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I'm looking to do something similar but for various locations in my parents' basement. What did you use for sensors and power? How about communication to the outside world?

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It's actually fairly simple. I used the analog pins, and the sensors were just a circuit with a resistor that would be bypassed by the water. I used the 5V pin on the Duemilanove board to put power through the circuit, and then hard coded the numbers from the analog pins into the main loop.

I would have done a simple setup that allowed the water to close the circuit, but the sensors are very sensitive, and would react to my hand being near them when there was no circuit. I don't know enough about electronics to explain why...

As far as communication goes, I have a simple LED setup, with rows of 5 LEDs indicating the water level.

The easiest way I've found for communication outside is with the ethernet shield. I have some motion sensors that phone home to a central server via a network connection and it works very well. I used a wall wart for those.

What about bluetooth?

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