Complete Guide: Control 2 DC Motors with Arduino via Bluetooth

1 HC-05 Bluetooth Module

The HC-05 is a popular Bluetooth module that operates as a Serial Port Protocol (SPP) device, creating a transparent wireless serial connection. It can operate in both master and slave modes, though for this project, we'll use it in slave mode to receive commands from a smartphone or computer.

Key Specifications:

• Operating Voltage: 3.6V - 6V (typically used with 5V)
• Communication: Serial communication at 9600 baud (default)
• Range: Approximately 10 meters (30 feet) in open space
• Pairing: Default pairing code is "1234" or "0000"

2 L298N Motor Driver Module

The L298N is a dual H-bridge motor driver that allows you to control the direction and speed of two DC motors independently. It can handle significant current (up to 2A per bridge) and includes built-in protection diodes.

Key Features:

• Dual H-bridge design for bidirectional motor control
• Maximum current: 2A per bridge (3A peak)
• Operating voltage: 5V to 35V for motors
• Built-in 5V regulator (can power Arduino with small motors)
• Heat sink and protection diodes included

3 Step-by-Step Wiring Instructions

Proper wiring is crucial for the success of this project. Follow these connections carefully:

Arduino to L298N Connections:

• Arduino Pin 5 → L298N IN1
• Arduino Pin 6 → L298N IN2
• Arduino Pin 9 → L298N IN3
• Arduino Pin 10 → L298N IN4
• Arduino 5V → L298N +5V
• Arduino GND → L298N GND

Motor Connections to L298N:

• Motor A terminals → L298N OUT1 and OUT2
• Motor B terminals → L298N OUT3 and OUT4

Power Connections:

• External power supply positive → L298N +12V input
• External power supply negative → L298N GND

Bluetooth Module Connections:

• HC-05 VCC → Arduino 5V
• HC-05 GND → Arduino GND
• HC-05 TX → Arduino Pin 0 (RX)
• HC-05 RX → Arduino Pin 1 (TX)

4 Complete Control Sketch

Below is the complete Arduino sketch that enables Bluetooth control of two DC motors:

// Define motor control pins
const int motorA1 = 5;
const int motorA2 = 6;
const int motorB1 = 9;
const int motorB2 = 10;

// Variable to store incoming Bluetooth data
char data = 0;

void setup() {
  // Initialize motor control pins as outputs
  pinMode(motorA1, OUTPUT);
  pinMode(motorA2, OUTPUT);
  pinMode(motorB1, OUTPUT);
  pinMode(motorB2, OUTPUT);
  
  // Initialize serial communication for Bluetooth
  Serial.begin(9600);
  
  // Initially stop all motors
  stopMotors();
  
  Serial.println("Bluetooth Motor Control Ready");
  Serial.println("Send commands: F, B, L, R, S");
}

void loop() {
  // Check if data is available from Bluetooth
  if (Serial.available() > 0) {
    data = Serial.read(); // Read incoming data
    Serial.print("Received: ");
    Serial.println(data);
    
    // Process the received command
    switch(data) {
      case 'F': // Move Forward
        forward();
        break;
      case 'B': // Move Backward
        backward();
        break;
      case 'L': // Turn Left
        left();
        break;
      case 'R': // Turn Right
        right();
        break;
      case 'S': // Stop
        stopMotors();
        break;
      default:
        // Ignore unrecognized commands
        break;
    }
  }
}

// Motor control functions
void forward() {
  digitalWrite(motorA1, HIGH);
  digitalWrite(motorA2, LOW);
  digitalWrite(motorB1, HIGH);
  digitalWrite(motorB2, LOW);
  Serial.println("Moving Forward");
}

void backward() {
  digitalWrite(motorA1, LOW);
  digitalWrite(motorA2, HIGH);
  digitalWrite(motorB1, LOW);
  digitalWrite(motorB2, HIGH);
  Serial.println("Moving Backward");
}

void left() {
  digitalWrite(motorA1, LOW);
  digitalWrite(motorA2, HIGH);
  digitalWrite(motorB1, HIGH);
  digitalWrite(motorB2, LOW);
  Serial.println("Turning Left");
}

void right() {
  digitalWrite(motorA1, HIGH);
  digitalWrite(motorA2, LOW);
  digitalWrite(motorB1, LOW);
  digitalWrite(motorB2, HIGH);
  Serial.println("Turning Right");
}

void stopMotors() {
  digitalWrite(motorA1, LOW);
  digitalWrite(motorA2, LOW);
  digitalWrite(motorB1, LOW);
  digitalWrite(motorB2, LOW);
  Serial.println("Stopped");
}

5 Configuring Your Control Device

Smartphone Control Options:

Pairing Process:

1. Power your Arduino circuit
2. Enable Bluetooth on your smartphone/computer
3. Scan for available devices
4. Look for "HC-05" and pair with it (default PIN is "1234")
5. Open your serial terminal app and connect to the HC-05 module

6 Adding Speed Control with PWM

To control motor speed, modify the code to use PWM (Pulse Width Modulation) on the enable pins of the L298N:

// Additional PWM pins for speed control
const int enableA = 3;
const int enableB = 11;

// Speed variable (0-255)
int motorSpeed = 150;

void setup() {
  // Previous setup code...
  pinMode(enableA, OUTPUT);
  pinMode(enableB, OUTPUT);
  
  // Set initial speed
  analogWrite(enableA, motorSpeed);
  analogWrite(enableB, motorSpeed);
}

// Add speed control commands to loop()
if (data == '+') {
  motorSpeed = min(motorSpeed + 20, 255);
  updateSpeed();
}
if (data == '-') {
  motorSpeed = max(motorSpeed - 20, 0);
  updateSpeed();
}

void updateSpeed() {
  analogWrite(enableA, motorSpeed);
  analogWrite(enableB, motorSpeed);
  Serial.print("Speed set to: ");
  Serial.println(motorSpeed);
}

This modification allows you to control motor speed by sending '+' to increase speed and '-' to decrease speed via Bluetooth.

7 Practical Implementations

8 Enhancing Your Project

Advanced Project Ideas:

• Wireless Camera: Implement FPV (First Person View) using a Wi-Fi camera module
• Voice Control: Integrate with Google Assistant or Alexa for voice commands
• Autonomous Features: Add ultrasonic sensors for obstacle avoidance
• Internet Connectivity: Add ESP8266 for control from anywhere via the internet
• Multiple Control Modes: Implement joystick control, gesture control, or path recording