int echoPin =2;
int trigPin =3;
int led1 =4;
int led2 =5;
int led3 =6;
void setup()
{
pinMode(echoPin, INPUT);
pinMode(trigPin, OUTPUT);
pinMode(led1, OUTPUT);
pinMode(led2, OUTPUT);
pinMode(led3, OUTPUT);
}
float ultrasonik()
{
digitalWrite(trigPin, LOW);
delayMicroseconds(2);
digitalWrite(trigPin, HIGH);
delayMicroseconds(10);
digitalWrite(trigPin, LOW);
int durasiPantulan = pulseIn(echoPin, HIGH);
return durasiPantulan *0.034/2;
}
void loop()
{
float jarak = ultrasonik();
if (jarak>100) 
 {
digitalWrite(led2, HIGH);
digitalWrite(led1, LOW);
 }
  else if
  (jarak<=100 && jarak>50)
  {
  digitalWrite(led1, HIGH);
  digitalWrite(led2, LOW);
  digitalWrite(led3, LOW);
  }
  else if(jarak<=50)
  {
  digitalWrite(led3, HIGH);
  digitalWrite(led1, LOW);
  }
  }