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Choosing a sensor for detecting swimming pool entry

pettitda

I'm looking for ideas on how to sense when a person or animal has entered a swimming pool.  There are several devices on the market that claim to do this, but the reviews are all pretty horrible.  False positives seem to be a big problem with existing products.  I'm thinking that something like an infrared camera would work but it would take considerable effort to set up the detection area (i.e. where the pool is) in the camera's view.  Does anyone have an idea that's not prone to false positives (i.e. leaves falling in the pool, wind blown water, etc)? 

  • I found the following FLIR camera that might work except that it is back ordered:  https://www.sparkfun.com/products/13233

  • Pretty tough to account for all possible sizes, methods of entry and entry points. If you need definitive sensing, I would use multiple sensors, a microphone, several capacitance sensors and a camera and software.

  • Look at the new Grideye or the new TI Time of Flight IR sensors.

     

    Both should cover the area you are looking for with the sensitivity you need.

     

    DAB

  • Fill the pool with green slime and add a "EWW" detector.

    >>"person or animal"

    What size animal?  Squirrel, dog, moose, chipmonk, tweety-bird, gecko, salamander.

    A big splash might be detected with a water level sensor.

    You could set up IR transmitters and receivers (break the beam type) around the perimeter.

  • in reply to DAB

    I looked at the grid-eye sensor and the range was only 16 foot.  I'm hoping to cover a 27 foot diameter pool.  Perhaps it could be done with multiple sensors. 

  • in reply to rsc

    Fill the pool with green slime and add a "EWW" detector.

    Filling the pool with something other than water would not please the wife.  But, thanks for the laugh. 

     

    What size animal?

    The animals are approximately 5 lb dogs.  For some reason they think they are cats and want to climb onto the ledge of the pool (above ground) and walk around the perimeter.

     

    A big splash might be detected with a water level sensor.

    I have a feeling a water level sensor will not detect a 5 lb object falling into a 18000 gallon pool.  The displacement is fairly small.  I believe this is what the currently available devices use and false positives are a problem.

     

    You could set up IR transmitters and receivers (break the beam type) around the perimeter.

    The IR transmitter/receiver sounds interesting but I'm concerned about the number of them required to produce a grid fine enough to detect the dogs.

  • Hi David;

    How about a water level sensor that looks at the change with respect to time of the level sensed. In other words a wave detector. Anything of any size that enters the pool is going to splash and move creating waves. If your wave sensor had a resolution that could sense one or two cm deviations you could program a microprocessor to apply a formula to differentiate between environmental waves such as those produced by the wind and more random waves such as those created by a dog or person.

    John

  • Hi David;

    Another idea might be to deploy a beam along each pool edge such as those used to detect something passing under a closing garage door. These light and sensor pairs seem to work quite well at 4 meters and probably can be extended. to greater distances. This would not detect the entry to the pool only a potential entry by an animal or person as they break the beam on their way to the edge.

    John

  • in reply to jw0752

    Ho John,

    IMHO it is not so efficient in a swimming pool where more than one can enter in the water. And there are mani other possibilities that other waves are generated unexpectedly. Then also add the option of different beaviour of the waves deoending in the entry point. This implies I suppose, using this method ti generate a lot of filters to detect the right event to sense, and only it.

    As far as I know this kind of detection is not new and I see teo possible teliable ways depending on the needs. In the case you should only detect the presence in water an rfid sensor is sufficient and the tag can be extermely small and easy to wear also for a swimmer (tipically wearing very few dresses   )

    In the case where the detection of the exact instant is a key factor instead a laser or IR sensor is better.

    In both cases therr is the advantage that very few electronic parts should be waterproof.

     

    Enrici

  • in reply to jw0752

    I guess I didn't make it clear that the pool is round.  So, there are no straight edges.  However, I might be able to use multiple pairs of sensors arranged in a pattern (see below).  Of course, it wouldn't detect something entering the center of the pool, but that is an unlikely occurrence.  I will calculate how many sensors it would require to cover a 27 foot diameter pool out to say 2 foot with gaps no bigger than 6 inches, but I think it must be large. 

     

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