KB313: 250 Square Feet Layout

This article was last updated on May 8, 2012, 2:27 p.m. | Print Article | Leave Feedback


I have an "M" shaped 250 square foot layout with 500 feet of track and twelve locomotives.

What Digitrax equipment would I need?

You don't say what scale this railroad will be modeled in, which is important since the locomotives in smaller scales draw less current than larger decoders.

However, for purposes of estimation:

Twelve Locomotives.

Each locomotive is going to draw, at the very least, 5 MA for the decoder.

If it has LED lights, then it will typically draw 15 MA more; conventional light bulbs will draw 50 MA.

A typical H0 locomotive will draw 600 MA when it is in operation.

An N-Scale locomotive will draw 300 MA.

So, just to get into the ballpark, each locomotive can be expected to draw 650 MA in H0, 350 mA for N.

This number will be higher if you are using a locomotive equipped with sound.

You state that there will be twelve locomotives, so, at its maximum, the total locomotive power consumption for your railroad will be 7.8 Amps (650 MA per locomotive x 12 locomotives) in H0.

For N-Scale, this would be 4.2 Amps.

Of course, you may have some of those locomotives sitting idle in the yards, so might be able to reduce this number a bit, remembering that these decoders will still be drawing power even when the locomotive is "idle".

Passenger cars with internal light bulbs will draw 50 MA per car, those with internal LED lighting will draw 15 MA per car.

500 feet of track
In this case, the length of track becomes an issue because the power bus which distributes power to the railroad itself cannot be more than 50' long.

From this power bus, smaller wires will connect to the track at 6' intervals.

Longer power buses should be avoided because of voltage drop caused by the electrical resistance of the bus wire.

That is, your command station / booster (such Super Chief) will be connected to a black wire and a red wire, which distribute the power to the railroad.

For 12 gauge wire, which is appropriate for this situation, the length will be around 50' from the booster, but you could locate the booster in the middle of a 100' long power bus, thus giving you 50' in each direction.

In practice, you may have to anticipate adding or moving the command station / booster and additional power boosters to achieve the best power distribution.

You don't say how many people will be operating this railroad, so we will guess that you will have four people.

So, just for purposes of estimation, you will need:

  • Starter Set - 5 Amp Super Chief.

    We recommend the 5 Amp version in this situation rather than the 8 Amp version because you will need a
    booster and its own power supply to serve the portions of the railroad which can't be reached by the command station.

    You will choose either the conventional
    Super Chief Premium Set or the Radio Equipped Super Chief Premium Set.

    It is also possible to consider using the 2.5 Amp
    Zephyr and two boosters to address this same problem, but without knowing what the specific track plan is, we can only guess.

    If you have a scale drawing of the railroad, you can plan the locations based upon the 50' bus lengths.
  • Power.

    Because you will have more than one booster, you may want to use the
    PS2012, but the power could just as easily be supplied by smaller power supplies for each booster and the command station / booster.

    Please see the our other articles about Powering your Digitrax Command Control Railroad.
  • Power Management.

    Although the Super Chief has an internal circuit breaker, you will probably want to add the

    The PM42 subdivides the output of the Super Chief into four sub-districts, each of which offers short circuit protection.

    The PM42 can be configured in a variety of ways; each of the PM42 nodes can be used to automatically operate a reverse loop, for example.

    One node of the PM42 can be used to protect track switch motors, also.

    In operation, if there is a short circuit on one part of the railroad (caused by a train derailment, for instance), operations can still continue on other parts of the railroad while the derailment is corrected.
  • Universal Panels.

    The Super Chief Sets come with either a
    UP5 or UR91 (for both infrared and radio operation).

    These have two LocoNet connectors on their face, so you will need an additional UP5, or a
    UR90 can be used (for infrared wireless operation), to allow all four operators to connect to the railroad.

    In practice, you will probably add more UP5's.

    Regardless of which Super Chief set you use, you will still need only one UR91 if you use radio throttles.

    If you choose to use infrared wireless control, one UR90 will probably be enough.

    (There are related articles about UR90 and UR91 performance).
  • Throttles.

    Your choice of throttles will be based on your needs.

    DT400 is intimidating, but it also gives you full access to all features of the Super Chief system.

    UT4 is a simpler throttle, perfect for those who do not need full access to the Super Chief's features.

    Even if you choose the conventional Super Chief, you can later add radio throttles, both
    DT400R and UT4R.

    And, visiting operators may bring their own Digitrax throttle.
  • Mobile Decoders.

    Each locomotive will need to be equipped with a mobile decoder.

    In many cases, locomotives are available with Factory installed decoders which will work in the Digitrax environment.

    Other locomotives can be converted; please see the
    Decoder Selector Guide.

    Locomotives not listed still can usually be converted to digital command control.

    The site that you are currently viewing also has information about some specific locomotive installations.
  • Stationary Decoders.

    DS64 will control track switches and such, in groups of four.

There is, of course much more.

The addition of sound decoders makes your railroad more realistic.

You can add signals and automated control, for instance.

Once your basic railroad is in place,
LocoNet allows you to easily expand its capacity and capabilities.

Have fun!

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