Capacitive Sensor for Sensing State of Waste Toner Box in an Imaging Apparatus

A method for determining the status of a waste toner box of an imaging apparatus, the method comprising:

• measuring a voltage within the waste toner box, the voltage corresponding to a capacitance that varies with an amount of waste toner in the waste toner box between a pair of separated plates;
• determining a prior state of the waste toner box to be one of a new waste toner box, a nearly full waste toner box and a full waste toner box;
• comparing the measured voltage with at least one of an empirically determined value corresponding to a new waste toner box, an intermediate toner level in the waste toner box, and a full toner level in the waste toner box;
• and
• determining an amount of waste toner in the waste toner box based on the prior state of the waste toner box and on the comparison.

An imaging apparatus comprising:

• a waste toner box that includes an inlet port for collecting waste toner;
• a pair of separated plates positioned within the waste toner box to form a capacitor, the capacitor having a capacitance that varies in correspondence with an amount of waste toner in between the separated plates;
• sensor circuitry in electrical communication with the capacitor for measuring a voltage at a beginning and an end of a plurality of intervals, the voltage value being indicative of a capacitance of the capacitor;
• and
• a controller in electrical communication with the sensor circuitry, the controller determining the amount of waste toner in the waste toner box by:
• determining a relative change in capacitance based on the voltage measured, the relative change in capacitance being determined by:
• calculating a difference between the voltage measured at the beginning and the end of each of the plurality of intervals;
• and
• dividing the difference by a predetermined number to determine the relative change in capacitance, the predetermined number being the number of pages printed during the plurality of intervals;
• comparing the determined relative change in capacitance with a predetermined threshold value, the predetermined threshold value being a substantially negligible value for the relative change in capacitance;
• and
• determining the relative amount of waste toner in the waste toner box based on the comparison.