US20200182602A1 - Proximity Detection - Google Patents
Proximity Detection Download PDFInfo
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- US20200182602A1 US20200182602A1 US16/681,036 US201916681036A US2020182602A1 US 20200182602 A1 US20200182602 A1 US 20200182602A1 US 201916681036 A US201916681036 A US 201916681036A US 2020182602 A1 US2020182602 A1 US 2020182602A1
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B7/00—Measuring arrangements characterised by the use of electric or magnetic techniques
- G01B7/14—Measuring arrangements characterised by the use of electric or magnetic techniques for measuring distance or clearance between spaced objects or spaced apertures
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03K—PULSE TECHNIQUE
- H03K17/00—Electronic switching or gating, i.e. not by contact-making and –breaking
- H03K17/94—Electronic switching or gating, i.e. not by contact-making and –breaking characterised by the way in which the control signals are generated
- H03K17/945—Proximity switches
- H03K17/955—Proximity switches using a capacitive detector
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N22/00—Investigating or analysing materials by the use of microwaves or radio waves, i.e. electromagnetic waves with a wavelength of one millimetre or more
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R27/00—Arrangements for measuring resistance, reactance, impedance, or electric characteristics derived therefrom
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R27/00—Arrangements for measuring resistance, reactance, impedance, or electric characteristics derived therefrom
- G01R27/02—Measuring real or complex resistance, reactance, impedance, or other two-pole characteristics derived therefrom, e.g. time constant
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R27/00—Arrangements for measuring resistance, reactance, impedance, or electric characteristics derived therefrom
- G01R27/02—Measuring real or complex resistance, reactance, impedance, or other two-pole characteristics derived therefrom, e.g. time constant
- G01R27/04—Measuring real or complex resistance, reactance, impedance, or other two-pole characteristics derived therefrom, e.g. time constant in circuits having distributed constants, e.g. having very long conductors or involving high frequencies
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R27/00—Arrangements for measuring resistance, reactance, impedance, or electric characteristics derived therefrom
- G01R27/02—Measuring real or complex resistance, reactance, impedance, or other two-pole characteristics derived therefrom, e.g. time constant
- G01R27/04—Measuring real or complex resistance, reactance, impedance, or other two-pole characteristics derived therefrom, e.g. time constant in circuits having distributed constants, e.g. having very long conductors or involving high frequencies
- G01R27/06—Measuring reflection coefficients; Measuring standing-wave ratio
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R27/00—Arrangements for measuring resistance, reactance, impedance, or electric characteristics derived therefrom
- G01R27/02—Measuring real or complex resistance, reactance, impedance, or other two-pole characteristics derived therefrom, e.g. time constant
- G01R27/26—Measuring inductance or capacitance; Measuring quality factor, e.g. by using the resonance method; Measuring loss factor; Measuring dielectric constants ; Measuring impedance or related variables
- G01R27/2605—Measuring capacitance
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R21/00—Arrangements for measuring electric power or power factor
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R23/00—Arrangements for measuring frequencies; Arrangements for analysing frequency spectra
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R27/00—Arrangements for measuring resistance, reactance, impedance, or electric characteristics derived therefrom
- G01R27/28—Measuring attenuation, gain, phase shift or derived characteristics of electric four pole networks, i.e. two-port networks; Measuring transient response
- G01R27/32—Measuring attenuation, gain, phase shift or derived characteristics of electric four pole networks, i.e. two-port networks; Measuring transient response in circuits having distributed constants, e.g. having very long conductors or involving high frequencies
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03K—PULSE TECHNIQUE
- H03K17/00—Electronic switching or gating, i.e. not by contact-making and –breaking
- H03K17/94—Electronic switching or gating, i.e. not by contact-making and –breaking characterised by the way in which the control signals are generated
- H03K17/96—Touch switches
- H03K2017/9602—Touch switches characterised by the type or shape of the sensing electrodes
- H03K2017/9604—Touch switches characterised by the type or shape of the sensing electrodes characterised by the number of electrodes
- H03K2017/9606—Touch switches characterised by the type or shape of the sensing electrodes characterised by the number of electrodes using one electrode only per touch switch
Definitions
- a proximity sensor detects the presence of a nearby person or object in a region or area.
- a proximity sensor may employ an electromagnetic or electrostatic field, or a beam of electromagnetic radiation, e.g., infrared, or acoustic energy and detect changes in the field or return signal.
