A Guide TO Dcc Page 9 A Guide to DCC

9 27 ohm 1/2 watt resistor 7 8 have become much smaller. Older analog and early digital sound decoders were large, and often would require a dummy unit or separate boxcar to contain all the required electronics. Decoders today can it in most locomotive models along with the motor and drive train. These full function decoders also have the full array of lighting effects and motor controls as do their non-sound brethren. Sound decoders are generally equipped with many of the basic sounds one hears from a locomotive. The diesel prime mover or steam chuff, bell and horn or whistle are always provided. Beyond that, sound decoders offer a plethora of additional sounds including air release, dynamic brakes, blower and blow off, rod clank, coupler clank and others. In most cases, the sounds generated automatically on the prototype are also automatically generated on the sound decoders. Bells, whistles and horns are actuated by function keys on the hand- held controllers. While the technology is amazing, the challenge in application is in the speakers themselves. Locomotives generate sounds and it is these sounds that we want to hear. Many of the generated sounds are low frequency, however the physics of sound does not change and to create low frequency sounds there is a need for bigger speakers. Installations vary, but it is common for speakers to be put into the tenders of steam locomotives to provide the largest possible area for the speaker itself. Diesel locomotives often have the speaker located the full width of the hood, or even installed sideways across the diagonal of the body. When installing a sound decoder and speaker, keep in mind the impedance of the speaker must match or be greater than the impedance rating of the decoder amplifier. Most decoders utilize an 8 ohm amplifier. So the speaker must be 8 ohms or freater. Going with speaker impedance ratings less than that of the amplifier will allow more current to flow through the circuit and can destroy the decoder amplifier section. Additionally, acoustic theory requires the speaker to be in some kind of enclosure (baffle) to prevent the sounds generated on the surface of the speaker to be short circuited by the sounds from the other side. Often these enclosures are separate boxes installed within the shell or frame. In some cases the body of the model itself acts as the enclosure, as is often the case with speakers in tenders. STATIONARY DECODERS At some point in using DCC, it becomes apparent that the DCC system can do more than just control trains. It is, after all, a data highway. So what about these stationary accessory decoders? Accessory decoders are decoders that are physically mounted to the layout, that is, they are stationary. Basically they are very much like a loco decoder they read the DCC signal, respond to commands and are powered by the same power bus as the tracks. Using them allows you to remotely control turnouts and accessories. Even on layouts with mostly manually thrown turnouts, having the option to fo with DCC controlled turnouts can be a wonderful option, especially for hard-to-reach locations. Less wiring. More control. Very slick. Differences Between Stationary and Mobile Decoders Electronically, the main difference between a stationary decoder and the mobile counterpart is that they use different addressing. Accessory decoders have a unique address that is different in structure from a mobile address. That is why your DCC controller has a separate button for accessing an accessory decoder. They also have different types of outputs, basically just turning things on and off, or reversing an output. This is very useful to control turnouts, but can be used to energize layout accessories by remote control. Like mobile decoders, the stationary decoders need to be programmed with some kind of address, and within each decoder, the programming allows each output its own address. In this way the DCC handheld controller can specifically actuate a specific accessory decoder output. Uses and Features Depending on what the need is, there are many accessory decoders available. The most common control turnouts. Stationary accessory decoders can be purchased to control either the twin-coil switch machine types or the slow motion, motor driven switch machines. Some stationary decoders can be purchased that not only can be controlled via DCC, but also can detect an improperly positioned turnout by monitoring the rail polarity, and automatically throw both the turnout and track polarity. These are very handy in applications such as reverse loops or wyes. Another feature of many DCC systems is that they can memorize several routes, that is, alignments of multiple accessory decoders. This is very useful when setting up automatic operation of a yard. Instead of having to command each turnout to throw, simply selecting a route will have the command station issue commands to all the proper turnouts. Besides control of turnouts, accessory decoders can be used to drive motors that open roundhouse doors, lower water tower spouts, and even activate water fill sounds from a stationary sound decoder. It is a wonderful time to be in the hobby where so many things that were dreamed about only a couple decades ago are not only within reach, but are on hobby store shelves. PULLING IT ALL TOGETHER A simple layout with a one person operation may not need a very complex system. In fact, there are DCC products out there where the hand-held controller includes the booster and command station, all in one. Most layout owners will, however, want to run with a friend or two. In these cases a separate command station and booster is the way to go. With a separate command station, additional controllers can be attached, and the fun of operating the layout is shared. Gone is the need to constantly ind toggle switches to throw or the cry of who has my train! DCC Equipment Installation Generally the command station and associated booster will be located near the tracks, where power feeders can be run. Many times, owners will provide a shelf under the layout for these electronics. Cables lead to the controllers, or optionally wireless transceiving components are attached to the command station to connect the controllers to the DCC system. This also keeps the electronics out of the way and protected. Wiring it Out Seems like its the little things can cause some of the greatest frustrations in life. Cutting a piece of trim too short, spilling some paint or even just finding

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