#define pinoRele 4

void setup() {
  Serial.begin(9600);
  pinMode(pinoRele, OUTPUT);

  digitalWrite(pinoRele, LOW);
  delay(5000);
}

void loop() {
  digitalWrite(pinoRele, HIGH);
  Serial.println("ligado");
  delay(5000);

  digitalWrite(pinoRele, LOW);
  Serial.println("desligado");
  delay(5000);
}