int Trig_pin =5;
int Echo_pin =18;
long duration;
float Speed_of_sound =0.034;
float dist_in_cm;

void setup() {
  Serial.begin(115200);
  pinMode(Trig_pin, OUTPUT);
  pinMode(Echo_pin,INPUT);

}

void loop() {
  digitalWrite(Trig_pin, LOW);
  delayMicroseconds(2);
  digitalWrite(Trig_pin, HIGH);
  delayMicroseconds(10);
  digitalWrite(Trig_pin,LOW);

  duration =pulseIn(Echo_pin,HIGH);

  dist_in_cm=duration*Speed_of_sound/2;
  Serial.print("distance in cm :");
  Serial.println(dist_in_cm);

  delay(1000); 
}