const int trigPin = 8;     // Pin Trig sensor ultrasonik 
const int echoPin = 7;     // Pin Echo sensor ultrasonik 
const int redLED = 9;      // Pin Lampu Merah 
const int yellowLED = 10;  // Pin Lampu Kuning 
const int greenLED = 11;   // Pin Lampu Hijau 
 
 void setup() {
    Serial.begin(9600);   
       pinMode(trigPin, OUTPUT);   
          pinMode(echoPin, INPUT);   
             pinMode(redLED, OUTPUT);   
                pinMode(yellowLED, OUTPUT);   
                   pinMode(greenLED, 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 / 2) / 29.1; // Menghitung jarak dalam centimeter 
                                                                
                                                                  
                                                                    if (distance < 80) {     
                                                                      digitalWrite(redLED, HIGH);     
                                                                        digitalWrite(yellowLED, LOW);     
                                                                          digitalWrite(greenLED, LOW);   } else if (distance <= 150) {    
                                                                             digitalWrite(redLED, LOW);     
                                                                                digitalWrite(yellowLED, HIGH);     
                                                                                   digitalWrite(greenLED, LOW); 
                                                                                     } else {     
                                                                                       digitalWrite(redLED, LOW);     
                                                                                         digitalWrite(yellowLED, LOW);     
                                                                                           digitalWrite(greenLED, HIGH); 
                                                                                             } 
                                                                                             }