Lengths Counter for Swimmers
An example application using speech synthesis, an accelerometer, and a magnetometer

There’s no lack of distance counters for walkers or cycling; but swimmers are reduced to mentally totting up how many lengths of the pool have been complete, for want of a counter suitable for their favourite sport. The project described on these pages got designed to build an electronic solution that takes care of this tedious counting. The result is a device that’s reliable, handy, light, discreet – and inexpensive.
Continue reading this Elektor article?
- Unlimited access to online Member Only articles
- 3 new editions Elektor Magazine (digital)
- More than 5000 Gerber files
- 20% member discount on e-books (at elektor.com)
- 10% member discount on Products (at elektor.com)
Stops Automatically.
What is Members Only
Elektor is committed to providing high-quality content on electronics, catering to tens of thousands of paying members. As part of this commitment, Elektor has launched Premium, an initiative that offers exclusive online articles to members sometimes even before they appear in the magazine.
Every day, members can access in-depth articles that showcase the best of Elektor's premium content.
This initiative aims to reward members with early access. Once logged in, members can easily enjoy this exclusive content and engage in discussions about featured projects. While Premium adds to the existing resources available, Elektor will continue to provide a wealth of free information.
Join the Elektor community today to take advantage of Premium and other benefits!
Materials
Gerber file
CAM/CAD data for the PCB referred to in this article is available as a Gerber file. Elektor GREEN and GOLD members can exclusively download these files for free as part of their membership. Gerber files allow a PCB to be produced on an appropriate device available locally, or through an online PCB manufacturing service.
Elektor recommends the Elektor PCB Service service from its business partner Eurocircuits or AISLER as the best services for its own prototypes and volume production.
The use of our Gerber files is provided under a modified Creative Commons license. Creative Commons offers authors, scientists, educators and other creatives the freedom to handle their copyright in a more free way without losing their ownership.
Extra info / Update
• small unit worn on the back of the swimmer’s head, under the goggles strap
• vocal announcement of distance without waterproof earpieces
• error rate < 5 %
• powered by two AAA cells
• compact: 96 × 47 × 24 mm
• system open to lots of other applications
Component list
Main components used in project
PIC18F27J13-I, Microchip, MCU, 8 bit, 128 KB Flash, 3 KB RAM (QFN28)
MAG3110FCR1, Freescale, 3-axis magnetometer w. I2C interface I2C (DFN10)
MMA7361LCR1, Freescale, 3-axis accelerometer w. analogue outputs (LGA14)
SSM2301RMZ-R2, Analog Devices, 1,5 W classe D audio amplifier (MSOP8)
ASLS-2, Assemtech, Acceleration sensitive switch (2G),
OKW Smart Case M A9066109 + A9166001 : recommended housing
ADS02008MR-R Projects unlimited : mini LSP 8 Ohm, Ø20 mm
Discussion (0 comments)