needed

• Arduino Uno/Nano (or any Arduino board)

• HC-05 Bluetooth Module

• L298N Motor Driver (for DC motors)

• Robot Car Chassis (with 2x DC motors & wheels)

• Battery Pack (6V–12V for motors)

• Smartphone (Android/iOS with a voice control app)

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2. Wiring Diagram

HC-05 Bluetooth Module Connections

⚠️ Warning: If using a 3.3V HC-05, add a voltage divider (1kΩ + 2kΩ resistors) on RX to avoid damaging the module!

L298N Motor Connections

(Refer to the previous robot car guide for wiring.)

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3. Arduino Code (Bluetooth Voice Control)

cpp

#include <SoftwareSerial.h>
SoftwareSerial BT(0, 1); // RX (Pin 0), TX (Pin 1)

// Motor control pins (L298N)
const int ENA = 9;   // Left motor speed (PWM)
const int IN1 = 8;   // Left motor direction
const int IN2 = 7;
const int ENB = 10;  // Right motor speed (PWM)
const int IN3 = 6;   // Right motor direction
const int IN4 = 5;

void setup() {
  BT.begin(9600);    // Start Bluetooth communication
  pinMode(ENA, OUTPUT);
  pinMode(IN1, OUTPUT);
  pinMode(IN2, OUTPUT);
  pinMode(ENB, OUTPUT);
  pinMode(IN3, OUTPUT);
  pinMode(IN4, OUTPUT);
}

void loop() {
  if (BT.available()) {  // Check if data is received
    char command = BT.read();  // Read the command

    switch(command) {
      case 'F':  // "Forward"
        moveForward(200);  // Move forward at speed 200
        break;
      case 'B':  // "Backward"
        moveBackward(200);
        break;
      case 'L':  // "Left"
        turnLeft(150);
        break;
      case 'R':  // "Right"
        turnRight(150);
        break;
      case 'S':  // "Stop"
        stopMotors();
        break;
    }
  }
}

// Motor control functions
void moveForward(int speed) {
  analogWrite(ENA, speed);
  analogWrite(ENB, speed);
  digitalWrite(IN1, HIGH);
  digitalWrite(IN2, LOW);
  digitalWrite(IN3, HIGH);
  digitalWrite(IN4, LOW);
}

void moveBackward(int speed) {
  analogWrite(ENA, speed);
  analogWrite(ENB, speed);
  digitalWrite(IN1, LOW);
  digitalWrite(IN2, HIGH);
  digitalWrite(IN3, LOW);
  digitalWrite(IN4, HIGH);
}

void turnLeft(int speed) {
  analogWrite(ENA, speed);
  analogWrite(ENB, speed);
  digitalWrite(IN1, LOW);
  digitalWrite(IN2, HIGH);
  digitalWrite(IN3, HIGH);
  digitalWrite(IN4, LOW);
}

void turnRight(int speed) {
  analogWrite(ENA, speed);
  analogWrite(ENB, speed);
  digitalWrite(IN1, HIGH);
  digitalWrite(IN2, LOW);
  digitalWrite(IN3, LOW);
  digitalWrite(IN4, HIGH);
}

void stopMotors() {
  digitalWrite(IN1, LOW);
  digitalWrite(IN2, LOW);
  digitalWrite(IN3, LOW);
  digitalWrite(IN4, LOW);
}

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4. Smartphone App Setup

Recommended Apps:

1. "Voice BT Arduino" (Android) – Simple voice-to-command app.

2. "Arduino Bluetooth Controller" (Android/iOS) – Customizable buttons & voice control.

How to Configure the App:

1. Pair HC-05 with your phone (default PIN: 1234 or 0000).

2. Open the app and connect to the HC-05 module.

3. Assign voice commands to send single letters:

   • Example: Say “Forward” → App sends 'F' to Arduino.

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5. How It Works

1. You speak a command (e.g., “Turn left”).

2. The app converts speech to text and sends 'L' via Bluetooth.

3. Arduino receives 'L' and executes turnLeft(150).

4. The robot car responds instantly!

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6. Troubleshooting

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7. Upgrades & Next Steps

• Add obstacle avoidance (Ultrasonic sensor + auto-stop).

• Use an ESP32 for Wi-Fi/Google Assistant/Alexa control.

• Implement a joystick app for manual driving.

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Final Thoughts

This Bluetooth voice control method is the easiest way to make your robot car hands-free!