A capacitance proximity detector turns hand distance into control voltage for touchless gestural control

The Buchla Model 117 Dual Proximity Detector uses capacitance-actuation — the theremin principle — to output a control voltage that varies with the distance of a hand or body from an antenna, which can be sited away from the cabinet. Unlike a theremin, whose output drives a fixed oscillator, the 117’s output is a general-purpose control voltage that can be patched to any CV input, so spatial gesture can modulate frequency, amplitude, timbre, or anything else. It is one of several Buchla non-keyboard controllers (touch voltage sources, pressure surfaces) that make gesture, not key-depression, the interface — an early ancestor of gesture-based performance controllers.

Examples

Model 117: ‘Two capacitance-actuated control voltage sources for enabling spatial control of sound parameters. Theremin-style antennas may be remotely located.’ Its CV can drive any module input, not just an oscillator.

Assessment

Explain how a proximity detector generates control voltage and why routing that CV (rather than a fixed oscillator) makes it more flexible than a classic theremin.