Since the beginning of our pursuit of 3D printing violins, we've had a very specific list of checkboxes in mind for our "no holds barred", perfect violin.
3D printable on a "Desktop" printer
Translucent with LEDs in it
Responsive to sound and pitch
Just checking off the first box was quite an endeavor. We're nowhere near done tweaking our design, but we were so happy to have our first working prototype of what I call, the"Synesthesia Projector" Hovalin.
Here's a clip of the violin in action:
Here's a quick walkthrough of the build:
We added a slot for a 5-string Barbera pickup, as well as an on/off switch for the electronics.
Below that pickup, (You can sort of see it through the F hole) we have a cheapo piezo pickup that will be used to drive the pitch and level detection.
In order to charge the LED system, we added a usb-micro extension cable. To mount it in place, we covered a chopstick in hot glue and proceeded to apply it liberally to the general area.
All signal processing is done by the Teensy3.6 and the Teensy Audio board. The goal of the Teensy is to convert the input microphone's pitch into a specific color, and have the volume drive the brightness.
Some interesting bugs I ran into:
If I started to drive more than ~40 neopixels, I would start to experience ring modulation in my audio processing sketch.
The noise generated from driving neopixels could be picked up by the audio circuit. If it picked up enough noise from driving the LEDs, it would eventually reach a never-ending noise/light/feedback loop where the noise generated from the LEDs would create audio which would make the LEDs brighter, and so on.
The Teensy 3.2 (or perhaps my poor soldering) was more susceptible to noise.
I'd love to improve the sketch, but for now, it's working just fine. My guess is that having a dedicated brain for the neopixels will make things run a lot smoother.
The violin has a gamut of connections rolling out of it. I didn't get a proper photo, but the Teensy on/off switch works by breaking a USB cable's 5V (red wire).
Last, but not least, we painted in the H logo on the Hovalin.
Well, there you have it, our 5 string Synesthesia Projector Hovalin is built and working. Can't wait to post more videos of it in action soon.
About the Author
Matt is an Electrical Engineer, Full Stack Software Developer, and likes fun things. Cat is the best.