const int trigPin = 2;  // Trigger pin of the ultrasonic sensor
const int echoPin = 3;  // Echo pin of the ultrasonic sensor
const int buzzerPin = 8;  // Buzzer pin

const int warningDistance = 20;  // Distance in centimeters, below which the warning will be triggered

void setup() {
  Serial.begin(9600);
  pinMode(trigPin, OUTPUT);
  pinMode(echoPin, INPUT);
  pinMode(buzzerPin, OUTPUT);
}

void loop() {
  long duration, distance;

  // Generate pulse for the ultrasonic sensor
  digitalWrite(trigPin, LOW);
  delayMicroseconds(2);
  digitalWrite(trigPin, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigPin, LOW);

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

  // Calculate the distance in centimeters
  distance = (duration * 0.0343) / 2;

  Serial.print("Distance: ");
  Serial.print(distance);
  Serial.println(" cm");

  // Check if the distance is below the warning threshold
  if (distance < warningDistance) {
    // If so, trigger the warning (turn on the buzzer)
    digitalWrite(buzzerPin, HIGH);
  } else {
    // Otherwise, turn off the buzzer
    digitalWrite(buzzerPin, LOW);
  }

  delay(500);  // Adjust the delay according to your needs
}