Locomotive has factory-installed decoder
with default programming.
DCC Ready
Decoder can be easily installed either by
replacing the existing circuit board in the locomotive,
or by plugging the decoder into a socket in the
locomotive.
DCC Capable
A decoder can be wired into the
locomotive. Soldering of wires is required. Some frame
modification may be required to provide space for the
decoder and/or channels for the decoder wires.
Classic
Locomotive not designed for DCC. Decoder
installation is more difficult and will require milling
of the frame and soldering wires.
DCC stands for Digital Command
Control. It is a system where digital commands are sent to the
locomotives through the rails. The layouts in the past used
block control, each required its own power pack and a complex
control panel to keep each locomotive electrically isolated from
each other.
Equipped with
DCC, locomotives on the same electrical section of track can be
independently controlled. While DCC is only one of several
alternative systems for digital model train control, it is often
misinterpreted to be a generic term for such systems. Several major
manufacturers offer DCC systems.
DCC provides for digital control of turnouts and
signalling as well. Other features include a multitude of sounds, block
detection, momentum control, and the ability to run locomotives together in
double headers or consists.
Watch this video to
learn more: Approximately 8 minutes.
DCC Origins:
The origins of DCC can be traced back
to 1940s when Lionel Trains introduced a commercial two channel
system using frequency control. An oscillator generated different
frequencies, depending on which button an operator might press. Then
a tuned circuit and relay in each engine controlled the direction of
the train.
GE, in the early sixties, introduced a
five-channel commercial carrier control system called ASTRAC
(Automatic Simultaneous Train Control), which could control more
than one train per block. Systems such as Dynatrol’s CTC-16
from late 1970s were popular but suffered from lack of compatibility
among competing systems. This is partly why National Model Railroad
Association (NMRA) introduced standards for Digital Command Control
based on proposal by Lenz. All manufacturers have to abide by this
standard in order to receive NMRA conformance approval. As a
result of NMRA conformance standards, a digital signal from a
command station can be received by any number of commercially
available decoders. (Tony's Trains, 2005).
Digital Command Control (DCC) systems are used to
operate locomotives on a model railroad (railway). Equipped with DCC,
locomotives on the same electrical section of track can be independently
controlled.
While DCC is only one of several alternative systems for digital model train
control, it is often misinterpreted to be a generic term for such systems.
Several major manufacturers offer DCC systems.
A DCC command station, in combination with its booster, modulates the voltage on
the track to encode digital messages while providing electric power.
The voltage to the track is a bipolar DC signal. This results in a form of
alternating current, but the DCC signal does not follow a sine wave. Instead,
the command station quickly switches the direction of the DC voltage, resulting
in a modulated pulse wave. The length of time the voltage is applied in each
direction provides the method for encoding data. To represent a binary one, the
time is short (nominally 58µs for a half cycle), while a zero is represented by
a longer period (nominally at least 100µs for a half cycle).
Each locomotive is equipped with a mobile DCC decoder that takes the signals
from the track and, after rectification, routes power to the motor as requested.
Power can also be routed to lights, smoke generators, and sound generators. A
stationary decoder can be attached to the rails to allow control of turnouts,
un-couplers, operating accessories (such as station announcements) and lights.
In a segment of DCC-powered track, it is possible to power a single analog model
locomotive, by itself or in addition to the DCC equipped engines. The technique
is known as zero stretching. Either the high or the low pulse of the zero bits
can be extended to make the average voltage (and thus the current) either
forward or reverse. However, because the raw power contains a heavy AC
component, DC motors heat up much more quickly than they would on DC power, and
some motor types (particularly coreless electric motors) can be damaged by a DCC
signal.
The DCC protocol is the subject of two standards published by the NMRA: S-9.1
specifies the electrical standard, and S-9.2 specifies the communications
standard. Several recommended practices documents are also available.
The great advantage of using DCC over traditional DC systems is the simpler
wiring needed to operate more than one locomotive at a time. Before, to operate
more than one locomotive independently, the track had to be wired into separate
"blocks" with switches selecting which controller powered which block of track.
