Slot car track voltage tester

I thought about the staged-zener approach, but it is not accurate enough to meet the requirements in posts #7 and #9 and the trip points are not adjustable. But beyond that, the LED transitions would be very soft. My guess is that when tracking a display that is moving around a track, having the LEDs change state crisply will be much easier to see to determine exactly where the trouble spots are.

ak