2.Light-Controlled LED Using an LDR and Arduino

Light-Controlled LED Using an LDR and Arduino

Components Needed:

1. Arduino board
2. LDR (photoresistor)
3. 10kΩ resistor
4. LED
5. 220Ω resistor
6. Breadboard and jumper wires

Circuit Connections:

1. LDR Circuit:

   • Connect one leg of the LDR to 5V on the Arduino.
   • Connect the other leg of the LDR to an analog input pin (e.g., A0) and a 10kΩ resistor.
   • Connect the other end of the 10kΩ resistor to GND.

2. LED Circuit:

   • Connect the anode (longer leg) of the LED to a digital pin (e.g., 13).
   • Connect a 220Ω resistor in series with the cathode of the LED, and connect the other end of the resistor to GND.

Example Code:

C++ Code
int ldrPin = A0;    // Analog pin for LDR
int ledPin = 13;    // Digital pin for LED
int threshold = 500; // Threshold value for light level

void setup() {
  pinMode(ledPin, OUTPUT);  // Set LED pin as output
  Serial.begin(9600);       // Start serial communication
}

void loop() {
  int ldrValue = analogRead(ldrPin);  // Read LDR value
  Serial.println(ldrValue);           // Print LDR value to Serial Monitor

  if (ldrValue < threshold) {
    digitalWrite(ledPin, HIGH);  // Turn on LED when it is dark
  } else {
    digitalWrite(ledPin, LOW);   // Turn off LED when it is bright
  }

  delay(500); // Wait for half a second
}

Explanation of Code:

• Threshold: The threshold value is used to decide when the LED should turn on or off. You can adjust this value based on your ambient light conditions.
• analogRead(ldrPin) reads the current light level, and if the value is below the threshold, it turns the LED on; otherwise, it turns it off.
• Serial Monitor: You can view the light readings on the Serial Monitor to help determine a suitable threshold value for your environment.

Applications:

• This project can be used to create an automatic night light that turns on when it gets dark.
• It can also be used in security applications where lights need to be triggered based on the ambient light level.