@Don Baird posted:
I will be able to follow the map you’ve laid out for me but I don’t entirely understand why it works.
A good place to start - in fact the fundamental question for me - is which parts of the system are DC, which AC, and WHY
@Don Baird posted:
Can I isolate the track at the end of the line to turn on a light or an accessory for the duration of time that the trolley is at the station? When it reverses direction it would leave the isolated section turning off the light or deactivating the accessory ( likely a crossing light or gate).
I think this diagram might answer both questions.
Once upon a time, you had a length of 3-rail track and a bump-n-go trolley that went end-to-end and self-reversed. You could control the speed within reason by adjusting the throttle voltage. Because of the 3-rail track, you could use the insulated-rail method to co-opt sections of the track to activate an accessory when the trolley is over an insulated-rail section. In principle, this method can handle either AC or DC. In your specific application the throttle happened to be AC and the trolley and accessories are compatible with AC so all's good.
But when you throw in station stop timing with sequencing "logic" implementation is generally easier using DC (solid-state) electronics. Remember that the original Lionel station-stop used the AC-compatible nichrome heater/resistor switch that warmed up and cooled down to time the stop and start. So while I'm sure we could have scoured eBay or wherever for such timing mechanisms I think that would have been riding the horse in the wrong direction.
So to take advantage of the modern and economical DC-powered electronics modules for optical detection, timing, logic, sequencing, etc., an AC-to-DC converter module was needed to provide such voltage. As shown in the orange box, in the big picture the 153IRs and timing module simply takes DC voltage and controls a relay to connect/disconnect AC track voltage to the rail at the proper time. The relay isolates the DC electronics from the AC track and AC accessory voltage.
The astute observer will correctly note that the 153IRs operate on AC voltage so why are they powered by DC? This is one of those ignore-the-man-behind-the-curtain situations. Yes, the 153IRs could be operated on AC...but then their outputs would be AC and would not be directly compatible with the DC timing module. This would have required additional component(s) to convert AC-to-DC. It's not that this is expensive (10 cents?) but in effect is performing the AC-to-DC conversion in two places. I also know from past experience that mixing versions of the 153IR is a minefield...and in general it's easier to manipulate-combine multiple DC signals than multiple AC signals.
So the use of the DC-powered station-stop system does NOT affect your ability to use the insulated-rail method for your AC-powered accessories.
Early on you said you had a Menards lighted building that came with its own power adapter (presumably a 4.5V DC-output "wall-wart"). If this is one of the accessories you want to turn on/off when the trolley reaches an insulated-rail section, there are additional instructions.