Capacitive level sensing for solid-waste collection

This paper presents a capacitive point-level sensor intended for improved solid-waste collection. The sensor is composed of two electrodes built from low-cost adhesive metal tape and can be applied to detect when a wastebasket that collects paper to be recycled is full. Two electrode arrangements have been analyzed: coplanar and face-to-face electrodes. A theoretical model qualitatively describes the effects of the presence of nearby conductive objects either grounded or ungrounded. Experimental results agree with theoretical predictions. Face-to-face electrodes are less sensitive to interference from nearby metallic objects and to the position of the paper. A capacitance threshold can be defined that corresponds to a full wastebasket.