Timing System Plans

This timing system was designed by Al Champlain of the Happy Hurdlers. They are excellent for training to get consistent and accurate times.

Features include

Materials Needed and Radio Shack Part Numbers

QtyNamePart #
2Infared beams49-551
1SPDT switch1275-634
2SPST switch2275-406
 #56 screws and nuts 
125 foot phone cord 
27.2 volt bat pack 1200mah3 
2Battery conn. female 
1double female phone jack4 
 Misc electronic wire 
1Fast charger for batteries323-232
22' x 4' x 24" for posts 
212" x 12" masonite base 
22 ft reflective tape 


  1. Single Pole Double Throw
  2. Single Pole Single Throw
  3. Unless you want to use a regulated power supply
  4. Take it apart and use half in hand-held part and half on the posts.
  5. You need to open the stopwatch and solder in three light guage wires and drill a slot for the wires to come out of 24 guage.

Circuit Design

Schematic of design

Description of operation

The beams at the top with the battery and switch. Turn on switch causing the beam indicators to light. If the two posts are aligned, the beams remain on.

The sensors have a relay which closes when a beam is broken. The contacts stay this way for 3 seconds, so you can not time any dog which can run down and back in less than 3 seconds. This generally isn't a problem timing line to line runs but could be a problem timing last jump to box to last jump. You can substitute more expensive infrared beams with a smaller delay.

There is a switch in the center that is marked first/only dog and laps. If the switch is up, then when the beam is broke the first time the stopwatch is started and when the beam breaks the seceond time, the stopwatch is stopped. In other words, it is like pressing the Start/Stop button on the stopwatch.

If after the first dog breaks the beam, you switch the switch to laps, the returning dog will trip the laps side of the stopwatch, and then the second returing dog will count as lap two, etc, etc,. The first dog's time is line to line. The second dog and each dog there after is passing time plus line to line. If the dog starting crosses the start line to soon, then the returning dogs time is faster then he/she really ran.

After the fourth or last dog, just press the start/stop on the stopwatch. This is necessary because the stopwatch does not record a lap when the STOP button is pressed. You may substitute another stopwatch that has this feature. Alternatively, you could put the switch in last dog mode which gives you a final time and the split at the third dog. Subtracting these two gives you the split for the last dog. Since the splits give you the lap time plus the accumulated time, we find the former method easier.

Press the recall button to see what each dog did.

There is another switch marked on and off. This is used to enable/disable the beams from starting and stopping the stop watch all the time. You could even leave it out. If you leave it out and turn on the beams, the stopwatch will start, and run while you set up the posts correctly.

After you recall all the times. Clear the watch and set the switch back to first/only.

I will be happy to answer any questions via e-mail.

Finished Systems

Photo of systemFull system Closeup of the timerCloseup of timer

Copyright © 1996 Kathryn Hogg,
Last Modified: Aug 28, 1996