Stan, tried your approach and it works perfectly. Using a 5.1K resistor I get relay activation and very good sensor sensitivity.
As to a sensor approach on the TT. We currently have 9 different locations for the TT. We are using a stepper motor/Arduino for position control. The stepper controller provides selectable steps/rev (up to 6400) plus the stepper to TT is gear driven for further resolution. We use a limit switch for initial positioning and the spur/engine house track fixed locations are in a table generated with a calibration program. There are currently only 2 main line entry/exit points and I am just trying to add a safety feature to prevent an engine from going into the pit if I have not positioned the TT. The TT is very complex and adding even a single emitter would be a mess.
I think I will use a 2nd relay to disable the sensor function and will activate it from the control panel, where I only have 12VDC available (5V is provided from a regulator under the layout near the slip ring and is fed off a 12V bus. My relays are all 5V, so can I just add a larger resistor (like 12K) from 12V to the relay control input?
Ken
