int relay_pin = 13;
  int ldr_pin = 16;
void setup() {
  // put your setup code here, to run once:
  Serial.begin(115200);
  pinMode(ldr_pin, INPUT);
  pinMode(relay_pin, OUTPUT);
}

void loop() {
  int ldrValue = digitalRead(ldr_pin);
  Serial.print("ldr Value =");
  Serial.println(ldrValue);
  if (ldrValue == LOW) {
    digitalWrite(relay_pin, HIGH);
    Serial.println("Dark");
  }else{
    digitalWrite(relay_pin, LOW);
    Serial.println("light");
  }
  delay(10); 
}