- Proximity sensing can utilize different sensor types for different types of target objects. For example a photoelectric sensor might be suitable for a plastic target; an inductive proximity sensor might be used to detect a metal target.
- Proximity sensors can have a high reliability and long functional life because of the absence of mechanical parts and lack of physical contact between sensor and the sensed object.
- Capacitance of a sensing element to ground is measured as an object moves into or out of proximity to the sensing element.
- FIG. 1 is a circuit diagram of an example of a proximity sensor utilizing capacitive charge transfer
- FIG. 2 illustrates a switching table depicting a switching sequence of the three switches of the sensor circuit of FIG. 1 ;
- FIG. 3 illustrates a variation to the circuit of FIG. 1 :
- FIG. 4 illustrates schematically various antenna examples
- FIG. 5 is a circuit diagram of another example of a proximity sensor, utilizing a LC oscillator
- FIG. 6 is a circuit diagram of another example of a proximity sensor, utilizing a generic oscillator.
- FIG. 7 illustrates schematically an example of an antenna configured as a loop antenna and shows field lines emanating from the antenna.
- the examples shown and described implement a form of proximity detection utilizing detection of capacitance of a sensing element, relative to ground, as objects move into or out of proximity to the sensing element.
- the proximity detection may occur over significant distances from a proximity sensor, compared to the dimensions of the sensor, or when the proximity sensor is touched by a person or other target object.
- the circuit diagram of FIG. 1 illustrates schematically the circuit of an example of a proximity sensor 100 that utilizes capacitive charge transfer for proximity detection.
- Sensor 100 may include control circuitry 110 , a sample capacitor 114 , and a sensing element, e.g., an antenna 120 .
- Sensor 100 senses changes in capacitance of the antenna 120 to ground Cx, as indicated by capacitance 122 .
- Sample capacitor 114 may be selected to be much larger than anticipated values of Cx.
- the control circuitry 110 may include switching functionality to charge the sample capacitor 114 and the capacitance to be measured Cx.
- the control circuitry 110 may also include switching functionality to selectively discharge the sample capacitor 114 and/or antenna 120 and to allow for measurement of the voltage Yes across the sample capacitor 114 .
- An example of how the switching functionality of control circuitry 110 may operate is described in further detail with regard to FIG. 2 .
- Cx As a person or other object approaches or moves away from the antenna 120 , changes in the capacitance Cx of the antenna 120 will occur. For example, as a person approaches antenna 120 , Cx will increase, and as the person moves away from the antenna 120 , Cx will decrease. The change in Cx produces a measurable effect, which can be utilized by the sensor 100 for proximity detection.
- a first switching element S 1 can be used to discharge sample capacitor Cs and the capacitance to be measured Cx.
- the circuit can include a second switching element S 2 and a third switching element S 3 as shown. Any suitable switching elements can be used for switching elements S l-S 3 .
- suitable transistors or relays can be used.
- the second switching element S 2 can operate to selectively connect the circuit to a voltage source, e.g., Vdd.
- the voltage source Vdd may supply a suitable voltage including, but not limited to, any voltage within a range of about 1.8 to about 5.5 V.
- the third switching element S 3 can operate to selectively connect the circuit to ground.
- An analog comparator 112 can be included to compare voltage on the Cs capacitor to a reference voltage signal, indicated by VREF. Any suitable reference voltage may be used.
- the output of the comparator 112 e.g., analog comparator output ACO, can be used to determine when the voltage on Cs has reached the reference voltage VREF. As Cs and Cx are in parallel, they form a capacitive voltage divider. The voltage on Cs is consequently influenced by Cx. The lower the reference voltage, the more energy can be maintained in the antenna 120 .
- the output of the comparator 112 can be provided to a clock input of a pulse width modulator (PWM) circuit 140 .
- the PWM circuit 140 can be used to gate a counter 150 that is clocked at a suitable frequency to count the number of pulses during a specified time.
- the control circuitry 110 may also include a processor 160 and storage functionality 170 , e.g., suitable ROM and/or RAM, for holding software instructions and buffered data.
- the processor 160 can receive the counter output and correlate the counter output to Cs, Cx, and the proximity of a person or object to the sensor 100 .
- the output of the counter 150 as received by the processor 160 may be suitably filtered for reducing noise effects.
- the processor 160 can process the output of the counter 150 for detecting proximity of an object relative to the antenna 120 .
