DCC

Wiring My layout (for DCC)

In this page, I will discuss the various steps I took for (re-)wiring my Susquehanna Ontario and Western RR for DCC.

Before doing anything on the layout, some planning is required so as to define what DCC will be controlling on the layout, how the layout will be broken up into sections and where the various DCC components will be located on the layout.

DCC control

After some time spent experimenting with my test layout, I decided which elements will be DCC controlled and which ones will remain manually controlled. Here is the set of rules I adopted for my layout :

  • Trains will be DCC controlled (of course !)
  • Mainline, branch line and staging tracks turnouts will be DCC controlled (only those turnouts which control train routing). All other turnouts (yard and industrial spur turnouts) will be manually controlled from local control panels.
  • Train occupancy detection will be performed on the mainline, branchline, staging tracks and access tracks to the yards, but not in the yards themselves.
  • No turnout feedback from DCC controlled turnouts, since Winlok remembers turnout positions and these turnouts will only be operated from Winlok. Turnout feedback (treated as general feedback) from manually operated turnouts on the mainline and branch line (industrial spurs) for reporting to Winlok.

Track sections

Next is the time to determine how many "track sections" the layout is made of, and their location.

But, first, what is a DCC track section ?
My own definition is : "a stretch of track, electrically isolated from adjacent tracks, long enough to hold a whole train of reasonable length and including no train routing turnout, except at its end(s)". The attached diagram shows a "typical" track section. It is divided into three subsections : a "stopping" subsection at each end (for stopping trains going in either direction, before reaching the end of the section) and a "main" subsection (the track in between). From my experiments, on my test layout, I determined that the "stopping" subsections should be around ft long (assuming a train enters the "stopping" subsection at slow speed). Each track section will thus require three train occupancy detectors (BD1 or 1/8 BD8, in my case).

But, no two track sections are made alike, because they may include one or more turnouts.
The diagram at left shows several possible arrangements (among many more) including one or more turnouts. All of them are based on the "three subsection" scheme and wiring/insulation is done so that there is electrical continuity within any subsection, and so that the power routing turnouts I'm using are properly handled (insulating rail joiner required on the frog rails).
When one or more turnout is present in the "stopping subsection", the subsection length is such that there is always 1 ft stopping space before reaching the turnout points.

Based on these rules, I was able to divide my layout into sections and subsections and to locate each of them on the track plan.

Note : The rules I adopted for defining track sections/subsections are based on the way I intend to operate my layout. Other people may want to use different rules, based on different operating schemes.

Components location

Once all turnouts and track sections are located on the track plan, it's easy to determine the best location for DCC components, on the layout. For my layout, I followed some basic rules :

  • BD1 should be located as close as possible to the track section it detects.
  • BD8 should be located as close as possible to the track sections it detects.
  • DS54 should be located as close as possible to the BD1's connected to it and , if possible, as close as possible to the turnouts it controls.

Based on these rules, I located all components on the track plan.

Now is the time to actually start installing parts and wiring the layout.

Wiring the layout

Wiring my layout has been done in several steps similar to those described in "DCC test layout". "Global" wiring of the layout (running all necessary wires/cables around the layout) was performed first. Then "local" wiring was performed in several stages.

Step 1 : Global wiring

The DCS100, its power supply, as well as the 24VAC power supply (required for my DS54 CD Drivers) were first installed in an appropriate location, under the layout. The following figure shows the basic wiring which was done all around the layout, starting from the DCS100 and the 24VAC power supply :

The track power (track "A" and "B") was run all around the layout, using a pair of #14 wires, to ensure no voltage drop from one end to the other (up to 5 amps can flow thru these wires). The same way, 24VAC was run around the layout, using two #18 wires (enough for my estimates of the current drawn on this power supply).
The LocoNet cables was then installed and connected to three UP3's (Universal panels for connecting throttles) distributed around the layout. Also some "T" (or "quad") connectors were installed at strategic locations, on the LocoNet, for later connecting DS54's and BD8's. The LocoNet cables were custom made, by crimping RJ12 modular connectors at both ends of 6 wire flat telephone cables cut to length.

Note : The feeder wires shown on the figure are for reference only. They will be added, as required, in the subsequent steps.

