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Ultrasonic Water Level Sensor

Discussion in 'Sensors and Actuators' started by SAMSTER5, Dec 2, 2017.

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    Dec 2, 2017
    I'm looking into creating a solid state (for the sake of longevity, and to avoid the need for maintenance) device that would detect when a water level has dropped below a certain level, and send a simple shutoff signal to external equipment when this happens. Ultrasonic was chosen because it is solid state, and because unlike a laser, there's no optics to get dirty over time.

    Going off of my limited understanding of electronics, it would likely involve an ultrasonic sensor, and something that would A) control the sensor, B) interpret the data from it (so that short-term changes in water level don't trigger the shutoff signal), and C) send the shutoff signal to the external equipment.

    Is there a microcontroller that would do the trick, or even a preprogrammed chip of some sort that I could simply connect to the sensor and call it a day?

    Thanks for the help.
  2. hevans1944

    hevans1944 Hop - AC8NS

    Jun 21, 2012
    The easiest, simplest, way to sense when water level has dropped below a certain level is to use a small plastic float (closed-cell styrofoam works well) inside a vertical plastic tube with one open end of the tube immersed in the water. The other open end extends into air. Now, just detect position of the float in the tube. Simplest way is to use a small rare-earth magnet, contained in or on the float, to actuate a small magnetic reed switch mounted externally to the outside wall of the tube. (Your requirement A) Be sure to waterproof the magnet and connections to the reed switch. You could use an ultrasonic transducer to detect water level, but IMO this is overkill, unless hazardous liquids require such "non contact" sensing.

    Any small microprocessor (Arduino, PIC, Basic STAMP, PicAxe, Raspberry Pi, etc.) can be programmed to ignore short-term oscillations in "trip point" actuation (your requirement B) before declaring an event that will send the shut-off signal to external equipment. Choice depends mainly on how you want to program it. Some of us here can help you with that.
    shrtrnd likes this.
  3. shrtrnd


    Jan 15, 2010
    I agree with hevans1944. I've installed many ultrasonic level meters for hazardous/toxic mixes. There's nothing cheap or easy about them. I don't know your application, but if this is just water level, there are plenty of cheap and easy ways to do it, and hevans1944 gave you several good options to consider for a start.
  4. Externet


    Aug 24, 2009
    There is a weirdish water level sensor used in foggers. I never understood its workings after reading the patent, but may be of use for ..."detect when a water level has dropped below a certain level"...

    That 'arch' in shrink tubing contains it, stops the fogger when water level drops to it. :

    Newer ones use a different looking sensor :


    Automotive coolant sensors plug to radiators, available at car parts stores, and are sturdy.


    And more :


    A neat one :


    available at :

    Last edited: Dec 5, 2017
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