Our model trains and accessories are electrically powered, which is great, because designing wiring schematics can be one of the most pleasurable aspects of our hobby. Joyfully, model railroading offers one of the only remaining places where a person can still create brand new electro-mechanical projects, while at the same time have the option of working with cutting-edge electronics and computer software. Therefore the very first consideration, even on a disposable "learning layout", should be how the layout will be wired.
The use of a 3rd rail for distributing variable power has been a device used for electric trains for well over a century, even on finely crafted models. It has many advantages over distributing power through only two rails, such as reverse loops not requiring special wiring, and accessories being able to use an insulated outside rail as a detection sensor. Current fine scale modelers may offhandedly look down on the use of an extra rail (most likely because all they envision is antique tubular toy track), but remember that, as can be seen on such pioneering fine scale model railroads as the Canandaigua Southern, even fine scalers themselves once employed unprototypical third point powering solutions [EXAMPLE] of centered tie studs and outside 3rd rails. Be proud to be different. Track after all is just a road surface, a piece of scenery like all the rest on the layout. Automobile modelers for example don't go into a tizzy about the electrical power slots in the middle of their road surfaces.
Modelers with antique equipment should bear in mind that twentieth century toy train manufacturers, in order to maximize profits, installed the cheapest and minimalist electrical solutions they could devise (for example, leaving it to the modeler to do such basics as mark the transformer plugs [EXAMPLE] to indicate their proper polarity). Therefore every electrical device installed in an older train or accessory is ripe for hobbyist refurbishment or expansion (or even total replacement with modern solutions; such as Light Emitting Diodes instead of incandescent bulbs, or Soldered-On track feeders [EXAMPLE] instead of "Lock-Ons") [EXAMPLE].
People feel closer to their model layout when they can physically touch components (which is why O-scale 3rail modelers are encouraged to gently handle cars to couple/uncouple them, or to add/remove freight loads). If you run Traction equipment equipped with two trolley poles/pantographs under live wire, you can specially wire the cars [EXPLANATION] so that manually lowering/raising the poles facilitate direction change. As a bonus, as is true on the prototype, when both poles are lowered these cars cannot be powered. Thus it becomes super easy to move a trolley car amongst multiple parked trolley cars with lowered poles that are occupying the same traditionally wired electrical block. You can even operate two locomotives independently within the same traditionally wired electrical block, if one is controlled from center rail and one is controlled from overhead wire.
Adding supports and stringing overhead wire does add some extra layout complexity; but note that overhead wiring can be greatly simplified, and provide better electrical contact, if you substitute a single inverted N-scale rail [EXAMPLE] for the wire. Traction can run from track power alone though, so many traction modelers (and at least one real-life traction line [EXAMPLE]) actually forgo stringing live overhead wire (or even installing the wire supports) entirely, and just imagine their presence.
With only a few reservations (e.g. not yet disconnected DC horns in some antique Lionel locomotives), all 3rail locomotives and passenger car lighting will operate properly on DC track power. It is a false myth that postwar locomotives require AC, as the frame motors installed were intentionally selected for their ability to be powered from either an AC wall outlet using a transformer or a DC automotive battery using a rheostat. It is also a false myth that DC will damage your classic toy trains, as is proven by the old-style locomotive horn button that worked by harmlessly injecting DC power into the track. In fact the only reason old toy train transformers output AC and not rectified DC into the track, is because at the time inexpensive high amperage silicon diodes were not yet available to manufacturers (a situation now rectified
[EXAMPLE] ...pun intended).
Exception: Battery power, or rectifiers that include "smoothing filters" to produce a more battery-like output, should not be connected to a toy "vibro-motor" because this particular device requires a moderately rapid low-to-high-to-low power cycling (such as 60hz AC) to produce its vibrations. A possible solution for vibro-motor "action" cars is to isolate the section of track on which the car is to be played with, and power it with appropriate voltage AC.
A full wave bridge rectifier attached to the output of an AC transformer produces Direct Current. DC is an ideal power source [EXAMPLE] for both accessories and track power (connect the + to the center rail). On rectified DC track power, universal motor locomotives will run quieter and will start to move at a lower applied voltage than before (because AC requires more wattage to produce the same amount of useable energy as DC). For realistic operations you want your locomotives to smoothly move at slow speed, so be sure to also clean, adjust, and properly lubricate [EXPLANATION] moving parts (preferably with modern lubricants such as Nano-Oil) on a regular basis.
To reduce electrical load on the track circuit, it is recommended that track power be used almost exclusively to only power locomotive motors. The high wattage drawing caboose and passenger car lighting can be disconnected, or better still, replaced with modern low wattage drawing flicker-free LED lighting. The analog DC whistle in antique Lionel locomotives is a major track power drain, and should therefore be physically disconnected whenever possible (Lionel produced identical whistles in trackside shanties, that can be used in their place at road crossings). Because the costly digital-sound generating electronics in modern locomotives are a common point of failure, and because the tiny diameter speakers required to be used are only capable of producing squawking low-fidelity sound, it is strongly encouraged that any onboard digital sound effects always also be turned OFF.
Lighting and other electronics in rollingstock draws its power from the rails, so you need to verify your track power supply has enough capacity for the load.
Accessories should be powered from a separate electrical circuit, and not connected to track power. Using separate circuits allows tailored voltage to be supplied to each accessory. Each accessory should be powered at the lowest voltage which will provide smooth operation (perhaps even tweaking with high current resistors if necessary). Special Effects [EXAMPLE] have always been a part of 3rail modeling. Ambient sounds around accessories and structures (from a quality larger diameter speaker) provides atmosphere, but it is important that the volume be kept barely audible, as if the sounds were coming from a great distance.
There are three classes of dynamic colored signals commonly used on prototype railroads, most of which can also be indicated with electric lamps. They are in order of necessity: 1- Relaying a special message (such as men at work, retrieve train orders, or stop immediately). 2- Track switch position indication. 3- Speed limit, including wait (note that a timetable could instead be used to communicate static speed limits, as well as "wait-until" instructions). Of the three, a Switch Position Indicator would be the most helpful to a beginning model railroader.
Lights in trackside accessories should always be operated at their lowest useful power level (ideally powered separately from the rest of the accessory), in order to both prolong bulb life and reduce heat damage to the accessory. Any burnt out bulbs should be replaced with equivalent bulbs that produce less heat (toy manufacturers often used the hotter bulbs because they were a single penny cheaper). Whenever practical (as this is not a direct swap scenario), replace bulb illumination with modern cool operating (and longer lived) LED illumination.
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![[EXAMPLE]](marked.jpg){kind=link}
![[EXAMPLE]](Lockon.jpg){kind=link}
![[EXPLANATION]](Trolly_Pole_Wiring_Diagram.jpg){kind=link}