©2004 Digitrax, Inc
www.digitrax.com
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The key to proper wiring for occupancy detection is planning. Your layout will
be divided into detection sections that can range anywhere from several inches
to several feet in length. This process is somewhat subjective, with the number
and length of a detection sections varying depending on your layout, train
length and the purpose of the detection.
It is best to plan your detection sections based upon the operations you want to
accomplish on your layout before cutting gaps in the track and installing the
BDL168. For instance, a grade level signal crossing may require from two to
four different detection sections in order to create the effects you want with the
lights and gates operating for trains traveling in either direction. Signal lights
will require information from two detection sections in front of the signal in
order to function like the prototype. Detection is not only useful but critical if
operating a hidden staging area--occupancy detection will let you know which
tracks are occupied in hidden staging areas. In your initial wiring installation,
not all sections have to be connected to BDL168s; they can be connected to a
terminal strip and then to boosters or power management devices. Additional
BDL168s can then be inserted later as needed to further develop your layout.
Additional information about planning and installing the BDL168 can be found
on the web site in the document:
Advanced Transponding Application Note
within the Digitrax Application Notes and Technical Information section of the
site. The form,
BDL16 Series Planning Worksheet
, is also available in the same
section for documenting your setup for future reference and trouble shooting.
Whether you are building a new layout or installing your BDL168 on an exist-
ing system, there are two basic wiring formats: direct home wiring and whole
layout common wiring.
3.1 Direct Home Layout Wiring
Digitrax strongly recommends direct home wiring where each power district
and its booster are electrically isolated. This method of wiring has safety
advantages and makes troubleshooting problems easier. In addition, direct
home wiring makes detection work more prototypically.
With direct home wiring, the BDL168 can determine and indicate whether any
of its 4 zones is powered or not (possibly short-circuited) even when there is
nothing on the rails in the detection sections. The BDL168 factory set logic
causes the detection sections to show "occupied" if the associated zone's power
is off (because in this case, detection is not possible). This factory setup match-
es typical prototype detection safety practices.
Figure 1
shows an example of a
direct home wiring layout with a single power district with multiple detection
sections. zone A with 4 detection sections (1-4) and zone D with one detection
section (16) has been wired in this example.