// Include the Ultrasonic sensor library
#include <Ultrasonic.h>

// Define pins for the Ultrasonic sensor
#define trigPin 9
#define echoPin 10

// Define pin for the alarm
#define alarmPin 8

// Define the distance threshold for triggering the alarm (in centimeters)
const int thresholdDistance = 50;

// Initialize the Ultrasonic sensor
Ultrasonic ultrasonic(trigPin, echoPin);

void setup() {
  // Initialize serial communication for debugging
  Serial.begin(9600);
  
  // Set the alarm pin as an output
  pinMode(alarmPin, OUTPUT);
}

void loop() {
  // Measure the distance using the Ultrasonic sensor
  int distance = ultrasonic.read();
  
  // Print the distance to the serial monitor
  Serial.print("Distance: ");
  Serial.print(distance);
  Serial.println(" cm");

  // Check if an object is within the threshold distance
  if (distance < thresholdDistance) {
    // If an object is detected, trigger the alarm
    digitalWrite(alarmPin, HIGH);
    Serial.println("Alarm triggered!");
  } else {
    // If no object is detected, turn off the alarm
    digitalWrite(alarmPin, LOW);
  }

  // Delay for stability
  delay(1000);
}