- DSCF0917.JPG (156.72 KiB) Viewed 13658 times
When I first experimented with a lap counter some time ago, all seemed fine but this time I have had more problems. The 5v counters which I used initially were no longer available and the higher voltage ones I did get seemed less reliable. The main problem was getting a double count each time. The counters I am now using have two downsides - the digits are small and are not backlit, so not so easy to read. However they are very cheap, power is a 1.5v AAA cell, they need only two wires to connect to the sensor and they work well. However I must admit that part of the problem was the extra magnets in the car, mainly those holding the battery in place, which were interfering with the sensor switches. I have reduced these in size, now using three instead of two to hold the battery in place and all now seems good.
The pic. shows the reed switches being installed. I have discovered that there are some switches made with different sensitivities.
In view of the problems I had, we need the least sensitive switch. I have only found one such switch so far ( Comus SPST-NO 40-50AT) The At being the sensitivity range. This is fitted flush with the track surface and operated by a 3mm diam x 2mm magnet under the car. So the magnets are approx. 2mm above the switch. There are 4 other similar magnets press fitted into the chassis at 10mm spacings across.
Pic also shows my 1/24 scale Porsche 908/3 prototype.