Abstract: Disclosed herein are capacitive sensors, and methods for their operation, that determine the presence of a user by detecting input forces and/or pressures. Capacitive sensors may be in the form of a flexible capacitive sensing mat. An electronic device incorporating a flexible capacitive sensing mat may include spacer fabric disposed between conductive layers. The spacer fabric may have a first thickness and may be configured to compress to at least a second thickness when a threshold pressure is applied to the layered sensor and revert to the first thickness when the threshold pressure is no longer applied to the flexible mat. A capacitive sense circuit electrically coupled to the second conductive layer and configured to generate a presence detection signal when the spacer fabric layer compresses to the second thickness may additionally be provided.

Abstract: A sensor system includes a sensor stack, a differential amplifier, an analog-to-digital converter, and a processor. The sensor stack includes a piezoelectric material having a first side opposing a second side, a first electrode connected to the first side, and a second electrode connected to the second side. The differential amplifier is coupled to the first and second electrodes and is configured to generate a differential output indicative of vibrations sensed by the piezoelectric material. The analog-to-differential converter is configured to digitize the differential output. The processor is configured to identify a type of biological vibration included in the digitized differential output.