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Additional Supplies

Twin Industries 4x5 Plated Prototyping Board (Mouser PN 589-8000-45-LF, $12.75)
LadyAda's USBtinyISP AVR Programmer (Adafruit Industries, $25.18 w/ shipping)
20MM Coin Cell Holder, 3V, #2016 (Mouser PN 12BH002-GR, $0.30)
Yellow-Green SMT LED (Mouser PN 645-598-8160-107F, $0.09)
ATTiny45V10SU (Mouser PN 556-ATTINY4510SU, $2.02)
Breakaway Headers 2x9 (Mouser PN 538-10-89-7181, $0.61)
Copper Foil Tape, 3/8" (Cline Glass, Portland, OR, $11.40)
Art Glass, 22x13" (Cline Glass, Portland, OR, $4.13/sqft)
Glass Cutter (Fry's Electronics, $2.99)
Weller WES51 Soldering Station (Fry's Electronics, $99.99)

Programming

Programming the AVR chip was probably the least time consuming task of this entire project. I purchased a USBtinyISP kit from ladyada.net for about $25 including shipping. The programmer was relatively easy to put together, although the kit has gone through a revision since the instructions on Limor's site were last updated, and so the placement of some of the parts were different from expected -- also, some parts were extremely tight: solder your big chips first!

Once that was done, I constructed a target board on a protoboard from Fry's ($12) that included 6 and 10-pin headers (the USBtinyISP supports both), and 8 and 20-pin DIP sockets for future AVR projects (Mouser PNs 517-4820-3000-CP, 517-4808-3000-CP). I used 30(?)AWG magnet wire to solder the board up, since I would be soldering directly to an SMT AVR chip. (Strip the magnet wire with a knife, or just tin the ends until the insulation melts back.

The AVR chip itself, I mounted upside-down on a piece of double-sided foam tape on the board, and soldered the speaker wires directly to the chip. I used these excellent resources to figure out how to make target boards -- as for what to solder to what, you'll have to look at the data sheets from Mouser for your AVR chip, and compare that to the pinouts for the USBtinyISP.

Once everything was all soldered in place, I plugged the USBtinyISP into my PC and used avrdude to flash the firefly.hex file from clamoring's instructable to the chip. I wired up the LED to the chip while it was still on the protoboard and tested to make sure everything worked before desoldering it and setting it aside for assembly later.

Planning

My design requirements for this project were the following:
1. Sturdy and Reliable: Parts can't come loose, and connections should be lasting.
2. Simple and Lasting: Switches break. Batteries die. Remove the switch, and add a replaceable battery.
3. Artsy: It needs beautiful art! Clamoring did a wonderful job on hers, and I wanted to make something equally interesting.

I essentially laid out the circuit board first, first using cardboard and card-stock before my parts arrived, and then using clear plastic, both with circuits drawn on. In doing it with cardboard, I was able to mock up a "battery holder" to figure out the geometry of how I would mount everything. Since I knew I was going to use a circuit board and battery holder, but still wanted it to be thin, I decided the best solution was to mount the SMT-style battery holder upside down, with the feet sandwiched between the circuit board and the art & glass.

 Once my supplies arrived, I did a final mockup on clear plastic again, but cut out a space for the battery holder and taped it in place to mimic the final design. I changed the orientation of the holder after seeing it in person -- originally I would have had the battery slot at the bottom of the piece, but decided a horizontal placement was more stable, and would also help prevent gravity from turning the thing off.

Art

I decided eventually on doing the art on cardstock against dyed rice paper. The cardstock would allow some fuzziness from ink bleeding, and the rice paper would take ink quickly and let light through. I used Windsor & Newton bottled inks with dip fountain pens to do the art, and then used a razor blade (xacto would have probably worked better) to cut the art out. I mixed the inks particularly for this project, to make some of the more subtle color gradations. I mimiced the illustration of Pyractomena angulata from this site, even though the song flashed to the AVR is allegedly a Japanese beetle! I had to alter it to have it back spread slightly to reveal the blinky abdomen. Lastly, once it was cut out, I used the same green that I dyed the rice paper with to color the edges of the cut beetle, so that it would be matted green instead of white on the rice paper.

