1. Disassemble a VCR and pull out its polished, drumlike head. Strip all wiring and gut the electronics.
  2. Harvest a mouse’s computer chip, oscillator (typically a two-pronged cylinder), and USB cable.
  3. Bend the mouse chip’s pins to fit into a two-millimeter-pitch veroboard. Solder surface mount capacitors between the chip’s power supply and ground pins.
  4. Drill two holes into a camera’s rear lens cap that align with screw threads on the VCR head’s lower half.
  5. Print an encoder wheel pattern and glue it inside the top of the VCR head. Encoders in mice convert a scrollwheel’s spin into data, but the jog wheel will instead log the speed of the pattern inside the top. This requires an optical encoder—so find two SG-105 photo-reflective sensors, which both emit and detect light (hobby stores carry them), and solder them onto a spare piece of stripboard.
  6. Glue your optical encoder inside the VCR head to face the printed wheel pattern. Solder the encoder to the mouse chip and the USB cable to the chip’s USB pins.
  7. Assemble the spinner with screws from the VCR head, plug in the USB cable, and get scrolling. For Rohit de Sa’s full jogwheel instructions, download this PDF or visit his blog.