// Define pins
const int trigPin = 10;  // Trig pin of the HC-SR04
const int echoPin = 11;  // Echo pin of the HC-SR04
const int greenPin = 5;
const int yellowPin = 6;
const int redPin = 7;

// Variables
long duration;
int distance;
int delayTime = 10;
int disRedLED = 10;
int disYellowLED = 20;
int disGreenLED = 30;

void setup() {
  Serial.begin(9600);
  pinMode(trigPin, OUTPUT);
  pinMode(echoPin, INPUT);
  pinMode(greenPin, OUTPUT);
  pinMode(yellowPin, OUTPUT);
  pinMode(redPin, OUTPUT);
}

void loop() {
  digitalWrite(greenPin, LOW);
  digitalWrite(yellowPin, LOW);
  digitalWrite(redPin, LOW);

  // Trigger the sensor by sending a 10 microsecond pulse
  digitalWrite(trigPin, LOW);
  delayMicroseconds(delayTime);
  digitalWrite(trigPin, HIGH);
  delayMicroseconds(delayTime);
  digitalWrite(trigPin, LOW);


  // Measure the duration of the echo pulse
  duration = pulseIn(echoPin, HIGH);

  // Calculate the distance in centimeters
  distance = duration * 0.034 / 2;

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

  if (distance > disGreenLED) {
    digitalWrite(greenPin, HIGH);
    digitalWrite(yellowPin, LOW);
    digitalWrite(redPin, LOW);
  }
  if (distance >= disRedLED && distance <= disGreenLED) {
    digitalWrite(greenPin, LOW);
    digitalWrite(yellowPin, HIGH);
    digitalWrite(redPin, LOW);
  }
  if (distance < disRedLED) {
    digitalWrite(greenPin, LOW);
    digitalWrite(yellowPin, LOW);
    digitalWrite(redPin, HIGH);
  }


  // Wait for a short time before taking the next measurement
  delay(500);
}