// Pin definition
const int trigPin = 2;
const int echoPin = 3;
const int led_red = 4;
const int led_green = 5;
const int led_white = 6;
const int buzzer = 7;

//Distance Threshold (in cm)
const int distanceThreshold = 25;

void setup() {
  // Initialize Serial Monitor
  Serial.begin(9600);

  //Set Pin Modes
  pinMode(trigPin, OUTPUT);
  pinMode(echoPin, INPUT);
  pinMode(led_red, OUTPUT);
  pinMode(led_green, OUTPUT);
  pinMode(led_white, OUTPUT);
  pinMode(buzzer, OUTPUT);
}

void loop() {
  // Measure Distance
  long duration;
  float distance;

  // Read Echo Pulse
  duration = pulseIn(echoPin, HIGH);
  distance = (duration * 0.0343) / 2;  // Convert to cm

  Serial.print("Distance: ");
  Serial.print(distance);
  Serial.print(" cm");

  // Check Distance and Control LEDs/Buzzer
  if (distance > 0 && distance <= distanceThreshold) {

    digitalWrite(led_red, HIGH);
    digitalWrite(led_green, HIGH);
    digitalWrite(led_white, HIGH);
    digitalWrite(buzzer, HIGH);
  } else {
    digitalWrite(led_red, LOW);
    digitalWrite(led_green, LOW);
    digitalWrite(led_white, LOW);
    digitalWrite(buzzer, LOW);
  }

  // Short delay for stable readings
  delay(200); }