Solid Relay Module 4 channel 5v low level trigger for Arduino

This is 4 Channel 5V Solid State Relay Module. A solid state relay (SSR) is just what it sounds like; an IC that acts like a mechanical relay. They allow you to control high-voltage AC loads from lower voltage DC control circuitry. They accomplish this by using infrared light as the ‘contact,’ a solid-state relay is really just an IR LED and a photo Triac sealed up into a little box. Solid-state relays have several advantages over mechanical relays.

A Solid State Relay is similar to a mechanic relay where it can be controlled through a digital signal. Solid State Relay generates no noise and has a much longer lifespan compared to the traditional mechanic relay.

One such advantage is that they can be switched by a much lower voltage and at a much lower current than most mechanical relays. Also, because there are no moving contacts, solid-state relays can be switched much faster and for much longer periods without wearing out.