If an operator failed to switch control of a block before his locomotive
entered, a short circuit or loss of control was possible. With DCC, many layouts
can be wired as a single large block, and each operator can control his
locomotive without worrying about crossing a block boundary.
DCC controllers can include an "inertia" simulation, where the locomotive will
gradually increase or decrease speeds in a realistic manner without continuous
inputs from the operator. Mobile decoders are available which will adjust the
power to try to maintain a constant speed, again without burdening the operator.
Most DCC controllers allow an operator to set the speed of one locomotive and
then quickly select another locomotive to control its speed.
Recent developments include on-board sound modules for locomotives as small as N
scale.
Before DCC, a scale locomotive would be controlled by applying a variable direct
current through the track. The train's direction would be changed by changing
current polarity and speed by varying the voltage. This is the system most
familiar to enthusiasts and has been used at every level from the train set oval
to the most extensive exhibition layouts. It is tried and tested and it works.
Through the application of electronics the level of control has been enhanced
and analogue systems can provide acceleration and braking delay, load
compensation, automatic operation and other sophistications that many people
erroneously believe are only possible with DCC.
The drawback of analogue DC is that the complications of control grow almost
exponentially as a layout grows and all because of one inescapable fact; all
locomotives on the same track will go in the same direction at the same speed
varying only because of their physical characteristics. From this comes the need
for numerous isolated sections, block control and complicated control panels.
The National Model Railroad Association (NMRA) in the USA, in co-operation with
manufacturers, set the standard for a new way to control locomotives. This was
called DCC.
The NMRA Digital Command Control Standard defines a basic communications
structure at the track level for digital control signals via the rails. The
standards specify a communication protocol between transmitter and decoder
without specifying transmitter and decoder hardware. The data needed to operate
each decoder is transmitted in packet format on the rails in the form of a
balanced square wave. This baseline packet format allows for interoperability
among equipment made by different companies that support the standard.
Interoperability is the most important advantage of the standard.
Interoperability means that if you have a DCC compatible decoder, you can run it
with any DCC compatible command station. This is very important since the major
part of your investment in any DCC system is in the decoders. We have all heard
the horror stories: “I have a fortune invested in this equipment and now I can’t
even get spare parts let alone expand my system!!!” Any system that is available
from more than one source is not as likely to disappear and leave its users
stranded. Also, having equipment available from multiple suppliers creates
competition in price and features to the benefit of the end user.
With Digital Command Control (DCC) you use a controller (also called cabs or
throttles) to send information to a command station telling it what you want
train X to do. The command station then takes this information, transforms it
into a stream of digital 'packets' and sends it to the booster. The booster will
add power to the packets, and broadcast the combined signal to the rails. In
most modern systems the basic set combines the command and booster functions in
a single unit; the NCE Power Pro and Gauge-master systems are typical examples.
DCC systems send commands and decoders receive and act on them.
The decoder-equipped locomotives on the railway constantly listen to the
’packet’ broadcast. Each information packet has an address component to it which
should match the address of one of the decoders. Any decoder which is not the
intended recipient of the packet simply ignores the data and its locomotive
keeps on doing whatever it is doing - running forward, backward, lights on etc.
The decoder, to which the data packet is addressed, will translate the packet
into a command for the locomotive such as ‘slow down’, ‘stop’ or 'reverse
direction’, and the locomotive will behave accordingly. The power on the tracks
is alternating current (AC), and not DC or direct current. Full power is running
through the tracks at all times while the decoder applies the appropriate amount
of voltage and polarity to the motor based on the speed and direction in which
you want the locomotive to travel.
Operation is far more exciting with each train running independently. You can
use double heading or banking and match the speeds of locomotives from different
manufacturers. You can program realistic acceleration and deceleration rates, or
limit the top speed of a locomotive.
DCC has advantages for everyone from the beginner to the advanced modeler and
for every layout from the smallest to the largest. Once you have the basic
system you can decide how much of the available functionality you want to use
and can expand the system as your layout grows; the equipment you already own
moves on with you as you add more features.
Your largest investment in time and money is often in the decoders you install
in the locos. These are upwardly compatible as you expand and add to your
system. By simply adding components you can grow into a more advanced system at
your own pace and as your budget allows. Most home layouts are small or medium
sized. They typically have a limited amount of track available for analogue
block control; DCC has a real advantage in these situations. Since blocking is
not required you can operate more locos in a smaller area.