- the control circuitry 110 can provide an output signal, e.g., as shown by the DETECT signal of FIG. 1 , that is indicative of the presence or absence of a person or object within proximity of the sensor 100 .
- the output signal of the control circuitry 110 may be a bit, a byte, or an analog signal if a D/A converter (not shown) is utilized.
- the output signal of the control circuitry 110 may indicate the presence or absence of one or more objects within proximity to the sensor 100 or may indicate a degree of proximity to the sensor.
- the control circuitry output signal may be used to indicate the presence or absence of an object within a detection range of the sensor 100 .
- the output signal may be used to produce an audible signal such as a particular tone or an optical signal such as a particular color when an object is detected. The sound or color may be changed to indicate a change in the proximity of an object to the sensor 100 .
- a dynamic reference voltage may be used to alter the sensing functionality of sensor 100 . Raising the reference voltage may lower the nominal range of the sensor, for example from one foot (30 cm) maximum sensing distance from the antenna down to a few millimeters maximum sensing distance for proximity detection of a touch.
- a sensor such as sensor 100 may be placed in a child's toy bear. If a child were to approach within a specified distance, e.g., six inches or so, the bear could respond with a verbal response such as “pick me up,” encouraging the child to hold the toy.
- the proximity detection of the sensor may then be changed, by simply altering the reference voltage of the sensor, to close proximity-based touch sensing, allowing the bear to subsequently respond to the child's actual touches.
- Dynamically changing the nominal detection range of a proximity sensor in such a way may add commercial value to the related good(s) or components.
- the control circuitry 110 can be implemented, for example, by a suitable microcontroller, a field programmable gate array (FPGA), or other standard logic devices.
- a suitable microcontroller for example, an ATtiny48 microcontroller, as made commercially available by ATMEL Corporation, and/or a suitable timer/counter may be used for implementation of the control circuitry 110 .
- the sample capacitor 114 may have a nominal capacitance of 4.7 nF and be 10 percent X7R ceramic.
- FIG. 2 illustrates a switching table 200 depicting a switching sequence of the three switches of FIG. 1 during a charge transfer cycle for operation of the sensor 100 .
- switching elements S 1 and S 3 are closed while switching element S 2 is open, grounding both capacitors and thereby allowing Cs and Cx to discharge.
- all switching elements are open, which allows the voltage on Cs and Cx to float.
- switching elements S 1 and S 3 are open while switching element S 2 is closed, applying voltage Vdd to both capacitors and thereby allowing charge to transfer to Cs and Cx.
- all three switching elements S 1 -S 3 are open, which allows voltage on Cs and Cx to float and settle.
- switching element 1 is closed while switching elements S 2 -S 3 are open, allowing the charge in Cx to discharge and for a comparison of the voltage on Cs with the reference voltage, e.g., VREF in FIG. 1 .
- the switching sequence of steps 2 to 5 may be repeated for later measurements of the capacitance. A desired number of repeated measurements using steps 2 to 5 can be performed. Changes in capacitance Cx can be interpreted to detect movement of an object toward or away from the antenna 120 .
- FIG. 3 illustrates schematically a variation 300 to the circuit of FIG. 1 with a reference voltage set by a voltage divider 130 including resistors 132 and 134 in series. Any desired values may be selected for resistors 132 and 134 so as to produce a desired reference voltage.
- the PWM, counter, processor, and storage are omitted to simplify the drawing.
- FIG. 4 illustrates schematically a collection 400 of antenna examples that may be used in a proximity sensor. Depicted in the drawing are a square loop antenna (A), a curved loop antenna (B), a line antenna (C), a dipole antenna (D), and a patch antenna (E). The configurations shown are representative, and other antenna configurations may be used for proximity detection.
- A square loop antenna
- B curved loop antenna
- C line antenna
- D dipole antenna
- E patch antenna
- antennas may be configured for proximity detection in one general direction. In other applications, antennas may be configured for proximity detection in multiple directions.
- plane charges such as produced by rectangular plates, e.g., as shown by the patch antenna (E), may offer good distance characteristics because the greatest field strength is expressed perpendicular to the surface of the plane.
- Such configurations may allow limited space for related components of a proximity sensor or a device incorporating such a sensor, e.g., control circuitry, key pads, etc.
- electric field lines from a sensor antenna can be oriented to form a directional antenna and still offer available space within or adjacent to the antenna, e.g., within the perimeter of the antenna.
- a square loop or dipole antenna may be used. Examples are shown in FIG. 4 as (A), (B), and (D).
