I'd first created fireflies for my White River & Northern II back in the late 1980s. It went like this: I inserted a few hundred fiber optic strands I'd painted green into a field made from thin foam rubber; the fibers stuck out of the ground like weeds. Then I filled in around them with ground foam vegetation. The other ends of the fibers were connected to a mechanism that slowly moved yellow-green lights past the fibers (I had to tint clear bulbs myself with transparent paints to achieve the right color). The result exceeded my expectations, and I've wanted to reproduce the effect ever since. Below is a view of the field after installing the fibers but before adding the vegetation, back in 1987.
I used the same device to make a campfire effect as well. The device had two rotating drums (copper-colored discs, below): one for the campfire, on the left, and one for the fireflies, on the right. The mechanism was designed so that the campfire drum rotated twice as fast as the firefly drum. Each drum had a series of colored GOW bulbs (LEDs were not yet cheap and plentiful) that passed the ends of the fibers as the drums rotated. Additionally, there were multiple layers of bulbs, which could be turned on in sequence to simulate increasing numbers of fireflies.
The thing I didn't realize about this crazy old contraption when I built it is just how strikingly realistic the effect would be. But I wanted to replicate it using LEDs and electronics. Several Christmases ago, after the season ended, I found a slew of "falling star" icicle lights on sale for dirt cheap, so I bought out two stores' worth and dismantled them (below left); I'd intended to use them for a fireworks display I'd never built. Around the same time, I'd stockpiled hundreds of yellow-green 3mm LEDs (below right) I'd intended to use for a 1:1 rock garden display I'd never built. Fast-forward to 24 April 2020, and I'm seeing all of this as the perfect way to make a "solid state" firefly effect, since the falling star LEDs blink on and then fade out gently, with a nice delay before the sequence repeats.
Each unit (above left) is relatively easy to dismantle and break down to its core component: a PC board with all of the electronics. As a proof-of-concept, I connected seven yellow-green LEDs to a board, and they started winking away just as I'd hoped.
The next step was to assemble twenty illumination modules (I had enough materials to build many more, but I figured this was enough for my little layout.) This involved bending the leads of 140 LEDs to various shapes, soldering them to the modules, and testing them (above left). Then I built a styrene rack to hold the modules (above right), drilled a #76 hole in the end of every LED, and installed the fibers. Finally came the moment-of-truth test (below), and I got lucky: the new effect was every bit as good as the original.
This time I took a slightly different approach to installation: I fabricated a completely self-contained chunk of scenery, since installing the fibers in situ on the layout would have been a virtual impossibility. I made a box from Gatorfoam having only a bottom, front and sides (below left). I topped it with a sheet of Martin Welberg Type C wild shrubbery (below right); however, the sheet was not opaque, and the LED modules would be directly beneath it, so I spray-glued it to a piece of aluminum foil, then pinned it to the edges of the box (bottom right).
After spraying the fibers flat green (above left), I painstakingly inserted all 140 of them through holes I poked in the shrubbery sheet with a pin (below left); this was the most nerve-wracking step, because the fibers would snap with the greatest of ease. In fact, I know I broke one fiber during the installation, so there are 139 fireflies instead of 140. Finally, I glued the LED rack into the back of the box, and clipped the fibers off flush with the shrubbery (below right).
Time to fire up the fireflies!
And here's a peek "under the hood" while it's running.
