So, is the ambient light sensor is the perfect optical train detec-
tor? No, not really. The ambient light sensor has its own quirk.
If you want to have night operations, and you turn off the
room lights and/or the lights over the railroad, it’s very likely
that the ambient light system will cease to function because
there’s now insufficient light to activate the detector in the
first place, and all, or almost all, of the sensors will indicate a
detection all of the time. It has been suggested that a second-
ary, point-source light system be placed above each detector
for just this reason. But this has its own problems.
For one, if your system uses visible light, the secondary lighting
systemwill have to use visible light too. So during night operations
there would be these spots of light at intervals down the track.
