How to use a photoresistor with Arduino

INTRODUCTION

A photoresistor known as LDR (Light Decreasing Resistance, or light-dependent resistor) is an active component that decreases resistance when receiving light on its sensitive surface.

APPLICATIONS

The photoresistor is used to detect the intensity of light in driverless cars. Night lights automatically turn on when the intensity of light detected by this sensor is below a threshold value.

WIRING DIAGRAM

VCC – 5V

GND – GND

Analog Pin A0 and Digital Pin 12 are used

CODE

 

int photopin = A0;
int ledpin = 12;

int value;


void setup() {
  // put your setup code here, to run once:
Serial.begin(9600);
pinMode(photopin,INPUT);
pinMode(ledpin, OUTPUT);
}

void loop() {
  // put your main code here, to run repeatedly:
value = analogRead(photopin);

if (value > 25){
  digitalWrite(ledpin, LOW);
  
}
else {
  digitalWrite(ledpin, HIGH);
}
}
int photopin = A0;
int ledpin = 12;

int value;


void setup() {
  // put your setup code here, to run once:
Serial.begin(9600);
pinMode(photopin,INPUT);
pinMode(ledpin, OUTPUT);
}

void loop() {
  // put your main code here, to run repeatedly:
value = analogRead(photopin);

if (value > 25){
  digitalWrite(ledpin, LOW);
  
}
else {
  digitalWrite(ledpin, HIGH);
}
}

END RESULT

Put your finger over the photoresistor and the LED will light up.

ADDITIONAL RESOURCES

https://www.instructables.com/id/LDR-Robot/

https://home.roboticlab.eu/en/examples/sensor/photoresistor