#include <LiquidCrystal_I2C.h>
LiquidCrystal_I2C lcd(0x27,16,2);
float cm;
const int relay = 4;
long  ReadUltrasonicTime(int pintrigger,int pinecho){
  pinMode(pintrigger, OUTPUT);
  pinMode(pinecho, INPUT);
  digitalWrite(pintrigger, LOW); //memastikan ultrasonik mati
  delayMicroseconds(2);
  digitalWrite(pintrigger, HIGH);//menyalakan ultrasonik
  delayMicroseconds(10);
  digitalWrite(pintrigger, LOW);//mematikan ultrasonik
  return pulseIn(pinecho, HIGH);//menghitung waktu ultrasonik untuk diterima oleh sensor
}

void setup() { 
  Serial.begin(20000);
  lcd.init();
  lcd.backlight();
  lcd.setCursor(4,0);
  lcd.print("BASARDANA");
  delay(1600);
  lcd.clear();
  pinMode(relay, OUTPUT);
}

void loop() {
  cm = 0.03420/2 * ReadUltrasonicTime(2, 3);

  if(cm <= 50){
    digitalWrite(relay, LOW);
  }
  else{
    digitalWrite(relay, HIGH);
  }
  lcd.clear();
  delay(1000);
}