Here's what I have so far: a relay for each of the two loops and a board that takes the incoming 14vAC to 12vDC for powering the relay. Now I need to turn the 18vAC ground from the trigger rail to DC so the relay doesn't chatter.
Hard to see from your pic, but it looks like the 14VAC to 12VDC converter is the hand-built board on the right...using, say, a 7812 type voltage regulator? And is there a bridge-rectifier or just a single-diode for the AC-to-DC conversion portion of the circuit?
Is the 14VAC electrically isolated from your traction (track) 18VAC supply. This is VERY important as was discussed earlier in this thread.
So if you're feeding the isolated outer-rail trigger to the trigger terminal of the relay module, the module must be configured for "low-level" triggering (vs. hi-level). Again, hard to see from the pic but I think you're using the module that has this configuration capability using the push-on jumper plugs. To provide anti-chatter, the capacitor goes between the module's VCC input (+) and the trigger input (-). Something like 100uF (25V) will be more than adequate.
And of course the reason for the electrically isolated 14V AC source is to allow you to tie the "-" of the derived 12V DC supply to the outer-rail.
