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volcon

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.

Revision 1

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.

Revision 2

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).

The completed volcon.