As a follow on to an old post ( viewtopic.php?f=10&t=124&hilit=working+signals ), I thought I'd document the making of the signals for The Bridge.
To try and get a sense of scale, I really had no choice than to use 0402 size LEDs in the signal head, and to make the signal post as near to scale diameter as possible....as I prototyped in the above referenced thread.
So here goes with the construction of a two aspect stop signal....
The first job I did was to identify the anode and cathode of a red LED, which is marked on the back...ironically, its a shallow "T" with the stem pointing towards the cathode. The identified LED was then pressed into a thick layer of spray-on peelable adhesive on a piece of paper so I could then put it under one of those cheap USB microscopes that have a x1000 magnification so I could see and photograph it.
With it immobile, I was then able to tin the two connector pads.....as shown here:
We're looking at the back of the LED; the cathode is on the left, and the anode on the right...honest! Ignore the lunar surface...that's the spray adhesive!!
I then scraped the insulation off the end of a piece of 0.1mm magnet wire, tinned it and then soldered it onto the cathode, The wire overhangs as there will be a green LED above it...note its been rotated 90 degrees clockwise! :
I then soldered another scraped & pre-tinned wire to the anode:
The second LED was now needed, a green. It was stuck into the adhesive and the pads tinned, then manoeuvred into place so it was above the red LED and the overhanging wire on the red LED soldered to its cathode. A third pre-tinned wire was then soldered to the anode of the green LED. The resultant assembly now looks like this:
Note up is at the four o'clock position! And both LEDs are facing down.
I checked that both LEDs actually worked by connecting the free ends of the three wires to my multimeter....which conveniently has a LED test output!
To be continued.....