#include <Servo.h>

Servo servo;
int const trigPin = 6;
int const echoPin = 5;

void setup()
{
  pinMode(trigPin, OUTPUT);
  pinMode(echoPin, INPUT);
  servo.attach(3);

  Serial.begin(9600);
}

void loop()
{
  int duration, distance;
  digitalWrite(trigPin, HIGH);
  delayMicroseconds(1);
  digitalWrite(trigPin, LOW);

  // Measure the pulse input in echo pin
  duration = pulseIn(echoPin, HIGH);
  distance = (duration / 2) / 29.1;

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

  // if distance less than 0.5 meter and more than 0 (0 or less means over range)
  if (distance <= 50 && distance >= 0)
  {
    servo.write(-90);
    delay(2000);
  }
  else
  {
    servo.write(90);
  }
}