Circuit Creation

Bluetooth Home Automation using Arduino Uno and HC-05

This project demonstrates how to control home appliances wirelessly using a Bluetooth module (HC-05), Arduino Uno, and a relay module. You can send commands from your smartphone to turn devices ON or OFF, making it a foundation for smart home automation.

Beginner

Components Required

Circuit Connections

Follow the steps below to connect the Bluetooth module and relay with Arduino.

  1. Connect HC-05 VCC to Arduino 5V.
  2. Connect HC-05 GND to Arduino GND.
  3. Connect HC-05 TX to Arduino RX (pin 0).
  4. Connect HC-05 RX to Arduino TX (pin 1).
  5. Connect Relay IN to Arduino pin 2.
  6. Connect Relay VCC to Arduino 5V.
  7. Connect Relay GND to Arduino GND.
  8. Connect the home appliance to the relay's normally open (NO) and common (COM) terminals.
Bluetooth Home Automation Circuit

The Bluetooth module receives commands from your phone and sends them to Arduino, which then controls the relay to turn the appliance ON or OFF.

Arduino Code

                
/*
   Project: Bluetooth Home Automation using Arduino Uno and HC-05
   Description: Control a relay wirelessly using HC-05 Bluetooth module and Arduino. Send "1" to turn ON and "2" to turn OFF the relay.

   Components:
     - Arduino Uno 
     - HC-05 Bluetooth Module
     - Relay Module
     - Home Appliance
     - Jumper Wires
     - USB Cable 
     - Smartphone with Bluetooth Terminal App

   Author: Circuit Creation RN

*/

char command;
int relayPin = 2;

void setup() {

  pinMode(relayPin, OUTPUT);
  digitalWrite(relayPin, HIGH); // make sure relay starts OFF
  Serial.begin(9600);

}

void loop() {
  if (Serial.available()) {
    command = Serial.read();

    if (command == '1') {
      digitalWrite(relayPin, LOW);  // Turn ON (active LOW)

    } else if (command == '2') {
      digitalWrite(relayPin, HIGH); // Turn OFF

    }
  }
}

Upload the Code

  1. Disconnect HC-05 TX/RX before uploading.
  2. Upload the code using Arduino IDE.
  3. Reconnect Bluetooth module after upload.
  4. Pair HC-05 with your phone (password: 1234 or 0000).
  5. Use a Bluetooth terminal app to send "1" to turn ON or "2" to turn OFF.

Code Explanation

Setup Function

pinMode(relayPin, OUTPUT) sets the relay pin as output. digitalWrite(relayPin, HIGH) ensures the relay starts OFF (assuming active LOW relay). Serial.begin(9600) initializes serial communication at 9600 baud rate.

Loop Function

if (Serial.available()) checks if data is available from Bluetooth. command = Serial.read() reads the incoming command. If command is '1', sets relay LOW to turn ON. If command is '2', sets relay HIGH to turn OFF.

Common Mistakes & Troubleshooting

What You Learned