// Define pins
const int trigPin = 9;
const int echoPin = 10;
const int ledPin = 3;

// Variables to store distance data
long duration;
int distance;

void setup() {
  // Initialize pins
  pinMode(trigPin, OUTPUT);
  pinMode(echoPin, INPUT);
  pinMode(ledPin, OUTPUT);

  // Begin Serial communication
  Serial.begin(9600);
}

void loop() {
  // Clear the trigPin
  digitalWrite(trigPin, LOW);
  delayMicroseconds(2);

  // Set the trigPin HIGH for 10 microseconds to trigger the ultrasonic pulse
  digitalWrite(trigPin, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigPin, LOW);

  // Read the echoPin and calculate the time taken for the echo to return
  duration = pulseIn(echoPin, HIGH, 30000);  // Add timeout of 30ms for more stability

  // Check if valid data is received (duration should be non-zero)
  if (duration > 0) {
    // Calculate the distance in centimeters
    distance = duration * 0.034 / 2;

    // Print the distance on the Serial Monitor
    Serial.print("Distance: ");
    Serial.print(distance);
    Serial.println(" cm");

    // Turn on the LED if an object is within 20 cm
    if (distance <= 20) {
      digitalWrite(ledPin, HIGH);
    } else {
      digitalWrite(ledPin, LOW);
    }
  } else {
    // If no valid data is received, keep LED off
    digitalWrite(ledPin, LOW);
    Serial.println("Out of range");
  }

  // Add a small delay before the next loop iteration
  delay(1000);  // 1 second delay for debouncing
}