Digital Command Control at SVL

NMRA Digital Command Control (DCC) is a system which allows independent control of locomotives without the use of electrical isolation, toggle switches, and a maze of complex wiring.

With DCC it is possible for multiple locomotives to be running at different speeds and different directions at the same time on the same track.

In an operating session, joint working time in blocks is not only possible, but commonplace. This keeps that dispatcher pretty darn busy on operations night.

In addition to the info about SVL's DCC system described here, Mark Gurries, one of our members, has created a several detailed presentations about DCC that can be found here.

Mark also provides some advice on choosing a DCC for your own layout or railroad club here.

DCC Basics

Instead of complicated layout wiring, the emphasis is placed on special circuitry in the DCC system and inside the locomotives themselves. Advances in microelectronics allow specialized microcontrollers called decoders to be installed in each locomotive.

Instead of a traditional variable DC power pack to control speed to control one locomotive, a DCC system sends messages to locomotives using an encoded AC track voltage.

In DCC systems, a Command Station is responsible for generating the DCC signal. A Booster converts that signal to an AC track voltage. A Decoder listens responds to commands send by the DCC system and controls the locomotive speed and direction independent of other devices on the track.

NOTE: On some systems, like the Digitrax Zephyr and Atlas Commander, the Command Station amd Booster are in the same box.

Our DCC Installation

Silicon Valley Lines uses a mixture of NorthCoast Engineering, Wangrow, and Lenz equipment to operate our layout.

A NorthCoast Engineering PH Pro is the layout command station and booster for the main yard. Additional NCE boosters are used to power the mainlines. Our dedicated engine programming facility uses a SystemOne (RamTraxx) RXC500F.

Throttles

Stereo-plug jacks are placed around the layout, and members use NCE-bus compatible cabs (RamTraxx, System One, or North Coast Engineering) to control their trains. We have recently installed an NCE RB-01 radio base station to allow wireless control of locomotives.

Several different controllers are used by different members in the club. Since personal preferences vary, members own their own controllers. The newer, smaller, handhelds are useful for locals and/or switching operations, but don't offer all the features of the larger advance cabs.

Using the advanced cab, it is possible for an engineer to create MU-lashups for heading up the grade.

Decoders

Many types of decoders are in use at the club, some of the most popular being the new "N-Scale" decoders on the market. These small wonders deliver 2 amp peak power, usually enough for newer HO road power, but is small enough to fit into even N-Scale engines.

One of the very nice things about the NMRA DCC standard is that any vendor's decoders are compatible with any control system. This means that Digitrax, Lenz, and Soundtraxx decoders all work with NCE, and vice-versa. The modeller can pick the best decoder for his or her engine without having to stick to a single brand.

Other popular decoders include the NorthCoast D102, Lenz LE103, and Digitrax DH121-- which deliver baseline DCC performance at or below a $20 price point.

Turnout Control

We have recently standardized on using Circuitron Tortise slow motion switch machines and NCE Switch-It™ accessory decoders for all mainline turnouts. In future operating sessions, the SVL dispatcher could be even busier, because the club is planning on having centralized control of all mainline turnouts.

Ironically, the need to handle both DCC and traditional push-button control panels has meant that the wiring for turnouts is probably more complicated than on most other layouts.

The Future

Because the dispatcher will ultimately control every mainline turnout, our future plans include developing a computer-based CTC system to keep everything running smoothly.

The goal is to integrate block occupancy monitoring, signals, and turnout control into a single system. The leading contender here is leveraging some of the work done in the JMRI project.