Step 2 : Basic DCC operation

In this step, track sections are connected to track power (track "A"/"B" wires). The figure below shows how these connections were made :

The "common" side of each section was connected to rail "B" wire by means of one or more #18 feeder wires. Rail "A" was connected to one side of a 8 position terminal board, using #18 wire and, from there, distributed to 8 track subsections using #18 wire also.

Electrical continuity : In order to ensure proper electrical continuity, it is important that all connections be soldered. At rail level, feeders are directly soldered to the rail. Junction between wires are made by wrapping one wire around the other and soldering, as shown on the diagram at right. It is also important that all non insulating rail joiners be soldered and that separate feeder wires be installed every 3 ft of track.

Avoiding troubles : I recommend that the work be thoroughly checked every time a section is completed, in order to avoid later problems. To do that a few simple steps are required :

  • Check continuity and insulation of the new wiring, using a Volt/Ohm meter.
  • Turn on the Command Station, put an engine on the newly wired track section and check for correct operation.
  • Short the section (with a metal part) and check that the Command Station detects the short.

If any problem is found during these tests, something is wrong in the wiring and should be fixed before going any further (remember that, with DCC, all track sections are wired in parallel and insulating a problem later will be much more difficult).

When all sections are wired, the layout is ready for DCC control of trains.

Step 3 : Turnout control

In this step, DS54's are added to the layout to control turnouts. In my case, I also added DS54 CD drivers required for driving the switch motors I'm using. The figure below shows how these parts were installed and connected :

Before installation, DS54's were programmed according to my needs (including feedback which will be added later) by temporarily connecting them to the programming track.

DS54's and their associated CD Driver cards (DS54 piggybacked on top of the Driver card - see the "DS54 CD Driver" subject, for details) were installed at defined locations, on the layout. DS54's were connected to Track "A"/"B" wires by means of #22 wires and to LocoNet by means of a custom made cable (see above - Global wiring - for details about making these cables). The Driver cards were connected to 24VAC supply, by means of #22 wires. Then, each of the four driver outputs (3 wires per output) were connected to the associated twin-coil switch motor, using #20 wires.

As soon as turnouts are connected to the Driver card outputs, they can be controlled from the DT100 throttle, or by Winlok, when the DCS100 is hooked up to the personal computer.

Step 4 : Train occupancy Feedback

In this step, BD1's and BD8's will be added for train occupancy feedback. BD1's are used where DS54 are available. BD8's are used elsewhere.

BD1's are connected as shown in the following diagram :

Since the DS54 is already in place and 8 track sections are gathered at the terminal board, installing BD1's is just a matter of inserting them between the DS54 and the terminal board, as shown.

The number of DS54's is not sufficient to handle all the track sections/subsections, on my layout. So I used BD8's where DS54 were not available. The following diagram shows how they are connected :

Step 5 : Turnout Feedback

Only a few turnouts need feedback, for reporting to Winlok : those manually operated turnouts located on the mainline or the branchline (industrial spur turnouts).

These turnouts were equipped with switch contacts and the contacts were wired to unused inputs of some of the DS54's (not all DS54 have their 8 inputs used for track occupancy detection).

Feedback implementation is presently in progress on my layout. When I complete it, I will have a "full featured" DCC controlled layout and will be able to automate some trains, using Winlok capabilities, while I manually operate other trains.

Improving turnouts

In the meantine, I found a few problems at turnout level, due to unreliable contacts between the points and the stock rails, causing engines to stall on some turnouts (PECO Electrofrog power routing turnouts).
I solved the problem by adding twin-coil latching relays, as shown on the figure at right. Installation of these relays is easy since their coils are wired in parallel with the turnout twin-coil switch machines. Their contacts are wired in parallel in order to handle the 5 Amps short circuit current. They power the frog from either stock rail, depending on the turnout position, ensuring perfect electrical continuity throughout the whole turnout.

At present, I only have a few turnouts with latching relays installed. As new problems arise, I'll be installing more relays and, eventually, all turnouts will be so equipped.

Note : Since my DS54 CD Drivers deliver 30 volt pulses, I'm using 24 volt latching relays which have a 18-40 volts operating range. Some test must be performed before using these relays, in order to determine the right way to wire their polarized coils (reversing the connections to any coil will result in contacts being reverted).

Here is where I stand, today, on my layout. I hope this experience may be of interest to some of you. Don't hesitate to contact me for any comment or question regarding this subject.

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A DCC test layout DS54 capacitor discharge driver

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