I bought a couple relay modules for the Arduino to Borg together more of my house.  The first objective will be for the Incubator to drive the sprinklers with the Cron and Arduino service.  Also, I'll be looking into a web interface so my wife can manually override the sprinkler system.

The boards came with no hard-copy manual - but that is what Google is for. 

Heh, was totally flummoxed by these thing for a little while.. 

These are the two flummoxors.

1. THERE ARE 2 GROUNDS EVEN IF YOU SHORT THE JD-VCC YOU HAVE TO CONNECT BOTH GROUNDS - DUH !
2. The signalling is done by SINKING - uC pin to ground - not pin to 5V which is what I'm used to when signalling...

The first one (as trivial as you might think it is) drove me nuts.. circuitry behaves very strangly when it has a floating ground ..

Anyway seems very rock solid .. so rock solid (just done some preliminary testing with raw 5V & gnd PSU).
Next comes hooking it up to a littl PCF8574 and hooking that up to the I2C bus on a Raspberry Pi (YAY) + wfi

If that all goes well I'll try designing a lovely Blender case for it & I have a killer control module - for anywhere in the house :)

References :

• Good Guide On Relay Isolation
• Arduino forum
• Amazon reference
• How to wire .. sort of