US 6,838,887 B2Granted

Proximity detection circuit and method of detecting small capacitance changes

AssigneeGeorgia-Pacific Corporation

InventorsDennis Joseph Denen, Gary Edwin Myers, Charles W. Groezinger, John J. Knittle

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Abstract

Apparatus for dispensing paper from rolls which feeds continuously, roll to roll, and does not require extra procedure to bring stub roll into position. The apparatus holds and positions at least first and second rolls of paper with respect to each other; dispenses paper from the first roll; dispenses paper from the first and second rolls simultaneously when the first roll reduces to a predetermined diameter of paper, positions the depleted first roll for replacement without the necessity of removing the second roll; and dispenses from the second and replacement rolls simultaneously when the second roll reduces to a predetermined diameter of paper. The apparatus also has a proximity sensor, which senses when a hand is placed near the dispenser, and thereupon dispenses a set amount of towel. The proximity sensor incorporates “static” and noise immunity circuitry.

Claims31

Dependent claims

A proximity detection circuit comprising:

an asymmetric oscillator circuit having its on-period set by a resistor network comprising a plurality of fixed resistors and at least one variable resistor and having its off-period set by at least one fixed resistor and by at least one first single diode;
a first static protection circuit comprising a first plurality of diodes, one said diode adapted to conduct away from ground, another said diode adapted to conduct toward the supply voltage;
a reset path wherein a second single diode provides a discharge path for an antenna wherein said antenna is discharged to the same voltage for every time period;
the asymmetric oscillator being adapted to send an approximately uniform amount of charge during its on-period to said antenna;
the antenna voltage being decreased when the capacitance of the antenna is increased by a detected object;
a second static protection circuit comprising a second plurality of diodes, one said diode adapted to conduct away from ground, another said diode adapted to conduct toward the supply voltage;
an antenna impedance buffer comprising operational amplifier operated as a unity gain follower with the output terminal of said operational amplifier being fed back to the inverting input terminal;
a voltage peak detector comprising a third single diode, a current-limiting resistor, a peak storage capacitor and a bleed off resistor, said third single diode and said peak storage capacitor being adapted to capture the positive peak of exponential waveforms from the antenna impedance buffer, said current limiting resistor being adapted to limiting current flow and to providing said antenna impedance buffer output with more phase margin to prevent oscillation, said bleed-off resistor adapted to providing a discharge pathway for said peak storage capacitor;
a low-pass filter adapted to filter out about 50 or about 60 Hz alternating current interference frequencies, said low-pass filter comprising an in-line resistor and a capacitor with one side tied to ground;
an amplifier with gain and voltage offset;
an auto-compensation capacitor adapted to filter out changes in DC voltage levels of signals while allowing transient signals to pass through;
a three-position switch adapted to provide three levels of detection sensitivity;
and
an output comparator adapted to generate an output on signal when the signal voltage, applied to the inverting input terminal of said comparator, is less than the reference voltage, which is applied to the non-inverting input terminal of said comparator.

11 more elements

A method for detecting small capacitance changes, utilizing a proximity detection circuit, comprising the steps of:

