Person detecting device
First Claim
1. A person detecting device for detecting the presence and absence of a person comprising:
- sensing means for sensing capacitance between at least a pair of electrodes facing to each other with a space, said capacitance varying depending upon the presence and absence of the person in said space;
oscillating means for providing a first pulse signal;
delay means for delaying said first pulse signal and providing a second pulse signal delayed in response to said capacitance of said sensing means;
duty ratio converting means for receiving said first and second pulse signal and providing a third pulse signal of a duty ration determined in response to said capacitance to convert said third pulse signal to a value representing said duty ratio;
comparing means for comparing said value representing said duty ratio with at least a reference value preset for judging as to the presence and absence of the person to provide a resultant signal of comparison; and
output means for receiving said resultant signal of said comparing means and judging as to the presence and absence of the person to output a signal of the result of judgement;
wherein said oscillating means includes means for generating a clock pulse signal at a predetermined frequency and means for dividing said clock pulse signal into a plurality of divided pulse signals of different frequencies and providing one of said divided pulse signals as said first pulse signal, and wherein said duty ratio converting means includes means for converting said third pulse signal to a digital value corresponding to said duty ratio based on said clock pulse signal.
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Accused Products
Abstract
A person detecting device detects the presence and absence of a person in a certain space such as a vehicle compartment. The device includes means for sensing the capacitance between a pair of electrodes with a space where a person may present, oscillating means for providing a first pulse signal and means for delaying the first pulse signal and providing a second pulse signal delayed in response to the capacitance. The device further includes means for receiving the first and second pulse signals and providing a third pulse signal of a duty ratio determined in response to the capacitance. The third pulse signal is further converted to a value representing the duty ratio which is compared with at least a reference value preset for judging as to the presence and absence of the person.
58 Citations
20 Claims
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1. A person detecting device for detecting the presence and absence of a person comprising:
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sensing means for sensing capacitance between at least a pair of electrodes facing to each other with a space, said capacitance varying depending upon the presence and absence of the person in said space; oscillating means for providing a first pulse signal; delay means for delaying said first pulse signal and providing a second pulse signal delayed in response to said capacitance of said sensing means; duty ratio converting means for receiving said first and second pulse signal and providing a third pulse signal of a duty ration determined in response to said capacitance to convert said third pulse signal to a value representing said duty ratio;
comparing means for comparing said value representing said duty ratio with at least a reference value preset for judging as to the presence and absence of the person to provide a resultant signal of comparison; andoutput means for receiving said resultant signal of said comparing means and judging as to the presence and absence of the person to output a signal of the result of judgement; wherein said oscillating means includes means for generating a clock pulse signal at a predetermined frequency and means for dividing said clock pulse signal into a plurality of divided pulse signals of different frequencies and providing one of said divided pulse signals as said first pulse signal, and wherein said duty ratio converting means includes means for converting said third pulse signal to a digital value corresponding to said duty ratio based on said clock pulse signal. - View Dependent Claims (3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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2. A person detecting device for detecting the presence and absence of a person comprising;
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sensing means for sensing capacitance between at least a pair of electrodes provided in a vehicle and facing to each other with a space, said capacitance varying depending upon the presence and absence of the person in said space; oscillating means for generating a clock pulse signal at a predetermined frequency and dividing said clock pulse signal into a plurality of divided pulse signals of different frequencies to provide one of said divided pulse signals as a first pulse signal; delay means for delaying said first pulse signal and providing a second pulse signal delayed in response to said capacitance of said sensing means; a coincidence circuit for receiving said first pulse signal and said second pulse signal to provide a third pulse signal of a duty ratio determined in response to said capacitance; a gate circuit connected to said oscillating means and said coincidence circuit for converting said third pulse signal to a digital value corresponding to said duty ratio based on said clock pulse signal; a first counter connected to said oscillating means for enabling said gate circuit for a predetermined period; a second counter connected to said gate circuit for receiving said digital value and permitting said digital value to gate for a period determined by said first counter; a first comparing circuit connected to said second counter for comparing said digital value in magnitude with a first reference value preset for judging the presence of the person and a second reference value preset for judging the absence of the person, and said first comparing circuit providing a first resultant signal representing the presence of the person when said digital value is more or less than said first reference value, and provides a second resultant signal representing the absence of the person when said digital value is less or more than said second reference value; control means connected to said oscillating means for providing a series of control signals in accordance with a predetermined sequence; a latch circuit connected to said second counter for latching said digital value received therefrom in accordance with a control signal from said control means; an adder-subtractor circuit connected to said latch circuit for adding or subtracting a third reference value to or from said latched value depending on the state of said first and second resultant signals;
a second comparing circuit connected to said adder-subtractor circuit for comparing a resultant value thereof with said digital value received in the following control signal from said control means; andoutput means connected to said first and second comparing circuits for receiving outputs therefrom and providing a signal indicating the presence of the person when said first resultant signal is fed and a signal indicating the absence of the person when said second resultant signal is fed, provided that the absolute value of difference between said resultant value of said adder-subtractor circuit and said digital value fed from said second counter is less than said third-reference value, said output means including means for holding said signal of the presence and absence of the person as in the preceding state thereof when said absolute value of difference exeeds said third reference value. - View Dependent Claims (16)
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15. A person detecting device for detecting the presence and absence of a person comprising:
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sensing means for sensing capacitance between at least a pair of electrodes facing to each other with a space, said capcacitance varying depending upon the presence and absence of the person in said space; oscillating means for providing a first pulse signal; delay means for delaying said first pulse signal and providing a second pulse signal delayed in response to said capacitance of said sensing means; duty ratio converting means for receiving said first and second pulse signal and providing a third pulse signal of a duty ration determined in response to said capacitance to convert said third pulse signal to a value representing said duty ratio; comparing means for comparing said value representing said duty ratio with at least a reference value preset for judging as to the presence and absence of the person to provide a resultant signal of comparison, said comparing means comprising coincidence comparing means coupled to said oscillating means for producing a reference pulse signal of the same frequency as said first pulse signal and comparing said third pulse signal with said reference pulse signal in periodic coincidence to provide an error signal to said output means when said third pulse signal do not synchronize with said reference pulse signal; and output means for receiving said resultant signal of said comparing means and judging as to the presence and absence of the person to output a signal of the result of judgement. - View Dependent Claims (17, 18, 19, 20)
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Specification