Tulsa Neons N-Scale Model Railroad

Power Systems

by Steve Gillett

Figure 1 - Power System on Store Layout

For many years the NEONS kept their head in the sand when it came to DCC. Because very few of us had decoder equipped engines we both resisted and avoided it. However, as DCC became more and more commonplace and our members began to acquire and/or convert some of their locomotives to DCC, it became clear we needed get with the program, move into the 21st century and get some of them thar new-fangled DCC thing-a-ma-jigs for both our permanent layout and our show layout.

Figure 1a - Power System on Store Layout

Our first decision was to select Digitrax as the manufacturer of choice since their equipment was used at most shows we attend. NEONS has a very large travelling layout plus a small, 8-module layout that is semi-permanently set up at sponsor's store, Challenger N-Scale Hobbies. The store layout benefits both our club and our sponsor since it allows club members to run trains whenever the store is open and provides the store with a place for customers to test new or potential purchases. This store layout was powered by three MRC Tech II Railpower 2500 power packs (one each for the red, yellow and blue lines.) We added a Digitrax Zephyr DCC system and built a panel with three toggle switches, thus allowing operators to toggle between DCC and the assigned DC power pack on each of the three lines (See Figures 1 and 1a).

Early research and experience by clubs across the country led to a few rules of thumb. The first and most critical rule is a Digitrax power distribution line should never extend more than 50’ in either direction from the power source. The longer the distribution line, the more resistance there is, and the more the signals degrade. Because our show layout loop is usually between 150’ and 240’ long, we decided to break our layout/loop into three blocks and locate a power supply near the center of each block so that the distribution lines never exceed the 50’ guideline. We initially installed Digitrax equipment only on the red line of our travel layout so we could tie into the Red Line Route™. The other two lines remained powered with Aristo-Craft wireless DC throttles. Eventually, the flexibility we became used to on our store layout led us to develop a similar system for shows.

Since we nearly always link up with other clubs at shows to form a multi-loop layout using the Red Line Route™ format (which is exclusively Digitrax DCC), we only need to offer the choice of DC / DCC on the yellow and blue lines. (The NEONS do not have the mountain line on any of our modules.) Using the North Raleigh Model Railroad Club's design as a base, we constructed three custom power boxes, each with a Digitrax 8 amp DB200 booster, a Digitrax PM42 to split the DCC power to the Red, Yellow, Blue and Green lines, two UP-5 loconet interconnects, and two Aristo-Craft DC analog power receivers and antennas that receive signals from our Aristo-Craft wireless remote throttles. Each box is powered by a Digitrax 2012 20-amp power supply that feeds the Digitrax and the Aristo-Craft units and also has two wall warts, one for the PM42 and one for the UP-5s. In order to protect the power equipment and all engines on the layout, each of the three units in each box (two Aristo-Craft receivers and one Digitrax DB200) is fused on both the inlet and outlet side. We keep a large supply of fuses just in case! (Figures 2-8 and Diagrams 1-4).

Figure 2 - Power Box Top & Front View

Figure 3 - Power Box Bottom View

Figure 4 - Power Box Bottom Left Side

Figure 5 - Power Box Bottom - Right Side

Figure 6 - Power Box Bottom - Doors Closed

Figure 7 - Power Box PM42 - Front View

Figure 8 - Power Box PM42 - Top View

Diagram 1 -- Power Box Schematics - Top View
Diagram 2 -- Power Box Schematics - Front View
Diagram 3 -- Power Box Schematics - Bottom View
Diagram 4 -- Power Box Schematics - Doors

Figure 9 - Master Command Station
Front View

The DCC equipment in all three power boxes is controlled by a Master Command Station. This unit contains a Digitrax DCS200 8-amp command station, an LNRP loconet repeater and our old Aristo-Craft 10 amp power supply. It does not power any track, but functions as the brains of the system. Its only connection to the layout is through the Loconet bus and a ground wire. If we link our loop with others to form a multi-loop layout, we can either use our Master Command station, or disconnect it from the loconet and use the host club’s equipment for that task. The Master Command Station also contains a programming/test track and a wheel cleaning tool. By toggling a switch, the 17” long track works as a programming track or a test track. Even though the DCS200 doesn’t power a block of track, we use an 8-amp unit here so that if one of the boosters fails, the DCS200 can do double duty as the Master Command Station and supply power to one block. An old-style beginner transformer powers the wheel cleaning tool. (Fig 9-12 and Diagrams 5-8)

Figure 10 - Master Command Station
Top View

Fig 11 - Master Command Station
Bottom View

Figure 12 - Master Command Station
Bottom - Door Closed

Diagram 5 -- Master Command Station Schematics - Top View
Diagram 6 -- Master Command Station Schematics - Front View
Diagram 7 -- Master Command Station Schematics - Bottom View
Diagram 8 -- Master Command Station Schematics - Doors

Each power box is 9” deep and 30” long so it can be clamped on the back of any module, including a corner module. The Master Command box is 18” long. At the back right corner of each box is a terminal block where ground wires can be connected. (Fig 13) All equipment in each box is tied to this ground block. We have several spools of ground wire that we use to interconnect the boxes. Even though all four of our power supplies have a grounded 110v plug, only one is connected to the grounding system so that there will be no possibility of a ground feedback loop.