Digital Command Control (DCC)

I first connected my computer to my old HO scale model railroad back in the late 1980s. Using a handful of simple voltage sensors in the discreet electrical track-power blocks to detect current flow induced by train presence, and a series of relays to control switches and power flow to the blocks, I was able to control a few trains with software I created myself in Basic. Looking back on it, this system was pretty clunky. For example, with no speed control, stopping a train at the station was accomplished by turning off power to the station block a specified number of seconds after the train entered that block. Meanwhile, in Germany, brighter technical minds were hard at work, and by 1989 Lenz Elektronik GmbH had developed and begun to market the prototypes of the tiny circuit boards that lie at the heart of today’s digital model railroad control systems. The National Model Railroad Association (NMRA) licensed the Lenz protocol in 1993 and extended it. This system was later named Digital Command Control (DCC). 

When equipped with Digital Command Control, locomotives on the same electrical section of track can be independently controlled. A DCC command station, in combination with its booster, modulates the voltage on the track to encode digital messages while also providing electric power. Each locomotive is equipped with a mobile DCC decoder that takes the signals from the track and, after rectification, routes appropriate polarity and the specified amount of power to the loco’s motor. Each decoder is given a unique address and will ignore all commands intended for a different decoder, thus providing independent control of locomotives anywhere on the layout. Stationary decoders can also receive commands from the controller in a similar way to allow control of turnouts, uncouplers, and other operating accessories such as crossing gates, sound generators, signals, room lighting, and other layout lights.

Toady’s DDC systems generally employ a small hand-held throttle(s) allowing the operator(s) to address any number of trains, switches, and other equipment on the layout. However, one (or even a few) operator(s), no matter how adroit, can control only a limited number of moving trains at once. The solution is automatic or semi-automatic computer control of the entire layout. There are several software packages on the market, but to my mind, far and away the most sophisticated of these is the Traincontroller Software created and marketed by Freiwald Software in Germany. The detail, flexibility, and depth of control offered by this system is truly remarkable. The user first uses the software to create a track plan that reflects the configuration of the layout to be controlled. (Click here to see my track plan screen in Traincontroller.) Each train can then be assigned a schedule from point A to point B (or assigned to a loop) along a specific route or along the best route as determined by the software. These schedules include automated turnout switching and can include specified station stops, layovers, sound events, etc. (Click here to see my schedule /“dispatcher” screen in Traincomtroller.) In addition, the operator can select to manually operate any of the trains in the midst of the automated routes being run by the other trains under the control of the computer. The software also allows for manual or automatic control of lights, whistles, signals, and so on.

 On the Altamont and Blue Ridge Railway a set demonstration routine runs nine trains along preprogrammed routes around the layout, disappearing into the hidden yard, stopping at stations, laying-over on sidings, and eventually retuning to their original starting points – all with full sound, prototypical signal and switch operation, housing and street lighting control, etc., and all without a single collision.  The whole routine takes about fifteen minutes. It’s remarkable!

None of this was easy, mind you. The wiring is complex, the programming of the individual components can be tedious, and the software’s learning curve is steep. In addition and perhaps most problematic, N-Scale is as delicate as a fine watch, and the slightest mechanical tracking or coupler problem can have chaotic consequences for automation logic. Still, with patience, fully computerized control is do-able, and the results have been gratifying indeed.