const int trigPin = 9;
const int echoPin = 10;

long duration;
long distance;


void setup() {
  Serial.begin(9600);
  pinMode(trigPin, OUTPUT);
  pinMode(echoPin, INPUT);
 
}

void loop() {  

  digitalWrite(trigPin, LOW);
  delayMicroseconds(2);
  digitalWrite(trigPin, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigPin, LOW);

  duration = pulseIn(echoPin, HIGH, 30000);
  distance =  duration*0.034/2;
  Serial.print("Distance : ");
  Serial.print(distance);
  Serial.println(" cm ");
  delay(500);
}