const int trigPin = 14;   // Pin for the ultrasonic sensor trigger
const int echoPin = 27;   // Pin for the ultrasonic sensor echo
const int led = 15;       // Pin for the LED
const int buzzer = 5;     // Pin for the buzzer

void setup() {
  Serial.begin(9600);   // Initialize serial communication
  pinMode(trigPin, OUTPUT); // Set trigger pin as output
  pinMode(echoPin, INPUT);  // Set echo pin as input
  pinMode(led, OUTPUT);     // Set LED pin as output
  pinMode(buzzer, OUTPUT);  // Set buzzer pin as output
}

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

  // Measure the echo duration
  unsigned long duration = pulseIn(echoPin, HIGH);

  // Calculate distance in centimeters
  unsigned int distance = duration * 0.034 / 2;

  if (distance > 0 && distance <= 100) { // If an object is detected within 100cm
    // Display distance in the serial console
    Serial.print("Distance: ");
    Serial.print(distance);
    Serial.println(" cm");

    // Sound the buzzer and blink the LED
    tone(buzzer, 250, 300);   // Sound buzzer with frequency of 250 Hz for 300 ms
    digitalWrite(led, HIGH);  // Turn on the LED
    delay(1000);              // Delay for 1 second
    digitalWrite(led, LOW);   // Turn off the LED
  } else {
    Serial.println("No object detected!"); // Print message if no object detected
  }

  delay(500); // Wait for some time before the next measurement
}