Chapter-5d-1 Page 33
Crossing Lights Here is a simple design to provide flashing crossing lights on a single track for trains going in either direction.
The circuit is similar to that of "An If it stops and reverses over the Intermediate Signal" and basically entry point the sequence is not detects the train entering and completed and the lights will exiting the area between the two continue going until the exit spot detectors. When a train is detect point is crossed. detected the circuit activates a set of alternately flashing LEDs on the The circuit will work on a double track but if two trains are in the crossing signs. The flash rate is detected area together the controlled by a Flashing LED. sequence will probably not be When ON it pulls power through two of the crossing LEDs and when correct. it turns off a transistor switches on and pulls power through the other How it works: two LEDs. The two timer circuits work Installing the spot detectors, called Entry and Exit, will need some thought. The spot detectors should be located an equal distance either side of the crossing. The distance being far enough away so that the last wagon of the longest consist just clears the crossing when the train has passed the exit detector. Use your longest consist running at its normal speed. Single locos or shorter consists can't be controlled so closely but most observer attention will be as the train approaches and the lights start up so any extended flashing after the train passes may not be significant. This is only a simple logic and the train is expected to pass the entry detector point then exit past the other detect point.
interactively. Either spot detector can start the sequence and the opposite one will finish it. After the exit detector is crossed there is a delay, about 5 seconds to allow a multiple loco consist the get over the detect points. Any crossing made-
after this time would be taken as another sequence being started . The timer that is triggered first cannot time out until the other one is triggered by the train crossing the exit detector. Then both time out in the delay time set by the 2.2 ufd capacitor and the 1.0 meg-ohm resistor. Either timer being on will activate the flashing LED and the lights. The flashing LED is not symmetrical, on to off times, so a 100 ufd capacitor has been added to even it up.
