DCC for NTRAK and T-TRAK Layouts
More than 75% of NTRAK Clubs have adopted Digital Command Control (DCC) for control of at least one track on their NTRAK layouts. Some of these clubs use DCC extensively, and some of these have gone DCC all the way. Many clubs still provide for combined DC/DCC operations since some members may not have DCC-equipped locomotives, and others may wish to operate locomotives that have not yet been converted for DCC.
More and more NTRAK clubs and users are also adding T-TRAK modules and layouts. DCC offers similar benefits for T-TRAK layouts that it does for NTRAK layouts.
This page is intended to provide information on the benefits of using DCC on an NTRAK and/or T-TRAK layout (or your home layout), and information on choosing your DCC system.
It is also intended to remove misconceptions and misunderstandings about DCC that work against its adoption for NTRAK layouts.
Benefits of DCC Control of NTRAK and T-TRAK Layouts
Why should we adopt DCC control of NTRAK and T-TRAK layouts? There are several reasons:
Run Your Train, Not Your Track
This Digitrax advertising slogan is exactly right, and that is what we primarily do on NTRAK and T-TRAK layouts — run trains. With DC operation, whether using the old NTRAK throttles, the current Aristo wireless throttles or just a standard DC power pack you are essentially running your trains by adjusting the voltage to the track. All trains under control of the throttle are receiving the same voltage with the same polarity and running in the same direction. With NTRAK throttles you give up control of your train to another throttle as you enter the next electrical block. With Aristo throttles you must change channels as you enter the next electrical block. In either case the voltage on the track is probably different from your current voltage with a resulting surge or slowdown of your train as it cross the block boundary.
DCC provides something better. With DCC there is constant voltage on the track and you are controlling your train through signals passed from your throttle through the Command Station and Booster(s) to a computer chip (decoder) in your locomotive which controls how much voltage the motor will receive and its direction. Speed and direction is unique to your locomotive, and independent from all other locomotives. Direction is controlled by the throttle and is independent of which direction the locomotive is placed on the track; forward is forward and backward is backward.
Multiple locomotives can be MUed or consisted together to be controlled as a single unit from one throttle, just like the prototype does. By adjusting the decoder parameters (Configuration Variables) you can fine tune locomotive operation so each locomotive in the consist runs at the same speed, even locomotives of different types and from different manufacturers. Locomotives can be added to or deleted from the consist at any time, even while the train is running.
Multiple trains can be operated close together without regard to switching track power. All tracks are powered so multiple actions can take place at the same time, such as switching and make-up of trains in a yard.
Electrical blocks (called districts) in a DCC system are provided for reasons other than locomotive control. The engineer of a DCC–controlled train need not know the location of electrical district boundaries as they are transparent to operation of the train.
Independent Control of Lights and Sound
Since decoders are essentially computer chips they can be programmed (to the extent a particular decoder is equipped with the capability) to provide many different lighting and sound effects. As well as directional headlight and rear lights some lighting effects include ditch lights, Rule 17 headlights, MARS-type lights, beacons, strobe lights, etc. All are under control of the function buttons of the throttle running the locomotive.
These lighting effects can also be added to rolling stock using a function-only decoder, available from several manufacturers. These decoders do not have control for a motor, but enable lighting effects in dummy locomotives, passenger cars, cabooses, etc.
Prototype realistic sound can be added to locomotives through decoders designed for sound. Sound-equipped N scale locomotives are available, and sound decoders have been available for several years for custom installations. Some sound decoders are sold with sounds for a specific prototype locomotive while others offer a custom sound download feature. In all cases separate adjustment of each sound feature is provided to enable customization — volume and effects. Prototypical operation of a locomotive's horn/whistle and bell becomes possible.
Most DCC systems provide for walkaround control which allows you to walk with your train around the layout, staying where the action is. Walkaround throttles can be tethered or wireless.
Tethered throttles must be plugged into a throttle bus to control the train, but they can be unplugged and plugged into another location on the bus as the train proceeds. The train will continue to run at the speed and in the direction it is going while the throttle is unplugged.
Wireless throttles transmit to a receiver using either Infra-Red (IR) like a TV remote control or radio, and provide complete flexibility for running your train. For NTRAK and T-TRAK layouts radio throttles are preferred since they do not have the line-of-sight restrictions of IR.
Accessory Decoders, Signals and Other Functions
These are specialized decoders used to operate turnout machines and other electrical accessories from the DCC throttle. This allows an engineer to control the route his train will take from his throttle without having to manually throw a turnout.
DCC-based signaling is now available from several suppliers, and is now seen on NTRAK modules. These signaling systems can also interface to a computer for dispatching purposes.
Accessory decoders and signaling so far have seen limited use on NTRAK and T-TRAK layouts, but this use is rapidly increasing.
Constant Track Power
With DC control the speed of the locomotive(s) is proportional to the voltage on the track. Slow speed means low voltage in the track which limits the ability to overcome dirt and other wheel-to-rail contact contamination. This results in inconsistent speed and operation. If a DC track is run in the same direction all the time it will also encounter a greater build-up of dirt and other contaminants in one rail than the other.
