The Star Trek franchise has a track record of predicting future devices. As a kid watching "Star Trek: The Next Generation" (TNG), it was hard to believe one day we would live in a world with mobile phones, wireless wearables, and tablet computers. Not only that, but kid-me would be floored to learn that future-me would create one of those futuristic things! My latest project, the Baldcorder, incorporated an Arduino, some sensors, and blinky LEDs to form a functional tricorder.
On the element14 Presents YouTube channel, we celebrated the 500th episode with a contest. Three video creators, myself as one, were challenged to build projects with the same eight components. Members of the element14 Community also participated in the Build Inside the Box competition.
In the kit were two sensors that screamed measurement device. They were an STMicro Time-of-Flight (TOF) and an analog Microchip temperature sensor. A third sensor hid inside of a Vishay photo interrupter. It became a light sensor by removing the phototransistor and its daylight filter (with sandpaper).
At the heart of the project is an Arduino MKR ZERO. These Microchip SAM D21-based boards come in a slim breadboard-friendly form factor. They also contain a LiPo battery charging circuit, making them perfect for a portable application. Two often overlooked capabilities of the SAM D21 are its ability to make sounds and built-in capacitive touch.
The Baldcorder streams a WAV file from a microSD card through the SAM D21's digital-to-analog converter (DAC) to output a tricorder scanning sound effect. Like most microcontroller DACs, the output drive current is relatively low. Fortunately, the e14 producers included an operational amplifier in the kit, which worked great to drive a small speaker from a single-rail supply.
On TNG-era shows, the characters almost always interact with touch-based controls. So it was important to me that the Baldcorder also have touch-based buttons. The SAM D21 contains a peripheral-touch-controller (PTC) that enables its analog input pins to act as capacitive touch buttons. Since time did not permit building a PCB, it was necessary to get creative with the touch panel. So I wrapped some bare copper around a 3D-printed part and covered it with a sticker!
It took about five iterations of the mechanical design to get the right size and figure out the hinges. All of the 3D printing used almost an entire roll of 1 kg filament. Spray paint gave it a flat grey look. To really make the Baldcorder look like it belonged to the Star Trek Universe, I created some vinyl decals with graphics similar to displays shown on the shows and movies.
The final product looks better than I initially imagined. Of course, being limited to the components provided in the contest did affect the final electrical performance. But given those limitations, I am thrilled with the result.
If you'd like to relive some of the project's creation with me, about 20 hours of live stream archives are available on the Baldcorder's element14 Community write-up page. You can also find an archive of the design files there or in the project's GitHub repo. Last, of course, check the video out on YouTube. There is an extraordinary introduction segment!