#define TRIG_PIN 9
#define ECHO_PIN 8
#define RELAY_PIN 10
#define LED_PIN 13
void setup(){
  Serial.begin(9600);
  pinMode(TRIG_PIN, OUTPUT);
  pinMode(ECHO_PIN, INPUT);
  pinMode(RELAY_PIN, OUTPUT);
  pinMode(LED_PIN, OUTPUT);
}
long readUltrasonicDistance(){
  digitalWrite(TRIG_PIN, LOW);
  delayMicroseconds(2);
  digitalWrite(TRIG_PIN, HIGH);
  delayMicroseconds(10);
  digitalWrite(TRIG_PIN, LOW);
  return pulseIn(ECHO_PIN,HIGH)/58,2;//konversi menjadi cm
}
void loop(){
  long distance = readUltrasonicDistance();
  Serial.print("jarak:");
  Serial.print(distance);
  Serial.println("cm");
  
  if(distance<20){//jika jarak kurang dari 20 cm
  digitalWrite(RELAY_PIN, HIGH);//Relay aktif
  digitalWrite(LED_PIN, HIGH);//LED menyala
  Serial.println("Relay ON, LED ON");
  }else{
    digitalWrite(RELAY_PIN, LOW);//relay aktif
    digitalWrite(LED_PIN, HIGH);//LED mati
    Serial.println("Relay OFF,LED OFF");
  }

  delay(500);
}