A Guide TO Dcc Page 1 A Guide to DCC

1 INTRODUCTION TO DCC What is Digital Command Control, or DCC? Before we can answer that question, it is worthwhile to step back to the way model trains were originally controlled, that was by direct current (DC) power. DC Control Direct Current, (DC control) is the most basic form of control for model railroads. A variable voltage is created by the power pack and transmitted to the rails. The locomotive is provided with power pickups on the wheels and directly connects a DC motor to that power supply. The motor runs faster or slower, simply by increasing or decreasing the voltage to the tracks. This works freat with a single engine, but what if you want to run more than one train at a time or maybe one going in the opposite direction? To do this, sections of track have to be insulated from each other, and electrical switches installed so the current to each can be turned on or off as needed. While multiple engines can stay on the layout, without power, only one train can still be run in each section at a time. To control more than one train, additional power packs could be bought and wired to the tracks, allowing operation of two trains with two separate controllers. Trains that are to be operated independently have tracks that have selector switches (often called block switches) that route the power from the throttles to the track that has the train we want to control. For many model railroaders this DC operation is still a control mainstay. The Roots of DCC- A Little History A dream extending back to the early days of model railroading is the ability to control 2 (or more) trains on the same length of track without the manual or automatic control of blocks. However, the technology was simply not there to allow this to be done affordably by the average hobbyist, nor was the technology small enough to fit into the average locomotive. Things started to change in the 80s when pioneering hobbyist- engineers developed circuitry that could impose a signal on top of the track power. This signal would be generated by a controller and picked up by circuits within the loco, feeding a regulator that powered the locomotive motor. Bulky at irst, these systems grew in complexity, including moving from analog signals to digital, and increasing the use of on- board microprocessors to decode the signals. At last, trains could be run independently, without being tied to the throwing of block switches. However, the systems were not standardized and equipment could not be run on competing systems. The model railroad community, through the cooperation of several manufacturers and the NMRA (National Model Railroad Association), addressed this issue in January 1994 when the DCC standard protocol was established. It defined the language that command station and decoders would use to communicate. This would allow equipment from one manufacturer to be compatible with others. Note that this did not define how the controller itself would operate, so the command bus on most systems are not compatible. But the equipment on the track could be run together. And this was an accepted standard, which provided a means whereby decoder equipped locomotives of different manufacturers could run together on the same model railroad. Each decoder is assigned a unique address that allows it to be discretely controlled by the DCC Command Station and Booster. Trains could inally be run together, on the same track at the same time by different people, allowing for the opportunity to have classic cornfield meets! A Guide to DCC OR - How to add more to your railroad! Reprinted Courtesy of Model Rectifier Corporation fun This article is designed to provide a basic understanding of the background, components, systems and operations of DCC (Digital Command Control) for use on model railroads. While it is fairly complete, keep in mind that it is intended to serve only as a basic preamble to the subject. Once familiar with the elements, you'll have the opportunity to dive deeper into the design and operation of all of its elements. At the same time, DCC has been designed to be fundamentally simple in its implementation. DCC can enhance the enjoyment of model railroading without requiring an electrical engineering degree. Article Sections 1. Introduction to DCC 2. Building Blocks of a DCC System 3. Selecting a System 4. Decoders 5. Mobile Decoder Installation 6. Sound 7. Stationary Decoders 8. Pulling it All Together 9. Advanced Operations 10. Glossary

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