producing an asymmetric oscillator circuit having its on-period set by a resistor network comprising a plurality of fixed resistors and at least one variable resistor and having its off-period set by at least one fixed resistor and by at least one first single diode;
providing protection from static utilizing a first static protection circuit comprising a first plurality of diodes, one said diode adapted to conduct away from ground, another said diode adapted to conduct toward the supply voltage;
resetting an antenna sensor voltage to a fixed amount utilizing a reset path wherein a second single diode provides a discharge path for an antenna wherein said antenna is discharged to the same voltage for every time period;
charging up an antenna with an antenna voltage wherein an approximately uniform amount of charge is sent by the asymmetric oscillator during its on-period to said antenna;
having said voltage lower when the capacitance of the antenna is increased by a detected object with a relatively high dielectric constant;
protecting against static in the proximity detector by utilizing a second static protection circuit comprising a second plurality of diodes, one said diode adapted to conduct away from ground, another said diode adapted to conduct toward the supply voltage;
impedance buffering with an antenna impedance buffer wherein said buffer comprises a unity gain operational amplifier with the output terminal of said operational amplifier being fed back to the inverting input terminal;
detecting a peak voltage utilizing a detector which comprises a third single diode, a current-limiting resistor, a peak storage capacitor and a bleed off resistor;
capturing the positive peak of the exponential waveforms from the unity gain operational amplifier utilizing said third single diode and said peak storage capacitor to capture the positive peak of the exponential waveforms;
limiting current flow utilizing said current limiting resistor to limit current;
preventing oscillation by providing said antenna impedance buffer output with more phase margin, by utilizing resistance of said current limiting resistor;
providing a discharge pathway for said peak storage capacitor utilizing a bleed resistor;
filtering out about 50 Hz and about 60 Hz alternating current interference frequencies utilizing a low-pass filter, said low-pass filter comprising an in-line resistor and a capacitor with one side tied to ground;
providing voltage offset;
amplifying signal with an operational amplifier;
filtering out changes in DC voltage levels of signals while allowing transient signals, as generated by a waving hand, to pass through;
providing three levels of detection sensitivity utilizing a three-position switch;
generating an output on signal, utilizing an output comparator, when the signal voltage, applied to the inverting input terminal of said comparator, is less than the reference voltage, which said reference voltage is applied to the non-inverting input terminal of said comparator.

15 more elements

A proximity detection circuit comprising:

an antenna;
an asymmetric oscillator circuit electrically coupled to the antenna, the asymmetric oscillator circuit having an on-period set by a resistor network comprising a plurality of fixed resistors and by at least one variable resistor and having an off-period set by at least one fixed resistor and by at least one first diode, wherein the asymmetric oscillator circuit is adapted to send an approximately uniform charge to the antenna during the on-period;
a reset path electrically coupled to the antenna and the asymmetric oscillator circuit, the reset path comprising a second diode to discharge the antenna to a predetermined voltage every time period;
an antenna impedance buffer electrically coupled to the antenna, the antenna impedance buffer comprising an operational amplifier operated as a unity gain follower;
and
an output comparator electrically coupled to the antenna impedance buffer, the output comparator receiving as input a signal from the antenna impedance buffer and a reference voltage, the output comparator being adapted to generate output when the signal has a predetermined voltage level as compared to the reference voltage.

3 more elements

A proximity detection circuit comprising in electronic communication:

an asymmetric oscillator circuit having its on-period set by a resistor network comprising a plurality of fixed resistors and at least one variable resistor and having its off-period set by at least one fixed resistor and by at least one first single diode;
a first static protection circuit comprising a first plurality of diodes, one of said first plurality of diodes being adapted to conduct away from ground, another of said first plurality of diodes being adapted to conduct toward the supply voltage;
an antenna;
a reset path wherein a second single diode provides a discharge path for the antenna wherein said antenna is discharged to the same voltage for every time period;
the asymmetric oscillator being adapted to send an approximately uniform amount of charge during its on-period to said antenna, the antenna voltage being decreased when the capacitance of the antenna is increased by an object proximately disposed to the antenna;
a second static protection circuit comprising a second plurality of diodes, one of said second plurality of diodes being adapted to conduct away from ground, another of said second plurality of diodes being adapted to conduct toward the supply voltage;
an antenna impedance buffer comprising an operational amplifier operated as a unity gain follower with the output terminal of said operational amplifier being fed back to the inverting input terminal;
a voltage peak detector comprising a third single diode, a current limiting resistor, a peak storage capacitor and a bleed off resistor, said third single diode and said peak storage capacitor being adapted to capture the positive peak of exponential waveforms from said antenna impedance buffer, said current limiting resistor being adapted to limit current flow and to prevent oscillation in said antenna impedance buffer output, said bleed-off resistor adapted to provide a discharge pathway for said peak storage capacitor;
a low-pass filter adapted to filter out about 50 or about 60 Hz alternating current interference frequencies, said low-pass filter comprising an in-line resistor and a capacitor with one side tied to ground;
an amplifier with gain and voltage offset adapted to amplify output from the low-pass filter;
an auto-compensation capacitor adapted to filter out DC voltage level changes in output from the amplifier;
and
an output comparator adapted to generate an output on signal when output from the auto-compensation capacitor is applied to the inverting input terminal of said comparator and is less than a reference voltage applied to the non-inverting input terminal of said comparator.

