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Drowning alarm

Detects when a swimmer is having difficulty
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NO, not pool guard, or a computer vision system.
This will work at the seaside, and at the pool, and it can be set to guard strong swimmers, and weak swimmers.
A new swim hat has a pressure sensor on the forehead. Immersion in water is detected by an increase in pressure. Once the forehead is in the water, it can be assumed that the face is also in.
When the immersed time limit expires, then a remote key fob is alarmed by a radio signal (similar to car remote system). Longer times are for those that jump in, briefly dive under and so on. Short times - 1 second - are for small kids who need instant assistance.
The cap is designed to float in case of removal, but it will float so that the sensor is under water.
Flashing LED's may be added to assist in location amongst many children.
Inspired by a trip to the pool with my 1 year old daughter.
This one is potentially a lifesaver - can anyone assist in improving any of the ideas?

Edit: I have reconsidered the sensor, and have found that a conductive level sensor would do the trick.
Simple: it consists of two electrodes widely set in an insulator. When there are a few splashes of water, the resistance between the electrodes is not changed much. But if immersed, then the resistance between the electrodes drops enough to be sensed. Cheaper and lighter than a pressure sensor, too.

I have also reconsidered the alarm signal: instead of a radio signal, there could be an acoustic transmission. A piezo device on the swim-hat sends sound to a hydrophone which is floating nearby. The hydrophone has an inbuilt alarm, and light. The hydrophone could be a permanent installation in pools.
This is because once the swimmer is under water, then any alarm on the swim-hat would not be heard.

Scad mientist had a brilliant idea: use a continuous radio signal, and when the transmitter is immersed, the signal is lost. Water is a very good signal attenuator, and the system would be fail safe.

Ling, Mar 22 2004

Underwater radio communications http://www.qsl.net/vk5br/UwaterComms.htm
A nice explanation of why I cannot use this technique [Ling, Oct 04 2004, last modified Oct 05 2004]

Drowning statistics http://www.poseidon.../us/statistics.html
[Ling, Oct 04 2004, last modified Oct 05 2004]

[link]






       While this is a good idea in principle, I'm not sure if a pressure sensor would work: the increase in pressure in shallow water would be slight compared to atmospheric pressure.
kropotkin, Mar 22 2004
  

       Maybe it polls/sniffs for the presence of nitrogen or some other component of air but not water.   

       Don't know how to do this but it would be nice if it could give some rough idea of the location of the swimmer. Signal strength is often an unreliable measure of distance but I don't know what else would make sense and be affordable.   

       Affordability is key for something like this. The system needs to be as pervasive as possible.
bristolz, Mar 22 2004
  

       With small children, there is no substitute for keeping a close eye on them at all times, so you should leave them out of the equation.   

       This might be an interesting solution for a pool with no attendant, or the sea, but I don't think you have come up with the right technology.
DrCurry, Mar 22 2004
  

       Having been a EMT responder on a 1 year old drowning, where the child was out of sight "only a minute", I understand your concern. I would hope that you do not intend to depend entirely upon electronics, but using it as a supplementary aid. Nothing beats the wary eyes of a protective parent or guardian.   

       Instant assistance means being close enough to respond immediately.   

       I am struggling with this at the moment. Sorry.
pilgrim, Mar 22 2004
  

       To avoid false alarms the device could monitor heart rate too. It usually goes up when air runs critically low.
kbecker, Mar 22 2004
  

       Thanks for the comments.
What I have in mind is a pool (or beach) full of shouting kids, and a lifeguard on duty. This is a supplement to that situation.
With 1 year olds, only a couple of seconds out of sight is too long: 1 minute is crazy. I agree the best is separation.
Ling, Mar 23 2004
  

       Has anyone realized that radio transmitters don't work when submerged? The antenna has to be in the air to work. This is why subs use sonar, not radar.
zigness, Mar 23 2004
  

       Perhaps attach a compressed air cartridge to the swim hat, filling the hat when triggered? I realize this won't keep the child's face out of the water, but it will bring them to the surface and provide a visual cue that something's wrong. Perhaps add a loud alarm, and nobody will miss the problem.
Worldgineer, Mar 23 2004
  

       "The CommuniCap is tomorrow's safety device for today's children. Notice the 50 foot long antenna - perfect for fishing and swimming at once. And the miniature nuclear power supply? It doubles as a neck warmer." (related to [bz]'s now deleted comment about VLF and ELF radio signals needing long antennas and very high power)
Worldgineer, Mar 23 2004
  

       refined main idea & tidied up
Ling, Mar 24 2004
  

       [UnaBubba], Actually I knew that about ELF, but those would require extremely large antennas, so I dismissed it.
zigness, Mar 24 2004
  

       Why not use the dificulty of transmitting radio waves through water to your advantage? Make the transmitter transmit continuously. If the antenna goes under water, the signal is lost. If the signal is lost for too long, sound the alarm. This also sounds the alarm if the child wanders too far away or if the battery in the transmitter dies.   

       Keep it simple...   

       Still, I wonder how effective it would be. It seems to me just as likely to give a false sense of security as to actually save lives.
scad mientist, Mar 24 2004
  

       [scad mientist], that is an excellent idea!
False sense of security? See link for number of "supervised drownings".
Ling, Mar 24 2004
  

       When I was wee I had a swimming cozzie with foam inserts in it all the way round, about 10 of them. They kept me up on top of the water without restricting my arms for swimming. During the course of about 6 months my parents removed the floats one by one which meant I slowly took more and more of my own weight by swimming and by the end of the process was swimming all by myself. I haven't seen these anywhere and can't find a link except for great big life jacket things which look terribly restricting as though the poor kid in it would just bob around like a cork.
squeak, Mar 25 2004
  

       world why fish with the 50foot antenna, just use it as a rope and haul the kiddy in
engineer1, Mar 26 2004
  

       A sad, sad note: today, an 8 year old boy drowned in the swimming pool where I normally take my daughter.
Ling, Jul 10 2006
  

       //There is a communications network using ELF (Extra low Frequency) radio, for communication with submarines.// Are you trying to call whales (not Wales) for help?   

       // A friend of mine has developed a pool alarm that triggers when the water surface is disturbed// [UnaBubba] I hope your friend doesn't think this idea is new... my grandfather had one of these 20 years ago.   

       [Ling] I am sorry to hear the news of the boy. As a parent, I can only imagine what that must be like.
MoreCowbell, Jul 11 2006
  
      
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