Interfacing Bluetooth Module with Arduino

In this project, we are going to learn about Bluetooth module and how to interfacing Bluetooth module with Arduino Uno. How the led can be control with your own smart phone using Bluetooth module.

Component Requirement : –

  • Arduino Uno
  • HC-05 Bluetooth Module
  • Breadboard
  • LED
  • 1kΩ Resistance


HC-05 Bluetooth Module

buy Bluetooth-module

The HC-05 Bluetoth module is one kind of bluetooth serial port protocol module which works with Arduino Uno through the serial communication. This module is used for wireless serial communication. This is fully qualified Bluetooth V2.0+EDR (Enhanced Data Rate) 3Mbps Modulation with complete 2.4GHz radio transceiver and baseband. In this module the maximum range for wireless communication is 10 meters.

Feature of HC-05 bluetooth Module: –

  • Operating Voltage: 4V to 6V (Typically +5V)
  • Operating Current: 30mA
  • Range: 10m
  • Comes with integrated antenna
  • Works with Serial communication (USART) and TTL compatible
  • Follows IEEE 802.15.1 standardized protocol
  • It can operate in Master, Slave or Master/Slave mode
  • It can be easily interfaced with Laptop or Mobile phones with Bluetooth
  • Supported baud rate: 9600,19200,38400,57600,115200,230400,460800.
  • Frequency: 2.45 GHz

 Pinout of HC-05 Bluetooth Module: –

  • EN: Enable pin.
  • VCC:Supply pin +5V
  • GND: Ground pin.
  • TXD: Transmitter pin of the UART
  • RXD: Receive Pin of UART
  • STATE: Status indicator pin.

Interfacing HC-05 Bluetooth Module with Arduino

Explanation of Bluetooth Module with Arduino:

we will connect HC-05 Bluetooth Module with the Arduino. Connect the module pins to the Arduino as follows –

Connect a LED negative to GND of arduino and positive to pin 13 with a resistance valued between 1KΩ.

Circuit Diagram of Bluetooth Module with Arduino:


How it works:

The android app is connected to the Bluetooth module and sending serial data to the Bluetooth module when certain button is pressed. The Bluetooth module at other end receive the data and send to ardunio through the TX pin of Bluetooth module (RX pin of arduino). The Arduino will decode this receive data and compare with the code. When it will match then the arduino will execute the commands. If received data is 1 the LED turns on and turns off when received data is 0.

Code of HC-05 With Arduino:

#define ledPin 13
int state = 0;
void setup() {
pinMode(ledPin, OUTPUT);
digitalWrite(ledPin, LOW);
Serial.begin(38400); // Default communication rate of the Bluetooth module
void loop()
if(Serial.available() > 0){ // Checks whether data is comming from the serial port
state =; // Reads the data from the serial port
if (state == '0') 
digitalWrite(ledPin, LOW); // Turn LED OFF
Serial.println("LED: OFF"); // Send back, to the phone, the String "LED: ON"
state = 0;
else if (state == '1')
digitalWrite(ledPin, HIGH);
Serial.println("LED: ON");
state = 0;

How to use android application of Bluetooth Module:

  • Download the Application(.APK) in your smart phone.
  • Turn on bluetooth in your smart phone
  • Scan for available device
  • Pair your device with HC-05 bluetooth module by entering default password 1234 or 0000
  • Install LED application on your android device
  • Open the Application


  • Press paired devices
  • Select your Bluetooth module from the List (HC 05)


  • After connect successfully
  • Press ON button to turn ON LED and press OFF button to turn OFF LED


  • If you press disconnect button to disconnect from Bluetooth module.

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