10 more elements

A method for detecting small capacitance changes comprising:

producing an asymmetric oscillator circuit having its on-period set by a resistor network comprising a plurality of fixed resistors and at least one variable resistor and having is off-period set by at least one fixed resistor and by at least one first single diode;
providing protection from static utilizing a first static protection circuit comprising a first plurality of diodes, one of said first plurality of diodes being adapted to conduct away from ground, another of said first plurality of diodes being adapted to conduct toward the supply voltage;
resetting an antenna sensor voltage to a fixed amount utilizing a reset path wherein a second single diode provides a discharge path for an antenna wherein said antenna is discharged to the same voltage for every time period;
charging an antenna with an antenna voltage wherein an approximately uniform amount of charge is sent by the asymmetric oscillator during its on-period to said antenna;
lowering said antenna voltage when the capacitance of the antenna is increased by a detected object with a relatively high dielectric constant;
protecting against static in the proximity detector by utilizing a second static protection circuit comprising a second plurality of diodes, one of said second plurality of diodes being adapted to conduct away from ground, another of said second plurality of diodes being adapted to conduct toward the supply voltage;
impedance buffering the antenna with at least a unity gain operational amplifier, the output terminal of said operational amplifier being fed back to the inverting input terminal;
detecting a peak voltage utilizing a detector which comprises a third single diode, a current-limiting resistor, a peak storage capacitor and a bleed off resistor;
capturing the positive peak of exponential waveforms from said unity gain operational amplifier utilizing said third single diode and said peak storage capacitor to capture the positive peak of the exponential waveforms;
limiting current flow from said unity gain operational amplifier utilizing said current limiting resistor to limit current;
preventing oscillation by providing said antenna impedance buffer output;
providing a discharge pathway for said peak storage capacitor utilizing a bleed resistor;
filtering out about 50 Hz and about 60 Hz alternating current interference frequencies utilizing a low-pass filter, said low-pass filter comprising an in-line resistor and a capacitor with one side tied to ground;
amplifying output from said unity gain operational amplifier;
filtering DC voltage level changes in output from said unity gain operational amplifier;
comparing output from said unity gain operational amplifier and a reference voltage with a comparator, said output being applied to the inverting input terminal of said comparator and said reference voltage being applied to the non-inverting input terminal of said comparator;
and
generating a signal with said comparator when output from said unity gain operational amplifier is less than said reference voltage.

15 more elements

Dependencies are inferred from the claim text.

Facts

Application: 09/966,275Filed 27 Sep 2001 · continuation in part
Priority: 9 Feb 2001
Published: US 2002/0109035 A115 Aug 2002
Granted: 4 Jan 2005
Term ends: Not estimatedThe source records don’t support an estimate.

Classification18 codes

A47K 10/3687
With mechanical dispensing, roll switching or cutting devices: with one or more reserve rolls
A47K 10/34
Dispensers for paper towels or toilet paper: dispensing from a web, e.g. with mechanical dispensing means
A47K 10/3643
The cutting devices being driven manually: by pulling the paper
A47K 10/38
Dispensing from a web, e.g. with mechanical dispensing means: the web being rolled-up

Family

Application09/780,733Parent of this continuation-in-part · filed 9 Feb 2001
US 2002/0109035 A1Pre-grant publication · published 15 Aug 2002
US 2002/0109036 A1Published application
US 6,592,067 B2Related patent
US 6,838,887 B2This patent

From the US filing history. Foreign family members aren’t listed.