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Introduction to DCC
DCC is an acronym for Digital Command Control. It is a standard developed by the NMRA (National Model Railroad Association) for controlling model railroads with digital signals. Notice we did not say "controlling model trains", that is because DCC allows you to control anything on your layout from your locomotives and all their features (lights, horn, bell, etc.) to your led lights and signals and even accessories like turnouts (the switches that control which track a train rides on).
Everyone probably remembers or knows a train set with a transformer that uses DC voltage and polarity to control a trains speed and direction. And that works great for one train, but what happens when you want to control two or three or thirty? What about when a friend or a child visits and you want to run trains with them? That is where DCC comes in.
Rather than varying the voltage, a constant power level is applied to the track and "decoders" in each locomotive and accessory read a signal that is encoded into the power on the rails. Each decoder has its own "address" and only responds to commands addressed to it and ignores everything else. In this way you can have a large number of trains and accessories all controlled from the same Command Station.
DCC creates a bipolar Pulse Width Modulated (PWM) square wave. That means it turns the DC voltage on and off in bursts, or pulses so that each track takes turns being at full positive voltage with reference to the other track. It does this about 10,000 times a second. A short pulse is a "1" and a long pulse is a "0". Ones and zeros make up the binary system by which virtually all computers work. These ones and zeros stand for pieces of information like the address of a locomotive or the position of a switch. They are put together in small "packets" and sent to the track for the decoders to decode. It is very similar to the way a computer network operates. In fact, you can think of all those devices either attached or rolling across your tracks as tiny computers all getting instructions from your Command Station.
With DCC it is possible for multiple locomotives to be running at different speeds and in different directions all at the same time on the same track! And you can control everything from the palm of your hand using a controller.
DCC is a standard, which means that all of the different products from different manufacturers can all work together. You aren't tied to one manufacturer and as new products come to market, you can add them to your layout.
The typical DCC System consists of the following pieces:
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Controller - This is also called a "Throttle" or a "Cab" (A Cab is where all the controls are in a real locomotive). The throttle can be a handheld device or an app on your phone connected via a cable or wirelessly. A controller can even be a sophisticated software application running on a computer like JMRI or our web based exWebThrottle. The controller sends signals (commands) to the Command Station. There are usually buttons, knobs or sliders that allow you to control all of the various features and functions on your layout.
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Command Station - This is the brains of the operation. The Command Station receives the commands from your Controller, interprets them, and creates the data packets in the standard DCC format to go out onto the track and out to all the decoders. In DCC++EX you can expand your system by connecting sensors and outputs directly to the Command Station without having to use a decoder
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Power Supply - You will need a power supply with an appropriate voltage and current rating to run your layout. You may need one power supply, or in the case of running more than 12V with an Arduino, you are going to need to power the Arduino and have another power supply going into the motor board to power the track. As an example, A 12-14.5V DC supply rated for at least 3 Amps is a good starting point for N-Scale. The more trains you want to run and the more things you want to connect to the track, the more current you will need.
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Booster - A Booster "boosts" or amplifies, the DCC signal to the proper voltage for the track. DCC++ EX already has a booster built-in to the Command Station, so you don't have to get one separately. On large layouts, other boosters may be required to inject power and signal to far parts of the layout.
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Decoder - You don't really need a decoder, per say, you just need locomotives and accessories that already have one in them. The decoder is what decodes the DCC signal to read commands and then operates the motor, lights and sounds on the loco and turns on and off your accessories. Make sure when purchasing a loco that is "DCC Equipped" and not just "DCC Ready". DCC equipped means it has a DCC decoder installed. DCC Ready means it is "plumbed" for a decoder. In other words it has space inside and the wiring or connector to accommodate and easily add a decoder into it, but you would have to buy the decoder separately and install it yourself.