// Define pins
const int trigPin = 5;    // Trig pin of ultrasonic sensor
const int echoPin = 18;   // Echo pin of ultrasonic sensor
const int ledPin = 2;     // LED pin

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

void setup() {
  // Initialize serial communication
  Serial.begin(115200);

  // Set pin modes
  pinMode(trigPin, OUTPUT);
  pinMode(echoPin, INPUT);
  pinMode(ledPin, OUTPUT);
}

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

  // Set the trigPin HIGH for 10 microseconds
  digitalWrite(trigPin, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigPin, LOW);

  // Read the echoPin and calculate the distance
  duration = pulseIn(echoPin, HIGH);
  distance = duration * 0.034 / 2; // Convert duration to distance (cm)

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

  // Check if the distance is less than 5 cm
  if (distance < 5) {
    // Blink the LED
    digitalWrite(ledPin, HIGH);
    delay(500);  // LED on for 500ms
    digitalWrite(ledPin, LOW);
    delay(500);  // LED off for 500ms
  } else {
    // Turn off the LED
    digitalWrite(ledPin, LOW);
  }

  // Small delay before next reading
  delay(100);
}