Birdhouses in production

In every big project I've been part of, the part that ends up taking the most time is rarely the most technically complicated, nor the part that the original design focused on. For the Field of Flowers, we've ended up spending over a month building the enclosures: these are little wooden boxes at the base of each flower that hold the battery, speaker, and electronics.

First we cut the sides and the base.

Then we had to cut nice looking holes in the sides (and later, the tops and back) so that the sound from the speakers can get out. We wanted nice looking holes (vaguely flower-like) so we used a technique called template routing.

Cutting around 380 of these holes (we made a lot of mistakes) left a ton of interestingly-shaped little offcut pieces.

I built jigs to help us assemble the components into approximately square birdhouses.

After a lot more drilling, we have 165 birdhouses on stalks.

There are a couple of interesting assembly steps here. First, drilling the holes for the tops is challenging because every stalk+birdhouse combination is unique because (of course) the stalks are curvy. Then, if you look closely, you can see there's a little bolt in the top that secures the top to the rest of the birdhouse (keeping the stuff inside safe). The placement of this hole is unique to each flower. Whew!

Today! we finished drilling the stalks and affixing the birdhouses to stalks. We have 165 ready for electronics, leaves+flowers, battery, and speaker. Next up: flower assembly.

Templates and jigs and scraps

I built a lot of templates and jigs so that our cutting and assembly is (approximately) consistent. We posted a video about how we did the template routing. This is the method we used to cut holes in the side panels. This method worked really well. We used two routers, each with a flush trim bit. The bearing on the bit tracked the template, which enabled us to reproduce the cuts in the template. We sure did cut a lot of those side panels.

I also built jigs to hold the parts for the birdhouse assembly.

All this woodworking has left us with a LOT of scrap.

But now we have the physical fabrication done!

I built jigs to help us assemble the components into approximately square birdhouses.

After a lot more drilling, we have 165 birdhouses on stalks.

For the next month, we will be casting leaves and flowers in resin, gluing LEDs into leaves and flowers, and assembling the flowers. This is the fun part, and so far, we've got 18 flowers completely done. Software development is going quickly now. Whew! Here we go.

Flower Electronics

We have had very good luck --- and good partnerships --- buying electronics directly from companies in China.

We started with the ESP32 boards and their accompanying audio+LED+power board. We got the boards from Makerfabs in Shenzhen, and I could not be happier. Their ESP32 boards are terrific and inexpensive (we paid about half of the listed price for 165 boards). Even more importantly, they helped us design a board that could output audio through a 3.5mm aux jack; include a level-shifter for the LEDs (because the ESP32 outputs 3.3v signals but the LEDs require a 5v signal, we used this chip); and we made a power plane so the +5v and GND from the battery have a clear path to the LEDs without going through the ESP32's power management.

This process went almost flawlessly. Makerfabs's engineer helped me think through the design, and we got the samples quickly. The samples output sound through a tiny JST connector, not an aux cable, and the sound was ok. Then the production boards arrived.

There was no audio from speakers attached through an aux cable! Well, there was a tiny echo of sound in the speaker, but no more than that. After a LOT of thinking about the schematic, by accident, I noticed that if I pulled the jack halfway out, the sound was fine. What?

Turns out that the tiny amplifier chip outputs only one channel. To get two channels (for the stereo aux cable), the engineer routed sound to both. However, one channel was inverted, so they were canceling each other out. I figured out we can fix it by cutting one channel. We could cut the cables, but instead, we decided to desolder a tiny resistor (R39, in case you wanted to know) from each board.

For perspective, this resistor is about 1.5mm long, the size of a deer tick (not a dog tick, that would be easy, no, a deer tick nymph; my choice of analogy may tell you how I feel about R39). Anyway, this doesn't take very long, and I've done 50 of the boards so far. Success!

The LEDs were simpler and had a similarly fantastic result. For over 10 years, I've bought strands of LEDs and cut them to the length I want, resoldering the leads onto the pads. This time is a little bit more complicated because we're buying the LED strands (just standard WS2812B LEDs but in the 2mm size) encased in a sheath that diffuses the light (called "neon" but it has nothing to do with the noble gas). I found a company in Hong Kong called Alitove Lighting that had great prices. After some discussion, they recommended that they cut and solder all the strands. What a game changer!

This vastly reduces the amount of soldering we have to do, and furthermore, Alitove's strands have protective caps on each end which will reduce the possibility that we'll damage the LED strands while we're gluing them into leaves and flowers. Alitove accommodated my specification for the orientation of the JST leads (I prefer the male-female orientation of the leads in the opposite direction relative to their standard).The price was great and the shipping was ridiculously fast. Yay!

We bought other stuff -- cheap bluetooth speakers, misc cables -- from vendors at Aliexpress. The cables hit some shipping problems (not the vendor's fault! Argh, DHL sucks) and the vendor worked really well with me to get it sorted out. On the whole, I am very impressed with the standard of business I found with these four companies. I'll definitely start here next time I have a big project.

Production!

The resin pouring team is working every not-humid hour, and we're getting lots of flowers and leaves.

First we glue the LEDs into them.

Which leaves (haha) us with a Whole Lotta Pieces to assemble.

Assembly is slow and meticulous: check the wiring, feed and attach the wires for each leaf, bolt the leaf onto the stalk (without stripping the insert), and do the next leaf.

Meanwhile we're still soldering the final boards together.

We've now got 49 flowers fully assembled and ready to make pretty lights. We're prototyping racks to carry them: 8 flowers fit easily in the back of my little truck, but I'll bet if we think harder, we can double that.

It looks like we'll have 165 full flowers, which gives us a little margin for failures and breakage. Getting a lot closer now, super exciting!