DCC provides a constant higher-level track voltage, nominal 12 volts for N scale, which helps with the dirt problem. DCC is also an alternating current which means each rail sees a constantly changing polarity. This results in a more even distribution of dirt and contaminants, and results in improved control especially at slow speeds, but it does not obviate the need to start with clean track.
The constant track voltage also provides for the operation of accessory decoders, turnouts, lighting and other accessories independent of train control.
Since your are running trains rather than the track, multiple trains can be run at the same time, even on the same track. This means more trains per NTRAK or T-TRAK track, and more for spectators to see and stay at your layout during a show. It also means that various forms of prototype operations can be carried out, from simple card order operation to timetable operation to a fully dispatched railroad.
Some DCC manufacturers have integrated a fast clock into their system where the fast time can be viewed on the throttle display or on a clock display that plugs into the DCC system. When desired this function can be used to enhance a prototype operating session.
The National Model Railroad Association (NMRA) established an open architecture for DCC and maintains the Standards and Recommended Practices for DCC. These Standards and RPs are followed by all DCC manufacturers. The standards set the interoperability point as the track, which means that any DCC system from any DCC manufacturer will work with any manufacturer's decoder.
This does not mean that every DCC component will work with every other component from any manufacturer — for example a throttle from one manufacturer may not work with the command station from another manufacturer, although most command stations can control boosters from other manufacturers. It does ensure interoperability at the track between the booster and decoder — decoders will understand the commands received from any booster.
You Don't Have to be an Electrical Engineer to Use DCC
The fact that DCC involves electronics and computer chips tends to intimidate many folks who are not electrical engineers. But computers have electronics and chips yet most people use computers. Many items — your stereo, television, cell phone, smart phone, tablet computer, microwave, etc. — also use electronics and computer chips but most people use them. DCC is not difficult nor complicated.
You can purchase locomotives with decoders installed. You can purchase locomotives ready for a decoder to be installed, either through a plug connector or by simple replacement of a circuit board in the locomotive. Either way provides an easy way to start — most locomotives available today from Athearn, Atlas, Bachmann, Con-Cor, Fox Valley, InterMountain, Kato, Micro-Trains and Walthers/Life-Like are either equipped with a decoder or capable of easy decoder installation.
Getting started with DCC on an NTRAK or T-TRAK layout is also not difficult. Simply connect the Booster track output to one of the NTRAK track power feeds and start running. Use this to get experience then plan what you need to expand DCC on your layout according to what your club desires. A great deal of information on doing this can be found on other pages in this web site.
Appoint a Digital Master for the club. This person, usually someone who is technically knowledgeable or who wants to learn, learns the nuts and bolts of DCC at the next level, and leads the club in planning for DCC and in setting up and operating NTRAK and T-TRAK layouts. There is also a great deal of information on this web site targeted specifically at the Digital Master.
Digital Command Control consists of several components that make up the overall DCC system. Following is an explanation of how each component functions in a DCC system.
The most visible part of the DCC system is the throttle (also called a cab in some systems) as this is the prime user interface to the DCC system. The throttle is used to control the speed, direction, lighting and sounds of the locomotive. It can also be used to control accessories such as turnouts, etc. if the layout or module is so equipped.
There are several styles of throttles available, even from the same manufacturer. There are throttles that have lots of buttons or few buttons, a display or no display, use knobs, wheels or push buttons or a combination to control the speed of the train, and buttons to control functions. Some throttles allow control of two trains simultaneously.
The following are some examples of throttles:
The Command Station is the brain of the DCC system. It interprets signals provided to it from throttles and converts them into the data packets that will control the locomotive and its functions. It adds an address to each packet so only the intended decoder receives and responds to the information. This packet with address is then sent to the Booster to be sent to the decoder through the track.
Note that most systems combine the Command Station with one Booster, such as the one at right (Digitrax DCS200 8A Command Station w/Booster).
The Booster amplifies the packets received from the Command Station and sends them to the decoders through the track. The Booster also provides the track voltage to power trains. The packets are superimposed on the track voltage.
The number of trains that can be operated by a Booster depends on the current output of the Booster and the total current draw of the locomotives and lighted cars in the train. Booster are available with different current outputs, anywhere from 2.5A to 5A to 8A to 10A, depending on the manufacturer.
Note that most systems combine the Command Station with one Booster, although most manufacturers also offer standalone Boosters.
There is a Booster configuration that works very nicely for NTRAK layouts that can provide power for an electrical district that is about 100ft long (assuming the modules are equipped with NTRAK Standard Powerpole connectors and 12ga buses). This configuration is a Digitrax DB200 8A Booster (shown in photo at left) feeding into a PM42 Power Manager, which then feeds the track. Each section of the PM42 feeds one of the NTRAK tracks (red/yellow/blue/green). The current trip on the PM42 is set to 3 or 4.5A as necessary to handle the load. Yes four times 3 or 4.5A is more than 8A, but it is unlikely that all four tracks will be drawing maximum current at the same time. Components from other manufacturers can be used in place of the PM42.
