Circuit Lake

Electronic Project and Circuit Collection

Personal Swimming Timer

03/28/2010 Category: AVR, Digital, Measurement, Microcontroller, Project, Timer

The AVR ATmega8 based swimming timer project help the swimmer to counts the lengths of the pool swum and calculates swimmer speed. The timer consists of two units – the timer unit, which counts and times length pairs; and the display unit which sits on the bottom of the pool and displays to the swimmer their lengths count and time. The timer unit has a small LCD display and buttons. Through this the swimmer sets up the pool size, the race length, and requests a race start. The timer unit then gives an audible start indication, and times the race. It sends the time and length count details to the display unit each time the swimmer turns. Both total times and split time (the time of the last two lengths only) are calculated and displayed. On the final turn it gives an audible last-lengths indication, said Clayton Gumbrell, the project designer.

Connected to the timer unit is a pool sensor (to detect the swimmer making their turn) and a transmitter (to send data to the display unit). The timer unit sits at the side of the pool with the sensor and transmitter device handing over the side in the water. The display unit consists of seven large 7-segment LED digits. It sits on the bottom of the pool, positioned to be visible to the swimmer just after their turn. It displays data sent to it by the timer unit.

Here is the unique features of personal swimming timer:

  • Optical buttons are used on the timer unit so that the unit may be completely sealed.
  • A pool sensor consisting of a series of optical beams is used to detect the swimmer. Two narrow tubes are hung in the pool at each side of the lane. Light beams are projected between these tubes which when broken indicate the presence of the swimmer.
  • The light beams and optical buttons use visible (red) LEDs. When activated these LEDs light up to indicate activation, and thus providing visible feedback to the user.
  • The timer unit sends data to the display unit through an optical link. It uses technology similar to that used for infrared remote controls, but adapted to operate using visible light, since infrared light is heavily absorbed by water.