#define echoPin 25 // attach pin D2 Arduino to pin Echo of HC-SR04
#define trigPin 23 //attach pin D3 Arduino to pin Trig of HC-SR04
int rLED=2;
int yLED=3;
int gLED=4;

// defines variables
long duration; // variable for the duration of sound wave travel
int distance; // variable for the distance measurement

void setup() {
  pinMode(trigPin, OUTPUT); // Sets the trigPin as an OUTPUT
  pinMode(echoPin, INPUT); // Sets the echoPin as an INPUT
  Serial.begin(9600); // // Serial Communication is starting with 9600 of baudrate speed
  Serial.println("Ultrasonic Sensor HC-SR04 Test"); // print some text in Serial Monitor
  Serial.println("with Arduino UNO R3");
  pinMode(gLED,OUTPUT);
  pinMode(yLED,OUTPUT);
  pinMode(rLED,OUTPUT);


}
void loop()
 {
  // Clears the trigPin condition
  digitalWrite(trigPin, LOW);
  delayMicroseconds(2);
  // Sets the trigPin HIGH (ACTIVE) for 10 microseconds
  digitalWrite(trigPin, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigPin, LOW);
  // Reads the echoPin, returns the sound wave travel time in microseconds
  duration = pulseIn(echoPin, HIGH);
  // Calculating the distance
  distance = duration * 0.034 / 2; // Speed of sound wave divided by 2 (go and back)
  // Displays the distance on the Serial Monitor
  Serial.print("Distance: ");
  Serial.print(distance);
  Serial.println(" cm");
  digitalWrite(rLED,HIGH);
  digitalWrite(yLED, HIGH);
  digitalWrite(gLED, HIGH);
  delay(500);
  
  digitalWrite(rLED,LOW);
  digitalWrite(yLED, LOW);
  digitalWrite(gLED, LOW);
  delay(250);
  
  digitalWrite(rLED,HIGH);
  digitalWrite(yLED, HIGH);
  digitalWrite(gLED, HIGH);
  delay(250);
 
  digitalWrite(rLED,LOW);
  digitalWrite(yLED, LOW);
  digitalWrite(gLED, LOW);
  delay(500);
  
  if (distance<150)

 { digitalWrite(gLED, HIGH);
  digitalWrite(rLED,LOW);
  digitalWrite(yLED, LOW);
  delay(500);
  digitalWrite(gLED, LOW);
  digitalWrite(rLED,LOW);
  digitalWrite(yLED, LOW);
  delay(500);
  digitalWrite(gLED, HIGH);
  digitalWrite(rLED,LOW);
  digitalWrite(yLED, LOW);
  delay(500);
  digitalWrite(gLED, LOW);
  digitalWrite(rLED,LOW);
  digitalWrite(yLED, LOW);
  delay(500);
 }
 else if(150<=distance, distance<=300)
 { 
  digitalWrite(gLED, LOW);
  digitalWrite(rLED,HIGH);
  digitalWrite(yLED, LOW);
  delay(500);
  digitalWrite(gLED, LOW);
  digitalWrite(rLED,LOW);
  digitalWrite(yLED, LOW);
  delay(500);
  digitalWrite(gLED, LOW);
  digitalWrite(rLED,HIGH);
  digitalWrite(yLED, LOW);
  delay(500);
  digitalWrite(gLED, LOW);
  digitalWrite(rLED,LOW);
  digitalWrite(yLED, LOW);
  delay(500);
  }
  if (distance>=300)
 { 
  digitalWrite(gLED, LOW);
  digitalWrite(rLED,LOW);
  digitalWrite(yLED, HIGH);
  delay(500);
  digitalWrite(gLED, LOW);
  digitalWrite(rLED,LOW);
  digitalWrite(yLED, LOW);
  delay(500);
  digitalWrite(gLED, LOW);
  digitalWrite(rLED,LOW);
  digitalWrite(yLED, HIGH);
  delay(500);
  digitalWrite(gLED, LOW);
  digitalWrite(rLED,LOW);
  digitalWrite(yLED, LOW);
  delay(500);
  }
}