const int relayPin = 4; // Define pins

void setup() {
  // Set the relay pin as an output
  pinMode(relayPin, OUTPUT); 
}

void loop() {
  // Turn on the relay for 2 seconds
  digitalWrite(relayPin, HIGH);
  delay(2000);

  // Turn off the relay for 2 seconds
  digitalWrite(relayPin, LOW);
  delay(2000);
}