Model Railway Arduino Signals – Design

As previously explained, I’m working on the use of an Arduino and an old laptop to control the points on my very small N Gauge model railway. Well, I’m also going to control the signals too.

Working on this track plan:

Simplified Garwick Track Plan

I consulted my tame signalling engineer (some say that he once completly ruined the brakes on my MG Montego, and that he spends his spare time writing cod-1950s hard-boiled detective story versions of his work, but all we know is that he’s called The Sig), explaining to him that all the lines were bi-directional. He put on his thinking-trilby, sharpened his crayons, and came up with this idea:

timmy2

(Only the signals inside the box are to be modelled. The ones outside it are off-scene, and therefore just implied to be there and functioning.)

So, 6 signals. As I only had six remaining outputs left on the Arduino, I decided on 2-Aspect light signals.

And, lo, these were on eBay:

z0a

Six of them for £19 incl shipping, actually from http://hezhiqing.com/NSIGNAL.html (yeah, it says 5 on the website, but all the eBay listings show 6 of them).

Nominally they run off 12v but are plenty bright enough with 5v from an Arduino supplied to them. Plus, if you tie the Green line to 5v and the Black to GND, putting 5v up the Red line from the Arduino will switch the signal from green to red. This is counter-intuitive to me, as surely the signals should fail-to-Red, not fail-to-Green?

No, matter, it still make the wiring easier.

sigwires

Eagle-eyes will spot the the lights are the wrong way up.  Ah, well, it’s too late now.

Next… build up the control board for one pair of points, and one signal as a test.

 

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