- a proximity sensor using a rectangular loop or dipole antenna placed in the perimeter of a wall mounted device e.g., a wall mounted thermostat or security keypad, may offer good proximity detection for approaches from all four sides.
- a sensor with such an antenna may also offer good detection distance when approached head on. Such head on proximity detection may be at distances greater than or equal to the dimensions of a particular antenna.
- a 6-inch diameter curved loop antenna may provide reliable proximity detection at 12 inches from the plane of the antenna.
- Such a sensor using the curved loop antenna could also, or alternatively, be set so that one would have to actually touch the sensor housing/casing before being detected by the sensor.
- Sensors or antennas configured as points, spheres and lines, because of their radial field spreading with distance, may be well suited for proximity detection in applications where the direction of approach is unknown or variable. As described previously, some applications may, however, require proximity detection from one general direction.
- the exemplary proximity sensors can utilize other types of measurement of an antenna's capacitance to ground for proximity detection.
- FIG. 5 shows one such example in which the variable Cx of an antenna is utilized to alter the resonant frequency of an LC circuit.
- the circuit diagram of FIG. 5 illustrates schematically a proximity sensor 500 utilizing a LC oscillator.
- Proximity sensor 500 includes control circuitry 510 , a tank circuit or LC oscillator 520 , and a sensing element, e.g., antenna 530 .
- the control circuitry 510 can include a suitable processor 540 and storage 550 .
- the LC oscillator 520 includes inductor 522 and sample capacitor 524 .
- the control circuitry 510 can include frequency counter and excitation functionality and can supply an excitation signal to the LC oscillator 520 .
- the control circuitry 510 can also supply a charge to the antenna 530 , which has a capacitance to free space or ground, Cx.
- the capacitance Cx can be influenced by people or objects coming into and moving out of proximity to the sensor antenna 530 .
- a microcontroller such as an Atmel® ATtiny48 microcontroller and/or a suitable timer/counter may be used for implementation of the control circuitry 510 .
- the capacitance Cx increases. As an object or person moves away and out of proximity to the sensing element 530 , the capacitance Cx decreases. Because Cx is in parallel with Cs, the new Cx changes the capacitance of the oscillator 520 , changing the resonant frequency, f, where f is given by:
- the control circuitry 510 can measure the change in the resonant frequency f, which can be correlated to capacitance Cx and corresponding proximity of an object or person within range of the sensor 500 .
- proximity sensors utilizing oscillators according to FIG. 5
- other types of resonant circuits and structures may be used in conjunction with a variable capacitance of a sensing element.
- the circuit diagram of FIG. 6 illustrates schematically another example of a proximity sensor 600 utilizing a generic oscillator.
- Proximity sensor 600 includes control circuitry 610 and a generic oscillator 620 connected to a sensing element configured as an antenna 630 .
- the control circuitry 610 can include a suitable processor 640 and storage 650 .
- the control circuitry 610 can include frequency counter and excitation functionality.
- a microcontroller such as an Atmel® ATtiny48 microcontroller and/or a suitable timer/counter may be used for implementation of the control circuitry 610 .
- any electric oscillator affected by a change in capacitance Cx may be used for proximity detection by sensor 600 .
- Examples may include, but are not limited to, RC network oscillators such as a Wien bridge oscillator, a twin T oscillator, and the like, or RLC networks. Changes in Cx will change the resonant frequency of the oscillator 620 . By recognizing the change in Cx, sensor 600 can provide for proximity detection. The detection range of the sensor 600 may be dynamically varied by adjusting the values of R and/or C in the oscillator 620 , e.g., by switching in or out resistive or capacitive elements.
- FIG. 7 illustrates schematically an antenna 700 configured as a loop antenna and shows field lines emanating from the antenna.
- Antenna 700 is configured as a rectangular loop, shown with perimeter 702 . Because of the field features, rectangular loop antennas can provide both lateral proximity detection and proximity detection in orthogonal directions.
- electric field lines for lateral proximity detection are indicated by field lines 1
- electric field lines for orthogonal or head on directions are indicated by field lines 2 .
- the open area A within the perimeter of the antenna 700 may be utilized for components that are to be used in conjunction with the proximity sensor.
- the area within the dashed lines within perimeter 702 may be used for a keypad or card reader or other components of a device that incorporates a proximity sensor that includes the antenna 700 .
