// Define the pins for the ultrasonic sensor
const int trigPin = 2;  // Trigger pin
const int echoPin = 3;  // Echo pin

// Define the pin for the buzzer
const int buzzerPin = 4;

// Variables for the duration and distance
long duration;
int distance;

void setup() {
  // Set up the serial communication
  Serial.begin(9600);

  // Set up the ultrasonic sensor pins
  pinMode(trigPin, OUTPUT);
  pinMode(echoPin, INPUT);

  // Set up the buzzer pin
  pinMode(buzzerPin, OUTPUT);
}

void loop() {
  // Generate ultrasonic pulse
  digitalWrite(trigPin, LOW);
  delayMicroseconds(2);
  digitalWrite(trigPin, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigPin, LOW);

  // Measure the duration of the pulse
  duration = pulseIn(echoPin, HIGH);

  // Calculate the distance in centimeters
  distance = duration * 0.034 / 2;

  // Print the distance to the serial monitor
  Serial.print("Distance: ");
  Serial.print(distance);
  Serial.println(" cm");

  // Check if the distance is less than a threshold
  if (distance < 10) {
    // If the distance is less than 10 cm, turn on the buzzer
    digitalWrite(buzzerPin, HIGH);
  } else {
    // Otherwise, turn off the buzzer
    digitalWrite(buzzerPin, LOW);
  }

  // Delay before the next measurement
  delay(1000);
}