Bluetooth Controlled LED using Arduino Uno and HC-05

 Wireless control is one of the most exciting features of modern electronics. In this project, we will control an LED using a Bluetooth module and a mobile phone. The Arduino receives commands from the phone through Bluetooth and switches the LED ON or OFF accordingly.

This project uses Arduino Uno and HC-05 Bluetooth Module.

---

🧰 Components Required

• Arduino Uno

• HC-05 Bluetooth Module

• LED

• 220Ω Resistor

• Breadboard

• Jumper wires

• Android mobile phone with Bluetooth app

---

🔌 Circuit And Connections

HC-05 to Arduino

HC-05 Pin	Arduino Pin
VCC	5V
GND	GND
TXD	Pin 10
RXD	Pin 11

LED Connection

• LED Anode (+) → Arduino pin 13 through 220Ω resistor

• LED Cathode (–) → GND

---

📜 Arduino Code

#include <SoftwareSerial.h>
SoftwareSerial bt(10, 11);

int led = 13;

void setup() {
  pinMode(led, OUTPUT);
  bt.begin(9600);
}

void loop() {
  if (bt.available()) {
    char c = bt.read();
    if (c == '1') digitalWrite(led, HIGH);
    if (c == '0') digitalWrite(led, LOW);
  }
}

---

⚙️ Working Principle

1. The mobile phone sends characters via Bluetooth.

2. HC-05 receives the data and sends it to Arduino using serial communication.

3. Arduino reads the received character.

4. If the character is '1', the LED turns ON.

5. If the character is '0', the LED turns OFF.

---

📱 Mobile App Setup

Install any Bluetooth terminal app:

• Serial Bluetooth Terminal

• Bluetooth Terminal

• Arduino Bluetooth Controller

Pairing HC-05:

• Default password: 1234 or 0000

Send:

• 1 → LED ON

• 0 → LED OFF

---

⚠️ Important Notes

• Disconnect HC-05 TX and RX while uploading the code.

• Use a voltage divider on Arduino TX → HC-05 RX.

• Default baud rate of HC-05 is 9600.

• Fast blinking LED on HC-05 = not connected.

• Slow blinking LED on HC-05 = connected.

---

🔍 Applications

• Home automation

• Wireless light control

• Robotics

• IoT starter projects

• Smart switch systems

---

🎯 Conclusion

This project demonstrates how Bluetooth communication can be used to control devices wirelessly using Arduino. It is a beginner-friendly project and a foundation for advanced Bluetooth-based automation systems.