Arduino Ultrasonic Sensor Test

sensor.ino

#define trigPin 11
#define echoPin 12
#define led 13

long distance, duration, lastDistance;

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

void loop() {

  lastDistance = distance;
  
  digitalWrite(trigPin, LOW);
  delayMicroseconds(2);
  digitalWrite(trigPin, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigPin, LOW);
  
  duration = pulseIn(echoPin, HIGH);
  distance = duration / 58;

  Serial.print("Distance: ");
  Serial.print(distance);
  Serial.println("cm");

  if (abs(distance - lastDistance) > 25) {
    digitalWrite(led, HIGH);
    tone(6, 1000);
  } else {
    digitalWrite(led, LOW);
    noTone(6);
  }
  
  delay(100);
}