#include <Arduino.h>
#define trigPin 7
#define echoPin 6
#define LEDlampRed 9
#define LEDlampYellow 10
#define LEDlampGreen 11
#define buzzer 3
int sound  = 500;

void setup() {
  Serial.begin (9600);
  pinMode(trigPin, OUTPUT);
  pinMode(echoPin, INPUT);
  pinMode(LEDlampRed, OUTPUT);
  pinMode(LEDlampYellow, OUTPUT);
  pinMode(LEDlampGreen, OUTPUT);
  pinMode(buzzer, OUTPUT);
}
void  loop() {
  long durationindigit, distanceincm, distance;
  digitalWrite(trigPin, LOW);  
  delayMicroseconds(2);
  digitalWrite(trigPin, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigPin, LOW);
  durationindigit = pulseIn(echoPin, HIGH);
  distanceincm = (durationindigit*0.0343) / 2;
 
  if (distanceincm < 50) {
      digitalWrite(LEDlampGreen, HIGH);
}
  else {
      digitalWrite(LEDlampGreen,  LOW);
  }
  
  if (distanceincm < 20) {
    digitalWrite(LEDlampYellow,  HIGH);
}
  else {
    digitalWrite(LEDlampYellow,LOW);
  }
  if (distanceincm  < 5) {
    digitalWrite(LEDlampRed, HIGH);
    sound = 100;
}
  else  {
    digitalWrite(LEDlampRed,LOW);
  }
 
  if (distanceincm > 5 ||  distanceincm <= 0){
    Serial.println("Outside the permissible range of distances: ");
    Serial.println(distanceincm);
    noTone(buzzer);
  }
  else {
    Serial.print(distance);
    Serial.println("  cm");
    tone(buzzer, sound);
  }
  
  delay(500);
}