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Detection of Water Level Using "Inter-digitized" Capacitative Plates and an Emitter Plate in the Washer/Laundry Machines.

IP.com Disclosure Number: IPCOM000031217D
Publication Date: 2004-Sep-17
Document File: 4 page(s) / 50K

Publishing Venue

The IP.com Prior Art Database

Abstract

The current washer uses a pressure switch to turn off the flow of water to the tub. The inter-digitized plates would give the microprocessor differing voltages that correspond to differing fill levels such as the super and small levels. Therefore, the microprocessor can "see" the level and predict how much hot and cold water to input in the tub for a "warm" temperature. This invention is similar to the pressure switch in that in has two levels.

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SUBJECT: Detection of Water Level Using "Inter-digitized" Capacitative Plates and an Emitter Plate in the Washer/Laundry Machines.

Summary of Invention:

The current washer uses a pressure switch to turn off the flow of water to the tub. The inter-digitized plates would give the microprocessor differing voltages that correspond to differing fill levels such as the super and small levels. Therefore, the microprocessor can "see" the level and predict how much hot and cold water to input in the tub for a "warm" temperature. This invention is similar to the pressure switch in that in has two levels.

Problem to be Solved and Detailed Description of Invention:

Below is a brief description of the capacitative plates.

Figure 1

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Figure 2

Figure 3

Once a schematic of the circuit is obtained, then H(s) = Vout/Vin was derived from figure #3.

Ignoring s because it is small compared to the ratio of (Co+Cl)/Cl, H(s) becomes a constant that does not change over frequency of interest.

Figures #4 and #5 shown below display the output of the Spice circuit simulation of figure #3. The Vin of Figure #3 was a square wave. Vout in figure #3 is the "Output" of the circuit, which is the voltage across Co. Figure #4 simulates the output of a full tub while figure #5 shows the output of an empty tub of water - The drop in capacitance is due to the characteristics of the tub. Note: if another medium was used, overall capaci...