#define LED_PIN 2     
#define TRIGGER_PIN 12 
#define ECHO_PIN 13
#define BUZZER_PIN 14
 
long duration;
int distance;

void setup() {
  Serial.begin(9600);
  pinMode(LED_PIN, OUTPUT);
  pinMode(BUZZER_PIN, OUTPUT);
  pinMode(TRIGGER_PIN, OUTPUT);
  pinMode(ECHO_PIN, INPUT);
}

void loop() {
  
  digitalWrite(TRIGGER_PIN, LOW);
  delayMicroseconds(2);
  digitalWrite(TRIGGER_PIN, HIGH);
  delayMicroseconds(10);
  digitalWrite(TRIGGER_PIN, LOW);
  duration = pulseIn(ECHO_PIN, HIGH);
  distance = duration * 0.034 / 2;

  Serial.print("Jarak: ");
  Serial.print(distance);
  Serial.println(" cm");

  if (distance < 20) {
    digitalWrite(LED_PIN, HIGH); 
    tone(BUZZER_PIN, 1000);        
    delay(1000);                   
    digitalWrite(LED_PIN, LOW);    
    noTone(BUZZER_PIN);            
  } else {
    digitalWrite(LED_PIN, LOW);    
  }
  delay(100); 
}