const int relayPin = 4; // 繼電器腳位
void setup() {
  // put your setup code here, to run once:
  Serial.begin(115200); // 啟動
  pinMode( relayPin, OUTPUT); //設定腳位為輸出
}

void loop() {
  digitalWrite(relayPin, HIGH); // Relay NO 導通
  Serial.println("Relay NO is ON!");
  Serial.println("LED is ON!");
  delay(3000); 
  digitalWrite(relayPin, LOW); // Relay NO 不導通
  Serial.println("Relay NO is OFF!");
  Serial.println("LED is OFF!");
  delay(3000); 
}