const int LED_PIN = 15;
const int BUTTON_PIN = 5;

void setup() {
  Serial.begin(9600);
  pinMode(BUTTON_PIN, INPUT_PULLUP);
  pinMode(LED_PIN, OUTPUT);
}

void loop() {
  if(digitalRead(BUTTON_PIN) == LOW){
    Serial.println("UID tag: 12 34 56 78");
    digitalWrite(LED_PIN, HIGH);
    delay(5000);
    digitalWrite(LED_PIN, LOW);
    delay(1000);
  }
}