About DCC/Which system should I get?

Wiring

Track and points

Decoders

CVs

Lighting

Q. What does "DCC" stand for?

A. Digital Command Control

Q. What is the difference between DC and DCC?

A. With a DC (analogue) system you apply power to the track when you want to move a locomotive. With a DCC system all of the track is live all of the time, so you can drive more than one train at a time on the same track. This does have its problems! There are ways around these problems, though, as you will see below. Each locomotive is controlled by the use of a decoder. This device allows additional features such as sound and lighting to be controlled through the electronic pulses that travel through the rails. In addition you can control points and signals from the DCC controller, or from a computer if you want to link the system into a PC.

Q. Can I use DC and DCC on the same layout?

A. In theory it is possible and there are some modellers who have set up this arrangement. However, DC and DCC do not talk to each other as they use different types of electrical supply so advice would be to avoid this setup if at all possible.

Q. Which DCC system is best for me?

A. Unfortunately there is no right answer to this question. The best system is the one that is right for you. The only way to find that out is to do some research and look at what systems are around and what features they have. Try them out if at all possible by going to shops, shows and/or fellow modellers but beware of the person who says that the only DCC system you should buy is the one they have!

Q. What should I look for in a DCC system?

A. Again, much of this is down to personal preference as well as looking for a system that will not only satisfy your needs now but can be expanded at some later stage to take into account further developments. Remember DCC is changing rapidly and new technologies will be increasingly used so it is important that systems are upgradeable. All model railway layouts are developing in some way. Look at how easy a system is to use and handle - is it user friendly? Will it handle all of my locos, i.e. does it provide enough power? A 5 Amp system is probably adequate for the average user. Do I want to control points, signals and other accessories with the system?

Q. What is a command station?

A. This is the control centre of the system through which all of the commands from CABS are sent to the devices you are controlling.

Q. What is a CAB?

A. Not something you would find in a bus! Sometimes called a throttle, the CAB is the device from which you control the locos and other accessories on your layout. It is also the device that is normally used to program decoders, though not all cabs can be used for this purpose. With many systems you can have a number of cabs around the layout, connected together with the COMMAND STATION via a BUS.

Q. Can I use radio to control my DCC layout in the UK?

A. Yes, provided the system uses a radio wavelength that is compliant with EU legislation. DCC systems manufactured in the US are generally NOT compliant and cannot be legally used in the UK - it would also be foolish to do so as the wavelengths used by some US systems conflict with mobile phone or air traffic control wavelengths here in the UK.

Q. What is a decoder?

A. A decoder is an electronic device which you need to install to operate devices, such as locos, point motors, signals and other accessories. Each locomotive needs its own decoder as it stores the loco number, used to call up and operate the loco, as well as other settings that apply to that loco. These other settings can control, for example, the maximum speed of the loco, light settings, sound settings and settings for any other add-ons that the loco might have. There are also accessory decoders that are used to control things such as points and signals. These are not the same as loco decoders, so make sure you order the right type! Many accessory decoders look the same as loco decoders.

Q. How do I know which loco decoder I need to install?

A. Decoders to control the motor inside a loco come in various sizes. You would be well advised to look inside the loco to see how much space there is. Steam locos in particular do not have much space inside for a decoder. You also need to see what the stall current is, i.e. how many amps are being drawn by the loco when the motor is stalled on the track? Most standard decoders have a stall current of about 2 amps. You also need to check that the decoder has sufficient output to control the motor in the loco you want to use - for example, you CANNOT use the R8215 Hornby decoder in a Heljan loco as the loco has a greater power requirement than the output of the decoder. One other factor you will need to take into account is how many functions you want in order to be able to operate the loco and all of its installed features, such as lights. Many modellers find that for a standard OO steam loco a 2-function decoder is adequate. However, for a DMU, for example, you might want a 4 or 6 function decoder in order to be able to control individual lights front and rear and any other lights that you might have fitted. If you want install a sound decoder you need to check that the decoder is of the right type for the loco.

Q. Can two loco decoders have the same loco address?

A. Put simply - YES. However, the two locos will be treated as one by the system so you you probably wouldn't want to do this in practice. If you want double heading (called consisting) this can be achieved in other ways. You might, though, want to have decoders in different carriages of a DMU with the same loco number so that they are treated as one. This makes the control of lights, etc. much easier.

