How to use optical train sensors to automatically switch track power in automated model railroad staging yards and at track crossings.

Does your model railroad layout have
•  staging yards
•  track crossings
•  hidden storage tracks?
  You can automatically disconnect power to one or more sections of track when a train arrives at a certain point. For instance, when a train nears the end of a hidden storage track, power to that track can be automatically disconnected to stop the train.

The MRD1 infrared train detector and MRAPR auxiliary power relay make it easy to do this. Place the infrared sensing elements where you want the train to trigger the shut-off action. The installation instructions show how to install the sensors.

When placing the sensors, remember that trains have momentum! Leave enough distance for your trains to come to a stop before reaching the end of the track.

Wire the detector and the auxiliary track power relay as shown here. The override switch allows you to restore track power while the train is on the sensor. In this schematic, 'NO' is a normally open switch contact, 'NC' is a normally closed switch contact, and 'C' is the common connection.

How it works: When the MRD1 detector senses a train, it closes the connection between Q1 and QC. This energizes the MRAPR relay, which disconnects power from the isolated track section.

The second set of relay contacts (2C - 2NO - 2NC) may be used

• to control power to another section of track,
• for signalling, or
• to make a latching relay function.

Exhibit Layout Control shows how to automatically run two trains on a single-track loop.

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