For the large home or club layout DCC offers truly prototypical operation and
minimum wiring complications. Layouts running with DCC can operate more than 2
or 3 trains at a time; the outside loop running clockwise and the inside loop
running anti-clockwise all day is not very exciting. The ease of wiring makes
connection simple and lets you get operating sessions up and running more
quickly.
The addition of sound or computer control are examples of the increasing range
of features that you can take advantage of. Your railway can be as simple or
complicated as you wish.
Above all DCC enables you to control your trains just like the prototype.
Although DCC offers great advances in control it is not a cure-all for old
problems and brings one new problem. If an item functions poorly using DC just
adding DCC will not cure it. If a locomotive runs badly using DC the cause will
still be there after you install your decoder. It is best to test a locomotive
on DC before conversion if possible, even for new locomotives, and undertake any
maintenance or repair that is needed. If your track is dirty or poorly
maintained your railway will not run well. Wiring for DCC is different because
all track is live all the time but there is just as much need for good
connectivity. Points with dead frogs produce the same problems as before and
live frogs are still better; the wiring is easier though. DCC cannot substitute
for care and attention; in some ways it demands more.
With DCC you really can run two trains at different speeds in opposite
directions towards each other on the same piece of track with the obvious
result. With even basic start sets able to run up to ten locos simultaneously
you need to pay attention.
For the newcomer it is too easy to look at the technical specifications of DCC
systems and be impressed by the numbers that are thrown at you without really
understanding them. It is generally true that the larger the numbers the more
powerful and capable the system is likely to be but it is not necessarily a
guide to how easy it is to use.
Command Station –
The heart or brains of DCC. The Command Station is a dedicated computer that
communicates with all other parts of the DCC system. Selecting the brand and
model of Command Station is key to selecting the type of Throttle controls as
well as feature expandability of the system.
Throttle
or Cab – The
man-machine interface between You, the engineer, and the Command Station
controlling the train. Various Throttle equipment styles exist. Some systems use
a plug-in, walk-around Throttle, with the possibility that more than one can be
used at the same time. Some systems have Throttles built into the Command
Station. Each brand of DCC system requires their own brand of Throttle or
Engineer’s Cab, and their specific type of Throttle to Command Station wiring
interface. You cannot easily intermix brands here.
Booster –
A power amplifier of the communication signals from the
Command Station into power applied to the track. Some starter systems combine a
Command Station and Booster into one box. Almost all Boosters require an
external Power Supply. The ampere rating of the Booster and Power Supply will
limit how many locos you can run at the same time. Some Boosters are in a
separately available box and may be controllable from a Command Stations of a
different brand.
Power Supply –
An AC transformer or DC power source for the Command Station and track power
Booster. The Power Supply is NOT INCLUDED with many DCC equipment systems and
must be purchased separately. An additional Power Supply is usually required
with each additional Booster.
Loco Decoder –
An electronic receiver inside the loco out on the track. The Decoder receives
communications from the Command Station and controls the loco motor and lighting
effects. Some Decoders also add locomotive sounds to operation. Every DCC
controlled locomotive must have its own decoder. But any brand of Loco decoder
should work with any brand of DCC Command Station / Throttle equipment.
Almost all starter sets will provide you with
enough to get you started. You may have to purchase a separate power
supply and locomotive decoders, however.
Basically, there are a number of
DCC systems and starter sets available. This data has been
provided for information only and we do not endorse or recommend any
specific DCC starter set.
There are a number of factors involved
in the DCC starter set. Price and features are a starting
point:
How big
is your layout?
What
scale do you operate?
How many
locomotives do you want to run?
Do you
want push button or rotary knobs?
These are
just a few of the considerations that need to be made when it comes
to choosing a DCC system.
I recommend that any new DCC user
intending to purchase a DCC starter set should try a range of
systems at their local hobby store or model railroad club prior to
buying, as each set has different features.
The truth of the matter is that
everyone has their own opinion on which DCC starter set is the best!
