tornado-relay-tester.ino

const int num_relays = 8;
const int relays[] = {2, 3, 4, 5, 6, 7, 8, 9};

const int duration = 1000;

void setup() {
  for (int i = 0; i < num_relays; i++) {
    pinMode(relays[i], OUTPUT);
    digitalWrite(relays[i], HIGH);
  }
}

void loop() {
  for (int i = 0; i < num_relays; i++) {
    digitalWrite(relays[i], HIGH);
    delay(duration);
    digitalWrite(relays[i], LOW);
    delay(duration);
  }
}