DCC

A DCC test layout

After some time spent studying the various DCC systems available, I decided to go with the Digitrax Chief system (DCS100 Command Station / DT100 Throttle) and Winlok as a control software.

Before switching to DCC, on my Susquehanna Ontario and Western layout, I wanted to experiment with DCC components to see if they met my expectations and also to get familiar with all these electronic (and software) parts. Also, I wanted to determine if there was any problem switching to DCC and find the suitable solution, if any problem arised, before making the "great jump".

In order to perform this evaluation, I built an N scale test layout on a 2x4 piece of plywood. This test layout included an oval of track with a passing siding. This layout was divided into four electrical sections.
The diagram at right shows the electrically isolated track sections (both rails isolated) and the power connections to the track sections (blue and red tabs). For this test layout, the turnouts were not electrically isolated, but rather were included in the adjacent electrical section (the section on the point side of the turnout).
From there, I built up the whole evaluation system, step by step.

Step 1 : Programming track

The first step was to add a spare piece of track (programming track) which will be used for programming engines in all subsequent steps. As shown in the left diagram, the programming track is connected to the gray terminals on the DCS100 Command Station.
Although not shown on the subsequent diagrams, for clarity, this programming track will stay connected to the DCS100 throughout all subsequent steps.
Any decoder equipped engine, placed on this piece of track, can now be programmed from the DT100 throttle, according to the specific decoder Users Manual.
The DCS100 red terminals were also connected to the power supply (a 16 Volts - 5 Amps transformer protected by fuses at the input and the output, as recommended in the DCS100 Users Manual).

Step 2 : Basic DCC operation

Here, I connected the track to the DCS100 output (Black terminals identified as "Rail A" and "Rail B"). Rail "B" was used as "common" to all track sections and connected to all "outside" rails (blue wires). Rail "A" was connected to a terminal board and dispatched, from there, to all "inside" rails (red wires). The reason for using a terminal board will appear later in this page.
At this point, I was able to run engines (decoder equipped engines and one "DC" engine) on my test layout, controlled from the DT100 throttle, while both turnouts were manually operated.

This step allowed me to verify the proper operation of the DT100/DCS100 system, and also to "play" a little with various programming setups of the engines. I also experimented with loadable speed tables and adjusted the speed tables of two engines in order to get matched speed so that the engines can be MU'ed together.

The basic DCC hookup was operating perfectly. So I decided to go a step further by controlling the turnouts from the DCC system.

Step 3 : Turnout control

In order to control turnouts, a new DCC component is required : a "stationary decoder". I choosed the DS54 from Digitrax, which in addition to turnout control (4 turnouts), allows various feedbacks to the system (8 feedback inputs) which will be used in the following steps.
The DS54 was programmed according to my needs, by temporarily connecting it to the programming track. Track "A" and track "B" were then connected to the DS54 terminals, since the DS54 receives its control informations from track wires.
Twin-coil switch machines were attached to both turnouts and connected to DS54 outputs 1 and 2. Shown on the diagram are two green connections. This is for clarity. In reality each connection is made of three separate wires (common, closed and thrown).

At this point, I came across a problem : when operating turnouts from the DT100, the turnouts didn't move, athough the switch motors seemed to be energized. Some tests quickly showed that the DS54 didn't deliver enough power for the switch motors I was using (which were on the balky side). I got a similar result when using an external power supply (a DS54 option to get more power to the switch motors). The reason for this problem is that DS54 is designed for modern solenoid type switch machines which require little current and not for older (balky) switch machines like the one which equipped all my turnouts. I was in trouble... After a while of thinking about this problem, I decided to design and build capacitor discharge drivers for DS54, since my switch motors were already operated by means of a CD unit, on my DC layout. It was done and worked perfectly. You'll find a complete description of these drivers, in the "DS54 CD Driver" subject.

Step 4 : Computer control

At this stage, it seemed to me a nice feature would be the capability to graphically display the layout and start controlling it from a computer. So, I hooked up an old and unused Personal Computer to the DCC system and downloaded Winlok software (Demo version) from Digitoys Web site.

Another DCC component is needed for connecting the Personal Computer to the DCC System : a computer interface. I used Digitrax MS100 Computer interface which plugs to the LocoNet, on one side, and one of the computer serial ports, on the other side.

