I designed this device as a birthday present and card for a friend of mine. She likes riddles... I don't know exactly how it started but I recall I didn't want to use any display (like OLED) in the next interactive device and not necessarily sound as a main interaction base for the scenario. 

The CFX and its lightsaber firmware of course provide a quality sound output, OLED support, motion sensing and gesture recognition but I didn't want it to be again the support of the story told. I had been wanting to play with those thermal printers for a long time, so I though, why not building something that prints the card out on the fly, an "automatic birthday machine".

For some reasons, Vader came to mind as my mind rambled, what would his birthday look like ? Would he be happy ? And I've always like this hilarious meme about the character and his emotion chart

The idea moved towards the concept that since he's a villain, no one would wish him his birthday and he would have an automatic machine to make it happen. And that would become popular enough that it's available to the masses under Vader's Licensed merchandizing under the name "Vader's Birthday-O-Matic"

I also thought the use of the printer would allows for slowing the time down, instead of the instant gratification and immediate notifications we get with social networks. Instead, things would be slowly printed out, almost like if it's voiced to the recipient, but this time without sound.

As the design kept going, I designed it so that the birthday cake would be topped with a (working) lightsaber, naturally powered by my CFX saber sound board, with an exact 38 micro addressable pixels, like the ones in the 1:1 sized lightsabers (WS2812 like, just much smaller, 1515 smd footprint).

To keep the interaction even closer to lighting up a birthday candle, I added a DHT22 temperature sensor coated with a double layer of heat shrinking tube, to be "ignited" with a real lighter.

As a result, I laser cut a wooden box out of 3mm MDF with engraved details and Vader's helmet + branding, a slot to integrate the printer and 3D printed a cake out of ABS. The mini vader saber (about 65mm long) got printed on the Forms 2 SLA printer at the office, then hand painted. The core of the system is a CFX with a slightly modified firmware to integrate a custom thermal printer library, that feeds some of the text and the BMP pictures out of the onboard SD card.

A special mode (pressing the Aux switch at the back, at boot time) prints the initial instructions out. From there, the card recipient would just power the unit on and enjoy the ride. The most difficulty to overcome here was to have the said recipient to actually use a lighter to ignite the sensor. The coded state machine is made in a way that unless you complete that ignition and cool down process, the final message (QR code with a link) cannot be obtained. Yet, when the whole birthday experience isn't wished the printer can be disconnected, and the back switches can operate the board is if it was a mini lightsaber, blade ignition / retraction, clash, swing, lockup. A single font is present on the SD card (most likely "Fire" from Kyberphonics, IIRC, revamped with Nyan Cat lockup and "blaster shots" ^^ ).

I even wrote and submitted an article for the TEI 2023 conference, unfortunately it didn't get accepted, despite the call was "be together beyond screen and pointers", a post covid-19 invite to celebrate without zoom and I still think this was pretty on par...     \_(ツ)_/¯
The PDF of the article is available below, if you have time to spare for it.

Video demo of the device