#define buzzerPin 7
#define trigPin 6
#define echoPin 5
#define greenPin 4
#define yellowPin 3
#define redPin 2
void setup() 
{
  pinMode(trigPin, OUTPUT);  
  pinMode(echoPin, INPUT);
  pinMode(redPin, OUTPUT);
  pinMode(yellowPin, OUTPUT);
  pinMode(greenPin, OUTPUT);
  pinMode(buzzerPin, OUTPUT);
  Serial.begin(9600);
}

void loop() 
{
  digitalWrite(trigPin, LOW);  
  delayMicroseconds(2);        
  digitalWrite(trigPin, HIGH); 
  delayMicroseconds(10);       
  digitalWrite(trigPin, LOW);  
  long waktu, jarak;           
  waktu = pulseIn(echoPin, HIGH); 
  jarak = (waktu * 0.0343) / 2; 
  Serial.print(jarak);     
  Serial.println("cm");    
  digitalWrite(redPin, LOW);    
  digitalWrite(yellowPin, LOW); 
  digitalWrite(greenPin, LOW);  
  noTone(buzzerPin);            
  if (jarak >= 50 && jarak <= 100) 
  {
    digitalWrite(greenPin, HIGH);   
    tone(buzzerPin, 1000);           
    delay(300);                      
    noTone(buzzerPin);               
    delay(300);                     
  }
  else if (jarak >= 25 && jarak <= 50) 
  {
    digitalWrite(yellowPin, HIGH);  
    tone(buzzerPin, 2000);           
    delay(200);                      
    noTone(buzzerPin);               
    delay(200);                      
  } 
  else if (jarak >= 0 && jarak <= 25) 
  {
    digitalWrite(redPin, HIGH);     
    tone(buzzerPin, 3000);           
  }
  delay(100); 
}