#include <LiquidCrystal_I2C.h>

int ldrPin =15 ;
int ledPin = 13;
const float GAMMA = 0.7;
const float RL10 = 50;

LiquidCrystal_I2C lcd(0x27, 16, 2); 

void setup() {

 pinMode(ledPin, OUTPUT);
 lcd.init();
 lcd.backlight();
}

void loop() {

int ldrValue = analogRead(ldrPin);
float voltase = ldrValue /1024. * 5;
float resistansi = 2000 * voltase / (1-voltase /5) ;
float kecerahan = pow(RL10*1e3*pow(10, GAMMA) / resistansi ,(1/ GAMMA));

lcd.setCursor(0,0);
lcd.print("cahaya:");
if(kecerahan >50){
  lcd.print("terang");
digitalWrite(ledPin, LOW);
}
else{
  lcd.print("gelap");
  digitalWrite(ledPin, HIGH);
}

lcd.setCursor(0,1);
lcd.print("lux:");
lcd.print(kecerahan);
lcd.print("  ");

delay(100);
}