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  1. #1
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    Liquid sensor question

    Hi,

    I am working on this leak detector project. I am just learning and don't know much about it. Maybe someone has an idea of how to correct the problem. It seems like it might be something very simple, but I just can't seem to figure it out yet.

    Here is a video!

    Thanks!

    Water Detector Problem - YouTube

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    Re: Liquid sensor question

    Ok u need make c mos oscillator using the capacitor (u make yourself with 2 plate held together with plastic screw holding them apart )the freq will change when in/out of water.
    didnt quit get it what happens with your first sensor and what kind of sensor is it .
    the two isolated plates can be used as resistance or cap. detector.
    for 2mm water depth use a old printed circuit with 2 copper lines as near as possible and u can also design your self a "double comb" like design , its like inserting right hand finger between left hand fingers not touching each other.
    Last edited by dselec; 19th February 2012 at 17:28.



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  3. #3
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    Re: Liquid sensor question

    A description of the problem with relevant supporting information would be more useful than a video.

    Keith
    I started life with nothing and I've still got most of it left. (Seasick Steve)



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    Re: Liquid sensor question

    Thanks!

    Okay, Description of the problem is:

    I want to make a leak detector that will detect a tiny amount of water. I want the horn to blow loud until the battery goes dead. Right now the horn blows loud for a few seconds then barely works at all after the sensor cap is drained. I guess it has a cap in it?

    It is a simple circuit. I found by moving the probes very close to each other my problem is solved, but it looks like crap. I would like to make my own sensor, but I don't know what parts to use or what parts are in the one that I purchased.

    New Video:

    Water Detector Problem 2 - YouTube

    Click image for larger version. 

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  5. #5
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    Re: Liquid sensor question

    Just told u how.
    u can also build comparator with a 1meg resistor as sensor or make 4011 multivibrator that will save batt cause u will have pulsating alarm.



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    Re: Liquid sensor question

    Information about the sensor seems scant. It is only normally required to trigger an alarm, not maintain it. As it is a self powered DC device I wonder if the sensing is done with DC rather than AC in which case electrolysis around the probe could be a problem, causing gas buildup which breaks the connection. If you have an oscilloscope it would be easy to check. Even with a multimeter you could probably deduce what is going wrong.

    Keith
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    Re: Liquid sensor question

    Thanks,

    The information sounds good, but is way over my head at the moment. Someone told me that I might be able to use a transistor to boost the power going to the horn as it receives the small signal from the sensor. If a transistor would work, where in the diagram do you place it and what value of transistor, or type would I use?

    Sorry, but I just joined the forum today and I am at kindergarden level as far as electronics.

    As the water reduces the voltage, I need to get the voltage back up enough to blow the horn loud again and keep it loud.



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    Re: Liquid sensor question

    It is difficult to guess at the problem without knowing more about the sensor or doing some tests and measurements. The suggestion of dselec is good, bit it depends on whether you understand what he is saying.

    I have designed reliable water detectors in the past but always used AC to prevent electrolysis, and also very low currents. If you use DC you will cause electrolysis and end up with hydrogen collecting on one electrode and oxygen on the other. As well as the explosion risk (hopefully small) it will potentially break the connection.

    Rather than trying to make a 2 wire system, which may not be possible with that sensor, the addition of a 3rd wire may allow you to trigger a transistor which triggers the alarm. Another enhancement would be to make the additional circuitry latching so it doesn't rely on the sensor detecting water once triggered.

    Keith
    I started life with nothing and I've still got most of it left. (Seasick Steve)


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  9. #9
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    Re: Liquid sensor question

    Hello Keith About the electrolysis problem didn't think about it so thanks and now ill change my water detector to ac volts connected to a shielded wire i use in my basement as detector central wire an ref to outer shield .



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