- a microcontroller may include firmware facilitating the control of the switching functionality for charging and discharging a sample capacitor and antenna of a proximity sensor as shown in the table of FIG. 2 and the measuring of capacitance to detect proximity.
- An article of manufacture may include the program, e.g., executable code and/or associated data, carried on or embodied in a machine readable medium.
- a machine readable medium may take many forms, including but not limited to, a tangible non-transitory storage medium, a carrier wave medium, or physical transmission medium.
- Non-volatile types of non-transitory, tangible storage media include any or all of the memory of the supporting electronics of a proximity sensor, computing devices, processors or the like, or associated modules thereof, such as various semiconductor memories, tape drives, disk drives and the like, which may provide storage at any time for the programming. All or portions of the programming may at times be communicated through the Internet or various other telecommunication networks. Such communications, for example, may enable loading of the programming from one computer or processor into another computer or processor, e.g., for installation in a microcontroller.
- another type of media that may bear the programming includes optical, electrical and electromagnetic waves, such as used across physical interfaces between local devices, through wired and optical landline networks and over various air-links. The physical elements that carry such waves, such as wired or wireless links, optical links or the like, also may be considered as media bearing the software.
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Abstract
Description
- This application is a continuation of U.S. application Ser. No. 15/595,471, filed May 5, 2015, which is a continuation of U.S. application Ser. No. 13/846,458, filed Mar. 18, 2013, patented as U.S. Pat. No. 9,651,355, which is a continuation of U.S. application Ser. No. 12/910,484, filed Oct. 22, 2010, patented as U.S. Pat. No. 8,400,209, the disclosures of all of which are incorporated herein by reference in their entirety.
- A proximity sensor detects the presence of a nearby person or object in a region or area. A proximity sensor may employ an electromagnetic or electrostatic field, or a beam of electromagnetic radiation, e.g., infrared, or acoustic energy and detect changes in the field or return signal. Proximity sensing can utilize different sensor types for different types of target objects. For example a photoelectric sensor might be suitable for a plastic target; an inductive proximity sensor might be used to detect a metal target.
- Different types of proximity sensors have different maximum distances within which the sensors can detect an object. Some sensors have adjustments of the nominal distance range or means to report a graduated detection distance. Proximity sensors can have a high reliability and long functional life because of the absence of mechanical parts and lack of physical contact between sensor and the sensed object.
- The following disclosure describes examples of proximity detection and proximity sensors. Capacitance of a sensing element to ground is measured as an object moves into or out of proximity to the sensing element.
- The drawing figures depict one or more implementations in accordance with the present teachings, by way of example only, not by way of limitation. In the figures, like reference numerals refer to the same or similar elements.
-
FIG. 1 is a circuit diagram of an example of a proximity sensor utilizing capacitive charge transfer; -
FIG. 2 illustrates a switching table depicting a switching sequence of the three switches of the sensor circuit ofFIG. 1 ; -
FIG. 3 illustrates a variation to the circuit ofFIG. 1 : -
FIG. 4 illustrates schematically various antenna examples; -
FIG. 5 is a circuit diagram of another example of a proximity sensor, utilizing a LC oscillator; -
FIG. 6 is a circuit diagram of another example of a proximity sensor, utilizing a generic oscillator; and -
FIG. 7 illustrates schematically an example of an antenna configured as a loop antenna and shows field lines emanating from the antenna. - In the following detailed description, numerous specific details are set forth by way of examples in order to illustrate the relevant teachings. In order to avoid unnecessarily obscuring aspects of the present teachings, those methods, procedures, components, and/or circuitry that are well-known to one of ordinary skill in the art have been described at a relatively high-level.
- The examples shown and described implement a form of proximity detection utilizing detection of capacitance of a sensing element, relative to ground, as objects move into or out of proximity to the sensing element. For example, the proximity detection may occur over significant distances from a proximity sensor, compared to the dimensions of the sensor, or when the proximity sensor is touched by a person or other target object.
- Reference now is made in detail to the examples illustrated in the accompanying figures and discussed below.
