Rain sensor with capacitive-inclusive circuit
First Claim
1. A rain sensor comprising:
- a sensing circuit comprising at least first and second sensing capacitors that are sensitive to moisture on an external surface of a window;
the sensing circuit further comprising at least one mimicking capacitor that mimics at least charging and/or discharging of at least one of the first and second sensing capacitors;
wherein a writing pulse causes at least the first sensing capacitor to be charged, and an erasing pulse causes each of the first sensing capacitor and the mimicking capacitor to substantially discharge;
wherein presence of rain on the external surface of the window in a sensing field of the first sensing capacitor causes a voltage at an output electrode of the mimicking capacitor to fluctuate in a manner proportional to fluctuation of voltage at an output electrode of the first sensing capacitor, even though the rain is not present in a field of the mimicking capacitor; and
wherein rain is detected based on an output signal from the output electrode of the mimicking capacitor, wherein the output signal is read at least between an end of the writing pulse and a beginning of the erase pulse.
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Accused Products
Abstract
A system and/or method for sensing the presence of moisture (e.g., rain) and/or other material(s) on a window such as a vehicle window (e.g., vehicle windshield, sunroof or backlite). In certain example embodiments of the invention, at least one sensing capacitor is supported by a window such as a vehicle windshield, the capacitor(s) having a field that is affected by moisture (e.g., rain) on a surface of the window. A sensing circuit outputs an analog signal that is based on and/or related to the capacitance(s) of the sensing capacitor(s). The analog output of the circuit may be converted to a digital signal, and subjected to processing (e.g., correlation) for determining whether moisture (e.g., rain, dew, fog, etc.) or the like is present on the surface of the window.
61 Citations
19 Claims
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1. A rain sensor comprising:
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a sensing circuit comprising at least first and second sensing capacitors that are sensitive to moisture on an external surface of a window;
the sensing circuit further comprising at least one mimicking capacitor that mimics at least charging and/or discharging of at least one of the first and second sensing capacitors;
wherein a writing pulse causes at least the first sensing capacitor to be charged, and an erasing pulse causes each of the first sensing capacitor and the mimicking capacitor to substantially discharge;
wherein presence of rain on the external surface of the window in a sensing field of the first sensing capacitor causes a voltage at an output electrode of the mimicking capacitor to fluctuate in a manner proportional to fluctuation of voltage at an output electrode of the first sensing capacitor, even though the rain is not present in a field of the mimicking capacitor; and
wherein rain is detected based on an output signal from the output electrode of the mimicking capacitor, wherein the output signal is read at least between an end of the writing pulse and a beginning of the erase pulse. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A method of detecting rain on a surface of a window, the method comprising:
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supplying first and second spaced apart writing pulses which respectively cause first and second sensing capacitors of a sensing circuit to charge, wherein the first sensing capacitor charges when the second sensing capacitor is substantially discharged, and the second sensing capacitor charges when the first sensing capacitor is substantially discharged, so that the first and second sensing capacitors are charged at different times;
each of the first and second sensing capacitors being sensitive to moisture on the surface of the window;
supplying a first erasing pulse, between times of the first and second writing pulses, the first erasing pulse causing the first sensing capacitor to substantially discharge, and supplying a second erasing pulse after the second writing pulse wherein the second erasing pulse causes the second sensing capacitor to substantially discharge;
wherein a magnitude of an output of the sensing circuit is affected by presence of rain on the surface of the window; and
converting an analog output signal of the sensing circuit to a digital signal and based on the digital signal determining whether rain is present on the surface of the window. - View Dependent Claims (13, 14, 15, 16)
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17. A rain sensor comprising:
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at least one sensing capacitor that is sensitive to moisture on an external surface of a window, the sensing capacitor including a first capacitor electrode that receives a charging signal and a second capacitor electrode spaced apart from the first capacitor electrode; and
wherein the second capacitor electrode is floating so that the sensing capacitor is isolated from ground. - View Dependent Claims (18, 19)
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Specification