#include <LiquidCrystal_I2C.h>
#define led 2 

const float GAMMA = 0.7;
const float RL10 = 50 ;
 LiquidCrystal_I2C lcd (0x27,20,4) ;
 void setup() {
   pinMode (led,OUTPUT );
   lcd.init();
   lcd.backlight ();

}

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 ("cahaya:");

  if (lux > 500 ){
    lcd.print ("Terang ");
    digitalWrite (led, LOW );

  }else {
    lcd.print ("Gelap" );
    digitalWrite (led ,HIGH );

  }
  lcd.setCursor (0,1);
  lcd. print ("Lux :");
  lcd . print (lux );
  lcd. print ("       ");
  delay (100);

}