#define TRIG 9
#define ECHO 10
#define LED 13

long duration;
int distance;

void setup() {
  pinMode(TRIG, OUTPUT);
  pinMode(ECHO, INPUT);
  pinMode(LED, OUTPUT);
  Serial.begin(9600);
}

void loop() {
  // Bersihkan pin TRIG
  digitalWrite(TRIG, LOW);
  delayMicroseconds(2);

  // Kirim pulsa 10µs ke TRIG
  digitalWrite(TRIG, HIGH);
  delayMicroseconds(10);
  digitalWrite(TRIG, LOW);

  // Baca pantulan dari ECHO
  duration = pulseIn(ECHO, HIGH);

  // Hitung jarak (cm)
  distance = duration * 0.034 / 2;

  if(distance<=20){
    digitalWrite(LED, HIGH);
  }else{
    digitalWrite(LED, LOW);
  }

  delay(500);
}