TelemetRing: A Batteryless and Wireless Ring-shaped Keyboard using Passive Inductive Telemetry

TelemetRing is a batteryless and wireless ring-shaped keyboard that supports command and text entry in daily lives by detecting finger typing on various surfaces. The proposed inductive telemetry approach eliminates bulky batteries or capacitors from the ring part. Each ring consists of a sensor coil (the ring part itself), 1-DoF piezoelectric accelerometer, and varactor diode; moreover, it has different resonant frequencies. Typing shocks slightly shift the resonant frequency, and these are detected by a wrist-mounted readout coil. 5-bit chord keyboard is realized by attaching five sensor rings on five fingers. Our evaluation shows that the prototype achieved the tiny (6 g, 3.5 cm^3) ring sensor and 89.7% of typing detection ratio.