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What is DCC?

The fundamental question: what exactly is this fancy digital system? There’s a long answer and a shorter one. To avoid confusion, I won’t go into any of the techie stuff about how the electronics of DCC work because unless you’re building your own system, it isn’t really relevant.

The best way to understand DCC is to think of a full size electric railway, such as the London Underground. Power is constantly supplied to the trains by conductor rails. The train driver on board each locomotive is then able to use this power to regulate the train’s speed by controlling how much goes to the traction motors.

In model form, the principle is the same. The difference is that instead of a miniature driver, we fit each loco with a small electronic decoder, which receives power directly from the track. Unlike conventional DC systems, this power is always on. This way, the locos are all separated from each other.

Instructions are sent down the track by the controller and picked up by each decoder. If the command is intended for it, a decoder will respond accordingly, such as to increase its speed or switch on the headlights. If not, the commands are ignored and the loco carries on whatever it was doing. All locos can therefore be controlled independently of each other. With DCC, you drive the train and not the track.

Some popular DCC myths and misconceptions busted:

1) DCC means computer control.
Not necessarily. While DCC is ideal for computer control (as the DCC controller is already working in binary code, a simple interface is all that’s needed for it to ‘talk’ to a PC) you don’t have to touch a computer to use DCC. You can (and most users do) control trains manually with a controller.

2) ‘Wiring for DCC’
This one just won’t go away. The prospect of ‘wiring for DCC’ often scares would-be newcomers with the thought of doing miles of complex wiring because of the more complex technology. Nothing could be further from the truth. Because you are controlling individual locos rather than sections of track, you don’t need to set up isolating sections just to hold one train stationary while you move another. The loco itself is isolated electronically. All we need to do is power the track, avoiding short circuits.

There’s still wiring to be done, as I’ll show in following chapters, since we need to ensure the power gets to all parts of the layout without causing any short circuits. But it ranges from slightly simpler to a lot simpler than a comparable DC layout. ‘Wiring for DCC’ is nothing more than ‘wiring for DC’ with bits left out.

3) ‘Two wire control’
Here’s one you’ll see in manufacturers catalogues. This one is semi-true, actually, since there are only two main wires to the layout. However, on anything but the simplest layouts, you’ll need extra feeds here and there to ensure continuity. Rather than wiring them all to a central panel though, all these feeds connect into the two main wires. So while there are only two wires leaving the controller, you will expect to see more than two connection points to the track.

4) ‘Programming’
Another myth that sparks fear and confusion. What is wrong with this one is the choice of word. ‘Programming creates mental images of computers, complex program-writing and lots of effort and head scratching.

The fact is, you don’t have to program anything to use DCC. Decoders come from the factory ready set up, and after installing into a loco will work right away. All you really need to do (unless you will only use one loco) is to allocate each loco a unique ‘address’ or running number (the default is usually 3). This enables the controller to 'talk' to each loco separately. However, this can be done with a few quick key presses and is very simple to do. After that, you can leave things how they are from the factory (which most of us are happy with under DC anyway)

Of course, there are lots of things you can alter if you want, but it’s all optional. You can set up the maximum speed to something more realistic, or play around with the acceleration rate. If you just want to get something going though, you don’t need to bother with any of it.

For the sake of clarity, I’ll be using programming here, but feel free to read it as ‘setting up’, ‘configuring’ or whatever word you want.

DCC on DC?

Questions on DCC often get asked about running a DCC fitted loco on a DC layout, and vice versa.
DCC decoders are designed so they will operate on DC layouts (though this can be disabled if you wish) On detecting the DC supply, the loco will respond as if it were a DC loco.

The reverse is not as simple. While many systems allow the running of one unconverted loco on DCC control (usually on address 0) the control method is rather crude. It works by 'stretching' the signal to give a DC bias. However, you are still running a DC loco on what is effectively an AC supply. This will cause motors to heat up sometimes burn out.

In short: DCC locos work fine on DC, DC locos are not recommended for use on DCC layouts.

DCC Controllers(manufactures descriptions)

Hornby - DCC Controller 'Select' (R8213)

"The Hornby Select digital controller is the perfect way to enter the digital world of model railways. Each locomotive can be coded with up to 99 levels of acceleration or deceleration speed (inertia). The LCD display screen of the Select shows the number of the loco or accessory which has been selected. Power is through a standard wall mounted transformer which supplies 1 amp 15V DC power to the track; a larger 4 amp transformer is available which will provide additional power to the track for more locomotives to be run at the same time."

and 'Elite' (R8214)

"For those who wish to take their train control to a new and advanced level, the Hornby Elite is the ideal companion. Capable of answering the needs of most railway layouts, this advanced unit with twin control and wide function LCD screen can carry 255 registered locomotive addresses and the same number of accessories, plus a USB portal for linking to a personal computer. Once inputted and assigned, the unit will also display the names and running numbers of locomotives, as well as train direction, speed and function indicators. A clock is also included on the display which can be set to real time or up to 10x faster. The Elite is supplied with a 4 amp transformer which is capable of providing enough power to run approximately eight locomotives at any one time."

Bachmann - EZ Command DCC Controller (Catalogue No. 35-500)

"E-Z COMMAND allows the operator to digitally control speed, lighting and direction of multiple locomotives. Unlike other complicated digital command control (DCC) systems, E-Z COMMAND provides simple and straight forward digital operation of your layout.

8 function buttons for control of specialist decoder
Simple on-track programming
Plug-in wiring
NMRA Standard DCC"

and Dynamis

Bachmann Dynamis DCC Controller (36-505)

Dynamis Review

(Click here)

"E-Z Command Dynamis allows the operator total freedom by integrating advanced infra red wireless technology into an affordable and powerful Digital Command Control System. Using a unique toggle style joystick both speed and selection of locomotive are controlled. A backlit LCD screen with graphical interface and easy to use menu buttons make programming of CVs and operation of the unit is simplicity itself. Locomotives can be recalled by either selecting the locomotives by Name or Number and both 2 and 4 digit addressing is supported. The 10 function buttons allow for simple One Touch Operation allowing for different sounds and lighting to be operated. In addition by simply selecting A or B bank on the menu button you can operate decoders which support up to 20 functions."