Capacitive sensing for washroom fixture

A hand-washing lavatory station comprising:

• a deck having one or more receptacles providing one or more hand washing stations, and a sink line defining the top of the one or more receptacles;
• at least one fixture located at least partially above the sink line and configured to deliver water to one or more of the hand washing areas;
• a first sense electrode integrated with the deck and located below the sink line, the first electrode configured to measure a first capacitive value in the one or more hand washing area;
• a second sense electrode integrated with the deck and located adjacent to the first electrode and below the sink line, the second electrode configured to measure a second capacitive value in the one or more hand washing area;
• a valve movable between an open position wherein water is permitted to flow through the fixture and a closed position wherein water is prevented from flowing through the fixture;
• a circuit coupled to the first electrode, the second electrode, and the valve, and configured to move the valve between the open position and the closed position in response to a change in the first capacitive value relative to the second capacitive value;
• wherein the circuit eliminates the effect of the presence of water proximate the first and second sense electrodes;
• and
• wherein the first sense electrode measures the first capacitive value relative to the second sense electrode and wherein the second sense electrode measures the second capacitive value relative to the first sense electrode.

A hand-washing lavatory system comprising a circuit configured to:

• provide a first oscillation signal to a first sense electrode located in a hand washing area;
• receive capacitance values from the first sense electrode that are sampled over a time period by the first sense electrode in response to the first oscillation signal;
• provide a second oscillation signal to a second sense electrode located in the hand washing area;
• receive capacitance values from the second sense electrode that are sampled over the time period by the second sense electrode in response to the second oscillation signal;
• determine a difference between the capacitance values from the first and second sense electrodes sampled during the time period;
• and
• regulate a valve movable between an open position wherein water is permitted to flow through a fixture and a closed position wherein water is prevented from flowing through the fixture based on the difference between the capacitance values from the first and second sense electrodes.