KB342: Powering your Digitrax Railroad - An Example

This article was last updated on Jan. 18, 2012, 5:03 p.m. | Print Article | Leave Feedback


I have a 14x24 foot room with a shelf layout on two levels.

1st level is about 24 inches with two main lines and some industries, a moderate freight yard, moderate intermodal facility and passenger station.

The second level is 18 inches and will contain one and two main lines with mostly industries.

This would qualify as a "medium to large" model railroad.

I would like to have 1-5 operators with 2-10 trains running at one time as permitting.

At least four Universal Panels would give all operators full access to LocoNet as necessary.

At least one UP each should be near the passenger facility, freight yard and intermodal facility.

At least one more should be out on the main line.

Additional panels will not hurt.

If I had the main controls at the middle of one of the 24 foot walls, could you suggest the power requirements I may need such as with the Super Chief and possible if any boosters, if needed.

Well, you're going to have to estimate things, but here are some guidelines.

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 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 up to 10 trains operating at a time, so the total locomotive power consumption for your railroad will be 6.5 Amps (650 MA per locomotive x 10 locomotives).

Of course, you may have more locomotives sitting idle in the yards, so add as much more as you feel is necessary.

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

So, you now have an overall idea as to the total power requirements for your railroad.

Also could you suggest the number of districts I should have?

I will be using 12ga bus wires with 20ga feeders.

Using 12 Gauge wire, you can anticipate a 1/2 volt drop over 50 feet of power bus.

In this case, it helps to have the command station / booster in a central location, so that you can have two or three power bus runs, each 50 feet long.

Because your railroad is two levels in a 14 x 24 foot room, the probable power bus lengths are going to be well within the limits of 12 Gauge wire.

At minimum, it sounds like you will need at least the command station / booster with power supply and an additional booster with its own power supply. The Super Chief is available in both 5 Amp and 8 Amp versions.
In cases such as these, it never hurts to have more power available than necessary, so probably add second booster with power supply.

Both the command station / booster and the two additional boosters would each be connected to a PM42, which would break the power distribution down a bit more.

Overall, a typical model railroad would have one power district for the main line, one power district for the locomotive pits (where there may be a lot of idle locomotives, each drawing 5 MA plus lighting requirements), a power district for the freight yard (where there might be two or three locomotives in operation at any given time) and a power district in the passenger yard (where there are lots of light bulbs in cars).

In some cases, each area would merit its own booster and power supply, but in other cases, you could draw upon a single booster & power supply and use the PM42 to break things up a bit.

The PM42 is helpful when there is a derailment in one area of the model railroad; other areas can continue in operation while the derailment is being fixed.

But, ultimately, the PM42 is just a power manager, you still need enough overall power to operate properly.

The turnouts will currently not be DCC, maybe in the future.

You may find it to be easiest to simply add another booster and power supply when that day arrives.

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