Sensor placement
All four sensor pairs of the TrainSpeed 4 must use the same
spacing. 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 cables
are ten feet long. Cable extensions can be purchased or made.
The TrainSpeed 4 display unit will work with cables as long as
30 feet. See the appendix for cable extension construction.
Note that you do not need to use all four sensors if you do not
need them. The unit will figure out which sensors are missing
and only use the sensors that are connected.
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
sensors). 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
