8.25 Fireworks Display

I still haven't talked myself into this one yet; it all depends on the result of test #2. I did test #1 using the same electronics I'd utilized for the fireflies, and it was... okay. It wasn't spectacular, but seemed worth thinking about.

I had enough parts to make at least five displaysóabout half as many as I'd thought about buildingóbut even then, the numbers are kind of staggering. One change I made from the test unit was switching from pre-wired 0402 SMD LEDs to 1.6mm discrete LEDs: they were easier to work with, and I had more of them; however, it meant two more solder connections per LED.

Each display consists of twelve banks of seven LEDs, or 84 LEDs, plus the "launch" pattern, which is 9 more LEDs, for a total of 93 LEDs per display. Five displays required 465 LEDs, plus 10 more for a glitter effect; with the wiring, this translated to a grand total of nearly two thousand solder connections, not including 280 power supply connections. Not to mention the work of extracting the chips from the original Christmas light displays, or a dozen solder joints per chip, for another 840 more solder operations. And this assumed there were no LED or chip failures, or errors I might makeóas it happened, thanks to my dyslexia, I wired an entire bank of chips backwards. No matter; it's not like I have anything of importance to do.

Work began on 6 October 2020 with the chip extraction process, which took a day and a half. Then I created a color-coded drawing of the five displays interleaved so as to create a quasi-3D effect. Note that the drawing (above) also shows a wiring diagram of sorts, specifically how the anodes were connected. This became crucial during assembly to determine which LEDs were part of which displays, since the five of them were highly integrated, and the LED colors were no longer evident once the LEDs were mounted. I printed the drawing on self-adhesive label stock and applied it to a piece of 0.030" black sheet styrene.

Next, I made a circuit board mounting plate from ⅛-inch thick sheet styrene the same size as the display sheet, and attached all 70 flasher chips with double-sided foam tape (above left). Just wiring the power leads (above right) took half a day. To keep the 545 wires relatively neat, I also drilled holes through the chip plate, one for each chip, so the chips would face outward to facilitate making the final connections (below left). To the back of the chip plate I attached strip styrene spacers that would eventually be used to fuse the two layers together permanently (below right), once the LEDs were wired.

Then came the excruciatingly tedious task of installing and wiring the LEDs, which had to be mounted in hand-drilled holesómy hand was pretty badly cramped after drilling 475 holes (below).

Each LED was bonded into a hole with CA (below left); afterward, all of the LED anodes were bent and soldered together (below right) to form twelve pre-wired "sprays" for each of the five displays.

It was awfully slow-going; the first two displays (above) took two days to install. The last three, however, took just one. That left the 45 launch sequence LEDs to install, along with the "glitter" effect, which will utilize the same electronics employed for the wedding photographers (green circuit boards, below right).

But if I thought that was slow-going, I was about to embark on an even slower process: cutting, soldering and bundling nearly 600 pieces of wire. I could only do a few bundles at a time before I'd go a little nuts, so this is looking like more than a week of work. Below is three days of work, and I've only got two of five displays wired.

This will be followed by threading, cutting and soldering the bundles once more. Oh, and before making the final connections to the chips, I'll have to test each wire to determine which LED it powered. Tedium doesn't begin to describe the process.

Meanwhile, on the Layout...

On 17 October 2020, I opened up a space at the back of the layout for the fireworks display unit. Driven by a motor, it will rotate around a pin at the bottom of the unit. When upright, it will occupy a small recess between a rocky hillside and the Bearcamp station; when lowered, it will duck behind the edge of the hillside, which ends at the roadbed with a slice of Cripplebush Valley rubber rock (below).

The following day, after taping up the gaps between the rock and roadbed, I filled them in with a slurry of thinned pre-colored sanded grout (below). I also added a thin layer of the grout around the disused siding and along the edge of the firefly meadow.

If I'm dissatisfied with the fireworks display, then I'll simply fill in the gap left for the device with a chunk of scenery.

Also See...


I like mechanical stuff; that's why the neon open sign in the laundromat has a motorized drum with wiper contacts. For the fireworks, I'd need something a bit more robust and flexible, and for inspiration I turned to the stoplights from the White River & Northern IV, built back in February 1998 (I used to date everything I built in those days).

A motorized drum with raised ribs tripped roller microswitches to control the stoplights for a five-way intersectionócomplete with left-turn signals and walk/don't walk signs. I would have repurposed the mechanism, which I still have (above), but it's short three channels, so I'll build a new one for the twelve channels I need to control the fireworks display. It will create an entire show, from the first few modest shots to the grande finale. Sound will of course be a part of the show.


I've attended dozens of fireworks shows in small-town New Hampshire back in the day, and they were all the same: truly pitiful by today's standards. But back then, small towns had small budgets, and families nevertheless had a terrific time gathering in the town's high school sports field for some hot dogs and a little light show. The people watching from their cars would show their appreciation for each individual rocketólaunched a minute or more apartóby flashing their headlights. The grande finale was usually just five or six rockets set off at once and, on occasion, some ground displays. I miss those simpler times. Now everyone is trying to out-do one another, with synchronized music and lasers and who knows what all. I used to love fireworks shows, but I haven't been to one in well over a decade.

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