• Relay module: 2" x 1" x 0.7"
• Sensor board: 2.15" x 1.55"
• Relay: 12 Vdc, SPDT, 10A contacts @ 125 Vac.
• Includes 2-wire jumper from sensor to board
• LED indicators for power and actuation Spec sheet available in PDF format.
(2 Reviews)
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Works well, really well, but...always powered. I know, duh. 
Had this all soldered in and configured after an initial test that I thought confirmed operation. But darn it if the thing doesn't need power to retain the "at rest state" of the relay.
So no matter if you configure it NC or NO with downstream components triggered based on water on the plate....WHEN YOU DROP POWER to the unit the relay goes to the opposite state.
In my case I have a small solar panel which charges a 12v battery and sometimes it doesn't top it up enough....so as evening comes the solar controller drops the power until recharge the next day. This is fine because the setup drives a greenhouse fan which only needs to run during peak sun of the day.
Well, the communicator I have this rain sensor tied to is still up running on a 3v coin battery and it sees the state change upon unit power down as rain on the plate ! I need to know for sure the next morning (before automated irrigation fires off) if there is water sitting on the plate in the tray I have it in.
I'm still thinking this through, maybe there's something I haven't tried between using NC vs NO but so far it's not looking that way. A loss of power causes a state change. Maybe my solution is to ignore all night time state changes, or get a bigger solar panel right ! ;-)
Yet another neat sensor 
Cool little device; made one myself a few years back. Any contact --- including moist breath, finger tip, metal strip --- will activate it. Only drawbacks: the connecting wire is short (6 inches) and NC and NO seem to be reversed, at least on mine.
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