Trains4Africa
Because all Boys (and some girls) love Trains

A DCC test layout

DCC – based Layout Example

The following layout demonstrates the use/implementation of DCC using the Digitrax Chief system (DCS100 Command Station / DT100 Throttle). This layout demonstrates that you can experiment with DCC, before actually switching to DCC, which will allow you to experiment with DCC components to see if they meet your expectations and also allows you to get familiar with all these electronic (and software) parts.

This also demonstrated the ability to determine if there will be any problem(s) switching to DCC, and to find suitable alternatives, if any problem arises, before making the “great jump”. dcct1 build an N scale test layout on a 2×4 piece of plywood. This test layout included an oval of track with a passing siding. This layout is divided into four electrical sections.

The track sections are electrically isolated (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).

Step 1 : Programming track dcct2

The first step is to add a spare piece of track (programming track) which will be used for programming engines in all subsequent steps. The programming track is connected to the gray terminals on the DCS100 Command Station.The programming track will stay connected to the DCS100 throughout all subsequent steps, but is not shown on the diagram in order to make the diagrams less cluttered.

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

Connect 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, you will be able to run engines (decoder equipped engines and one “DC” engine) on the test layout, controlled from the DT100 throttle, while both turnouts were manually operated.

This step allows you to verify the proper operation of the DT100/DCS100 system, and also to “play” a little with various programming setups of the engines. You can also experiment 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.

Step 3 : Turnout control

dcct4In order to control turnouts, a new DCC component is required : a “stationary decoder”.

One possible solution is to use 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 is programmed according to your 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, you may run into 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 used.

Similar results may be experienced even 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.

One possible solution is use a capacitor discharge drivers for DS54

Step 4 : Computer control

At this stage, you may start connecting the DCC system to a computer in order to experience the capability of graphically displaying the layout and also start controlling the layout from the computer.

dcct5
Another DCC component is needed for connecting the Personal Computer to the DCC System : a computer interface.

For Digitrax, the MS100 Computer interface which plugs to the LocoNet, on one side, and one of the computer serial ports, on the other side offers an inexpensive solution.

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.

dcct5
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 dcct6 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.

a full featured DCC controlled (miniature) layout with a minimal number of components is feasible.

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 allows you to test and get familiar with all the major DCC components that you probably will be using on your “actual” layout, before starting modifying it.

You will also able to perform some limited (because of the small number of sections) automated train running.

Step 6 : More tests (BD8)

BD8’s offers the ability to track train movement on the layout, and this refered to as track occupancy detection.

Testing a BD8 is very simple since it will replace the BD1’s : you just disconnected the BD1’s and replace 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 will be 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).

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.