Hi,
what would be your suggestion of approaches to make the pool wall triggering part of a pool bottom stopwatch to show lap times?
Something simple and reliable to detect when the swimmer touches the wall to mark a lap as complete and finish the time counting?
really greatful for all your thoughts!
Martin
What technology is used in existing and mastership proved pools? Probably built in and You are not prepared to crack the wall in the pool to install anything like that.
Some water tight tiny pillow sensing the preasure from a pushing hand?
many thanks for the answer! Will think along this line...
I guess probably there isn't an easy way to detect capacitance/magnetic field or anything just with an wire loop, or maybe with a motion sensor
some pressure sensor fixed on the wall would be easier to implement, I guess...
Keep it simple is an advice given in a veriaty of situations.
What do they use at the Olympics?
The pool wall is very solid, water conducts electriciy, swimmers aren't magnetic.
Clearly an optical beam-break detection would work, but you'd need enough beams to cover the various depths at which the swimmer contacts the wall, and waterproof accurately aligned optics at each corner of the pool. Might be an issue with light absorbtion at IR wavelengths and long optic paths though.
However with more than one swimmer how can you tell them apart?
I think you have to line the wall with some sort of thin hydraulic pressure pad, with a separate chamber for each lane, and a little bit of pipework to the pressure sensor array. Or simple plates/boards with vibration sensors?
Distinguishing between finger pressure and waves slapping the wall will be difficult.
But it is obviously possible. Find out how the commercial units do it.
It seems to be not a "simple" job to create a "reliable" system...
Our familiar touch pads mounted on the wall in each swimmer’s lane register a touch of between 1.5 and 2.5 kg anywhere on the pad’s surface. This amount of pressure eliminates “ghost touches” resulting from water movement.
That's from: https://www.swisstiming.com/sports/swimming/
Commercial touch pad...60" x 22"....approx 900 US dollars:
Wow, thanks for all your awesome input, I didn’t expect so many useful answers.
What about then the use of a wristband/ankleband with a strong magnet and a wire loop to detect an induced current? What would be your thoughts about this approach?
Thanks,
Martin
Look at Load Cells. You can make something like this to hang into the water. The swimmer would hit the pad with enough force to be seen by an analogInput.
The wrist magnet detector would not be reliable. First, the swimmers would probably complain about the weight, and second, they would have to get pretty close to a loop for this to work, and last, the sensitivity of each sensor would vary because of background magnetic interference, such as wiring conduit for the pool lights, water pipes, etc.
Buy a waterproof wristwatch with stopwatch function.
what if I forget to hit the the split time button in one lap?
I guess, for the use planned, that kind of approach would be more elegant:
