Our DCC Installation

Updated: 2-APR-2010

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Command control is an essential element of the Operations Road Show layout. Jack Ozanich put it succinctly when he said "I'd sooner give up Kadee couplers than give up command control." We're largely in agreement with Jack-- we cannot conceive of trying to run timetable and train order operations while having to mess around with toggle or rotary switches to assign power blocks. It would be just too distracting.

Digital command control was the obvious choice for our layout, given its availability, its relatively low cost, and its inherent ability to support functions other than simply controlling train speed and direction. We put this extra capability to good use on the Operations Road Show layout, because in addition to controlling the speed and direction of the trains, we wanted to use it to:

• Control the signals for the train order system
• Control the six fast clocks (later increased to eight) installed around the layout, permitting us to synchronize them as well as start and stop them simultaneously
• Control the alerter buzzers for the phone system

That last application was a last-minute solution to solve a problem we hadn't considered in the design of the phone system. We think that it shows the flexibility of digital command control quite nicely.

One other requirement we had for the system was the availability of radio throttles. We felt these were necessary to provide the type of user experience we wanted our guests to have- we felt that hunting for plug-in panels was part of the experience that our guests could do without.

Although we'd been using Digitrax equipment for a few years prior to building this layout, we looked at all of the major DCC brands available in the US at that time (Digitrax, EasyDCC, Lenz and NCE) in order to be sure that we would select the right system for our purposes. We chose to use Digitrax DCC products for this project due to the availability of Digitrax supplies from a local dealer (Michigan Model Train Center) and several other dealers not more than 30 minutes' drive away, the availability and robustness of Digitrax's radio throttles, and the availability of LogicRail Technologies' LocoNet Fast Clock. Digitrax also had the best selection of accessory decoders to choose from for automating our train order signals.

The Equipment

The core of our Digitrax installation is a Digitrax Chief system which interacts with:

• Four power boosters
• Two PM4 power management cards, controlling several power districts in the Fiddle Yard and Lafayette Junction/East Yard area, as well as the reversing section needed by the NYC/Monon/NKP interchange arrangement.
• Eight LocoNet Fast Clocks, two of which are wall-mounted at the layout's home base.
• Three DS54 I/O cards to interface with the dispatcher's train order signal controls. For technical details of our train order signal system, see Building the DCC-Controlled Train Order Signal System, elsewhere on this site.
• Ten DS44 accessory decoders to control the train order signals, the indicator lights in the signal control panel and the phone alerter buzzers.
• Two UR91 (simplex) and one UR92 (duplex) radio receivers. Having the two simplex receivers is not required for a layout this size, but provides a reserve for use as an emergency backup.
• 38 UP3 and UP5 throttle jack panels installed around the layout in case we need to set up the layout in an environment that is completely inhospitable to radio operation. They also serve as battery savers for the throttles during sessions.

Even with all of the DS44 and DS54 accessory decoders, we do not use the command control system to throw turnouts- all turnouts are thrown by hand, using a variation of the old choke cable system.

We use up to 18 radio throttles, including a DT400, a couple of DT400Rs, three DT300Rs, ten UT4Rs and a couple of DT100Rs we keep in reserve. A single UR91 receiver located at Lafayette Junction has afforded excellent coverage across the entire layout area, and generally handles the throttle traffic quite well.

Our guest crews have been able to understand easily how to use the various throttles after being shown only the speed controls and the reverse button. Digitrax's introduction of the UT4R utility throttle was very welcome, as it provides an inexpensive radio throttle with a familiar knob-and-direction-switch control.

Nearly all of the RJ12 cables we use to carry LocoNet signals around the layout were custom-made using flat wire and connectors bought in bulk. In a couple of cases we tried to use six-conductor phone extension cables purchased from a local hardware store, but we found that we couldn't rely on the cables working due to poorly-crimped connectors on an unacceptably high percentage of them. We are great believers in using a cable continuity testing box to test every cable before connecting it in place. Doing that has saved us many hours that we would have likely spent diagnosing problems caused by defective cables.

Layout Design Considerations

Although we decided from the outset to design the layout to operate exclusively under DCC, the only thing that we did differently on this layout as a result of our DCC focus was to use 12-gauge stranded wire for the track bus wiring. This minimizes current and signal loss along the lengthy runs of wiring. To ensure continuity through the rails, every segment of rail on the layout has a feeder soldered to it. We do not rely on rail joiners to carry power between sections of track.

Despite planning to use radio throttles, we installed 38 of Digitrax's UP3 and UP5 panels in the fascia. The main reason for this was to ensure that we could operate the layout if for some reason our ability to use the radio throttles were impaired. This is in recognition of the fact that radio interference from outside sources is a variable are unable to control when the layout is being used at a convention.

