#define ldr A1
#define relay 2 
void setup() {
 pinMode(ldr, INPUT);
 pinMode(relay, OUTPUT);
 Serial.begin(9600);
}

void loop() {
  int cahaya;
  cahaya = analogRead(ldr);
  Serial.println(cahaya);
  delay(100);
  if(cahaya>700){
    digitalWrite(relay, HIGH);
  }else{
    digitalWrite(relay, LOW);
  }
}