SCMES Track Signals

I’m currently designing and building an electronic signalling system for the South Cheshire Model Engineering Society.

A view across the track site

The Track Site

This consists of a set of 10, 3 aspect (red, amber and green) signals to control and 10 track sensors (the nature of which is to be determined) as well as 3 other special-case sensors (two on traverser locking mechanisms, and one station master switch).

The original system was based around a control unit which worked on digital relays and used 36V lamps.
Unfortunately the designer was involved in a car accident and died, leaving the system unfinished, and futhermore, the method of detecting a locomotive passing a signal (microswitches on plates in the track) resulted a far-too-short pulse length to actually trigger the relays.

This left the system in an unfinished state for several years, during which I finished my degree, and now I have time to work on the project.

A development signal's internals

The three high-brightness LEDs inside the head of a signal

The first order of business would be to determine what the control unit is required to drive, in this case high brightness LEDs are used for each aspect, and, although my development unit had a dead red LED, the LEDs could easily be powered by a simple 6v source (in my case, AAA batteries, as can be seen in the larger image).

The LEDs are more than bright enough to be seen far away, so will be acceptable as lamp replacements.

A signal showing all lights on, except red is broken

They're bright (shot taken from an angle to see anything at all!) except for red, in this case!

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