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Swimming lap counter

Mon Sep 01, 2014 5:02 pm


I'm a swimmer and I'm tired of having to keep track of my lap count. There are some automatic lap counters on the market, but I haven't found one that I like (it usually involves wearing a bulky watch).

So I thought I might be able to make one myself. What I've been thinking is that I could use RFID – me wearing a RFID tag and having something (a Raspberry Pi) on the pool edge sensing me every time I pass and keeping count.

Is this possible? Does anyone have a better idea of how to do it? Is the Raspberry Pi even the right thing to use?

How do I go about doing this, then? I have no experience with the Raspberry Pi, but I have done some PIC programming (Assembly) and some "ordinary" C programming.


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Re: Swimming lap counter

Tue Sep 02, 2014 3:32 am

RFID won't work very well with water. The water will decrease the signal and it won't be powerfull enough.

Also the range you want will need a very strong transmitter like the one you have on toll highway.

There is some other options which doesn't need anything to wear.

- Sonar detector.
- Light curtain.
- Acoustic sensor. ( you will make more noise in water when you are near). With 3 sensors you could figure out your position.
- Pressure sensor on the wall of the pool.
- Webcam motion Just a webcam on a 4 feet pole will do the trick. Use motion and adjust the trigger.
- Infrared sensor . The one for alarm system. You should be able to adjust the sensitivity to trigger it when you are less than 2 feet of the sensor and it could be done into a very small box with a small cpu since you know how to program them.

I think the simplest will be the pressure sensor. A small template that you push when you switch side.
But the I.R. sensor will be ideal in a public pool but it won't work if you go under water when you turn.

What about an sealed accelerator that will detect the change in direction and count them. This could be very small with a small 2532 3V battery. Check My egg crashing emulator ... 37#p377337


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Re: Swimming lap counter

Tue Sep 02, 2014 7:10 am

You're going to find it hard (if you're not alone in the pool) to detect yourself but not anyone else.

So you need some way to recognise your head in the water amongst all the others.

If you wear goggles, you could put an IR LED on both sides, with a simple square wave oscillator (and a button battery and a layer of epoxy or latex insulation), say at 8Hz. Then use the NoIR camera at a low resolution and look for pixels that flash at 8Hz. If you can put that on the balcony then you might be able to track your progress with a reasonable resolution.

I don't know what water does with IR - you might get a lot of reflections off the surface.

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Re: Swimming lap counter

Tue Sep 02, 2014 7:27 am

...or just learn to count. It will help stave off Alzheimer's in later life.

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Re: Swimming lap counter

Tue Sep 02, 2014 12:03 pm

I think you need to apply a KISS principle here. You'll probably do much better with a physical micro switch activated by a board you'll use to touch or kick off from as you complete your tumble turn.

The timing mechanisms for competitive swimming use that type of simple hardware. ... s/touchpad

If you do that you'll not just get a lap count you can also get interval times.
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Re: Swimming lap counter

Sat Sep 06, 2014 11:20 am

Hi all,

I also want to make this project. I have been searching some alternatives to check proximity or to check every lap...

I'm looking for any device to take it in the swimsuit, swimming goggles o under swim cap, something small that provide proximity to RB PI or phone.

Any idea of how could I make it?

Off topic: Goolge have some patent to do it:

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Re: Swimming lap counter

Wed Aug 29, 2018 6:53 pm

Hello, what? I wanted to ask you if you finally found something about this. I would like to build exactly this. Panels that control the total and partial time.
Thinking of swimmers who are alone in the lane, as in a competition.
Thanks for any information you can give me, and sorry for my "English".

¿Hola que tal?, queria consultarte si finalmente encontraste algo sobre esto. Yo quisiera construir exactamente esto. Paneles que controlen el tiempo total y parcial.
Pensando en nadadores que van solos en el carril, como en una competencia.
Gracias por cualquier informacion que me puedas dar, y perdon por mi "ingles".

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Re: Swimming lap counter

Thu Aug 30, 2018 9:43 am

The way I'd do it is to wear a magnetometer so you can tell when you have changed direction, count how many times you have. Indicate which lap you are on, that is "start from 1", and it will also be number of laps completed when you leave the pool.

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Re: Swimming lap counter

Thu Aug 30, 2018 10:14 am

It looks like things like fitbit can track swim lengths.

You might be able to use an accelerometer to get a crude estimate of position or direction. Integrating acceleration gives velocity and integrating velocity gives you position. That its basically adding values. It's usually noisy data and the value drifts a lot but it might be good enough to tell which end of a pool you are at.

You could use haptic feedback (e.g. vibration motor) to tell you how far through a pre-set distance you are so you don't gave to look at a display.

You could wear an armband or swim cap with a colour code (single colour or combination)

Something like this ... olor_Codes
When the colour code is detected you are in view on another lap.

You could do something similar with QR codes or the like.

You could wear an IR LED that sends an IR remote control code and a receiver poolside. Setup so that it only reads the transmitted code at short range. Each period of a few seconds where reads occur is a lap.

You might be able to limit the range of a 433 MH transmitter / receiver pair, BLE, ZigBee etc so that it only connects at short range (say <5m) at one point on a lap by using directional and/or low gain antennas.

RFID is probably too short range, especially if it has to get through water.

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