void setup (){
  pinMode(3, INPUT);
  pinMode(LED_BUILTIN, OUTPUT);
}
void loop(){
  int a=digitalRead(3);
  Serial1.println(a);
  delay(1000);
  if (a==0)
{
Serial1.println("object Detected");
digitalWrite(LED_BUILTIN, HIGH);
  }
  else
  {
    Serial1.println("object is not Detected");
    digitalWrite(LED_BUILTIN, LOW);
  }
}