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Easiest water alarm, period.

Discussion in 'Electronic Projects' started by joecool85, Apr 18, 2007.

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  1. joecool85

    joecool85 New Member

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    [​IMG]

    I have it all working now, simple and works perfect.
     
  2. Sceadwian

    Sceadwian Banned

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    The circuit will work fine to start, but long term use poses problems. The electrodes will build up an oxide layer, or a sludge (hard water or other sollution impurities) So will require cleaning on a frequent basis to sustain any kind of reliability.
     
  3. joecool85

    joecool85 New Member

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    Sort of, ideally it will never be submerged. I'm putting mine next to my sump pump, and unless I have a sump failure (it does happen every so often) they won't get wet. But the few times they do shouldn't create a lot of corrosion. Also, even with corrosion, this circuit should function fine as it isn't horribly critical what the resistance is between the two probes as long as there is some. I tried it with filtered water from the sink and it worked still! Heck, even moist fingers set it off.
     
  4. dave

    Dave New Member

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  5. Sceadwian

    Sceadwian Banned

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    Electrodes, especially copper still corrode in air, at the very least it should be suggested that the leads should be tinned, or preferably gold electrodes. My work environment is massivly corrosive (even ambient air) so something like this would have to be cleaned every day.
     
  6. mneary

    mneary New Member

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    Most of us know what you actually intend, but:

    The emitter should not be connected to "ground". It should be shown connected to the negative terminal of the supply (battery), which in the practical application should not be grounded.
     
  7. mneary

    mneary New Member

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    I don't know what your impurities are, but at copper.org, they say copper oxide is a conductor. [edit] Sometimes it's used as a semiconductor, and at extremely low temperatures it's a superconductor. [/edit] Since this circuit will trigger when the electrode resistance is megohms, I don't see daily cleaning needed in a basement or cellar.

    More likely they will need occasional cleaning because dust, mold, and insects could cause false triggers.
     
    Last edited: Apr 18, 2007
  8. joecool85

    joecool85 New Member

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    I don't see dust or insects causing a false positive, but I suppose mold could eventually. The circuit itself is good though. I'm using stainless steel for my probes, I doubt I'll ever really need to clean them.
     
  9. TheVictim

    TheVictim Member

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    It is also conceivable that the electrodes could oxidize over time without any contact with water and present enough resistance when wet that the transistor would not have enough base-to-emitter voltage to be in an active state. Having a bias on the transistor would then require you need more circuitry to determine a trigger threshold. Once again simplicity would have to be sacrificed for reliability.
     
  10. Sceadwian

    Sceadwian Banned

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    Pass the tips of your electrodes through a lighter flame to add a little carbon, see if it still works.
     
  11. Nicksan

    Nicksan New Member

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    Does this circuit work on a breadboard?
    I just tried it and nothing, except the piezo kept going off, I checked it and made sure the Transistor was good and still nothing.
     
  12. Hero999

    Hero999 Banned

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    Have you check you're connecting it up correctly?

    Is there any mositure residue on the breadboard?

    Try drying it with a hair dryer, it might have condensation or sweat from your fingers on the board.
     
  13. Gaston

    Gaston Member

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    why not just use a float with a mechanical switch? it seems like that would be the simplest and most reliable
     
  14. joecool85

    joecool85 New Member

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    Flip your transistor around, sounds like you may have it in backwards.
     
  15. Leftyretro

    Leftyretro New Member

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    I have seen many methods of detecting liquid level in sumps working in a large refinery. The most reliable I've seen is a mercury switch mounted inside a rubber oblong bulb about 3" in diameter and 5" long. When liquid is below the bulb it hangs straight and stays an open circuit. When floating it would turn on it's side and close it's contacts. The problem with direct electrical probe type detectors is that we sometimes get oil and other hydrocarbons instead of water at other times, so we can't count of the dielectric or resistance properties of all the possible liquids.

    Some time we use two such float switches at different levels to start and stop sump pumps to keep the sump level clear. Also a third even higher mounted float switch is used to generate a high priority alarm to let us know that there is a problem with either the pumps or too much liquid for them to keep up with.

    Lefty
     
  16. joecool85

    joecool85 New Member

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    While I agree about the floater being better for multiple fluid types, I designed this for water and only water. Hopefully that would be the only fluid flooding out my basement.
     
  17. Rolf

    Rolf Member

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    Simplest of all; Paper sensor.......

    I guess it is a little difficult resetting this one:
    http://www.pbase.com/sinoline/simple_moisture_sensor
    But I am sure that could be worked out, because I have.
     
  18. Leftyretro

    Leftyretro New Member

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    Of course water is probably all your basement will ever see, but think about long term reliablity and ease of testing, fewest components, etc. This kind of application can help save you a ton of $$ in damage and the the sensor portion needs to be as failsafe as you can come up with. I still vote the simple float switch if it was my basement. Basements are rare in California but sump alarms are common.

    Now what I need is an earthquake alarm circuit that gives about 5 mins warning of a big one :D

    Lefty
     
  19. joecool85

    joecool85 New Member

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    I trust my circuit. Besides, I'm living in an apt and my landlord didn't find it necessary to install an alarm, so I made one.
     
  20. Rolf

    Rolf Member

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    I would like to see.............

    So if you don't have a sump pump; where do you find a float switch that operates in a (aprox) 0.01" of water? After all you do want an alarm that senses the very appearance of water.
     
  21. Leftyretro

    Leftyretro New Member

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    Well never owning a basement, I don't know their normal drainage management. Is there no normal exit for water? If the floor is completely sealed then I guess one would need to find the lowest spot (unless non-slopped and perfectly level) and utilize something other then a float switch of course..

    Lefty
     
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