const int trigPin = 8;
const int echoPin = 7;

int pingTravelTime;
int dt = 250;

void setup() {
  // put your setup code here, to run once:
  pinMode(trigPin, OUTPUT);
  pinMode(echoPin, INPUT);
  Serial.begin(9600);
}

void loop() {
  // put your main code here, to run repeatedly:
  digitalWrite(trigPin, LOW);
  delayMicroseconds(5);
  digitalWrite(trigPin, HIGH);
  delayMicroseconds(5);
  digitalWrite(trigPin, LOW);

  pingTravelTime = pulseIn(echoPin, HIGH);
  Serial.println(pingTravelTime);
  delay(dt);
}