Reflective Infrared Proximity Sensor



"I was having problems with the sensors for my grade crossing flashers... As soon as I replaced the sensors with the ISE sensors, all the problems went away and the crossing signals have worked flawlessly."Jason Klocke.  View Jason’s spectacular CGW layout here.

This device is a simple infrared sensor that makes detection of locomotives or rolling stock easy and reliable.  Just place the sensor where its invisible light beam will reflect off the object of interest and you're done - no time-consuming or frustrating adjustments!  Based on modern silicon technology, this sensor is tolerant of ambient (background) lighting conditions, be it completely dark or under full lights, with no false triggering.  Combined with a discrete under-track installation, this low-profile sensor solves many of the challenges that plague other optical detector products.


  • Small size (0.25" x 2.25")
  • No adjustment needed!
  • Simple, discrete under-track installation
  • Variable release time up to 23 seconds (or 23 minutes with Long Delay option)
  • Two opposite polarity, open-collector outputs (40V / 250mA capable)
  • Tolerant of ambient (background) lighting conditions - no false triggering
  • 9" pre-stripped wire leads attached to the sensor
  • Powered from 5V to 24V

Typical Applications

  • Activate grade crossing signals
  • Trigger sound events
  • Simulate a spring switch using an MRServo switch machine
  • Build an automatic interchange
  • Occupancy detection for signal systems or hidden tracks
  • End-of-track indication in hidden staging yards
  • C/MRI track occupancy inputs


The detector is designed to be installed up through the benchwork in a 3/8 inch (10 mm) hole.  Because the sensor itself is so small, only a single hole is required and no complicated drilling jigs are needed.  The sensor can be secured in the hole using a variety of methods such as hot glue or by using a bracket.  An example mounting bracket can be found here.

Electrical Connections

The CKT-IRSENSE needs 5-24 volts of clean direct current (DC) power to operate.  Two opposite polarity outputs are provided, both of which are “open drain” (otherwise known as “open collector”) and act like a switch to the ground or negative lead.

Logic level outputs can be generated by connecting a resistor to pull up the output to the positive supply.  Other devices, such as LEDs or relays can also be driven directly and the outputs from multiple sensors can be connected in parallel to combine them into one signal.


2.25"(L) x 0.25"(W) x 0.25"(H)

By default, the release time is programmable from 0.1s to 23s using an external resistor.  A long-delay option is also available with release times from 6s to 23 minutes - contact us for details.

The activation time is preset to 0.1s.

The sensing distance varies with the reflectivity of the object being sensed, but is typically 1.5".


The complete gEDA design files are available on GitHub.

User Manual


  • $19.00

  • 12 or more $18.00
  • 5 in stock

Available Options

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News & Application Notes

2018 Optical Detector Roundup

Many of you already know that Iowa Scaled makes both kinds of detectors – an optical detector known as the CKT-IRSENSE, and a current detector known as the CKT-BD1.  When discussing detectors a few months back, Michael and I thought it would be interesting to compare ours with the various other products on the market and figure out who really has the best stuff.   In this installment, we’ll look at six of the most popular optical sensors on the market, comparing and testing them, and try to give you a fair and honest comparison between all your options.  We’re a weird company, and just to prove it again we’re going to say some nice things about other peoples’ products, and some bad things about ours.  Read on…


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.


DCC Auto-Reverser

We were recently asked to build a module that could automatically reverse a locomotive between two end points for use on a small point-to-point switching layout. The idea was to provide a means for continuous running of a train while working on the layout or to break in new locomotives without user intervention.  The end result is described here, with instructions for building your own.  At the current time, this is a mostly a DIY project, but if you want help building one, please let us know.


Auxiliary Power from a DCC Bus

While DCC is primarily meant to power and communicate with the trains on the tracks, there are circumstances where having some auxiliary power available would be nice without having to run an extra set of wires.  Maybe powering a remote turnout, an IR sensor, some animation or building lighting, or a fast clock secondary display?


Adventures in Lighting: Part 2

Addressing some of the problems of the design in Part 1, a new lighting system for the pantry has been installed.


Simulate a Spring Switch

Spring switches are used by some prototype railroads to save the crew from having to re-align the switch points after passing through the switch.  The switch is sprung in one direction (typically the mainline), allowing any train to pass through the switch from the frog end without manually aligning the points.  When entering the mainline from a siding, this allows the train to continue on its way without having to realign the points to the main – the spring action takes care of this automatically.  Modeling this unique feature can be easily accomplished with an IR sensor and switch machine.Read More...

Infrared Proximity Sensor

The CKT-IRSENSE is an inexpensive reflective infrared proximity sensor, designed primarily for model railroad use, utilizing the latest in proximity sensor technology.  It can be used to trigger a variety of sound and visual effects as well as provide track occupancy status.  The sensor’s small size (0.25″ x 2.25″) makes installation simple with only a single 3/8″ hole required.  The technology used in the CKT-IRSENSE makes it highly tolerant of background lighting conditions, thus requiring no user adjustments.



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