/*#include <HCSR04.h>*/

long dauer=0; 
long entfernung=0; 
#define TRIGGER 12 
#define ECHO 13  
#define LED_Green 8 
#define LED_Yellow 9  
#define LED_Red 10 

void setup()
{
  Serial.begin (9600); 
  pinMode(ECHO, INPUT); 
  pinMode(TRIGGER, OUTPUT);
  pinMode(LED_Green, OUTPUT); 
  pinMode(LED_Yellow, OUTPUT); 
  pinMode(LED_Red, OUTPUT); 
}

void loop()
{
  digitalWrite(TRIGGER, LOW); 
  delay(5); 
  digitalWrite(TRIGGER, HIGH); 
  delay(5); 
  digitalWrite(TRIGGER, LOW);
  dauer = pulseIn(ECHO, HIGH); 
  entfernung = (dauer/2) * 0.03432; 
  Serial.print(entfernung); 
  Serial.println(" cm"); 
  delay(200); 
     
    if (entfernung > 100) 
  {
    digitalWrite(LED_Green, HIGH); digitalWrite(LED_Yellow, LOW); digitalWrite(LED_Red, LOW); 
  }
    if (entfernung >= 50 && (entfernung) <= 100) 
  {
    digitalWrite(LED_Green, LOW); digitalWrite(LED_Yellow, HIGH); digitalWrite(LED_Red, LOW); 
  }
    if (entfernung < 50) 
  {
    digitalWrite(LED_Green, LOW); digitalWrite(LED_Yellow, LOW); digitalWrite(LED_Red, HIGH); 
  } 
}