Build a Wireless Water Meter for Your Home
California, where I once lived, is in the midst of a severe drought. Thankfully, I now reside in North Carolina, a much wetter state. But even here there have been years when water was in short supply and people were asked to conserve.
Most folks are happy to comply with such requests. But that’s not easy to do when information about your usage comes only once a month on your water bill. You could, of course, track usage more finely by hoofing it out to your water meter periodically and noting the readings. But who has the discipline for that? So I cobbled together a monitor that can show how much water my household is using in real time.
My system doesn’t require plumbing alterations, and it transmits the information via my home wireless network, so I can view water use on a connected device anywhere in the house. Now when my teenage kids take profligate showers, I can berate them with quantitative measurements!
To measure water flowing from the municipal supply, I employed a digital compass—that is, a 2-axis magnetometer—that I originally purchased some time ago from SparkFun Electronics to use as a direction finder. SparkFun no longer sells that module, but for even less money (US $15), you can now purchase a 3-axis magnetometer, which I suspect would work just as well or even better.
A magnetometer is valuable here because of the way mechanical water meters work. To isolate the gears of the actual meter from water exposure, a rotor is typically attached to a magnet in a separate chamber through which the water flows. As the water spins the rotor, this magnet turns another magnet in the meter’s gearbox. Consequently, these coupled magnets produce a magnetic field around the meter that varies depending on how fast the water is flowing.
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