// Ultrasonic Sensor HC-SR04 with Active Buzzer and LED Alert

#define TRIG_PIN 9    // Trigger pin
#define ECHO_PIN 10   // Echo pin
#define BUZZER 6      // Active buzzer pin
#define LED 7         // LED pin

long duration;
int distance;

void setup() {
  Serial.begin(9600);
  pinMode(TRIG_PIN, OUTPUT);
  pinMode(ECHO_PIN, INPUT);
  pinMode(BUZZER, OUTPUT);
  pinMode(LED, OUTPUT);

  Serial.println("=== Ultrasonic Distance Sensor with Active Buzzer Alert ===");
}

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

  // Read echo time
  duration = pulseIn(ECHO_PIN, HIGH);

  // Calculate distance in cm
  distance = duration * 0.034 / 2;

  // Print distance
  Serial.print("Distance: ");
  Serial.print(distance);
  Serial.print(" cm  -->  ");

  // Check distance and act
  if (distance < 10) {
    digitalWrite(LED, HIGH);
    digitalWrite(BUZZER, HIGH);   // Active buzzer ON
    Serial.println("Object too close!");
  } else {
    digitalWrite(LED, LOW);
    digitalWrite(BUZZER, LOW);    // Active buzzer OFF
    Serial.println("Safe distance");
  }

  delay(500);
}