- The circuit diagram of
FIG. 1 illustrates schematically the circuit of an example of aproximity sensor 100 that utilizes capacitive charge transfer for proximity detection.Sensor 100 may includecontrol circuitry 110, asample capacitor 114, and a sensing element, e.g., anantenna 120.Sensor 100 senses changes in capacitance of theantenna 120 to ground Cx, as indicated bycapacitance 122.Sample capacitor 114 may be selected to be much larger than anticipated values of Cx. Thecontrol circuitry 110 may include switching functionality to charge thesample capacitor 114 and the capacitance to be measured Cx. Thecontrol circuitry 110 may also include switching functionality to selectively discharge thesample capacitor 114 and/orantenna 120 and to allow for measurement of the voltage Yes across thesample capacitor 114. An example of how the switching functionality ofcontrol circuitry 110 may operate is described in further detail with regard toFIG. 2 . - As a person or other object approaches or moves away from the
antenna 120, changes in the capacitance Cx of theantenna 120 will occur. For example, as a person approachesantenna 120, Cx will increase, and as the person moves away from theantenna 120, Cx will decrease. The change in Cx produces a measurable effect, which can be utilized by thesensor 100 for proximity detection. - In the circuit depicted in
FIG. 1 , a first switching element S1 can be used to discharge sample capacitor Cs and the capacitance to be measured Cx. The circuit can include a second switching element S2 and a third switching element S3 as shown. Any suitable switching elements can be used for switchingelements S l-S 3. For example, suitable transistors or relays can be used. The second switching element S2 can operate to selectively connect the circuit to a voltage source, e.g., Vdd. The voltage source Vdd may supply a suitable voltage including, but not limited to, any voltage within a range of about 1.8 to about 5.5 V. When the second switching element S2 is closed, charge can be applied to thesample capacitor 114 and Cx of theantenna 120. The third switching element S3 can operate to selectively connect the circuit to ground. Ananalog comparator 112 can be included to compare voltage on the Cs capacitor to a reference voltage signal, indicated by VREF. Any suitable reference voltage may be used. The output of thecomparator 112, e.g., analog comparator output ACO, can be used to determine when the voltage on Cs has reached the reference voltage VREF. As Cs and Cx are in parallel, they form a capacitive voltage divider. The voltage on Cs is consequently influenced by Cx. The lower the reference voltage, the more energy can be maintained in theantenna 120. - For measuring capacitance on Cs as affected by Cx, the output of the
comparator 112 can be provided to a clock input of a pulse width modulator (PWM)circuit 140. ThePWM circuit 140 can be used to gate acounter 150 that is clocked at a suitable frequency to count the number of pulses during a specified time. Thecontrol circuitry 110 may also include aprocessor 160 andstorage functionality 170, e.g., suitable ROM and/or RAM, for holding software instructions and buffered data. Theprocessor 160 can receive the counter output and correlate the counter output to Cs, Cx, and the proximity of a person or object to thesensor 100. The output of thecounter 150 as received by theprocessor 160 may be suitably filtered for reducing noise effects. Theprocessor 160 can process the output of thecounter 150 for detecting proximity of an object relative to theantenna 120. Thecontrol circuitry 110 can provide an output signal, e.g., as shown by the DETECT signal ofFIG. 1 , that is indicative of the presence or absence of a person or object within proximity of thesensor 100. The output signal of thecontrol circuitry 110 may be a bit, a byte, or an analog signal if a D/A converter (not shown) is utilized. The output signal of thecontrol circuitry 110 may indicate the presence or absence of one or more objects within proximity to thesensor 100 or may indicate a degree of proximity to the sensor. The control circuitry output signal may be used to indicate the presence or absence of an object within a detection range of thesensor 100. For example, the output signal may be used to produce an audible signal such as a particular tone or an optical signal such as a particular color when an object is detected. The sound or color may be changed to indicate a change in the proximity of an object to thesensor 100. - For some applications, a dynamic reference voltage may be used to alter the sensing functionality of
