Relay is a passive electronic component that is very common in parctical applications because of its stability, high capacity, and ease of maintenance. Relay modules are widely used in control and automation. The article suggests how to connect a relay to Arduino to control the on/off electrical devices in a smart home.Relay is a passive electronic component that is very common in parctical applications because of its stability, high capacity, and ease of maintenance. Relay modules are widely used in control and automation. The article suggests how to connect a relay to Arduino to control the on/off electrical devices in a smart home.