#include <LiquidCrystal_I2C.h>
#define LDR_PIN 2
// LDR Characteristics
const float GAMMA = 0.7;
const float RL10 = 50;
LiquidCrystal_I2C lcd(0x27, 20, 4);
int led = 13;                // the pin that the LED is atteched to
int sensor = 3;              // the pin that the sensor is atteched to
int state = LOW;             // by default, no motion detected
int val = 0; 
void setup() {
  pinMode(LDR_PIN, INPUT);
  lcd.init();
  lcd.backlight();
  pinMode(led, OUTPUT);      // initalize LED as an output
  pinMode(sensor, INPUT);    // initialize sensor as an input
}
void loop() {
  int analogValue = analogRead(A0);
  float voltage = analogValue / 1024. * 5;
  float resistance = 2000 * voltage / (1 - voltage / 5);
  float lux = pow(RL10 * 1e3 * pow(10, GAMMA) / resistance, (1 / GAMMA));
  lcd.setCursor(2, 0);
  lcd.print("Room: ");
  if (lux > 50) {
    lcd.print("Light!");
  } else {
    lcd.print("Dark  ");
    val = digitalRead(sensor);   // read sensor value
 if (val == HIGH) {           // check if the sensor is HIGH
    digitalWrite(led, HIGH);   // turn LED ON
    delay(500);                // delay 100 milliseconds 
    
    if (state == LOW) {
     
      state = HIGH;       // update variable state to HIGH
    }
  } 
  else {
      digitalWrite(led, LOW); // turn LED OFF
      delay(500);             // delay 200 milliseconds 
      
      if (state == HIGH){
      
        state = LOW;       // update variable state to LOW
    }
  }
  }
  lcd.setCursor(0, 1);
  lcd.print("Lux: ");
  lcd.print(lux);
  lcd.print("          ");
  delay(100);
}