Electric XMAS: Making Poinsettias sing!

December 23, 2012

in Projects

Cream Colored Ponies and Interactive Matter were working on a very special christmas card for our customers this year (and here google-translated to something like English).

Instead of a normal, boring card our customers got a little PCB to make some music with their otherwise pretty non-interactive Euphorbia pulcherrima.

The Basic Idea

Of course there was no way to make the plant sing itself, so some electronics need to provide the necessary musical output. An Arduino and the very nice TouchBox synthesizer built the musical base for this project. Add some melody lines and you got a nice little 8-bit music player (sound-wise and processor-wise). But this still lacks some interactivity – so the Arduino Capacity Sensing Library was used to interpret touch events (on the plant). The touch sensing is simply used to switch the various background tracks and change the sound envelopes of the lead track. Big thanks to Cream Colored Ponies for all the programming!

Thanks to open hardware is was a pretty straight forward task to create schematic and PCB from a reduced Arduino Uno schematic.

The PCB was first created in Adobe Illustrator to define the size and silkscreen print and then imported into EAGLE CAD to add the electronics (a process that makes much sense and leads to exceptionally great silkscreen printing).

Building the Electric XMAS Card

The main adventure in this build was the extremely short timeline and and high number of cards (we had two weeks until shipping date and in the end we produced more than 150 cards in 4 days). The layout of the card was pretty straight forward and simple.

But the real challenge was that we got only one shot for the PCB, since there was no time for any corrections. So we ordered all the parts for the cards to test if everything fits on the footprints and the card itself – and to ensure that we did not forget anything.

After the check we finished the PCB and ordered it. It looked really nice in EAGLE CAD.

And after the PCBs returned fro the board house we saw that the green PCBs looked nice seasonal fitting. But the sheer amount of boards made us shiver – it was a tad more stuff than we anticipated at first.

But soldering the first two test boards went very smooth. Obviously there was one error in the schematics, but nothing a fix wire cannot cure.

We went home very pleased this evening, knowing that we can go full scale production the next morning. And how full scale the production was we discovered during the next days. We worked hard to solder all the boards. One person was adding solder paste with a stencil and adding the parts, one was reflowing the boards and one was correcting all solder bridges and doing manual inspection of the boards – pretty straight forward but a lot of work if you go through 150 pieces.

But finally all boards were done! Even though it was a quite intense, labor intense and stressful time we were quite happy to achieve an impressing number of boards.

The last step was programming all the boards while also doing the final testings. Unfortunately I did not have the necessary pieces at hand for the great ISPTouch programming adapter – so we had to work with some creative pogo pin programming adapter (which worked exceptionally well as programming adapter and hand training device).

The Result

In the end everything worked out exceptionally well. All parts fitted into their footprint. The failure rate was a tad worse than we hoped for (~15% – blame it on too much manual labor). And we finished the assembly right in schedule.

So what did we learn from this? Producing an electronics product in 2 weeks is absolutely possible, if you take extreme care about design and logistics. Hand assembling all those pieces is not as bad as it sounds, still a bit bad. It is essential to optimize the stencil for production, our stencil had a tad to big holes for the solder paste – so that we got a lot of problems with solder bridges. A proper soldering oven is needed! It makes life so much easier than the hot air reworking station.

But it was great fun and an entertaining and intense build time. Our customers were really happy and it was a great project. And I cannot overstate it enough: Big thanks to Arduino to publish the Uno Board as Open Source Hardware – else it would have not been possible. And also big thanks for Adafruit and Sparkfun for their exceptionally great EAGLE part libraries (Adafruits here, Sparkfuns here) – we use them a lot and it makes life much easier!

And big thanks to Cream Colored Ponies for the idea, programming and artwork, it was the monster share of the success of this board! It was great fun!

So if you want to check it out yourself head over to github to grab the source code and schematic. An please be a bit nice to the source code – it was just a one off, fast sketch. Not very elaborate and quality wise just to be hidden inside a christmas card.


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