Many Command Stations and Boosters do not come with power supplies. Each Command Station, Command Station/Booster combination or standalone Booster has its own voltage and current requirements. A power supply chosen to power a DCC component should be rated at the correct voltage and at least the maximum current output of the device being powered.
A decoder is needed for every item that is to be controlled from a DCC system. All decoders receive all packets sent from the Booster through the track. When the decoder detects a packet addressed to it the decoder's processor chip reads the packet and provides the appropriate command to the motor, lights and/or sound functions.
NMRA DCC-compatible decoders are available from several manufacturers, and can be selected to meet size, current capacity and feature needs of a locomotive.
Selecting a DCC System for Your NTRAK Club
The is no formal standard for a particular DCC system for NTRAK or T-TRAK, but there is a "de facto" standard — Digitrax. Some 88% of NTRAK clubs operating with DCC have chosen the Digitrax system. While any club is free to chose whatever system it feels will best meet its needs the overall preponderance of Digitrax systems means that almost all major NTRAK and T-TRAK layouts at conventions and shows will be Digitrax controlled.
Most DCC manufacturers provide the manuals for their DCC systems and components on their web site. You can learn a lot about the system you are considering by reading the manual. Almost all DCC systems have an Email list on Yahoogroups and/or other sites that are not run by the manufacturers, plus there are some non-system specific lists. These lists provide a place where questions can be asked and answers received — Click here for an index of the lists
In purchasing a system an NTRAK club should steer clear of starter systems and go for the top of the line system offered by the manufacturer. This will provide the most flexibility for DCC operations and growth potential as your usage of DCC grows. Definitely stay away from any starter systems that have minimal or no growth potential. For many T-TRAK layouts the basic Digitrax starter sets, the Zephyr and Zephyr Extra, meet the needs of operating the layout.
An NTRAK and/or T-TRAK club adopting DCC also needs to decide who owns what among the various DCC components. A general rule of thumb would be for the club to own the main Command Station/Booster. Additional Boosters can be either club-owned or member-owned and loaned to the club whenever the layout is set up.
Throttles should be member-owned. Each member can then purchase his preferred throttle (from the selected manufacturer) depending on the features and capabilities desired. Also, with the individual member being responsible for maintenance and repair of his own throttle he is likely to take better care of it than if club-owned.
The cab bus is the communications bus between the various components of a DCC system that are not part of the track bus. These include communications between throttles and the Command Station, Boosters, detection systems, signaling systems, radio/IR receivers, etc. The Digitrax cab bus, called LocoNet®, provides a significant advantage over other systems that use polling on the cab bus.
LocoNet is a peer-to-peer distributed network system on which all devices can monitor the network data flow. The network is event driven by different devices in time, and is not polled by a centralized controller in normal operation (like other DCC systems). LocoNet is a powerful decentralized and scalable distributed system.
LocoNet is a peer-to-peer Local Area Network (LAN) and is based on the Ethernet CSMA/CD (Carrier Sense Multiple Access with Collision Detection) Local Area Network protocol, the most universal worldwide hookup standard for computer networks. LocoNet has been optimized for use with Digitrax systems to allow 100% traffic capacity with less than 0.33% collision rate.
The LocoNet design allows very simple free form wiring, which makes adding extra devices and features simple, and provides expandability so new features can be added by simply connecting and overlaying the capabilities to an existing LocoNet system.
The Digitrax DCC system is fully Expandable and upward compatible. All Digitrax DCC components and devices manufactured since 1995 are fully compatible and operational with systems purchased today. All devices, even starter sets, are fully expandable to work with other components of the Digitrax system without scrapping anything. You can make the system as simple or as complex as necessary to accomplish what you want to do with the layout.
Digitrax DCC and the LocoNet cab bus have a significantly larger Number of Accessories both Digitrax manufactured, third party manufactured and do-it yourself than any other system. You can do things with a Digitrax system that you cannot do with any other DCC system.
There is a widely used computer interface software for DCC systems from multiple manufacturers called the Java Model Railroad Interface (JMRI). However, the capabilities of JMRI with the various systems varies; what you can do with JMRI with a Digitrax system is significantly more than with any other DCC system.
Maximizing the Potential of DCC
DCC removes virtually all limits to prototype operations on a model layout, whether NTRAK, T-TRAK or not. This includes bi-directional running on each track including trains passing each other, crossing over to another track, switching, helpers, etc. This, however, requires some planning to ensure there are working passing tracks and crossovers suitably located in the layout. For full operations this may even entail dedicated operators (e.g. dispatcher) and the use of two-way radios for communications between engineers and with the Dispatcher.
What could normally be just roundy-round running can now become operating a railroad. Spectators at a train show pay attention to activities, and may stay longer watching the layout. For someone who is asking questions and shows real interest hand them a throttle and let them run a train. Perhaps this will help recruit a new member, or kindle an interest in adopting model railroading as their hobby.
Copyright © 1997–2018 North Raleigh Model Railroad Club. All rights reserved. The NRMRC is a Not-For-Profit Corporation incorporated in North Carolina. The various logos and heralds shown here are the property of their respective organizations.