Optical Detectors Installed

I can hardly believe it myself.  I’ve completed the installation of all 24 of the photo-transistors (herein known as PTs) and their accompanying infrared LEDs (IR-LEDs) as used in my optical detection system.  Whew, what a job!  Nothing about the project was particularly difficult…at least not on paper.  The premise was simple, the wiring was simple, the hardware was simple.  But the effort to do each task wasn’t trivial, and the collective effort expended was nothing short of colossal.

Installing the PTs was by far the fastest and easiest thing to do.  Simply drill a 3/16″ hole and stick the PT into it.  Didn’t even have to secure them…they are held by friction.  I then ran a 26 pair phone cable around the layout and tapped into it with the PT leads, each PT on it’s own circuit.  The cable ends at a backboard beneath the layout where the circuit cards are located.  I made the tie-ins and the detection circuit was complete.

The IR-LEDs required much more effort.  The IR-LEDs are used as the illumination for the PTs.  I chose to install these up over the track, with the LEDs pointed down over the PTs.  I ended up fabricating a “tower” for each IR-LED.  In fact, I actually fabricated three types of towers as required by different installation requirements.  Using flat metal framing straps procured from Home Depot, the fabrication involved was drilling a couple holes, making some bends in the metal, then installing the towers onto the benchwork.  Later I made up some assemblies, each consisting of an IR-LED, a current limiting resistor, and some wire leads.  I installed these on the towers, ran the leads down below the sub-roadbed, and attached them to the 12 volt DC bus.

Today I applied the power, checked that each IR-LED was in fact illuminated (had to use my digital camera for that since you can’t see light emitted from them with the naked eye), then rolled a boxcar through all the “traps”.  All worked perfectly with no adjustments required!

Here’s a photo of a couple of the towers.  The one in the foreground is a double tower, in that it supports two IR-LEDs (one over each track).  If you go over to the main website, I have photos of all three types.

IR-LED Support TowerThere is one final task to do before the system is operational, and that is to build three small panels which will contain track diagrams with red LEDs located at appropriate locations.  This will be the visual indication to the engineer as to where his train is on the hidden staging track, and most importantly, when to stop.  I  need to install the fascia before building and installing the panels, so that task will be a ways down the road.

But having the hardware installed over the staging tracks clears the way for me to start the sub-roadbed and trackwork for the upper level above.

Progress is surely sweet!


2 thoughts on “Optical Detectors Installed

  1. Progress in surely sweet. I’ll be so glad to get my layout started. Modeling the ICG early ’80’s as I remember it in south Mississippi. Keep up the good work Jack and look forward to keeping up with what’s happening on the Louisiana Central.

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