This page describes portable timer system device that is designed to measure the walking speed of a person over a fixed distance (4 meters). It consists of two IR (infra-red) sensor boxes with companion reflectors and a central timer unit.

'Final Design:  Photo Album


Rev 2 System

These documents apply to the second Four systems under construction in June, 2007. Some small changes were made to correct errors in the PCB layout. The assembled PC boards should be interchangeable with the Rev 1 System.

Rev 1 System

These detailed documents apply to the first two systems delivered in January, 2006.

Design Notes

  • Measure time interval between interruption of two IR light beams

with 1ms resolution

  • Display last two measurements (with time stamps?)
  • Permit measurement of travel in either direction

A sketch of the timer unit front panel is shown below. The display is a 20 character x 2 line Optrex 51848 high-contrast LCD with white LED backlight. The display control and timing functions are performed by an Atmel ATMega8 microcontroller ( Data Sheet and a Dallas DS1305 real-time clock ( Data Sheet

Power will is supplied by batteries (6xAA size) inside the box, or a "wall wart" power transformer.

The sensor units are small boxes with an IR emitter/detector pair and a very small microcontroller to generate and receive the required pulse train for the sensor. A cable connects each sensor board to the timer unit.

'Future Improvements

When the Timer is first powered on, it should wait for a short period to eliminate the possibility of a sensor being falsely triggered before the initial test is ran.

Front Panel Sketch


Parts Options