Automatic Interchange

Iowa Scaled Engineering products were recently mentioned  in one of the Model Railroader Video Plus episodes, featuring Tony Koester’s Nickel Plate Road.

In this video (subscribers only) you’ll see our CKT-IRSENSE and ACC-RELAY1 products used in an automatic interchange.  Each time a cut of cars is picked up, a new cut of cars is automatically pushed forward.  For those wanting more details, Tony has written an article about automated interchanges that appears in the December 2016 issue of Model Railroader.



The automatic interchange is simple to install.  A complete description can be found in the CKT-IRSENSE User Manual and a wiring diagram appears below.  Basically, when the IR sensor detects no cars, it waits a preset amount of time, then re-energizes the track to push forward the next cut of cars until the IR sensor is again covered.


The circuit requires a 12V DC power source.  This can come from an auxiliary bus on the layout, or by using a dedicated power supply such as the PSU-12V1A.

Setting the Delay

The Normal Delay version of the CKT-IRSENSE has a variable release time from 0.1 to 23 seconds.  Typically, for an automatic interchange application, a longer delay is desired.  The Long Delay Release Time option provides this with a 6 second to 23 minutes variable delay.

By default, the CKT-IRSENSE will use the shortest delay.  However, by connecting a resistor between the yellow wire and ground (black wire), the delay can be increased.  See the table on page 4 of the CKT-IRSENSE user manual for the resistor value to use for your desired delay time.  Each CKT-IRSENSE comes complete with four standard resistor values: 24k, 10k, 4.7k, 1.3k.  These can be used alone or combined in series or parallel, to get other delay times.  By shorting the yellow wire directly to ground, the maximum delay time will be selected.


See the CKT-IRSENSE product page for ordering information.


  1. Dear ISE team,

    Does the Auto_interchange system work with DCC-controlled locos, or only analog 12v-DC?

    Happy Modelling,
    Aim to Improve,
    Prof Klyzlr

    1. The auto interchange will work with any type of control system. It simply drives a relay to provide / cut power to the interchange track. You do need to provide a dedicated throttle to control the locomotive pushing the rolling stock. See the CKT-IRSENSE user manual for more details of the implementation.

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