int trigPin = 2;
int echoPin = 3; 

// defines variables
long duration;    // variable for the duration of sound wave travel
int distance;     // variable for the distance measurement
int buzzer = 4;
void setup()
{ 
  pinMode(buzzer, OUTPUT);
  pinMode(trigPin, OUTPUT);     // Sets the trigPin as an OUTPUT
  pinMode(echoPin, INPUT);     // Sets the echoPin as an INPUT
  Serial.begin(9600);        // Serial Communication is starting with 9600 of baudrate speed
  Serial.println("Ultrasonic Sensor HC-SR04 Test");      // print some text in Serial Monitor
  Serial.println("with Arduino UNO R3");
}


void loop(){
  // put your main code here, to run repeatedly:


// Clears the trigPin condition
  digitalWrite(trigPin, LOW);
  delayMicroseconds(2);    // Sets the trigPin HIGH (ACTIVE) for 10 microseconds
  digitalWrite(trigPin, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigPin, LOW); // Reads the echoPin, returns the sound wave travel time in microseconds
  duration = pulseIn(echoPin, HIGH); // Calculating the distance
  distance = duration * 0.034 / 2; // Speed of sound wave divided by 2 (go and back)
   // Displays the distance on the Serial Monitor
  Serial.print("Distance: ");
  Serial.print(distance);
  Serial.println(" cm");



 if (distance < 10) { 
    tone(buzzer, 1000); 

    Serial.println(("on"));
  } 
  
  else {
    noTone(buzzer);
}


}