A standalone capacitively coupled occupancy sensor

Abstract

This thesis presents the design and implementation of a standalone, capacitively coupled, occupancy sensor. Unlike previous iterations, the new sensor is decoupled from the fluorescent lamp. A well controlled, high voltage amplifier and autotransformer are designed as a replacement source and operate over a wide range of output frequencies and amplitudes. The sensor electronics are implemented with active sensing electrodes and resistive and capacitive feedback modes are evaluated for performance. Optimal front end feedback, electrode spacing, and signal source amplitude are explored. The sensor achieves a detection range of 11 feet for occupancy detection, with capacitive measurements down to the attofarad level. The application of the sensor as a material detector, using a linear mixing algorithm, is also found to be feasible.