#define trigPin 6<br>#define echoPin 7
#define GreenLED 11
#define YellowLED 10
#define RedLED 9
#define buzzer 3
int sound = 500;
void setup() {
  Serial.begin (9600);
  pinMode(trigPin, OUTPUT);
  pinMode(echoPin, INPUT);
  pinMode(GreenLED, OUTPUT);
  pinMode(YellowLED, OUTPUT);
  pinMode(RedLED, OUTPUT);
  pinMode(buzzer, OUTPUT);
 
}
void loop() {
  long duration, distance;
  digitalWrite(trigPin, LOW); 
  delayMicroseconds(2);
  digitalWrite(trigPin, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigPin, LOW);
  duration = pulseIn(echoPin, HIGH);
  distance = (duration/5) / 29.1;
 
  if (distance < 50) {
      digitalWrite(GreenLED, HIGH);
}
  else {
      digitalWrite(GreenLED, LOW);
  }
  
  if (distance < 20) {
    digitalWrite(YellowLED, HIGH);
}
  else {
    digitalWrite(YellowLED,LOW);
  }
  if (distance < 5) {
    digitalWrite(RedLED, HIGH);
    sound = 1000;
}
  else {
    digitalWrite(RedLED,LOW);
  }
 
  if (distance > 5 || distance <= 0){
    Serial.println("Out of range");
    noTone(buzzer);
  }
  else {
    Serial.print(distance);
    Serial.println(" cm");
    tone(buzzer, sound);
   
  }
  delay(300);
}