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(Signals) Switch Point Detector

Posted: Mon May 13, 2019 10:23 am
by ChuckHackett-844
I am starting to make a Switch Point Detector:
• It’s reliable.
• It’s adjustable to account for notched/not notched railhead, point rail profile, etc.
• It can detect a point open by as little as about 0.010” caused by rocks, leaves, sand, etc.
• It’s weather resistant.
• It says where the points are – not subject to where the throw or switch motor thinks they are due to springs in the linkage.
• Current model is for 1 ½” scale rail but it can be adapted for 1” scale rail (I believe the rail shown is “West Coast Rail”).
• Can be installed without disturbing the point rail or point linkage.
• Can be used on manual or motorized switches.
• Can be used to feed “dwarf” switch signals or as an input to signal systems for route signals, etc.

In this case I drilled and tapped the rail 6-32, but, if you have room you can use nuts instead.
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I am looking into adding a 3 mm LED in the top to indicate point closure to make adjustment easier.

Here is the field prototype that was installed at Ridge Live Steamers (Dundee, Florida):
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In the final version I made the body as small as I could and eliminated the mounting 'ears' in favor of through bolts. I also eliminated the 'tail' assembly on the back that I felt could be an entry point for water, dust, etc.

Two are required per turnout. The switch point presses on the brass rod (which is adjustable). I think a point opening of as little as 0.010” can be detected reliably.

No more issues with switch motors causing false “Clear” signals because it thinks the points are closed but there’s a rock in there or the points are binding.

The sensor itself outputs a voltage signal. I am working on a small PCB that will provide relay outputs to control dwarfs, feed a signal system, etc. It will provide "Locked-Straight", "Locked-Turnout", and "In-Transition" outputs. One use would be a 3-lamp dwarf that displays Green for Locked-Straight, Yellow for Locked-Turnout, and Red for In-Transition.