If you are tired of fiddling with your keyboard to adjust the volume on your computer while sitting back and watching movies, and if your speakers and the volume knob are located out of the way, try this dedicated USB volume knob.
This is a USB volume knob device made to house a rotary encoder and an Arduino-compatible Adafruit Trinket.
The setup is described in detail on Adafruit's excellent website: https://learn.adafruit.com/trinket-usb-volume-knob/overview
Common Issues With Trinket
If you've never worked with Adafruit's Trinket board, read the setup instructions carefully: https://learn.adafruit.com/introducing-trinket/setting-up-with-arduino-ide
We had to install this driver first: https://learn.adafruit.com/introducing-trinket/windows-setup
You also need to hit the reset button on the Trinket before hitting the upload button on the Arduino IDE to upload the sketch. Experiment with the timing. For ours, we had to hit reset and immediately hit upload after we heard the USB disconnect chime on our desktop.
We permanently soldered the wires from the encoder to the Trinket. BE CAREFUL when wiring your project. Switched wires can burn out your Trinket!!!
You can make this as is, or you can mix 3 parts sand, 1 part cement and add a concrete infill as pictured to give it a nice weighted feel. The knob comes with a cover, so you can add concrete in the knob as well, then friction weld or glue the cover in place.
Leave the concrete to dry overnight. Test fit the knob cover to make sure you didn't place too much concrete in. If there is excess concrete, the day after you can still scratch out the excess material and fit the cover.
Other popular methods of providing infills include hot wax and metal pellets. We didn't do this because 3D printing uses thermoplastic and heat could warp the parts. Experiment at your own risk.
Securing the Knob
To secure the knob onto the rotary encoder, use some hot glue. We used an earlier knob version with a semi-circle interface that did not fit our encoder. We drilled it out, but the knob now is slightly lopsided. The knob included in the STL files is a full circle so glue will be required to secure it to the rotary encoder. Double check alignment to avoid leaving it lopsided.
Securing the Rotary Encoder
Since we don't know what encoder you have, we made the encoder bracket a separate part that can be redesigned in SketchUp to fit whichever one you have on hand. It is essential that the encoder sits in the channel centered. We friction welded the bracket in place and can slide the encoder in and out of the channel. We used a dab of hot glue to secure it in place after prototyping was done.