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Basic Components of a DCC System

Many questions pertaining to DCC come my way, both at train shows and through my web site or telephone. In this installment of “DCC Basics” we will deal with the question that is probably asked more than any other. It goes something like this:  “If I were to change my layout over to DCC what all would I need to buy?” So let’s take a look at the basic components that are necessary in any DCC controlled system.

The Power Supply:Power Supply

First of all, there must be a source of power to make everything go!  In most DCC systems, the power supply is an external transformer that converts 120 V AC (house current) to 15 volts AC to run the equipment that creates the DCC signals that run the trains. Most of the smaller DCC sets come with a power supply included but in most of the higher amperage sets a power supply must be purchased separately.  Fortunately power supplies are not very expensive to buy. It is also possible to use an existing DC power pack’s AC output terminals to power your DCC system. What really needs to be evaluated in this case is the amperage rating of the DC power pack. Most DC power packs have relatively small amp ratings and do not have the power to run a DCC layout where a relatively high amperage is in the rails at all times, usually powering multiple trains and accessories.

The Command Station:Command Station

The command station is the “brain” of the system. It reacts to the commands you give with your throttle and generates the DCC signals which control the speed and direction of the trains, and even the operation of a loco’s lights or sounds.  Many command stations will enable you to operate accessory decoders (such as the ones attached to switch machines), control layout lighting or animated accessories, link engines together in consists, and unless it is one of the most basic command stations, allow you to program the decoders. Before purchasing a DCC system it is important to evaluate your amperage needs based on the number of trains you want to run at the same time. A command station is designed to be able to use a pre-determined number of input amps and no more. Buying a 5 amp power supply and using a 2 amp command center will only provide your layout with 2 amps of power.

The Booster:Booster

Boosters take the DCC signals produced by the command station and combine them with power from the power supply to make the signals powerful enough to run through the rails and operate the trains. The command center alone is not powerful enough electrically to do the job. If the command center is “the brains” of the system, then the booster is “the brawn”.  An important fact to know is that almost all DCC command centers today are sold together with the booster in the same case.  However, boosters are available separately, as in the above picture, for increasing power as your layout or power needs expand.  Also, some boosters have the capability of being used as “auto-reversers” for no-hands operation of your trains through reverse loops!

The Throttle:Throttle 1Throttle 2

DCC throttles come in two general categories: “full feature” throttles, as shown in the left picture above, and “utility” throttles, shown on the right. Although no two manufacturers’ throttles are exactly the same, full feature throttles generally allow the user traditional speed and direction control as well as the ability to access all locomotive and accessory decoder functions and also to program those decoders.  The throttle in the left picture above even has two speed control knobs to control two separate trains at the same time.

Utility throttles allow for speed and direction control and most or all decoder functions but cannot perform programming. It does not come as a surprise that full feature throttles are quite a bit more expensive than utility throttles. Thankfully, if you want to purchase extra throttles for your guests or operating friends utility throttles are normally all you would need.

Decoders:Decoder 1     Decoder 2     Decoder 3    Decoder 4

Most DCC systems today let you run one non-decoder equipped engine (or consist) on your layout at one time. This allows you to convert your locomotive roster to DCC gradually. But to fully benefit from a DCC system you will probably want a decoder in every engine where it is practical. You may have an antique engine that you want to keep in its original condition or certain inexpensive locos in your collection might not be worth the expense and effort of installing a decoder.

Decoders are like most items in today’s high tech world: Prices have come down considerably over the last few years as reliability and performance has increased. Good, basic decoders with 2 or 3 lighting functions can now be purchased for under $20.00!  DCC decoders can be programmed to control many functions in addition to speed and direction, such as multiple lighting functions (including mars lights, strobes, blinking lights, constant lighting, directional lighting, etc). Locomotive performance features such as acceleration and deceleration rates, starting, mid-point and top speed, sounds and others.  And control is extremely precise! Today’s decoders are able to provide a normal 128 speed steps from 0% to 100% of full power!

I should also mention that accessory or “switch” decoders are made to control from one to eight switch machines of any style from slow motion to solenoid. You command these decoders from your throttle just like the “mobile” decoders in the locomotives.

These are the basic components of any DCC system. DCC systems can be very simple or as complex as you want. One thing is certain:  DCC control offers the potential for more prototypical model train operation. If you have questions I would be happy to do my best to answer them or point you in a direction where an answer lies.

John Thut --- DCC Hobby Supply
(970) 586-3161

--- (March 15, 2007) --- Back to What's New