Digital Command Control
I recently diassembled this DCC HO locomotive to re-paint the shell, and while it was apart I thought I would show you what is under the shell, and explain what DCC is all about in model trains.
This HO scale model diesel locomotive is modeled after a full scale EMD SW9 prototype (1950's vintage), and is typical of model DCC locomotives. The trucks are geared assemblies, all axles powered, and driven by a 12 volt DC double shafted can-motor with brass flywheels on either output shaft.
Located on top of the motor is the DCC decoder, and to the left is the sound speaker in its enclosure.
A DCC command station, in combination with its booster, modulates the voltage on the track to encode digital messages while providing electric power.
The voltage to the track is a bipolar DC signal. This results in a form of alternating current, but the DCC signal does not follow a sine wave. Instead, the command station quickly switches the direction of the DC voltage, resulting in a modulated pulse wave. The length of time the voltage is applied in each direction provides the method for encoding data. To represent a binary one, the time is short (nominally 58 µs for a half cycle), while a zero is represented by a longer period (nominally at least 100 µs for a half cycle).
The DCC decoder then takes the signal from the track and, after rectification, routes power to the motor as requested. With more than one DCC locomotive on the layout, each decoder is given a unique running number (address) for the layout, and will not act on commands intended for a different decoder, thus providing independent control of locomotives anywhere on the layout, without special wiring requirements.
Extra functions can be operated remotely from the DCC controller in a similar way to allow control of turnouts, uncouplers, other operating accessories (such as station announcements) and lights.
The decoder in this particular model is programed with 28 different sounds, that ranges from the engine starting up, then the sound of the engine ramping up and down while under way, air brakes being applied and released, brake squeal, radiator cooling fan coming on and off, air compressor cycling, just some of the sounds that happen automatically.
Then there are things you can select on the power cab, some being the horn, bell, lights front or rear, and more.
Being I like all things related to radio, I like the chatter of the engineer with other yard personal to be heard over the engine sounds that can be selected at anytime and heard coming through the speaker located to the left of the decoder board.
Expand the photo for a closer look.....
The locomotive painted, weathered, and reassembled back on the layout switching cars.....