Once you get past LED-like power levels on your microcontroller or single-board computer project, you’ll need a more robust way to control things. Transistors and/or mechanical relays can be appropriate in many situations, and while this type of relay is well proven and, they are relatively slow, and eventually wear out.
Solid-state relays, however, isolate two circuits via an LED signal, This means they can switch loads much faster than the mechanical variety, without mechanical movements that wear out over time. They also don’t make any noise like the electromecanical variety, which can be important in some situations.
For an easy way to use 8 of these relays—at the cost of only two of your IO pins—this 8 Channel I2C Solid State Relay Module presents an attractive option. 8 SSRs are lined up on the board, and each can be used to control up to 2A of AC current. LEDs indicate the status of each SSR module, helpful in troubleshooting situations.
Relay output pins, along with an I2C header ( GND, SDA, SCL, and VCC) are broken out with screw terminals. This means that installation can be accomplished without breaking out the soldering iron, perfect for home automation or even industrial automation applications.