Taking a "belt and suspenders" approach to ensuring that we could continue to operate in the event of failure of a radio system component, we installed a second UR91 radio receiver panel in the Delphi/Clymers corner of the layout. This provides an installed spare that we can bring up if anything should happen to the "main" UR91 located at Lafayette Junction.

Since the layout is designed to be set up in only one configuration, we chose not to install the LocoNet cable permanently into each module, with the attendant connectors and jumper between them, but instead to custom-build cables for the specific runs between UP-panels. We tagged and numbered each so that we could identify its intended use. We do not feel that this particularly increases our setup time as compared to connecting short telco cable jumpers between each and every module. It also reduces the number of cable segments and the number of connectors needed in the system.

In Use

To date, the only hardware failures we have experienced with our Digitrax installation were from a batch of defective DS44 accessory decoders we used to control the train order signals. We found that we had to continually re-program them, as they would lose their memory whenever a short-circuit occurred on the section of track from which they were taking their control signals. Once they were replaced with new ones, we had no further problems.

One disadvantage we found to having the train order signals take their command signals from the rails on the module is that it is possible for signal commands to be missed if a short circuit on the track has shut down the power district it's connected to. This is similar to a situation other modelers have encountered when controlling turnouts using accessory decoders. Our solution to this was to run a second two-wire DCC track signal bus solely for the train order signals and phone buzzers beneath the layout. While we chose to dedicate a booster to controlling this bus, we could have chosen to feed it from one output of a PM42 power manager connected to one of the other boosters.

The radio system reliability has been excellent, and we have no complaints. The only time we have experienced persistent reception difficulties due to site environment issues has been at the NMRA National Convention In Cincinnati. Bringing the second UR91 on line solved that problem quickly.

We have discovered, as have other users of virtually all radio throttle systems, that having the receiver mounted above head height improves radio reception by drastically reducing signal loss dues to bodies being between the receiver and a throttle. This was driven home to us during a session in Saline where we had far more guests than we had jobs. At one point, six people were viewing the layout from the aisle adjacent to our UR91 radio receiver, which at that time was mounted in the fascia. While they were standing in front of the receiver, we had considerable difficulty controlling our locomotives. Once the crowd had moved on, the system resumed operating as reliably as we are accustomed. We were able to duplicate this under controlled circumstances at a work session later that week, and so moved both the primary and back-up UR91 receivers up onto poles so that they are approximately seven feet above the floor during operating sessions. We have not had any reception problems since.

At the Hartford National 2009 NMRA Convention, we began experimenting with Digitrax's then-new duplex radio system. Having acquired one of the first UR92s and DT402D throttles sold to the public, we used the duplex throttle primarily in the Fiddle Yard to reduce cable-tangle when two of us were making up and breaking down consists. Even with the early-release firmware, this worked very well for us.

Since the Hartford convention, the UT4D duplex throttle has been released and we have been experimenting with one as a road throttle. In doing so, we have discovered that the UR92 receiver benefits just as much from being raised to a position above head-height as the UR91. The way we operate, however, we did not see any significant advantage to having crews use a duplex throttle on trains out on the layout, so we are not very likely to convert our existing UT4Rs to duplex throttles.

Most of our locomotives are outfitted with headlights, Gyralights and a red warning light. The headlight is controlled by the F0 key, as on most locomotives. When the locomotive is running in reverse and F0 is ON, the headlight is extinguished and the red warning light turns on, simulating Wabash practice. The F1 key turns the Gyralight on and off, and the F4 key dims the headlight. A notation on the locomotive card which accompanies each train's pack of car cards indicates which locomotives are equipped with lighting effects.

The four LocoNet Fast Clocks we have mounted facing inward at the four corners of the layout are visible across the length of the layout. We also have one at the Dispatcher's desk and one in the Fiddle Yard. The only thing more we could wish for would be that they were available in an analog design more fitting the era we're modeling, which dates to a good seven years before digital clocks began to emerge. Since all of the LocoNet Fast Clocks can be controlled from any clock unit around the layout, or from a DT300 or DT400 throttle, it is very easy to adjust the time or clock speed.

During the summer of 2007, we added another LocoNet Fast Clock to the system in the form of a wall-mounted clock in the crew break room in the basement in Saline. Based on feedback from guests at the Great Lakes Express 2007 operating sessions and clinics, we have also added a large LocoNet Fast Clock high up on one of the room walls, to make it easier for crew members under 5'2" tall to be able to see at least one fast clock from anywhere on the layout. Since that time, we added an eighth LocoNet Fast Clock, mounted high on the wall of the break room/bullpen, so that off-duty crews can watch for their call times.

In Conclusion

We've been extremely happy with our DCC installation, and the Digitrax equipment in particular. Using DCC simplified the wiring to the extent that it was even possible to have completed the construction of the layout in time for the NMRA Convention in Toronto. It also relieves us of having to provide training for power-routing block controls on the layout itself and spares our guests the distraction of dealing with power-routing issues while getting their minds around our implementation of timetable and train order operation.

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