A USB volume controller that uses a VCR head drum for the knob.
More photos and information can be found here.
Proudly mentioned at hackaday.com, and also on episode 106 of the hackaday podcast.
This project began as an experiment when I wanted to learn how an optical quadrature encoder worked (FYI, 2-bit Gray code).
It transformed into a learning experience around USB - specifically the HID protocol. Ultimately I ended up with a simple gadget that now sits on my desk and allows me to control the PC volume.
A salvaged optical encoder was used to detect rotation along with a reclaimed head drum from a VCR which was repurposed as a control knob. I very much like the smooth bearings combined with the heavy mass that let the drum spin forever.
Key concepts for the project were:
- The optical encoder parts (sensors and disk) were salvaged from an old track-ball.
- The "knob" was made from the head drum of a VHS VCR (remember those?). This is the part that spins and is used to adjust volume on my PC.
- This assembly is mounted to a custom PCB with some nylon stand-offs. The PCB became the base of the whole unit.
- The optical disk was fixed to the shaft and optical sensors mounted to one of the nylon standoffs.
- I cut some wooden rings to enclose the electronics and the base of the VCR drum.
- The original custom PCB was designed in eagle and etched at home from some single-sided copper-clad board. The circuit was designed around an AVR AT90usb162.
- The code is written in C and implements the LUFA library developed by Dean Camera.
- The whole unit plugs into a PC via USB and is automatically identified as a HID - no drivers required (tested in Debian, Ubuntu and Windows).
- It's a very simple device - rotate clockwise to increase volume, counter-clockwise to decrease.
I used the LUFA (lightweight USB Framework for AVRs) library to implement the USB HID protocol.
After some time (about six years!) of having this device in-use on my desk, I got sick of the simple (ugly) stained pine wood enclosure. With some scrap spotted gum and a router (with a Roman ogee and a roundover bit) I made a slightly nicer enclosure for volcon.
After even more time, I gave the project an overhaul. Revision 2 uses the same head drum, optical encoder sensors and wooden enclosure. The upgrades from revision 1 include:
- Schematic and PCB layout completely redone but using KiCad instead of Eagle.
- Microcontroller changed from an AT90usb162 AVR to an ATmega32U4 (simply because I have a few of these).
- Remove the serial Tx/Rx connector (only used this for debugging revision 1).
- Remove the reset tact-switch (also was only used when debugging).
- Use smd components instead of through-hole.
- Connect with a USB type-C connector instead of a USB type-B.
- Have the PCB fabricated (JLCPCB) instead of the home-made copper-etch method.
- A couple of LEDs on the bottom of the PCB purely to visualise the gray code (revision 1 had LEDs, but they only barely shone through etched sections of the PCB).
- Generally improved and cleaner code (still using the LUFA library).
