• 1
    Wiring All The Components

    Wiring the LDR SensorCreate a voltage divider

    • LDR leg1 - 5v
    • LDR leg 2 - A0
    • 10k resistor between A0 and GND

    This setup gives the Arduino a changing voltage that represents brightness.

    Wiring the Relay Module

    • Relay VCC - 5v
    • Relay GND - GND
    • Relay IN - Digital Pin 2

    LEDStripPower

    For a 12v LED Strip:

    • LED strip + directly to 12V supply
    • LED strip - to COM on relay
    • Relay NO to the 12v supply ground

    The relay will switch the strip ON/OFF by controlling the ground connection.

  • 2
    Uploading The Code

    Use the Arduino IDE The sketch below reads the LDR, checks if it's dark, and switches the relay.

    // Beginner-friendly: Read button on pin 6 and control a relay on pin 2
// Wiring (recommended):
//  - Relay module VCC -> 5V
//  - Relay module GND -> GND
//  - Relay module IN  -> Arduino digital pin 2
//  - Button one side -> Arduino pin 6
//  - Button other side -> GND
// Note: This sketch uses INPUT_PULLUP, so button connects to GND when pressed.
const int RELAY_PIN = 2;    // Relay control pin
const int BUTTON_PIN = 7;   // Input pin (button or switch)
// If your relay module is "active LOW" (common for many modules), set true.
// If your relay turns ON when IN is HIGH, set false.
const bool RELAY_ACTIVE_LOW = false;
void setup() {
Serial.begin(9600);                 // Optional: debug output to Serial Monitor
pinMode(RELAY_PIN, OUTPUT);         // Relay pin is an output
pinMode(BUTTON_PIN, INPUT_PULLUP);  // Use the internal pull-up resistor
// Make sure relay starts OFF
if (RELAY_ACTIVE_LOW) digitalWrite(RELAY_PIN, HIGH); // HIGH -> off for active-low relay
else digitalWrite(RELAY_PIN, LOW);                   // LOW  -> off for active-high relay
Serial.println("Ready. Press the button to turn the relay ON.");
}
//Made By Rohan Barnwal
void loop() {
// Read the button. Because of INPUT_PULLUP, pressed == LOW.
int raw = digitalRead(BUTTON_PIN);
bool pressed = (raw == LOW); // true when button is pressed
// Simple debounce: when we detect a press state change, wait briefly and re-read.
static bool lastPressed = false;
if (pressed != lastPressed) {
delay(30);                     // small debounce delay (30 ms)
raw = digitalRead(BUTTON_PIN);
pressed = (raw == LOW);
lastPressed = pressed;
}
// Turn relay on or off based on button
if (pressed) {
// Turn relay ON
if (RELAY_ACTIVE_LOW) digitalWrite(RELAY_PIN, LOW);  // active-low -> LOW turns ON
else digitalWrite(RELAY_PIN, HIGH);                  // active-high -> HIGH turns ON
Serial.println("Relay: ON");
} else {
// Turn relay OFF
if (RELAY_ACTIVE_LOW) digitalWrite(RELAY_PIN, HIGH); // active-low -> HIGH turns OFF
else digitalWrite(RELAY_PIN, LOW);                   // active-high -> LOW turns OFF
Serial.println("Relay: OFF");
}
delay(100); // small loop delay to avoid flooding Serial
}
  • 3
    Testing
    • Cover the LDR with your hands - LED strip should turn ON
    • Shine a light - LED strip should turn OFF

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