water-activated switch

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H2IZZO

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I would like to make (or buy if it exists) a switch that will switch off 120V electrical outlet if a probe gets wet.

I live in Fairbanks, AK and it has been -25F at my house for over a week.

The drain that my washing machine and water softening unit drain into recently froze and backed up despite being well encased with spray foam insulation where it passes through the crawl space under the house.

I have made further improvements to the insulation but am nervous that it might freeze up again, especially since I am about to install new hardwood flooring.

So, I would like install a branch in the drain that upon backing up will back water into a catchment. In the catchment I would like to place a sensor, that when wetted will cut power to the outlet that supplies the washer and water softener so that they shut down and do not output anymore water.

Any and all suggestions would be greatly appreciated!

Stay warm!

DR
 

First thing I would try is heat tape for the pipe inside the insulation, possibly with a thermostat, to help prevent the pipe from freezing.

Is the catchment deep enough to use a float switch?


Torben
 
I googled on "water sensor" and on the first page I found numerous commercially available sensors as well as some do-it-yourself circuits that could be adapted to your situation. I would have expected to get way too much back by googling so I am not criticizing you. I know they make sensors like that to detect overflow, leaks, condensation, etc.

I'd try to adapt a float switch (already suggested) though it may not be as much fun as developing the circuit. I'd even experiment with a very low current relay with the "switch" being two plates with a small separation. When flooded with water sufficient current might flow to close the relay. Without knowing your skill level it's hard to make a specific recommendation.
 
Hi,

water sensors switching 110 and 230V power are normally installed in each laundry washer. Try to get one of a junk yard. They use a diaphragm and a rubber hose to dunk into the water to move the diaphragm. In some machines you can find adjustable pressure switches of that kind. Some of them use a worm screw and others have a three position lever to change sensitivity.

Boncuk
 
Bizarrely, the Lee Valley catalog which arrived today included a product I haven't seen them selling before: a water leak alarm for which you can buy additional sensors at $6.95 (for just the sensor).

http://www.leevalley.com/garden/page.aspx?c=1&cat=2,42194,51137&p=51137

Seems like that could be just about perfect for your application. You could even buy the whole thing and hack the alarm to trigger another circuit to shut the valve instead of (or in addition to) sounding the alarm.


Torben
 
Water sensor switch actuator


I have "invented" the worlds simplest water actuator for a switch that requires less than one pound of pressure. It uses no batteries and can be made for just a few cents! For pictures and description, go to:
Simple Moisture Sensor. Photo Gallery by Rolf at pbase.com
 
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Simple and elegant (and a cool example of lateral thinking). One-shot, but for an emergency alarm which isn't expected to be triggered very often I'd think that's fine.

If the water's rising high and fast then keeping the switch dry might be important.
.

Torben
 
Dry switch or low voltage......


Good point Toben. For safety's sake there should be no 110v /220v exposed connections where there is a chance of standing water.
But that doesn't detract from the usefulness of the "invention". The use of safe low voltage control voltage to control the line voltage is a simple and common practice. It slipped my mind because I am using this as a low voltage alarm.
 
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Oh, I just meant a low voltage control signal anyway, say run to a micro roller switch or something. Or the clothespin could even just separate two wires.

I seem to remember making switches with clothespins when I was a kid, by sticking 2 thumbtacks through the wood of the pinching end of the clothespin with the heads of the tacks facing inward (toward each other) and attaching wires to the slightly protuding points, then bending the points over flush with the wood. Then I glued one side of the clothespin to a base to keep it steady, and the free side of the clothespin then acted like a spring-loaded NC switch. I never considered trying to make an automatic water switch like you did, though--very nice idea.

Darned if I can remember *what* I switched with the things; I just remember making them.


Torben
 
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