4
Sensor placement
The sensors are designed to use available ambient light.
Mounting them in tunnels or dark corners of the layout is not
recommended. It is best to pick a well lit section of the layout
where the light source comes from above and ‘inside’ the
layout. If the light source is ‘outside’ the layout a person
walking by may trigger the unit. The included sensor cable is
ten feet long. Cable extensions can be purchased or made.
The TrainSpeed display unit will work with cables as long as
30 feet. See the appendix for cable extension construction.
Using a #20 drill bit (5/32” also works but is a bit tighter),
drill the sensor holes through your roadbed and sub-roadbed to
the chosen spacing (watch out for switch machines and the
like under the layout when choosing the location of the
sensor). Make sure that the edges of the holes are ‘clean’,
especially on the bottom as this will make sensor insertion
much easier. The sensors should then be inserted into the
holes from the bottom and pushed up until the top of the
sensor is flush with the top of the ties.
Warning: Power to
the rails should be off when inserting the sensors,
especially if you are using DCC
. An insertion tool can be
made out of small tubing by cutting a slot in the tubing to
provide clearance for the wires. This tubing can then be used
to push the sensor up through the hole to avoid damaging the
wires. If you are having trouble getting the sensor through the
roadbed use a larger drill bit (the #20 and/or 5/32” bits provide
a ‘press fit’ for the sensors that will usually hold them in place
without any adhesive or tape). Make sure the sensors do not
exceed the railhead height as you will damage them the next
time you clean the rails with an abrasive rail cleaner. If
needed the ribbon cable can be split easily for wider sensor
spacing. The sensors can be held in place by tape over the
bottom of the hole. If you must glue them in place, be sure to
use a water based, clear drying glue.