sensor 100. Raising the reference voltage may lower the nominal range of the sensor, for example from one foot (30 cm) maximum sensing distance from the antenna down to a few millimeters maximum sensing distance for proximity detection of a touch. For example, a sensor such assensor 100 may be placed in a child's toy bear. If a child were to approach within a specified distance, e.g., six inches or so, the bear could respond with a verbal response such as “pick me up,” encouraging the child to hold the toy. The proximity detection of the sensor may then be changed, by simply altering the reference voltage of the sensor, to close proximity-based touch sensing, allowing the bear to subsequently respond to the child's actual touches. Dynamically changing the nominal detection range of a proximity sensor in such a way may add commercial value to the related good(s) or components. - The
control circuitry 110 can be implemented, for example, by a suitable microcontroller, a field programmable gate array (FPGA), or other standard logic devices. For example, an ATtiny48 microcontroller, as made commercially available by ATMEL Corporation, and/or a suitable timer/counter may be used for implementation of thecontrol circuitry 110. In an example, thesample capacitor 114 may have a nominal capacitance of 4.7 nF and be 10 percent X7R ceramic. -
FIG. 2 illustrates a switching table 200 depicting a switching sequence of the three switches ofFIG. 1 during a charge transfer cycle for operation of thesensor 100. Referring to the table, atstep 1, switching elements S1 and S3 are closed while switching element S2 is open, grounding both capacitors and thereby allowing Cs and Cx to discharge. Next, atstep 2, all switching elements are open, which allows the voltage on Cs and Cx to float. Following atstep 3, switching elements S1 and S3 are open while switching element S2 is closed, applying voltage Vdd to both capacitors and thereby allowing charge to transfer to Cs and Cx. Atstep 4, all three switching elements S1-S3 are open, which allows voltage on Cs and Cx to float and settle. Following, atstep 5, switchingelement 1 is closed while switching elements S2-S3 are open, allowing the charge in Cx to discharge and for a comparison of the voltage on Cs with the reference voltage, e.g., VREF inFIG. 1 . The switching sequence ofsteps 2 to 5 may be repeated for later measurements of the capacitance. A desired number of repeatedmeasurements using steps 2 to 5 can be performed. Changes in capacitance Cx can be interpreted to detect movement of an object toward or away from theantenna 120. -
FIG. 3 illustrates schematically avariation 300 to the circuit ofFIG. 1 with a reference voltage set by avoltage divider 130 includingresistors resistors -
FIG. 4 illustrates schematically acollection 400 of antenna examples that may be used in a proximity sensor. Depicted in the drawing are a square loop antenna (A), a curved loop antenna (B), a line antenna (C), a dipole antenna (D), and a patch antenna (E). The configurations shown are representative, and other antenna configurations may be used for proximity detection. - For some proximity sensor applications, antennas may be configured for proximity detection in one general direction. In other applications, antennas may be configured for proximity detection in multiple directions. For antennas suitable for exemplary proximity sensors, plane charges such as produced by rectangular plates, e.g., as shown by the patch antenna (E), may offer good distance characteristics because the greatest field strength is expressed perpendicular to the surface of the plane. Such configurations, however, may allow limited space for related components of a proximity sensor or a device incorporating such a sensor, e.g., control circuitry, key pads, etc.
- For some applications, electric field lines from a sensor antenna can be oriented to form a directional antenna and still offer available space within or adjacent to the antenna, e.g., within the perimeter of the antenna. In some applications, a square loop or dipole antenna may be used. Examples are shown in
FIG. 4 as (A), (B), and (D). For example, a proximity sensor using a rectangular loop or dipole antenna placed in the perimeter of a wall mounted device, e.g., a wall mounted thermostat or security keypad, may offer good proximity detection for approaches from all four sides. A sensor with such an antenna may also offer good detection distance when approached head on. Such head on proximity detection may be at distances greater than or equal to the dimensions of a particular antenna. For example, a 6-inch diameter curved loop antenna may provide reliable proximity detection at 12 inches from the plane of the antenna. Such a sensor using the curved loop antenna could also, or alternatively, be set so that one would have to actually touch the sensor housing/casing before being detected by the sensor. - Sensors or antennas configured as points, spheres and lines, because of their radial field spreading with distance, may be well suited for proximity detection in applications where the direction of approach is unknown or variable. As described previously, some applications may, however, require proximity detection from one general direction.
- The exemplary proximity sensors can utilize other types of measurement of an antenna's capacitance to ground for proximity detection.
