// Define the pins to which the ultrasonic sensor is connected
int trigPin = 2;
int echoPin = 3;

// Define the pin to which the buzzer is connected
int buzzerPin = 4;

// Variable to store the distance measured by the ultrasonic sensor
long distance;

void setup() {
  // Set the trigPin as an OUTPUT
  pinMode(trigPin, OUTPUT);
  // Set the echoPin as an INPUT
  pinMode(echoPin, INPUT);
  // Set the buzzerPin as an OUTPUT
  pinMode(buzzerPin, OUTPUT);

  // Start serial communication for debugging
  Serial.begin(9600);
}

void loop() {
  // Trigger the ultrasonic sensor to send a pulse
  digitalWrite(trigPin, LOW);
  delayMicroseconds(2);
  digitalWrite(trigPin, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigPin, LOW);

  // Measure the time it takes for the pulse to return
  distance = pulseIn(echoPin, HIGH) * 0.034 / 2;

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

  // Check if the distance is less than a threshold (e.g., 50 cm) to activate the alarm
  if (distance < 50) {
    Serial.println("Intruder detected! Activating alarm!");
    // Activate the alarm by turning on the buzzer
    digitalWrite(buzzerPin, HIGH);
    delay(1000); // Delay for 1 second
    // Turn off the buzzer
    digitalWrite(buzzerPin, LOW);
  }

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