const int trigPin = 9;  // Pin connected to the Trigger pin of the ultrasonic sensor
const int echoPin = 10; // Pin connected to the Echo pin of the ultrasonic sensor
int led = 13;           // Pin connected to the LED

float duration, distance; // Variables to store the duration and calculated distance

void setup() {
  pinMode(trigPin, OUTPUT); // Set the trigPin as an OUTPUT
  pinMode(echoPin, INPUT);  // Set the echoPin as an INPUT
  pinMode(led, OUTPUT);     // Set the led pin as an OUTPUT
  Serial.begin(9600);       // Initialize serial communication at 9600 baud rate
}

void loop() {
  // Clear the trigPin by setting it LOW for 2 microseconds
  digitalWrite(trigPin, LOW);
  delayMicroseconds(2);

  // Trigger the sensor by setting the trigPin HIGH for 10 microseconds
  digitalWrite(trigPin, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigPin, LOW);

  // Read the echoPin, pulseIn() returns the duration (length of the pulse) in microseconds
  duration = pulseIn(echoPin, HIGH);

  // Calculate the distance based on the speed of sound
  distance = (duration * 0.0343) / 2;

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

  // If the distance is less than or equal to 50cm, turn the LED on, else turn it off
  if (distance <= 50) {
    digitalWrite(led, HIGH);
  } else {
    digitalWrite(led, LOW);
  }

  // Wait for 100 milliseconds before the next loop iteration
  delay(100);
}