#define relay 2
#define ldr A0

const float GAMMA = 0.7;
const float RL10 = 50;

void setup() {
  pinMode(relay, OUTPUT);
  
}

void loop() {
  int analogValue = analogRead(ldr);
  float voltage = analogValue / 1024. * 5;
  float resistance = 2000 * voltage / (1 - voltage / 5);
  float lux = pow(RL10 * 1e3 * pow(10, GAMMA) / resistance, (1 / GAMMA));
  
  if (lux > 50) {
    digitalWrite(relay,LOW);
  } else {
    digitalWrite(relay,HIGH);
  }

  delay(100);

}