#define trigPin A0
#define echoPin A1
int duration, distance;
int buzzer = 2;

void setup() {
   Serial.begin(9600);
      pinMode(trigPin, OUTPUT);
         pinMode(echoPin, INPUT);
            pinMode(buzzer, OUTPUT);
            }

            void loop() {
               digitalWrite(trigPin, HIGH);
                  delayMicroseconds(10);
                     digitalWrite(trigPin, LOW);
                        duration = pulseIn(echoPin, HIGH);
                           distance = (duration / 2) / 29.1;
                              
                                 Serial.print("Jarak: ");
                                    Serial.println(distance);

                                       if (distance < 30) {
                                             Serial.println("Awas!!!");
                                                   digitalWrite(buzzer, HIGH);
                                                         delay(100);
                                                               digitalWrite(buzzer, LOW);
                                                                     delay(50);
                                                                        } else {
                                                                              Serial.println("Aman...");
                                                                                    digitalWrite(buzzer, LOW);
                                                                                       }
                                                                                          
                                                                                             delay(500); 
                                                                                             }