As part of designing and planning my next model railroad layout, I am considering methods for distribution of power. The layout will fill a 20x25 foot area of my basement, with two levels and somewhere around 300 linear feet of track. Track will be DCC powered and have its own bus. Turnouts will be servo operated, with a circuit I am designing. Signals and detection will be a mix of a controller circuit I am designing and some commercial bits for current detectors.
There are several components of the DCC system that need between 14 and 18V DC to operate. My initial plan was to put a fairly high current 12V AC power bus around the layout and tap off with small fused full wave rectifier circuits at the point of power need. That nets about 15V DC after rectification and filtering - perfect. Now, all my OTHER circuits are 5V DC - servos, the ATTiny85 servo controllers, and the Arduino-based signal controllers. Rather than run another 5V DC bus, I was considering using inexpensive buck converter modules (with a rectifier and filter) at the point of use. 15V down to 5 seems a bit much for a linear regulator, as in an awful lot of wasted power int he form of heat. Or instead of 12VAC and rectifier modules, I could run 15V DC which saves building a whole lot of full wave rectifier modules.
As I type this it starts to make more sense to do the multiple power circuits, but there is another possible catch. The servos can be rather noisy and I'd like to isolate their power feed from the one that drives the micros. That would mean TWO 5V power busses. Now I'm up to 3 aux power lines plus the at least two track power busses in any given area and I haven't even started on structure lighting yet. That is, assuming pulling one drop of a 5V bus for the servos and a second for the circuit controlling the servo (said circuit to have reasonable bypass capacitors in place on the power input and directly across the controller power pins) isn't good enough.
A third option is a single 5V DC line and use a boost converter for the devices that need 14V DC (maybe 4-6 total, and they each draw no more than 150ma).
The design goal is to minimize the number of wire runs while not using a ton of expensive regulators and converters, but maintaining reasonable enough isolation to ensure reliable operation of the various micros. The power supplies, regardless of which way it ends up getting done, are no problem, I can build or buy whatever I need.
Any and all suggestions appreciated. One thing I absolutely do not want is dozens of individual power supplies all over the place. Otherwise, whatever makes the most sense. I'm probably overthinking this already.
TL;DR - 1 higher voltage AC supply, with local rectifiers and regulators, 1 higher voltage DC supply with local regulators, 1 lower voltage DC supply with boost converters where needed, or multiple DC supplies of various voltages. Or some other option I haven't thought of.