Circuit Board

Construction of the circuit board and subsequent assembly took the longest amount of time. I took my protoboard, laid my final plastic prototype from earlier on it, and traced it. I then marked what areas to shave off, took my dremel to it, and ended up with the shell for the components. If I were to do this again, I would use protoboard with pads on only one side, as the through-hole pads were a pain to dremel, and ended up causing the potential for shorting where I didn't want any. Where the LED would be mounted, I beveled the out-facing side of the board so that the board would not block the light from reaching the face.

I also attached and soldered the battery holder at this point. I refined the edges of the gap with my dremel to get it to fit, before soldering the pads directly to the board. I used a pair of pliers to keep the pads flush against the board while I soldered it so that the solder would not push it up and away from the board, since the feet would be between the board layer and art layer.

The next step was insulation. Since the board had pads on both sides, I needed to insulate the interior pads away from what would eventually be the negative terminals of the battery. I used cardstock again, and electrical tape, to isolate the interior side of the board. This also leveled off the inside face, so that the feet of the battery holder would not bulge the glass or art.

Sandwich

Finally, I constructed the negative terminal of the piece by applying copper tape to a piece of aluminum can cut to size (with a hole for the LED to shine through). I layered 3 pieces of copper tape over each other where the battery would go, and then applied solder to complete the connection between the pile and the lead that would wrap over onto the back side of the board to where the AVR would connect to it. At first I had hoped to use the aluminum can as a contact directly, but gave up when I became too lazy to buff the insulating layers off of the entire piece of metal. Instead I simply applied a bit more copper foil around the edge of the circuit board, and a tail wrapping around that edge to form a contact. Finally, I put the two pieces together (including the art), and soldered the two negative copper tape contacts together.

Assembly

The final part of this process was assembling the circuit with art, and glass, and applying the copper tape. I had bought 3/8" copper tape from Cline Glass in Portland, and it was too wide for this piece, so I cut some of it off and applied it as described in the Instructables article. I left a gap for the battery holder, and then applied an even thinner portion there. I also soldered the edge copper tape to the negative battery terminus inside, to provide a smoother transition for the battery.

I used silver bearing lead-free solder, which unfortunately didn't flow as well as 60/40 solder. However, I can rest assured that death will only come more slowly from the scant leaded solder I did use to solder components in it! Lastly, I made a ring of steel wire and soldered it with copious amounts of flux and solder to the top of the piece.

Once the piece was soldered together, I stuck a glob of glue-stick in the socket for the AVR, and placed it, soldered it to the magnet wire, and then soldered those wires to the positive terminus (pad from the battery holder), negative terminus (copper tape pad wrapped around) and to the LED, which went in the smaller hole. The negative end of the LED soldered to the bezel directly next to it, since it was connected to negative as well. I applied copious amounts of glue stick for the time being to hold everything down, until I obtain some clear epoxy or lacquer to waterproof and isolate the components even more.

Final Thoughts

To turn it on, one only needs to insert the battery. Time will tell what the life of a single 2016 battery is. I found right away that it's pretty easy to short it out by letting the chain dangle against the battery holder, since chain=negative, and holder=positive. Also, since the glue stick was apparently water soluable, finding a water resistant lacquer is a top priority for me now. I also plan on applying it sparingly to the outside of the battery holder, in order to isolate it. Also, the battery is a tight fit, and I gave a toothpick along with the pendant to push it out, since there's no easy way to pry it out otherwise.

Flux cleans up easy with isopropyl alcohol, I used glass cleaner to do a final cleaning, and the whole piece is rather lightweight, and balances perfectly despite having the battery on one side. In all, I spent a large amount of time on this project, mostly due to the modifications I made from the original by clamoring, and also because I had to learn almost everything from soldering SMT components to programming an AVR to do it, as well as cutting glass, application of the copper tape, and so forth. It was rewarding, education, fun!

In Action