Control an LED or Appliance over Bluetooth using HC-05

Wireless control is a key feature of modern projects. Set up a simple Bluetooth serial terminal to toggle outputs.

Introduction & Concept

The HC-05 is a class 2 Bluetooth module that communicates using Serial Communication protocol (USART). It handles RF signal protocols transparently, sending data packets received from a mobile phone directly into the Arduino serial buffer. We will capture these commands to toggle outputs.

Required Component

Component Name	Store Link
HC-05 Bluetooth Module	Buy HC-05 Bluetooth

Wiring Connections Schematic Diagram

   [Arduino Uno]                   [HC-05 Module]
   +-----------+                   +------------+
   |        5V |------------------>| VCC        |
   |       GND |------------------>| GND        |
   |   Pin 0RX |<------------------| TXD        |
   |   Pin 1TX |------[ 1k/2k ]--->| RXD        | (Use Resistor Divider)
   +-----------+                   +------------+
          

Control Code

void setup() {
  Serial.begin(9600);
  pinMode(13, OUTPUT); // Built-in LED
}

void loop() {
  if (Serial.available()) {
    char val = Serial.read();
    if (val == '1') {
      digitalWrite(13, HIGH); // Turn LED ON
    } else if (val == '0') {
      digitalWrite(13, LOW);  // Turn LED OFF
    }
  }
}