int pin_photo = A5;
int pin_led = 6;
float val_res;

void setup() {
  pinMode(pin_photo, INPUT);
  pinMode(pin_led, OUTPUT);
  Serial.begin(9600);
}

void loop() {
  val_res = analogRead(pin_photo);
  if (val_res >= 500) {
    digitalWrite(pin_led, HIGH);
  }
  else {
    digitalWrite(pin_led, LOW);
  }
  delay(1000);
}