Arduino Project

Arduino Automatic Night Light Project

Kit purchase

Looking for parts? Check out our all-in-one kits below — packed with components, beginner-friendly guides, and tons of fun.

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Name	Includes Arduino board	PURCHASE LINK
Elite Explorer Kit	Arduino Uno R4 WiFi	BUY
3 in 1 Ultimate Starter Kit	Arduino Uno R4 Minima	BUY
Ultimate Sensor Kit	Arduino Uno R4 Minima	BUY
Universal Maker Sensor Kit	×	BUY

Course Introduction

This Arduino project uses a photoresistor (LDR) to detect ambient light levels and automatically control an LED.

When the environment gets dark, the LED turns on; when it’s bright, the LED turns off. The light threshold can be adjusted for sensitivity.

This simple system is ideal for automatic night lights or basic light-sensing applications.

Note

If this is your first time working with an Arduino project, we recommend downloading and reviewing the basic materials first.

1.1 Install Arduino IDE(Important)
1.2 Introduction of Arduino IDE

Required Components

In this project, we need the following components:

SN	COMPONENT INTRODUCTION	QUANTITY	PURCHASE LINK
1	Arduino UNO R4 Minima	1	BUY
2	USB Type-C cable	1	×
3	Breadboard	1	BUY
4	Wires	Several	BUY
5	LED	1	BUY
6	Photoresistor	1	BUY

Wiring

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Common Connections:

LED
Blue: Connect the LED anode to 9 on the Arduino, and the cathode to a 1kΩ resistor, then to the negative power bus on the breadboard.

Photoresistor
VCC: Connect to A0 on the Arduino.
GND: Connect to breadboard’s negative power bus.

Writing the Code

Note
You can copy this code into Arduino IDE.
Don’t forget to select the board(Arduino UNO R4 Minima/WIFI) and the correct port before clicking the Upload button.

// Define pins
const int sensorPin = A0;   // Photoresistor voltage divider output to A0
const int ledPin = 9;       // Blue LED connected to D9

// Sensitivity threshold (higher = darker, can be adjusted)
const int threshold = 500;  // Recommended initial value 500, adjust via Serial monitor

void setup() {
  pinMode(ledPin, OUTPUT);
  digitalWrite(ledPin, LOW);  // LED off by default
  Serial.begin(9600);         // For monitoring light level and threshold
}

void loop() {
  int sensorValue = analogRead(sensorPin);  // Range: 0~1023

  Serial.print("Light sensor: ");
  Serial.println(sensorValue);

  if(sensorValue < threshold) {
    // Environment is dark, turn on LED
    digitalWrite(ledPin, HIGH);
  } else {
    // Environment is bright, turn off LED
    digitalWrite(ledPin, LOW);
  }

  delay(100); // Slight delay to avoid Serial flooding
}

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Arduino Project

Arduino Automatic Night Light Project

Kit purchase

Course Introduction

Required Components

Wiring

Common Connections:

Writing the Code

Arduino Project

Arduino Automatic Night Light Project

Kit purchase

Course Introduction

Required Components

Wiring

Common Connections:

Writing the Code

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