//Car-parking IOT app

int echopin = 2; //getting the input of the Ultrasonic sensor.
int trigpin = 3; //starts sending signal from sensor.
int Time;
int Distance;

void setup() 
{ // put your setup code here, to run once:
pinMode(trigpin, OUTPUT);
pinMode(echopin, INPUT);

}

void loop() 
{// put your main code here, to run repeatedly:
  digitalWrite(trigpin, LOW); //stop the functioning of the ultrasonic sensor
  digitalWrite(trigpin, HIGH);//starts sending signal
  digitalWrite(trigpin, LOW);//stop receiving signal from the arduino.
//pulseIn() used to get  time taken by the sound wave to reflect back after hitting the object.
  Time = pulseIn(echopin,HIGH);
  Distance = Time * 0.0172;  //0.0172 is constant(speed of wave-ultrasonic sensor)

  if (Distance>30){
    digitalWrite(11, HIGH);//Pin 11 producing the output of the green LED. 
    digitalWrite(13, LOW);  //red LED
  }

  else{
    digitalWrite(11, LOW); //green LED
    digitalWrite(13, HIGH);//Pin 13 producing the output of the red LED. 
    
  }
}
//OUTPUT- Click on sensor and change distance to get output