Arduino Experiment: Light-Sensitive Night Lamp

1. Required Components

• 1 x Arduino board (e.g., Arduino Uno)
• 1 x Light Dependent Resistor (LDR)
• 1 x 10kΩ Resistor (for LDR)
• 1 x LED
• 1 x 220Ω Resistor (for LED)
• Breadboard and jumper wires
• USB cable to connect Arduino to PC

2. Wiring

Follow these steps to wire your circuit:

• Connect the LED’s long leg (anode) to digital pin 9 on the Arduino.
• Connect the LED’s short leg (cathode) to GND through a 220Ω resistor.
• Connect one end of the LDR to 5V.
• Connect the other end of the LDR to analog pin A0 and to GND through a 10kΩ pull-down resistor.

3. Code Explanation

The code below reads light intensity using the LDR and controls the LED based on a predefined light threshold. Key functions include:

• analogRead(): Reads the voltage from the LDR, which changes with light intensity.
• digitalWrite(): Turns the LED on or off based on the light intensity.
• if condition: Compares the light intensity to a threshold to determine the LED's state.

4. Arduino Code

Copy the following code into your Arduino IDE:

// Define pins for the LDR and LED
const int ldrPin = A0;    // LDR connected to analog pin A0
const int ledPin = 9;     // LED connected to digital pin 9

// Variable to store LDR reading
int ldrValue = 0;

void setup() {
  // Set the LED pin as output
  pinMode(ledPin, OUTPUT);

  // Start serial communication (optional, for debugging)
  Serial.begin(9600);
}

void loop() {
  // Read the value from the LDR
  ldrValue = analogRead(ldrPin);

  // Print the LDR value to the serial monitor (optional)
  Serial.println(ldrValue);

  // Define a light threshold (adjust based on your environment)
  if (ldrValue < 500) {
    // If it's dark, turn the LED on
    digitalWrite(ledPin, HIGH);
  } else {
    // If it's bright, turn the LED off
    digitalWrite(ledPin, LOW);
  }

  // Add a short delay
  delay(100);
}
            

5. Upload and Test

1. Connect your Arduino to your PC using a USB cable.
2. Open the Arduino IDE and paste the code above into a new sketch.
3. Select your Arduino board and the correct port in the IDE.
4. Click the "Upload" button to program your Arduino.
5. Observe the LED: It should turn on when the light level drops below the threshold and turn off in brighter conditions.

6. Additional Tips

• Adjusting the Threshold: Change the threshold value (500) in the code to suit your lighting conditions.
• Serial Monitor Debugging: Use the serial monitor to view real-time light intensity values for fine-tuning.
• Expand the Project: Add more LEDs, control other devices, or use a relay to manage larger lights.

7. Conclusion

Congratulations! You’ve built a light-sensitive night lamp using an Arduino and an LDR. This project is a stepping stone to more complex applications, such as automated lighting systems or smart home setups. Explore and expand!