CAPACITIVE POINT LEVEL SENSOR

The present invention is directed to a capacitive sensor that has electrodes externally positioned on or proximate to the surface of a non-metallic container for detecting a usage level inside the container, where the contents may be liquid or granular solids. By generating an excitation signal to the electrodes and processing the resulting signal waveform, the usage level may be detected with respect to the position of the electrodes. Consequently, embodiments provide a marker that is indicative of usage conditions such as a refill condition or an empty condition in order to inform the user to purchase a refill of the contents. Embodiments may operate with an Internet of Things device so that physical goods may be automatically ordered when the contents are at or below a predetermined level. Embodiments may provide a low cost design and may be used in many applications, such as an oil diffuser.

TECHNICAL FIELD

Aspects of the disclosure relate to determining a usage level of contents in a container using a capacitive sensor.

BACKGROUND OF THE INVENTION

There are applications for dispensing contents stored within a container. However, the level of the contents may not be readily visible to the user, and thus the user may not readily know when the contents needs to be refilled. Corresponding applications are numerous including essential oil diffusers, fragrant oil diffusers, air freshener dispensers, air odor eliminators, sprayers, automatic hand sanitizers, mist humidifiers, water dispensers, and coffee machines. However, traditional approaches often rely on sensors being immersed into the contents within the container. Consequently, there is a real market need to provide a non-obtrusive approach to determining a usage level of contents within a container.

SUMMARY OF THE INVENTION

The present invention provides methods and apparatuses for determining a contents level inside a non-metallic container by using a variation of the capacitance between sense electrodes that are externally located to the container. Container contents may include a variety of liquids or granular solids including, but not limited to, hand cleaners, fragrant oils, water, coffee, and the like. In addition, the container may be constructed from a variety of materials including, but not limited to, plastic, cardboard, glass, and so forth.

With an aspect of the embodiments, an apparatus determines a usage level of container contents in a non-metallic container. A capacitive sensor includes a pair of electrodes that comprises a first electrode and a second electrode and is externally positioned on or proximate to a surface of the non-metallic container at a point level. A signal generator generates an excitation signal to charge an equivalent capacitor associated with the capacitive sensor at a pre-defined amount of charge, and a signal receiver subsequently measures the voltage across the capacitor. A processing circuit determines whether the usage level of the contents is below the point level of the electrode pair. With another aspect, an excitation signal charges an equivalent capacitor of a capacitive sensor with a pre-defined amplitude of voltage, and a signal receiver measures the charge stored in the capacitor.

With another aspect, an excitation signal charges an equivalent capacitor of a capacitive sensor. The voltage across the capacitor is then measured at an appropriate time while the capacitor is discharging.

With another aspect, an apparatus has a plurality of electrode pairs positioned along a container, where each electrode pair corresponds to different point levels. Measurements are obtained from each selected electrode pair and processed to determine the usage level of the container contents.

With another aspect, a measuring circuit is electrically connected to a capacitive sensor in one of two ways. First, the capacitive sensor may assume a one-port typology, where one of the electrodes of an electrode pair is grounded while the measuring circuit is connected to the other electrode. Second, the capacitive sensor may assume a two-port typology, where the driver of the measuring circuit is connected to the first port and an analog to digital converter (ADC) is connected to the other port.

With another aspect, an apparatus includes a reporting circuit that generates an alert notification and/or ordering request when the usage level of container contents is below an alert level.

With another aspect, a capacitive sensor comprises M electrode pairs positioned in decreasing point positions along the non-metallic container. A processing circuit selects a next electrode pair through an electrode selector until the usage level is below an associated point position of the selected electrode pair.

DETAILED DESCRIPTION

An apparatus with a capacitive sensor with one or more pairs of electrodes externally positioned on or proximate to a surface of a non-metallic container non-intrusively detects the level of the contents (for example, a liquid or granular solids) inside the non-metallic container. The apparatus supports one or more markers that are indicative of an usage condition, refill condition, or empty condition.

The apparatus can further notify a user to obtain/purchase a refill when the level is at or below a predetermined alert level. For example, the apparatus may operate with an Internet of Things (IoT) device and may automatically order more container contents in conjunction with the IoT device at the appropriate time. Embodiments support a variety of applications including, but not limited to, essential oil diffusers, fragrant oil diffusers, air freshener dispensers, air odor eliminators, sprayers for weed killers herbicides and insecticides, automatic hand sanitizers, mist humidifiers, water dispensers, and coffee machines.

