// Define pins for the ultrasonic sensor and LED
const int trigPin = 5;
const int echoPin = 18;
const int ledPin = 19;

// Variable for storing the duration of the sound wave travel
long duration;
// Variable for storing the distance
int distance;

void setup() {
  // Initialize the serial communication
  Serial.begin(115200);
  
  // Set the ultrasonic sensor pins as output and input
  pinMode(trigPin, OUTPUT);
  pinMode(echoPin, INPUT);
  
  // Set the LED pin as output
  pinMode(ledPin, OUTPUT);
}

void loop() {
  // Clear the trigPin
  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, returns the sound wave travel time in microseconds
  duration = pulseIn(echoPin, HIGH);
  
  // Calculate the distance
  distance = duration * 0.034 / 2;
  
  // Print the distance to the Serial Monitor
  Serial.print("Distance: ");
  Serial.print(distance);
  Serial.println(" cm");

  // Check if the distance is less than 10 cm
  if (distance < 100) {
    digitalWrite(ledPin, HIGH); // Turn on LED
  } else {
    digitalWrite(ledPin, LOW);  // Turn off LED
  }
  
  // Wait for a short period before the next loop
  delay(100);
}