Since Coketown was a modern mainline station the signalling needed to be 4 aspect with red, yellow, two yellows and green.  I decided that if I made my own signals I had the option of them having working lights or, if I couldn't get the lights to work, make them dummies.

I drew the basic signals using simple shapes in Sketchup which at the time was free. It's now part of Autocad but I still have a copy from 2017 which is about the last free version available. I had the files printed by Shapeways and got back some very small N gauge signals!

The signals were designed around surface mount leds which are 0603 size which is about 1.6 by 0.8mm. The first signals were assembled at work under a stereo microscope (for two eyes so you still have depth perception). I then found a cheap stereo microscope on ebay so was able to carry on building N and OO  signals at home for Coketown and our club layouts.

The leds were dropped into the head of the signal...

and then enamel coated wires attached to the led pads. The intention was then to put a printed back on the signal but it was so small I just covered the wires with superglue and painted over the whole lot after it had been tested.

I think thats a penny....

The signal driving electronics were made using a Arduino Nano pcb which I added circuitry to to rectify the DCC control signal to power it and decode the DCC signal to receive the signal messages. The code for the DCC Decoder came from here https://github.com/mrrwa/NmraDcc/.

In addition to the post signals I also bought several brass signal gantry kits from TrainTronics which are unfortunately now discontinued. I needed a gantry across three lines for the main line and then several cantilevered gantries where a signal needed to be suspended over two tracks. I had Shapeways print some heads without posts and built those up with leds in the same way.

The route indicator is a smaller 3D print with a row of 0402 white leds. There was no room for current limiting resistors in the route indicator so the leds are simply wired in parallel. It seems to work okay with a single resistor for the five of them. It is somewhat oversized but that just comes from working around the available leds.