Embodiments may provide advantages with respect to traditional approaches including low cost, simple implementation, broad application range, and non-intrusiveness that does not affect or alter the property of the material (container contents) being measured.

FIG. 1shows non-metallic container101with a pair of sense electrodes102and103for determining a usage level151.

Electrodes102and103may be on or proximate to a surface of non-metallic container101. While embodiments support applications with non-metallic containers, non-metallic container101may be comprised of a variety of materials including, but not limited to, plastic, cardboard, glass, and so forth. Moreover, the container contents may comprise a variety of liquids or granular solids including, but not limited to, hand cleaners, fragrant oils, water, coffee, and the like.

With an aspect of the embodiments, the determination a usage level of the container contents is based on a measured change of capacitance. Each pair of electrodes (for example electrodes102and103) are positioned adjacent to a corresponding measuring point level (for example, alert level151) as shown inFIG. 1. While not explicitly shown, electrodes102and103are electrically connected to a measuring circuit as will be discussed in further detail.

An equivalent capacitance is dependent upon whether the contents is above or below alert level151. In general the equivalent capacitance (as measured in relation to electrodes102and103) is higher when the container contents is above alert level151than when below. The capacitor may be modeled with electrodes102and103and an equivalent dielectric layer based on the electrical characteristics of the container contents and container material. For example, the value of the capacitance may depend on the dielectric constant of the material filled inside container101(where the dielectric constant of the container contents is typically greater than 1), area of the electrodes102and103, and the gap between electrodes102and103. Consequently, the equivalent capacitance is dependent on the type of container contents as well as on the material of container101and may be determined through experiment or by electrical analysis.

Electrodes102and103may be positioned close (for example, within 0.3 millimeters) to or even on the surface of container101. For example, electrodes102and103may be printed on container101or held into position by a fixture or product casing.

Embodiments may support applications with different containers. For example, container101may have different shapes and capacities (typically 20 ml or more). Container101may support a variety of applications from small dispensers to large storage containers. Depending on the desired equivalent capacitance and size/shape of container101, electrodes101and103may assume different dimensions, for example, where the length, width, and thickness are 10 mm, 3 mm, and 0.2 mm, respectively.

The equivalent capacitance changes when the container contents is above or below a point level for a corresponding pair of electrodes. For example, the equivalent capacitance of a plastic container may be about 3 pF when the essential oil (the container contents) is above the point level and about 2 pF when the essential oil is below the point level.

FIG. 2shows equivalent circuit200of a modeled capacitor with a first connection type (type 1) for electrodes102and103as shown inFIG. 1. With circuit200, electrode102is electrically connected to a measuring circuit (for example, circuit401as shown inFIG. 4) while electrode103(as shown inFIG. 1) is connected to electrical ground. Consequently, circuit200is modeled as a one-port circuit.

With a type 1 connection, a measuring circuit measures a self-capacitance, where one electrode (for example, electrode103) is connected to ground and one electrode (for example, electrode102) is connected to a driving and measuring path of a capacitance measuring circuit (for example, circuit401as shown inFIG. 4). The capacitance measuring circuit drives (excites) electrode102to charge up the equivalent capacitor formed by the two electrodes102and103, and then measures the capacitance difference with or without the liquid or granular solids between the two electrodes102and103. Based on the measured capacitance, it is determined whether or not the level of the container contents is above or below the position (which may be referred to the as the point level) of electrodes102and103.

Referring to circuit200, Rs201is the equivalent resistance from the measuring circuit to electrode102, Cp202is the parasitic capacitance between the connecting path from the measuring circuit to electrode102and electrical ground, and Cs203is the capacitance between electrode102and electrode103.

FIG. 3shows an equivalent circuit with a second connection type (type 2) for electrodes102and103as shown inFIG. 1. With circuit300, electrode102is connected to driver503of measuring circuit501as shown inFIG. 5while electrode103is connected to ADC504of measuring circuit501. Consequently circuit300is modeled as a two-port circuit.

With a type 2 connection, a measuring circuit measures the mutual capacitance, where one electrode (for example, electrode102) is connected to transmit path and one electrode (for example, electrode103) is connected to receive path of measuring circuit501as shown inFIG. 5. The measuring circuit charges up the capacitor through its transmit path, and then measures the capacitance difference with or without the liquid or granular solids by collecting the charge from the capacitor through its receive path.

