Simple PhotoCell Timing System
(S.P.T.S.)
INSTALLING PHOTOCELLS IN THE TRACK

(c) Bryan Brown & Art McEwen 1997-1999
All rights reserved, not to be copied without permission.

Before you start crawling under your track table and working overhead, get everything working above the table. You can check and double check everything right beside your computer if you build a small simulated track surface with a scrap of wood, as seen in the photo below. This way you can simulate a car passing with a wave of your hand over the sensor. The Scuderia McEwen programs should recognize the signals. When you are happy with the setup, the actual installation under the table is fast and easy.


Test bed built to facilitate testing "above the table"
Note installation of PhotoCell using PushPin and
wire connections using alligator clips.


The best place to put the PhotoCells is probably at the start/finish line. I didn’t put mine there, however, choosing instead the middle of the long straight-away. Don’t put them too close to the exit of a corner or a car swinging out may trigger a hit on the other lane. Also, don’t put the sensors near the beginning of a corner as drivers have a tendency to floor it on their fast lap and often end up going straight into the wall at full speed (ouch!).

Once you find the ideal position:
  1. Drill a hole just a little larger than the width of the PhotoCell right in the middle of the slot and going all the way through to the underside of the table.
  2. Glue or nail a small block of wood on the underside of the table with one surface right against the edge of the hole.
  3. Cut a piece of softwood (e.g. balsa wood) about 1/4" x 1/4" x 2" long and tape (or epoxy) it to the bottom of the PhotoCell. The butt end of the wood should be against the bottom of the PhotoCell and the tape can go around the circumference of the wood and include the two wires from the PhotoCell.
  4. Coming up from the bottom of the table, position the PhotoCell in the hole so that the surface of the Photocell is flush with the bottom of the slot. A car should be able to pass over it without hitting it.
  5. Push a pin or small nail through the wooden stick taped (or epoxied) to the PhotoCell into the surface of the block of wood by the edge of the hole. The pin will hold the PhotoCell in place but allow you to reposition as required.
  6. Repeat for the second lane/PhotoCell.


You have some adjustment with the PhotoCell as you can raise and lower it in the hole. This will have the effect of increasing or decreasing the intensity of the source light.

Click here for a new and improved method of mounting PhotoCells under the table.




PhotoCell ready to install, taped/epoxied to wooden stick.
Note holes in wooden shaft for push pin mounting and identification
number to facilitate testing (all PhotoCells look alike!).



Last Updated April 21,2000

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