Q. What is a function only decoder?

A. A function only decoder is not able to control the loco motor but will be able to control things such as lights or smoke units. In a DMU, for example, you would want a standard decoder in the carriage with the motor but you could use function only decoders in the other carriages where you might want to control lighting features. You need to check that the decoder has sufficient output to control the physical device you want to use.

Q. Can I map functions to particular buttons on my controller?

A. Yes, but this will depend on the decoder in use. You will need to consult the instructions that came with the decoder to find out which CVs you need to change. For remapping of functions on TCS decoders see their Simple Programming Guide here.

Q. Do I need to remove capacitors from loco motors?

A. Not always. Also bear in mind that removing the capacitor(s) could render the warranty invalid. Some decoders do operate more efficiently with capacitors removed (TCS, for example) and many modellers find that Bachmann models in particular run better without the capacitors installed. However, this does not always seem to be necessary. The answer seems to be try running the loco and if it is difficult to control at slow speeds or suddenly takes off like a jack-rabbit then remove the capacitor - if there is not a need, leave the capacitor alone.

Q. What does "DCC Ready" mean when applied to a loco?

A. This is an interesting question. The term is misunderstood by many including, apparently, manufacturers. Essentially all the term means is that a 6 or 8-pin NMRA socket has been installed into the loco. This should enable a decoder to be installed by just plugging it in to the socket. Whether the decoder will actually fit into the loco is another question! UK steam locos seem to be the worst offenders where manufacturers install a socket but leave little room for the decoder. Also check under the socket to ensure that none of the solder pinnacles come into contact with the metal body and also that there hasn not been any solder "bleed" between one pin and another. Both of these are faults we have discovered whilst installing decoders into DCC Ready locos.

Q. How do I stop my Loksound decoder (also used in Bachmann sound locos) from resetting itself?

A. It is possible to set the decoder so that it "remembers" (at power up or when the loco is selected and the sound activated) that it does not have to go through the whole sound start-up process every time.

Set CV124 to a value of 6.

Q. What are CVs?

A. CV stands for Configuration Variable. Setting these variables (CVs) enables decoders to control various features of the loco or accessory. By changing these variables you alter the characteristics of the device you are controlling. For example, you can control individual lights, sounds, speed or even the direction the loco travels in.

Q. Why is CV29 so important?

A. CV number 29 is one of the CVs that all decoder manufacturers have to follow the same (NMRA) rules for how it can be used. This CV tells the command station whether the decoder has been configured for 4-digit addressing, whether it is set up for use on a DC (analogue) system, how you have set the decoder to control the direction of the loco, the number of speed steps you want to use and whether you are going to use a separate speed table. You can find out more detail about CV29 and a lot of other CVs by clicking here.

Q. What is a BUS?

A. No, it's not a vehicle for transporting people! Well, not in the world of DCC. It is a cable for transmitting data. In DCC there are normally 2 buses that are referred to - the POWER BUS (cable connecting different parts of the layout with electrical power and along which data is sent to decoders) and the COMMAND BUS (a cable connecting CABS together with the COMMAND STATION).

Q. What are power districts and do I need them?

A power district is a section of track that is powered separately from other sections of track on a layout. How many power districts you have usually depends on the size of the layout. For larger layouts some power districts may have additional power boosters if they are a long way from the main power supply. Even on a small layout, though, you might want (or need) more than one power district. Separating a layout into power districts means that if one section becomes inoperable for some reason (like a short circuit, for instance) the rest of the layout will keep functioning. It is possible to have a number of power districts using only one power supply. The NCE EB3 Circuit Breaker, for example, will enable up to 3 power districts and will indicate (via LEDs) whether each section is running correctly or whether it has a fault. The EB3 also has a user adjustable time delay at power-up which helps to protect locos on the layout that might be affected by a sudden power surge at switch on.

Q. What are DCC friendly points?

A. Any points can be used on a DCC system, so the simple answer is any!

Q. Do I have to modify points for use on a DCC system?

A. The simple answer is no. Both insulfrog and electrofrog points can be used without modification. HOWEVER, it is VITAL with electrofrog points that rails leading to the inner part of the V MUST be insulated or otherwise you will get a short circuit - that is guaranteed and will not do your loco decoders any good at all!! In the ideal world, though, there are some modifications you could/should make, and there are several sources of information on how this can be done - one example here, and another perhaps simpler example here.