Winlok was installed and set up as per the instructions and I started drawing the layout on my computer, which took little time for such a simple layout.
The figure at right shows the track diagram on the computer screen with tracks, turnout activators (the red/green round buttons) and turnout position indicators (the green bars on the turnouts).

At this point, it is possible to control trains from the DT100 throttle and/or from the throttle(s) integrated in Winlok. Also, the turnouts can be operated either from the DT100 throttle or by clicking on the appropriate switch activator, in the track diagram. Winlok remembers the turnout positions, even between sessions.

Note : Winlok Demo version has the same functionality as the full version, but a "Demo version reminder window" comes up every minute which prevents using it to actually control a layout. So this version is good only for evaluation of the product. As soon as I made sure it suited my needs, I ordered the full version.

In order to complete the full DCC "test" system, one last thing is missing : feedback (track occupancy feedback and switch position feedback). We're getting at it...

Step 5 : Feedback

In this step, we connect both the switch position feedback (in case someone manually operates turnouts) and the train occupancy feedback which will allow to display, on the computer screen, where trains actually are on the layout.

Switch position feedback was achieved by adding contacts to the turnouts and connecting them to inputs 1 and 3 (corresponding to outputs 1 and 2), on one side, and to the DS54 common wire (not shown on the diagram), on the other side.

For track occupancy feedback, four Digitrax BD1's (detectors) are required (one per track section). The "power" side of the BD1's are connected between the Rail "A" wire and each track section ("inside" rail). Hence the need for a terminal board. The "signal" side is connected to DS54 outputs 5 thru 8, on one side, and to the DS54 ground wire (not shown on the diagram), on the other side.

Feedback information from the DS54 card goes through the LocoNet, so DS54 has to be connected to it, by means of a 6-wire LocoNet cable (RJ12). Since no LocoNet socket was available on the DCS100 side, the connection was made through a 6-pin "T" connector.

The DS54 was re-programmed (by temporarily disconnecting it from the track wires and hooking it up to the programming track) to set up the proper feedback configuration and Winlok track diagram was updated to display feedback informations.
The figure at right shows the new track diagram with feedback. Turnouts now display their actual positions, even when they are manually operated. Track occupancy detection shows one train in the siding and another one on the main.

I finally reached a full featured DCC controlled (miniature) layout with a minimal number of components. At this point, it is possible to exercise the full power of DCC with Computer control, the only limitation being the size of the layout. It allowed me to test and get familiar with all the major DCC components I will be using on my "actual" layout, before starting modifying it. I was also able to perform some limited (because of the small number of sections) automated train running.

However, One more component had to be tested : the BD8 detector from Digitoys that I intended to use at some places on my layout, besides DS54/BD1's.

Step 6 : More tests (BD8)

BD8's will be used on my layout for track occupancy detection, where I don't need a DS54 (for switch control) because of its lower cost, as compared to DS54/8xBD1's.

From the previous setup, testing a BD8 is very simple since it will replace the BD1's : I just disconnected the BD1's and replaced them by 4 of the 8 circuits of the BD8 and connected the BD8 to the LocoNet, in place of the DS54, and to the track wires, and everything was up and running.

This test showed some differences between DS54/BD1's and BD8 behaviours when detecting trains : DS54/BD1's have a turn-on delay (clear to occupied track) of approximately 1 second and a turn-off delay (occupied to clear track) of approximately 2 seconds, while BD8 reacts almost instantly in both cases, causing some flickering of the track occupancy information (due to wheel/track contact problems, especially emphasized with N scale lightweight rolling stock). Finally, I found a way to modify BD8's so that they behave pretty much the same as DS54/BD1's (see "Improving BD8's").

Conclusion

I hope this page allowed some of you not familiar with DCC to better understand what DCC really is, what improvements it can bring to your layout and how easy it is to implement. All the steps described above can be implemented one at a time over a long period of time and you can stop the implementation at any step you wish, depending upon your needs. Of course the type and quantity of required DCC components will vary depending upon the size and configuration of your layout and your needs, but the implementation steps will basically be the same.

Don't hesitate to contact me for any comment or question regarding this DCC test layout.

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A DCC experience Wiring my layout

Page created by Jean-Louis Simonet
Last update : 10/26/1998
© 1998, Jean-Louis Simonet