Referring to circuit300, Tx351is the transmit path of the capacitance measuring circuit, Rx352is the receive path of the capacitance measuring circuit, RTX301is the equivalent resistance from the transmit path to electrode102, RRx305is the resistance from the receive path to electrode103, CpTx302is the parasitic capacitance between the transmit path and electrode102, CpRx304is the parasitic capacitance between the receive path and electrode103, and Cm303is the capacitance between electrodes102and103.

FIG. 4shows measuring circuit401interacting with the sense electrodes406and407(corresponding to electrodes102and103as shown inFIG. 1) via a type 1 connection (which is based on a one-port circuit typology). Capacitance measuring circuit401comprises driver403, analog to digital converter (ADC)404, and electrical switch405. ADC404may be a simple voltage to a computer readable value conversion circuit. With some embodiments, ADC404may include a charge amplifier that produces a voltage output proportional to the charge from the electrodes and then converts it into a computer readable value. With some embodiments, ADC404may comprise an oscillator that oscillates at a frequency determined by the capacitance formed by the electrodes. A frequency counter then counts the frequency to obtain a computer readable value that is indicative of the capacitance formed by the electrodes with or without liquid or granular solids between the electrodes.

Driver403charges up (corresponding to charge or voltage waveform (pulse)451) equivalent capacitor402formed by electrode406and electrode407through switch405. Capacitor402is then connected to the receive path via switch405so that ADC404can measure the voltage across capacitor402or the charge on capacitor402. When the level of the container contents is above the corresponding point level (in other words, there is liquid or granular solids inside the container between the electrodes406and407, the relative permittivity is larger than that without the liquid or granular solids. The capacitance is smaller when there is no liquid or granular solids inside the container between electrodes406and407(in other words, the container contents is below the point level).

As will be discussed in greater detail, the voltage across capacitor402will be different as capacitor402charges and discharges when the level of the container contents is above or below the point level since the equivalent capacitance is correspondingly different.

FIG. 5shows measuring circuit501interacting with sense electrodes505and506(corresponding to electrodes102and103as shown inFIG. 1) via a type 2 connection (which is based on a two-port circuit typology). Capacitance measuring circuit501comprises driver503and analog to digital converter (ADC)504.

Driver503charges up (corresponding to charge or voltage waveform551) equivalent capacitor502formed by electrode505and electrode506through the first port. ADC504then measures the charge or voltage across capacitor502, which is indicative of the capacitance of capacitor502. ADC504may be a simple voltage to a computer readable value conversion circuit. With some embodiments, ADC504may include a charge amplifier that produces a voltage output proportional to the charge from the electrodes and then converts it into a computer readable value. With some embodiments, ADC504may comprise an oscillator that oscillates at a frequency determined by the capacitance formed by the electrodes. A frequency counter then counts the frequency to obtain a computer readable value that is indicative of the capacitance formed by the electrodes with or without liquid or granular solids between the electrodes.

When the level of the container contents is above the corresponding point level (in other words, there is liquid or granular solids inside the container between the electrodes505and506), the relative permittivity is larger than that without the liquid or granular solids. The capacitance is smaller when there is no liquid or granular solids inside the container between electrodes505and506(in other words, the container contents is below the point level).

FIG. 6Ashows driving (excitation) charge waveform651, andFIG. 6Bshows driving (excitation) voltage waveform652(corresponding to waveforms451and551as shown inFIGS. 4 and 5, respectively) applied to electrodes102and103as shown inFIG. 1. While waveform651or652is shown as a pulse from T0601to T1602, embodiments may support other types of waveforms with different characteristics (for example, shape). During the time duration between T0and T1, waveform excitation waveform charges capacitor402(with a type 1 connection) or capacitor502(with a type 2 connection). When waveform651or652terminates at T1602, capacitor402or capacitor502starts to discharge at T2.

FIGS. 6C-Eshows exemplary voltage and charge waveforms653,654, and655, respectively, from sense electrodes102and103in response to driving waveform651or652. However, waveforms653,654, and655correspond to the container contents below (corresponding to a lower equivalent capacitance) and above the point level, respectively.

Measuring circuit401(for a type 1 connection) and measuring circuit501(for a type 2 connection) measures the charge or voltage across capacitors402and502, respectively. As shown inFIG. 6, measuring circuit401,501measures the voltage or charge at Tm, where the measured voltage is V1604for waveform653or the measured charge Q2607for waveform654(when the container contents is below the point level) and V2605for waveform653or Q1606for waveform654(when the container contents is above the point level). In general, the measured capacitance at Tmis smaller when the container contents is below the point level and is larger when the container contents is above the point level.

