Electronics > Projects, Designs, and Technical Stuff

Water leak alarm

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saturation:
This device is designed to work under those conditions.

http://www.amazon.com/Glentronics-BWD-HWA-Basement-Watchdog-Sensor/dp/B000JOK11K/ref=sr_1_3?ie=UTF8&qid=1343837094&sr=8-3&keywords=water+alarm



I paid $4 each for mine.  Essentially its a CD4000 series oscillator with a buffered switch connected to those contacts; the contacts are on a 3' long wire than can be removed from the unit and positioned anywhere that water collects.  If you short the contacts, it lets out a piercing siren, and its powered by a 9V battery.

Just remember to replace the battery every 5 years and you're set.  I've had mine for almost 15 years, and its saved my floors 2x when a pipe burst and a water heater leaked.  To remember to change batteries I put the change schedule on my Casio databank watch, which can keep recurring dates in memory indefinitely.  In rings annually, but it reports the install date, and reminds me to also check the operational status.  I write the install date with sharpie pen on the battery and change it every 4 years instead of 5 for a safety margin.

You can easily build this circuit, but I doubt you can do it for $5-10 each unit.


--- Quote from: ProDrawerCom on July 31, 2012, 01:20:06 am ---I know almost nothing about electronics. Tried a year or so ago at age 65 to learn it. My eyesight went bad within a few months and I could no longer read schematics or component numbers, etc. But I’d like to build something to protect my new kitchen hardwood floors. Thought I’d get some kind of a plastic pan to put under dishwasher and refrigerator and sink. The pan would be slightly tilted to let any water drippage roll down to a collector trough which would set off an alarm or just an LED. Can someone tell me where to start? Thanks

PS: I know that water leak alarms are commercially available, but none of them are designed just the way I want mine to be.

--- End quote ---

6502nop:
This basic circuit was originally designed for your purpose, but used as a simple continuity tester. All you need to do is use galvanized probes for the water detection (anything that won't corrode), and make sure you get a -buzzer-, not a piezo element. A buzzer will have it's own built-in driver. If you're in the States, Radio Shack has them for about $5. Add three resistors, a transistor, and a 9V battery/clip on a perf board, and you're done.

My water alarm was made on perf, screwed to an old 5.25" plastic panel from a PC case, with two copper stand-offs poking out the bottom for the probes. I just plopped it on the floor with the stand-offs hanging over the edge of the sump, and if the pump failed, the water level would rise, contact the two probes, and sound off. Worked great, but I had lots of probe corrosion problems.

nop

jucole:
Some dishwashers etc are fitted with a shallow tray underneath, and in the tray is a polystyrene float which triggers a microswitch, the switch in turn tells the controller to shut the inlet water off and run the drain pump, the inlet water system is called an Aquastop.  I think catching the water is important, as a small drip unnoticed does a great deal of damage before you even know you have a leak.

saturation:
With this transistor design the input impedance at turn on is at worst ~12k compared to the CMOS design which is in the megaohms, corrosion is faster with higher current.  For the 'watchdog' the amount of corrosion on the probe tips has been ~ nil in 15 years.


--- Quote from: 6502nop on August 03, 2012, 05:58:41 am ---This basic circuit was originally designed for your purpose, but used as a simple continuity tester. All you need to do is use galvanized probes for the water detection (anything that won't corrode), and make sure you get a -buzzer-, not a piezo element. A buzzer will have it's own built-in driver. If you're in the States, Radio Shack has them for about $5. Add three resistors, a transistor, and a 9V battery/clip on a perf board, and you're done.

My water alarm was made on perf, screwed to an old 5.25" plastic panel from a PC case, with two copper stand-offs poking out the bottom for the probes. I just plopped it on the floor with the stand-offs hanging over the edge of the sump, and if the pump failed, the water level would rise, contact the two probes, and sound off. Worked great, but I had lots of probe corrosion problems.

nop


--- End quote ---

6502nop:
Actually, the problem with my alarm wasn't corrosion due to excess current draw, but corrosion due to my probes being copper and suspended over a constantly wet sump pit. The petina that developed was so bad, it failed to alert when needed. I plucked it up off the edge, put my wet finger across the two screws on the top (nickel plated, I think), and off it went. I then flipped it over, and there was my problem. The wires, solder, connections, and components were all good - just the copper went bad. Hence, my recommendation for galvanized probes.

Remember, I also built this to use as a continuity tester, which I threw into a small cardboard box. That was... gee!... 14 years ago, and it's still working. So, input impedance had nothing to do with it. One had copper terminals, the other just regular alligator clips. It was enviornment and materials, not current draw when activated (practically NO current draw when idle - no on/off switch is needed!).

nop

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