int relayPin = 19;
int buttonPin = 8;

bool state = false;
bool lastButton = HIGH;

void setup() {
  pinMode(relayPin, OUTPUT);
  pinMode(buttonPin, INPUT_PULLUP);

}

void loop() {
  bool currentButton = digitalRead(buttonPin);

  // phát hiện nhấn (HIGH → LOW)
  if (lastButton == HIGH && currentButton == LOW) {
    state = !state;

    // relay active LOW
    digitalWrite(relayPin, state ? LOW : HIGH);
  }

  lastButton = currentButton;
  delay(50);
}