As will be discussed in further detail, apparatus700(shown inFIG. 7) uses the measured voltage (V1or V2) or charge (Q1or Q2) at Tmto determine the usage level for container101.

While embodiments may measure the charge or voltage across capacitors402or502after charging, some embodiments may measure the charge or voltage while charging or discharging.

As previously discussed, measuring circuit702provides the value of the charge or voltage across the equivalent capacitor that models sensing sensors701. Processing circuit703(for example, that may be implemented with a microcontroller) determines whether the container contents is above or below the point level based on the capacitance information provided by measuring circuit702. For example, referring toFIG. 6, processing circuit703may determine that the usage level is above the point level when the measured voltage is within a first voltage range centered about V2605and is below the point level when the measured voltage level is within a second voltage range centered about V1604.

With some embodiments, processing circuit703may initiate a notification via wireless communication circuit704(for example, supporting a Bluetooth Low Energy (BLE) or a WiFi communication channel) to inform a user about the determined usage level. When the usage level is below a level that is below an alert level, the notification may further generate an order for container contents to replenish the container.

FIG. 8shows computing system703(corresponding to processing circuit703as shown inFIG. 7) within apparatus700. Processor801controls operation of apparatus700by executing computer readable instructions stored on memory device802. For example, processor801may execute computer readable instructions to perform process900as will be discussed withFIG. 9. Embodiments may support a variety of computer readable media that may be any available media accessed by processor801and include both volatile and nonvolatile media, removable and non-removable media. By way of example, and not limitation, computer readable media may comprise a combination of computer storage media and communication media.

Computing system703may include input interface803to obtain voltage information from measuring circuit702and output interface804to initiate a measurement by measuring circuit702.

Computer storage media may include volatile and nonvolatile, removable and non-removable media implemented in any method or technology for storage of information such as computer readable instructions, data structures, program modules or other data. Computer storage media include, but is not limited to, random access memory (RAM), read only memory (ROM), electronically erasable programmable read only memory (EEPROM), flash memory or other memory technology, CD-ROM, digital versatile disks (DVD) or other optical disk storage, magnetic cassettes, magnetic tape, magnetic disk storage or other magnetic storage devices, or any other medium that can be used to store the desired information and that can be accessed by the computing device.

Processing circuit703may be implemented in a number of ways. For example, processing circuitry703may be implemented with a microcontroller that typically includes a central processing unit (CPU), in addition with a fixed amount of RAM, ROM and other peripherals all embedded on a single chip. However, processing circuitry may be implemented with a plurality of integrated circuits and/or discrete electronic components.

FIG. 9shows process900for determining a usage level of container101as shown inFIG. 1. At block901, measuring circuit401or501generates an excitation signal to charge equivalent capacitor402or502, respectively.

At block902, measuring circuit401or501measures the charge or voltage across equivalent capacitor402or502at a measuring time Tmafter charging or while the capacitor is charging or discharging. At block903processing circuit703then compares the measured voltage with predetermined voltage ranges to determine whether the corresponding capacitance is indicative of the usage level being above or below the point level of the electrode pair.

When the usage level is below the point level, block904determines whether the point level corresponds to an alert level. If so, apparatus700generates an alert notification at block905to inform a user about the situation via a reporting circuit (for example, wireless communication circuit704as shown inFIG. 7). For example, apparatus700may automatically order container contents by generating an order request to a distributor via the Internet on behalf of the user. With some embodiments, the ordering process may be transparent to the user.

FIG. 10shows container1001with a plurality of sense electrode pairs1002-1005for determining a usage level of the container contents. Each electrode pair1002-1005has an associated point level (for example, 75%, 50%, 25%, and Empty) similar to point level151as shown inFIG. 1.

As will be discussed, each electrode pair1002-1005may be selectively connected to a measuring circuit to obtain measurements indicative of the equivalent capacitance of the selected electrode pair.

Measuring circuit1107is electrically connected to a selected electrode pair via electrode selector1102(as configured by processor1105) so that the selected electrode pair can be charged and measured as previously discussed withFIGS. 6A-Eand7. Electrode sensor1102may assume different forms including an analog multiplexer or electrical switch.

Measuring circuit1107may further comprise detection circuit1103and A/D converter1104. Detection circuit1103includes a signal generator that charges the equivalent capacitor of the selected electrode pair and a signal interface that presents the discharging waveform to A/D converter1104. A/D converter1104captures the charge or voltage level at the appropriate measurement time (Tm) and presents the value in a digital format to processor1105.

