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Pool alarm project

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mikesmixes

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Does anyone have any ideas on how to sense if something has fallen into the pool, ie. kids, animals, thieves. I am looking at this as a project idea.
 
a would suggest detecting a rise in water level (i.e. use a float sensor) but this suffers from false detection from the water rippling.

Other than that, maybe there is some way of using a PIR sensor? or maybe you could cover the pool with enough IR 'beam-break' detectors.

Tim
 
mike,

If something or someone falls into the pool it will create waves and this movement could be sensed whit a float. Maybe you could use an old style fueltank transmitter.

Ante :roll:
 
Sound waves are generated when a person (or object) falls in the water, too. Maybe you coulde use a piezoelectric-type transducer connected as a microphone and have your circuit listen for sound waves. This arrangement is also known as a hydrophone.
JB
 
They make a commercially available pool alarm, battery powered with enclosed tilt switch and piezo buzzer, it floats freely in the pool. When the water is disturbed the waves activate the tilt(pendulum?) switch which turns on the piezo thru a scr which has to be manually reset. The one I took apart also had a load resistor across the piezo to keep the scr turned on since the piezo draws very little current..The reset switch was a normally closed reed switch that required placing a magnet nrxt to it, this was done to keep it enclosed and water tight I suppose..
 
I was also thinking of some sort of float device, but i dont think that will pick up a crawling baby that falls in at the other end of the pool. I think the best mite be a "blanket" of IR. the "hydrophone" isnt a bad idea either, but wont that pick up the noise from the "creepy-crawly" pool cleaner?

Thanks for all the ideas, still looking into it. Let me know if any other ideas come up
 
I think you will find that the IR field will result in a large number of nuisance alarms caused by leaves, rain, wind etc. Many alarms use submerged hydrophones that have circuitry designed to recognized te disruptions caused by someone entering the pool, but ignore wave action of wind and automatic cleaners. Another concern is being able to detect entry under a solar blanket, which causes it's own set of problems with IR and surface disturbance.

As suggested above, I think a hydrophone, with filters to discriminate sudden changes in "backgroud" noise might be the most feasable, but likely the most difficult to design.

There is a ASTM standard # F2208-02 "Standard Specification for Pool Alarms." The ASTM document can be purchased from the ASTM website, but many are available in larger reference libraries on microfiche, often they will describe the technologies used, reference materials, and design criteria.

link to ASTM standard:

https://www.astm.org/cgi-bin/SoftCa...PAGES/F2208.htm?L+mystore+vdcr0992+1094078235
 
The pool alarm should be very precise and should not permit false alarm that's why i suggest that you should use a water level alarm that monitor the pool and will activate an infra red alarm to verify the alarm .
By this method you can save a lot of power because water level alarm can be mecanic more than electric and the IF will be activated only to assure the alarm and for a little time .

www.electronic-circuits-diagrams.com/alarmsimages/alarmsckt6.shtml
**broken link removed**
 
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