IoTBeginner 2 hours

Smart Home LED Control

Build a Bluetooth-controlled lighting system. Pair your phone with an HC-05 module and toggle LEDs from anywhere in the room. A perfect intro to wireless IoT.

Required components

Arduino UNO
HC-05 Bluetooth Module
LEDs (3)
220Ω Resistors
Breadboard
Jumper Wires

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Circuit diagram

Arduino UNO sits at the center. HC-05 connects to digital pins 10 and 11 for serial communication. Three LEDs branch out to pins 6, 7, 8 — each through a 220Ω current-limiting resistor to ground.

Interactive 3D circuit viewer coming in the Virtual Lab.

Step-by-step guide

1
Place Arduino and breadboard side by side.
2
Connect HC-05: VCC→5V, GND→GND, TX→Pin 10, RX→Pin 11.
3
Wire 3 LEDs to pins 6, 7, 8 through 220Ω resistors to GND.
4
Upload the sketch and pair your phone with the HC-05.
5
Send 'A'/'a' to toggle LED 1, 'B'/'b' for LED 2, 'C'/'c' for LED 3.

Code

#include <SoftwareSerial.h>
SoftwareSerial BT(10, 11); // RX, TX

void setup() {
  BT.begin(9600);
  for (int p = 6; p <= 8; p++) pinMode(p, OUTPUT);
}

void loop() {
  if (BT.available()) {
    char c = BT.read();
    if (c == 'A') digitalWrite(6, HIGH);
    if (c == 'a') digitalWrite(6, LOW);
    if (c == 'B') digitalWrite(7, HIGH);
    if (c == 'b') digitalWrite(7, LOW);
    if (c == 'C') digitalWrite(8, HIGH);
    if (c == 'c') digitalWrite(8, LOW);
  }
}

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