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(2020) implemented a signal system for both main lines on
the layout. As is the usual practice, it was decided to
design the entire system rather than purchasing a commercial
product. The reasons for this were to figure out how to
do this (a common goal for the railroad) and, perhaps more
importantly, to make it compatible with the other components
of the Automated Operations Control Centre (AOCC).
new semi-prototypical signal system monitors trains and
adjusts the signals around the layout. The signal system
is controlled by the AOCC which runs on a Windows
computer using JMRI, a model railroad computer interface.
Details of how this works are presented below for those
with a technical interest.
masts (see below and at bottom) were purchased on-line.
The ones used were of a single-target design similar to
the one shown below. Each target has three LEDs (light-emitting
diodes) contained in the signal head with separate wires
for each colour and a common ground. These can be easily
operated on 12 volts DC with an appropriate resistor for
separate signal has four aspects, as used on RHJ Rail:
Green, Yellow, Red and Dark (no colour displayed)
matter of how to control and operate the signals was examined
and it was determined that the current draw for each LED
was about 25 mA, an appropriate match for the lighting outputs
of a DCC decoder.
control boards were constructed as shown at the bottom
of this page. Each board controls two separate signals.
There are 20 signals on the two main lines, 10 on each,
designed for directional right-hand running. Additionally,
two more signals were added at intermediate points to control
train access in the middle of blocks.
signal control board contains one 6-function DCC mobile
decoder. Three functions control one signal and the other
three control another signal. The mobile decoder is just
the same as would typically be put in a locomotive but instead
it is mounted on a board as shown below and connected to
the DCC control bus.
means that a DCC throttle can address the decoder and set
any of its six functions to True (on) or False (off). With
RHJ Rail, the throttles are actually included
in JMRI scripts. A sub-system has been designed to address
and set any signal head (actually a DCC throttle and a specific
function) to any of the four possible aspects.
sub-system, integrated with the AOCC, can change
any signal to any aspect when requested from any JMRI script.
A call to the script for the signal sub-system provides
the necessary information to select a specific signal and
set its aspect as required.
such calls not only specify which signal is to be set to
which aspect but also to set trailing signals in the same
when a train passes a given location on the layout (as detected
by the AOCC system), the signal beside the lead locomotive
of a consist can be set to Red, and signals behind that
set to the appropriate aspect.
when a locomotive passes a signal, that signal will be set
to Red and the signals immediately behind set to (for example)
Red, Yellow, Green.
of course depends upon several factors, the most important
of which are the train length and the block length. If a
train is longer than the current block, then the sequence
of signals would be RRYG. If the train is longer that two
blocks (rarely, but it does happen), then the sequence of
signals could be RRRYG. Up to seven signals are allowed
for in the programming for the AOCC system. Since
there are only 10 signals on each main line, this was considered
a reasonable number but it could be adjusted if necessary.
these standards don't apply exactly as described. For example,
if a train is backing up, then
the signals may be set to indicate that the block BEHIND
the train is Red and the blocks behind that are set appropriately.
example is the track-cleaning train which traverses the
entire layout multiple times, regardless of right-hand running,
signal status, and the like. In this instance, that train
is considered to be running in "Dark" territory
and the signal system is turned off (all signals are set
to Dark). The train uses a "track warrant" to
grant it authority to occupy any main track on the layout
as long as it is not occupied. This process takes about
15 minutes of real time and after it is finished the train
returns to its "home" location and then the signal
system is activated again, ready for any scheduled run.
familiar with DCC programming will recognize that, "out
of the box", DCC mobile decoders will not likely use
functions (F1 - F6 for example) to do precisely what is
required for this system to work. What is needed is that
each of the six functions of the DCC mobile decoder must
respond independently, that is F0 must not be dependent
on the direction travel (Fwd or Rev) and F2 (normally the
horn or whistle) must "latch", that is stay active
as long as the function remains on.
order for the signals to work independently of direction-of-travel
or key press remaining ON, a few CVs (control variables)
need to be re-programmed.
Rail decided to use Digitrax DH 166 decoders as
they were readily available and several were already on-hand.
Any six-function decoder will do but the following programming
sequence is specific to that decoder. The goal is to set
each of the six outputs so they can be independently controlled
and do not depend on direction-of-travel, non-latching (horn
or whistle) or anything else.
38, 39, 40 could be set to 1, 2, 4 as are CV 35, 36, 37 if
the wiring were changed a bit)
35 - 1
CV 36 - 2
CV 37 - 4
38 - 1
CV 39 - 4
CV 40 - 2
Signal Mast with 3-LEDs
Decoder Board for controlling two signal masts,
with three colours each, using a Digitrax DH 166
mobile decoder. Each signal mast consists of R-Y-G-B
wires corresponding to the colour of the target
and a ground wire (black).
label on the board shows (l - r) the signal number,
the decoder/throttle address, and the segment of
the signal on the decoder (i.e. A = 1 - 3 for the
first signal and B = 4 - 6 for the second signal).
electricity is colour-blind, four-conductor (RYGB)
telco wire makes it much easier to keep track of
the wiring from the Signal Decoder Board to each
yes, it all works according to plan.