The RelayBoard is an expandable board with just 3 pins to control It allows you to trigger up to 8 relays per board. With more than one board connected, it makes it possible to control 8, 16, 24, up to 80 relays using just one microcontroller. It was developed library for Arduino to facilitate the control of all relays, that way it could determine which board will be triggered.

It's a easy-to-use board and extremely practical, is a great solution to applications where it will be need to do several triggers, generally found in automations projects.