The Relay Plug is a small board containing two miniature relays, rated up to 3A @ 250V (both AC and DC).
This plug is designed to switch low voltage, low power lights, motors, fans etc. The contacts are isolated, meaning there is no electrical connection between the switched connector pins and the rest of the circuit board.
The Part-assembled version comes with the SMD driver chips already soldered-on and all the remaining parts needed, including a high-power terminal block with individually wirable connectors to solder on to the board. Note that no 6-pin headers are included.
The PCB only variant contains just the board for the Relay Plug. No parts, no headers.
As connectors you can use a Plug Headers set with 10 male and 10 female 6-pin headers, which makes it easy to connect multiple plugs and JeeNodes in a “standard” way. Or you can solder the board directly in place for more permanent use.
The documentation and full design details are freely available.
Ensuring satisfactory life for the relay contacts requires consideration of the type of load current (resistive, inductive, with switch on surge etc.) and correct technique for reducing contact arcing for heavier currents.