Photocell Detector Module


The CDS4 photocell detection module provides model railroaders with the ability to easily add train detection using simple sensors and ambient light.

In stock


The CDS4 is an optical train detection device for model railroad hobbyists.

Photocells sensors change their electrical resistance with ambient light level.  When light reaches the sensor, no train is declared.  When a train shadows a sensor the CDS4 photocell detector module detects the train.

The CDS4 converts the electrical properties of photocell sensors to usable train detection status.  The CDS4 allows for up to four strings of photocells.  These 4 detection zones or track circuits can be used for: signaling, crossing activation or any other model railroad train detection application such as staging yard occupancy status.

The CDS4 also provides light sensitivity adjustment. The four detection inputs allows for an independent light level range.  The CDS4 additionally allows the user to choose between three difference levels of occupancy delay similar to loss-of-shunt techniques used with prototype railroad track circuits.   This delay ensures reliable train detection as light flickers occurs between railcars.

The CDS4 can be easily used with other products requiring open-collector detection outputs.  The following Signalogic Systems products are designed to work with the CDS4:

The CDS4 includes 10 photocells.


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