FIG. 5 shows one such example in which the variable Cx of an antenna is utilized to alter the resonant frequency of an LC circuit. - The circuit diagram of
FIG. 5 illustrates schematically aproximity sensor 500 utilizing a LC oscillator.Proximity sensor 500 includescontrol circuitry 510, a tank circuit orLC oscillator 520, and a sensing element, e.g.,antenna 530. Thecontrol circuitry 510 can include asuitable processor 540 andstorage 550. TheLC oscillator 520 includesinductor 522 andsample capacitor 524. Thecontrol circuitry 510 can include frequency counter and excitation functionality and can supply an excitation signal to theLC oscillator 520. Thecontrol circuitry 510 can also supply a charge to theantenna 530, which has a capacitance to free space or ground, Cx. The capacitance Cx can be influenced by people or objects coming into and moving out of proximity to thesensor antenna 530. A microcontroller such as an Atmel® ATtiny48 microcontroller and/or a suitable timer/counter may be used for implementation of thecontrol circuitry 510. - For
sensor 500, as an object or person approaches or comes into proximity with thesensing element 530, the capacitance Cx increases. As an object or person moves away and out of proximity to thesensing element 530, the capacitance Cx decreases. Because Cx is in parallel with Cs, the new Cx changes the capacitance of theoscillator 520, changing the resonant frequency, f, where f is given by: -
- The
control circuitry 510 can measure the change in the resonant frequency f, which can be correlated to capacitance Cx and corresponding proximity of an object or person within range of thesensor 500. - In addition to proximity sensors utilizing oscillators according to
FIG. 5 , other types of resonant circuits and structures may be used in conjunction with a variable capacitance of a sensing element. - The circuit diagram of
FIG. 6 illustrates schematically another example of aproximity sensor 600 utilizing a generic oscillator.Proximity sensor 600 includescontrol circuitry 610 and ageneric oscillator 620 connected to a sensing element configured as anantenna 630. Thecontrol circuitry 610 can include asuitable processor 640 andstorage 650. Thecontrol circuitry 610 can include frequency counter and excitation functionality. In exemplary embodiments, a microcontroller such as an Atmel® ATtiny48 microcontroller and/or a suitable timer/counter may be used for implementation of thecontrol circuitry 610. - As indicated in
FIG. 6 , any electric oscillator affected by a change in capacitance Cx may be used for proximity detection bysensor 600. Examples may include, but are not limited to, RC network oscillators such as a Wien bridge oscillator, a twin T oscillator, and the like, or RLC networks. Changes in Cx will change the resonant frequency of theoscillator 620. By recognizing the change in Cx,sensor 600 can provide for proximity detection. The detection range of thesensor 600 may be dynamically varied by adjusting the values of R and/or C in theoscillator 620, e.g., by switching in or out resistive or capacitive elements. -
FIG. 7 illustrates schematically anantenna 700 configured as a loop antenna and shows field lines emanating from the antenna.Antenna 700 is configured as a rectangular loop, shown withperimeter 702. Because of the field features, rectangular loop antennas can provide both lateral proximity detection and proximity detection in orthogonal directions. InFIG. 7 , electric field lines for lateral proximity detection are indicated byfield lines 1, and electric field lines for orthogonal or head on directions are indicated byfield lines 2. - With continued reference to
FIG. 7 , the open area A within the perimeter of theantenna 700 may be utilized for components that are to be used in conjunction with the proximity sensor. For example, the area within the dashed lines withinperimeter 702 may be used for a keypad or card reader or other components of a device that incorporates a proximity sensor that includes theantenna 700. - Some implementations of proximity detection may involve programming. For example, a microcontroller may include firmware facilitating the control of the switching functionality for charging and discharging a sample capacitor and antenna of a proximity sensor as shown in the table of
FIG. 2 and the measuring of capacitance to detect proximity. An article of manufacture may include the program, e.g., executable code and/or associated data, carried on or embodied in a machine readable medium. A machine readable medium may take many forms, including but not limited to, a tangible non-transitory storage medium, a carrier wave medium, or physical transmission medium. Non-volatile types of non-transitory, tangible storage media include any or all of the memory of the supporting electronics of a proximity sensor, computing devices, processors or the like, or associated modules thereof, such as various semiconductor memories, tape drives, disk drives and the like, which may provide storage at any time for the programming. All or portions of the programming may at times be communicated through the Internet or various other telecommunication networks. Such communications, for example, may enable loading of the programming from one computer or processor into another computer or processor, e.g., for installation in a microcontroller. Thus, another type of media that may bear the programming includes optical, electrical and electromagnetic waves, such as used across physical interfaces between local devices, through wired and optical landline networks and over various air-links. The physical elements that carry such waves, such as wired or wireless links, optical links or the like, also may be considered as media bearing the software. - Various modifications may be made to the examples and embodiments described m the foregoing description, and any related teachings may be applied in numerous applications, only some of which have been described herein. It is intended by the following claims to claim any and all applications, modifications and variations that fall within the true scope of the present teachings.
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US16/103,895 Continuation US10563133B2 (en) | 2017-02-12 | 2018-08-14 | Multi-stage device and process for production of a low sulfur heavy marine fuel oil |
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US8400209B2 (en) | 2013-03-19 |
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