6
Using between-the-rails infrared
The IR components should be mounted between the rails. Drill two 11/64” holes, through
the ballast, roadbed, and sub-roadbed. These holes should be located one tie apart (Figure
8a) and drilled at a slight angle from vertical (see Figure 8b). The benefit of mounting
them at an angle is increased detection reliability in smaller scales or irregular bottoms on
rolling stock. For the smaller scales this drilling may end up hitting the ties. Take your
time so you do not mangle them! Insert the leads of one IR emitter (white and black
wires) into one of the holes (it does not matter which one!) from the top of your layout.
Repeat for the IR detector (blue and black wires). The tops of the components should sit
no higher than the top of the ties for optimal IR performance; in some cases (e.g. false
triggering) it may be necessary to locate the components a little below the ballast line.
You can extend the leads with similar (or larger) wire. We recommend soldering and
insulating these connections. We also recommend using terminal blocks/strips since you
will have mu5V and GND connections to make. Once you have wired the IR
components and verified their operation you may wish to put a dab of white glue or
silicone caulk where the wires exit the holes underneath the layout. This will help to hold
the components in place; make sure you do not get any substance (e.g. ballast or glue) on
the top surface of the IR components as this may prevent them from operating properly. In
extreme cases where you may be getting interference from overhead lighting you can
mount the IR detector in some plastic or metal tubing. You can also recess the IR detector
slightly below the ties and roadbed.
Figure 8a
Figure 8b
Using across-the-rails infrared
With this sensor mode and physical arrangement a train is detected when the
infrared (IR) beam is broken by the train. The IR components should be located
across the track as shown in Figure 9a and 9b; the distance between them has
been tested up to 16 inches. The detectors (dark lens, blue and black wires)
should be mounted with a slight downward angle in order to minimize the
possibility of false triggering from visible light sources; this is illustrated in
Figure 9a. We would also recommend that you angle the emitters and detectors
across the track as shown in Figure 9b. This will minimize false “clear”
situations due to the space between rolling stock. You can bend the IR emitter
and detector components IF you are VERY careful and, preferably, use a pair of
“smooth jaw” (no teeth/serration) pliers!! Make the bend on the IR component
NO CLOSER than 0.5” from the tip. You don’t want to pierce the insulated heat
shrink tubing and potentially cause a short.
In the event the leads do not reach the circuit board you can extend them with
similar (or larger) wire. We recommend soldering these connections or using
terminal blocks/strips especially when you have multiple connections to make.
Aligning the IR components for reliable detection might be a bit challenging.
We recommend the use of a straight edge or ruler for initial “rough” alignment.
You can tweak the final alignment once you are ready to test the circuit.
Since the IR components are located trackside, you will probably want to
consider “hiding” them. There are numerous ways to do this such as using
shrubbery, small equipment buildings or fixtures. We leave this exercise up to
your imagination and creativity! We would strongly suggest that you get the
circuitry working properly first, and then address the physical appearance.
Figure 9a
Emitter
Detector
Figure 9b
