[CMOTD]

My timing system has developed a very strange fault. One lane keeps throwing up completely random lap times, it happens when there is no car on the track to trigger any. When a car is circulating it also does it in between genuine times.

It is not a program glitch as both RC and LapTimer 2000 do it. It only affects one lane, the other works normally and I have tried switching both the sensors and the overhead LEDs over - same lane plays up so they are not at fault.

Also it only occurs when the pit garage lighting system is switched on. Turn it off and everything works normally. I have changed nothing in the wiring etc and it has only started recently. I can't see why there should be any interaction between the timing system and the garage lights so I am stumped. Any ideas folks?

[DPJ]

It sounds like the wavelength of the Pit lighting is causing the issue with the IR lap counter

[Scuderia_Turini]

Hello Brian, aplogies for the interrogation...
Is it the lane nearest the pits that has the problem? Are any of the pit lane LEDs dimmer than the others? Might be that one has become electrically noisy. Are the overhead lights powered from the same source as the pit lane lights, if so can you separate them?

Leo

[CMOTD]

I didn't expect the Spanish Inquisition Leo.  

Yes, it is the lane nearest the pit wall.

No, all lights appear same brightness.

Yes, both powered from same source and linked together. I can separate them but it involves crawling about underneath the track amid much banging of head and swearing but I will give that a try. May be a short delay while I do it.

[Savage GT]

If it only happens when the pit garage lights are on, then logically, that must be the culprit.
Are the pit garage lights powered from a separate supply to the timing lights ?

As you have swapped the lane sensors and bridge lights around, and the same lane plays up, try temporarily blocking the pit garages lighting at the rear so that does not shine near the timing sensors.
If that cures it, you may need to reposition those.

[CMOTD]

All Fixed. Separating the wiring did the trick so definitely electrical interference between the two for some reason. Good job I have two individual power supplies to use. An unexpected bonus was that I found some long lost spare parts while ferreting under the track. Thanks for your help folks. One thing puzzles me though - why did it only affect one lane when the other one was connected to exactly the same power source?

[Scuderia_Turini]

One thing puzzles me though - why did it only affect one lane when the other one was connected to exactly the same power source?

Might be due to the path that the wiring takes. With my opto-sensors, I always wire a small capacitor (like the suppressor ones on motors) across the sensor wires at the sensor. That helps reduce any "spikes" that come up the wires. Also I use screened audio cable to connect to the parallel port or the Arduino.

Leo

   

[CMOTD]

I don't think the interference was with the sensors but with the I/R overhead lights. The sensors are wired with screened cable direct to the parallel port on the laptop and the wiring is nowhere near the 12v DC supply for the LEDs and light bridge. Presumably there was some sort of overload or voltage drop which caused the the overheads to flicker and register false laps but why it only affected one lane remains a mystery. In fact the whole thing is beyond anything I have experienced before, the system has worked faultlessly for several years and LEDs draw a miniscule amount of power so the wiring was perfectly adequate for the current drawn. Anyway, lesson learnt for the future - don't put different functions on the same power supply.