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Water level meter

Discussion in 'Sensors and Actuators' started by HyOxy7, Feb 11, 2020.

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  1. HyOxy7

    HyOxy7

    5
    0
    Feb 11, 2020
    Hi,
    I´ve been searching for a 12V water level meter for my HHO generator but I´m having some trouble finding the right meter.
    The 5L plastic reservoir contains distilled water with potassium hydroxide as the electrolyte.

    I need a sensor to detect Low water level, preferably a non-contact type like this guy:
    https://www.ebay.com/itm/5-12V-Non-...hash=item1f0b149ab5:m:mZMLQ22VaddyZgdT6xoWVzA

    You´ll find plenty of these on ebay, but from what I´ve read they only get triggered if they detect water, not the other way around.

    In my application, I would need a sensor closer to the bottom of the tank to make the buzzer go off when the water level drops below it.

    Thanks
     
  2. Bluejets

    Bluejets

    3,974
    818
    Oct 5, 2014
    It's an npn output and one can use it whichever way around one desires.
    AS the instructions in the link you provide near the circuit diagram explains.

    If you connect a relay, for example, to this output with change over contacts , you can drive whatever.
     
  3. HyOxy7

    HyOxy7

    5
    0
    Feb 11, 2020
    You´re right, it´s just a matter of connecting the black wire to the blue wire to reverse it. Thanks man!
     
  4. Bluejets

    Bluejets

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    818
    Oct 5, 2014
    Just be aware that output has a maximum handling current of 200mA and whatever you intend to drive with the sensor may draw more current than that.
    In which case a relay or similar would be required.
     
  5. HyOxy7

    HyOxy7

    5
    0
    Feb 11, 2020
    I´ll be using a small piezo buzzer in my generator, it shouldn´t pull more than that.
    I´m thinking about putting one in my car´s water tank since I had so many leaks already. Is it ok to drive it off the battery directly?
     
  6. Bluejets

    Bluejets

    3,974
    818
    Oct 5, 2014
    Piezo will be ok.
    As for the rest, the link shows a few different types of sensor.
    Some are 5 to 12v and others 5 to 24v so depends which unit you have as to use in your vehicle.
    Most 12v cars will go at least to 13.8v on charge so it depends on the unit as to whether or not it will survive.

    If your car has system leaks, then putting any device on the reserve tank would be pretty useless.
    It may dump excess water in there during heat-up period, but when required, the system has to suck the water back.
    If you have leaks, there'd be little vacuum.
    You'd have no excess water to pump into there anyhow.
    Most radiator detectors are a probe in the main tank top section so any loss is immediately obvious.

    I used to make them here. A 555 and probe in the tank with an audible alarm in the dash.
    Problem with most probe designs is the dc to the probe creates electrolysis that rots the probe and gives abnormal readings. Got around that by feeding a sort of 555 generated ac pulse just to the probe circuit.
    All my drawings went in the 2013 flood though so no longer here........more likely than not there would be many similar circuits out there.
    Then of course there are the newer type capacitive probes, all invasive though with metal radiator.
     
    Last edited: Feb 14, 2020
  7. HyOxy7

    HyOxy7

    5
    0
    Feb 11, 2020
    Sorry man, I completely missed the notification to your reply.
    About the voltage, I already ordered the 12V one, it might fry with ~14V. Didn´t think of that. We´ll see.

    I´m a bit confused about the car´s water system you explained...I´ll read more about it.
    My car is a bit old, it´s a Rover 25 from 2001. It just has a temperature gauge. When it ran without problems the water stayed at a constant level in hot or cold environment. When the water level dropped or the tank went dry I always found a leak somewhere. The engine has redline overheated a few times because there is no warning light. Hence my idea of putting one of those sensors to warn me before all the water is gone.

    Did the probes you use corrode with destiled water or did you use tap water?
     
  8. Bluejets

    Bluejets

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    Oct 5, 2014
    If you intend putting a level sensor in the reserve tank it will not work as you expect when a system leak is present.
    Look up how these systems work to get an understanding of why.

    Distilled water is not going to work either.
    Probes in my application were, as already quoted in my reply above, fed with a (simple explanation) "type of AC" from a 555 timer which eliminated any corrosion possibility.
     
  9. HyOxy7

    HyOxy7

    5
    0
    Feb 11, 2020
    You said: "Problem with most probe designs is the dc to the probe creates electrolysis that rots the probe and gives abnormal readings"

    I´m curious to know if you used destiled water or tap water when you tried the dc probes (before to switched to the Ac type)
     
  10. duke37

    duke37

    5,329
    750
    Jan 9, 2011
    AC will not guarantee hat there is no corrosion. A capacitance probe could be made from a piece of insulated wire and energised with high frequency signal. A special detector circuit would need to be used.
     
  11. Bluejets

    Bluejets

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    Oct 5, 2014
    As I said earlier, conductive probes will not work in distilled water.

    There are capacitive probes available quite cheap on Ebay.
    Normally used as a sensor for Arduino.
    Output is analog i.e. from 0v to 3v so you will need to use with Arduino or some other form of interface if you need to operate a relay or whatever.

    Just a side note:- if used, seal the sides of the pcb with epoxy or similar as the sides are porous.

    https://www.ebay.com.au/itm/Analog-...320889?hash=item3d97a72db9:g:bL0AAOSwWqtdt6xT
     
  12. Spie

    Spie

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    Mar 15, 2020
  13. Bluejets

    Bluejets

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    818
    Oct 5, 2014
    That was the Op's first choice in the first post.
     
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