DCC  

This page describes my DCC setup. DCC stands for "Digital Command Control". It is a method by which model trains can be controlled. One unique feature is that more than one train can be independently controlled on a single piece of track. When I was still building my starter 4' x 8' layout in 1999, a fellow N-scaler highly recommended that I check out DCC rather than the "old" block system. He ran DCC and I loved the idea of having the freedom to drive locomotives anywhere on the layout regardless of where other locomotives were. I thought about it and decided to go with the Digitrax Chief system.


The Brain

Digital Command Control (DCC) refers to the computer network developed to control locomotives and other electro-mechanical devices. Essentially communication is done through a computer network protocol, much like a computer network works. There is a central processor, additional boosters (for heavy loads), one or more handheld controls (either wired or wireless), and decoders that receive the commands and do something useful with the commands.

A DCC system is a pricey investment. The Digitrax Chief system came with the DCS100 Command Booster (see photo on the right), a DT100 hand throttle, and one decoder. I also bought the Digitrax PS515 power supply (15 VAC, 5 Amps, 75VA) to power the Command Booster.

Since that day I have bought many decoders, a couple of UP-3 fascia panels for plugging in the throttles, a PM4 for reversing track, and a UR91 for wireless control. I have also added a DT400 throttle, and had Digitrax convert the DT100 to a wireless throttle. The DT400 still needs to be converted. The point is that you can expand the system as your needs grow and funds allow.

I prefer and am happy with the Digitrax products, but there are other companies who make DCC equipment. Because they all use the same standard, you can intermingle parts from one company in with another.


Installation

The diagram below is my attempt at graphically displaying how all the main components fit together. The programming track is used to program the decoders that are installed in the locomotives. This track can be an electrically insulated part of the layout (a spur). In my previous layout I had a separate piece of track in a staging yard that was controlled by a DPDT toggle switch. In one position the track was powered in the same manner as the rest of the layout, in the other position is was powered by the Programming Track output of the DCS100 command station. I could then drive the train on the track, flip the switch, reprogram the decoder in the locomotive, and flip the switch back. Pretty cool. I also have a separate piece of track glued to a board connected to the programming track output jacks of the Command Booster.


Control

The DT400 is the latest "top-of-the-line" throttle from Digitrax. It works well. I specifically got this one to make it easier to control turnouts and locomotives at the same time.

The DT400 has increased display space and you can monitor and control both the moving locomotive and the stationary turnout. However, as is true-to-form with Digitrax, this thing is a beast to learn. I still have to think about how to turn the track power on with this thing. I don't know how many times I have moved the knobs on the throttle with no corresponding movement in the locomotives.

I recently experienced a problem with my throttle. I wanted to start using 4-digit addresses for the decoders, so that the road numbers of the engine match the decoder ID's. I followed the instruction manual of the DT400, and it seemed pretty straight-forward to program the first two engines I tried. However, when I placed the engine on the mainline, pressed the LOCO button on the DT400 (in normal/run mode), entered in the new address, let's say "8512", and pressed the ENTER key on the throttle, the throttle immediately showed "64". The engine, of course, doesn't respond. For the fun of it, I selected a random 4-digit address in the throttle, and I got the same kind of behavior. In other words, it appeared that my throttle doesn't like 4-digit addresses in general. I posted this message to the N-scale DCC mailing list, and got the following solution from Al Silverstein. The idea is to reset the Command Booster to the factory defaults.

  1. Move the MODE toggle switch to the "OP" position.
  2. Remove all LocoNet connections to the DSC100.
  3. Plug in a DT400 throttle into either "A" or "B" LocoNet socket.
  4. Press the SWCH button on the DT400
  5. Press the #3 button followed by the #9 button on the DT400
  6. Press the CLOC c Key on the DT400
  7. The Command Booster will beep.
  8. Move the MODE toggle switch to "RUN" position.
  9. Remove your throttle and reconnect your LocoNet cables to the DSC100
  10. Shut down your command system.
Automatic Polarity Switching (Reversing)

The PM4 allows automatic control of a reversing section of track. This is a piece of track that turns around onto itself which would normally cause a short. Part of this track will be insulated from the rest of the layout. This insulated piece of track is powered/controlled by the PM4. When the locomotive crosses the insulated section, the PM4 automatically adjusts the polarity of the current to match that which the locomotive is expecting. It automates a process that would otherwise require a special switch on the layout's control panel. A switch that is easy to forget to set and hence be the cause of lots of shorts.

I have found the manual that comes with the board is very easy to follow. It does involve a lot of soldering and paying attention as to which pins are to be soldered to what. The PM4 works well.



Decoder Programming

Yeah! I finally got the PR-1 decoder programmer to work. The challenges were many, but here is the final configuration that made this picky device and software work:

  • Pentium 133 NEC laptop computer.
  • PR1DOS software application.
  • A 25-pin to 9-pin Belkin adapter, because the laptop has a 9-pin serial port.
  • The PR-1 device.
  • 4-conductor cable (supplied with the PR-1 device).
  • two fresh 9V batteries connected in series to generate around 18V of pure DC.
  • A piece of track.
  • A locomotive with decoder (in this case Kato's PA-1).

Previous failed attempts included using my main desktop machine with a 18V custom-built power supply using the WinPR1 software program. This didn't even detect the PR-1 device hooked-up to the machine's serial port. I since then learned that the older the PC, the better the success rate. I dusted off the old 8088, but then I re-acquired my old laptop computer. The laptop is definitely more portable and convenient, especially since space in the model railroad room is at a premium. Here's a photo of the setup used to program the locomotives' decoders.


References
Copyright © 1999-2008 Peter Vanvliet