// Define pins for HC-SR04
const int trigPin = 18;
const int echoPin = 19;

// Variable to store the duration of sound wave travel
long duration;

// Variable to store the calculated distance
int distance;

void setup() {
  // Begin serial communication at a baud rate of 115200:
  pinMode(12, OUTPUT);
  Serial.begin(115200);
  
  // Set the trigPin as an OUTPUT:
  pinMode(trigPin, OUTPUT);
  
  // Set the echoPin as an INPUT:
  pinMode(echoPin, INPUT);
}

void loop() {
  // Clear the trigPin by setting it LOW:
  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:
  // Speed of sound wave divided by 2 (there and back) in cm:
  distance = duration * 0.034 / 2;

  // Print the distance on the Serial Monitor:
  Serial.print("Distance: ");
  Serial.print(distance);
  Serial.println(" cm"); 
  
  if(distance>=350)
   {
    digitalWrite(12, LOW);
    Serial.println("OBJECT NEARER");
   }
   else if(distance>=150)
   {
    digitalWrite(12, HIGH);
    Serial.println("OBJECT IS LONGER");
   }

  // Wait for 100 milliseconds before taking the next measurement
  delay(100);
}