This project was more difficult than I imagined! Inspired by both the glass armonica and the party trick of spinning a wet finger around a wine glass to make sounds, I wanted to make a contraption that would spin a wine glass for the user and change the water level inside to control pitch. The path from concept to execution was challenging but informative. The first issue was figuring out how to spin the glass. I originally mounted a glass onto a hobby DC motor, but quickly learned that though it would spin, there wasn’t enough torque to continue spinning once the friction of a finger was applied. Scott’s suggestion to use a turntable was instrumental: I used a USB turntable for a mount that had enough torque at 78rpm to continue spinning when a finger was touching the rim of the glass. Once I got that running, I built a housing for it that the risers for the rest of the mechanism would rest on.
The rest of the mechanism: this was really the challenge. What would be the best way to fill/remove water from the glass to change pitch? At first I wanted to use servos attached to homemade linear actuators, but they were far too weak. I decided to use a threaded rod connected to a motor to move a platform up and down on guide rails. I used the laser cutter for the first time (yay!) to make a template to drill holes in the wooden pieces. The mechanism worked well, it was just a matter of figuring out how to drive it and how to pump the water in and out. I looked up “bellows syringe” and ordered what I found: plastic bellows used to apply glue. To my surprise, the bellows were much tougher and springier than I thought. The motors that I was considering using would not have enough torque to depress the bellows to release water into the glass (I tried a few and they didn’t come close). I ordered a stepper motor with more torque online and am currently waiting for it to arrive for testing. Other alternatives include a syringe, or perhaps an electric pump. My most recent idea was to connect the threaded rod to an electric drill mounted above the device and use solenoids to control the on/off, clockwise/counterclockwise switches. Although I love this hypothetical mechanism, it might be inviting more trouble.
The last question: how to control the motor once connected? I decided to use an IR sensor. I connected it to the Arduino so that the presence of movement would spin the stepper clockwise or counterclockwise. I would like to refine the code so that the distance to the sensor would affect the direction and perhaps speed of the motor controlling the water level in the glass.
What’s next? I have most of the individual mechanisms working, but not all at once. I will test out motors and other devices until I can find a way to draw water in and out of the glass. When that happens, I would like to make this more robust! Instead of using scrap wood planks and dowels, I would like to laser cut acrylic to construct the platforms, and brass for the guide rails. Hopefully that will create a structure that is aesthetically pleasing and water-resistant.