Notes concerning “Input devices”

• A four-dimensional keyboard matrix made of linear voltage differential transformers (LVDTs) to get 30 or 180 keys on five pins 02021-05-12 (updated 02021-12-30) (4 minutes)
• Planetary screw potentiometer 02021-05-12 (updated 02021-12-30) (1 minute)
• Notes on what would be needed to drive a PS/2 keyboard from an Arduino 02021-06-20 (updated 02021-12-30) (12 minutes)
• The spark-pen pointing device 02021-10-10 (updated 02021-10-12) (1 minute)