Based on the measured capacitance from measuring circuit1107, processor1105determines whether the usage level is above or below the point level of the selected electrode pair. If the usage level is below the point level, processor1105may select the next electrode pair physically below the previous electrode pair and initiate another measurement. This may be repeated until the lowest positioned electrode pair (for example, pair1005as shown inFIG. 10) is reached.

If processor1105determines that the usage level is below an alert level, processor1105may initiate an alert notification and/or ordering request via reporting circuit1106.

FIG. 12shows process1200for determining a usage level of container1001by processor1105as shown inFIG. 11. At block1201, process1200selects the top positioned electrode pair (for example, pair1002as shown inFIG. 10) and measures the charge or voltage of the equivalent capacitance at block1202. Based on the measured capacitance, process1200determines whether the usage level is above the corresponding point level at block1203.

If so, at block1205process1200determines whether the usage level is above the alert level. If not, process1200generates an alert notification at block1206.

Referring back to block1203, if process1200determines that the usage level is below the corresponding point level, process1200selects the next electrode pair physically below the previous electrode pair at block1204. A measurement is then repeated for the next selected electrode pair at block1202.

FIG. 13shows process1300, which may be performed by process1105, for installing container1001, monitoring contents of the container1001, and alerting a user as necessary.

At block1301, container1001is installed by positioning container1001with monitoring apparatus such as apparatus1100. For example, when electrode pairs1002-1005are not located on container1001, the electrode pairs may be positioned within a desired distance from container1001.

At block1302, the monitoring apparatus (for example, apparatus1100) determines whether container1001is empty (for example, based on measurements provided by electrode pair1005). If so, an error message (notification) may be sent to a user at block1303(for example, via reporting circuit1106through a mobile app executing on the user's mobile device).

If container1001is not empty, process1300continues to determine whether the container contents is below an alert level (for example, 25% as shown inFIG. 10) at block1304. If not, process1300determines the usage level at block1305(for example, whether the usage level is above or below 50% or 75%). If the container contents is under level (for example, an alert level corresponding to 25%), process1200initiates an alert notification and/or a goods order at block1306. The alert notification may include information about the contents status as determined at blocks1307and1308.

With a first exemplary embodiment, an assembly determines a level of contents within a non-metallic container. The assembly includes a capacitive sensor having at least one pair of electrodes that is positioned on or close to the surface of the container.

With a second exemplary embodiment, a capacitive sensor has one or more pairs of electrodes that are arranged to form one or more capacitors.

With a third exemplary embodiment, an assembly with a capacitive sensor detects a presence or absence of liquid or granular solids within a container at one or more predetermined levels within the container.

With a fourth exemplary embodiment, an assembly with a capacitive sensor generates an alert signal to a user.

With a fifth exemplary embodiment, an assembly comprises a microcontroller, wherein the microcontroller receives a first signal from a capacitive sensor. The first signal is indicative of a detected presence or absence of liquid or granular solids at a point level. The assembly may then generate a second signal to alert a user or to order physical goods.

Various aspects described herein may be embodied as a method, an apparatus, or as computer-executable instructions stored on one or more non-transitory and/or tangible computer-readable media. Accordingly, those aspects may take the form of an entirely hardware embodiment, an entirely software embodiment (which may or may not include firmware) stored on one or more non-transitory and/or tangible computer-readable media, or an embodiment combining software and hardware aspects. Any and/or all of the method steps described herein may be embodied in computer-executable instructions stored on a computer-readable medium, such as a non-transitory and/or tangible computer readable medium and/or a computer readable storage medium. Additionally or alternatively, any and/or all of the method steps described herein may be embodied in computer-readable instructions stored in the memory and/or other non-transitory and/or tangible storage medium of an apparatus that includes one or more processors, such that the apparatus is caused to perform such method steps when the one or more processors execute the computer-readable instructions. In addition, various signals representing data or events as described herein may be transferred between a source and a destination in the form of light and/or electromagnetic waves traveling through signal-conducting media such as metal wires, optical fibers, and/or wireless transmission media (e.g., air and/or space).

As can be appreciated by one skilled in the art, a computer system with an associated computer-readable medium containing instructions for controlling the computer system can be utilized to implement the exemplary embodiments that are disclosed herein. The computer system may include at least one computer such as a microprocessor, digital signal processor, and associated peripheral electronic circuitry.