Patent Application
20210310974
Embodiments of the subject matter disclosed herein generally relate to a multi-sensory device or tag for determining plural parameters, and more particularly, to a single structure that is configured to detect three or more parameters of the ambient and/or parameters that affect the structure.
An asset can be defined as an object that holds a certain market value, as for example, a painting, jewelry, a laptop, etc. For the owner of the asset, the safety of the asset is important. Over time, technologies have developed so that various systems are now available for tracking and/or managing the asset's condition/location. In essence, most of the time, these systems are put in place to prevent theft or unauthorized handling of the asset. Such an asset can be hidden away in a secure vault, but often times the asset that needs protection is an object of daily use, which is exposed to an unregulated environment and/or people, for example, a laptop in a workplace, an expensive piece of decoration inside of a home, or a painting hung in an art gallery.
With an ever-increasing number of theft of high-value art assets, it has become a continuing challenge to find the right protection system for the right price. Radio-frequency identification (RFID) technology is the most popular and widely used system for inventory management, asset management, and anti-theft systems. An object tagged with an RFID tag can then be detected if it comes in proximity of an RFID reader, where the readable distance depends upon the technology and the surroundings of the tag. The maximum readable distance ranges, for most RFID systems, from a few centimeters to a couple of meters.
The limitation of this technology, however, is that it can only identify if the object is present in a close range of an RFID receiver. Furthermore, the RFID tags do not have the ability to track movement or mishandling of the object. Another serious issue with the RFID tags is that these tags can be easily removed from the object, with no way left for the RFID system to track the object once the tag is removed since the RFID technology depends on the unambiguous identification of the tagged object by the reader. There are many scenarios where a notification about an unauthorized object mishandling is desired, for example, one may want to know if anybody attempts to use the laptop or try to mishandle a precious item. The other important aspect for the protection of the assets is the capability to identify tag removal attempts to ensure that the tag stays in contact with the asset for its continuous monitoring. While the RFID technology is a vital utility for many applications, it fails to deliver when somebody tries to remove the tag.
A paper-based triboelectric nanogenerator (TENG) has been proposed as an anti-theft sensor for books. It adheres to a page of the book, where the triboelectric generator harvests energy from the movement of the pages. Consequently, when the book is moved vigorously, it can use the harvested energy to signal an alarm using an LED or a buzzer. This approach has some limitations as it is largely dependent upon the frequent use of the same page in order to harvest sufficient energy. Most assets like artworks, paintings, and laptops stay in one place and do not move enough to generate useful energy. Thus, such a sensor would fail to notify the owner of the asset about the movement of such assets. Furthermore, this type of sensor, although self-powered, lacks integration into a wireless sensor networks. An LED or small buzzer cannot stop someone from stealing the object. Lastly, for the same reason as the RFID tags, this sensor lacks any anti-tampering detection or capability, and the sensor can be easily removed from the asset to which is attached, thus leaving the asset without protection.
Wireless Sensor Networks are being proposed for anti-theft and they are made using a combination of sensors like light sensors, vibration sensors, GPS, pressure, and other sensors [1, 2]. The combination of multiple sensors to track the asset and then the bulky processors needed to analyze that data, result in large-sized tracker boxes. These trackers, while they can track large objects like laboratory equipment, cannot be attached as a tag to most everyday objects, like a laptop or a painting.
Thus, there is a need for a new multi-sensory device that is compact, easily attachable to an asset of any size, inexpensive, and also has the capability to detect a removal of the device from the asset to be protected.
According to an embodiment, there is a sensor for determining plural parameters, and the sensor includes a housing that defines a chamber, and a parallel plate capacitor having a first plate located inside the chamber and a second plate fixedly attached to a first external side of the housing. A dielectric multi-layer placed between the first and second plates includes a pressure sensitive layer and a humidity sensitive layer.
According to another embodiment, there is a sensor assembly for determining plural parameters, and the sensor assembly includes a housing that defines a chamber, a parallel plate capacitor having a first plate located inside the chamber, a second plate located outside the chamber, and a dielectric multi-layer that includes a pressure sensitive layer and a humidity sensitive layer, an electronic interface attached to an outside of the housing, a processor and a memory attached to the electronic interface and configured to measure the plural parameters based on a change of a capacitance of the parallel plate capacitor, a communication device configured to transmit at least one of the plural parameters to an external device in a wireless manner, and a power source attached to the electronic interface and configured to power the processor, the memory and the communication device.
According to still another embodiment, there is a method for assembling a sensor system for measuring plural parameters. The method includes placing a first electrical terminal on a first side of an opened box so that the first electrical terminal is partially located inside of a chamber defined by the opened box, placing a first plate inside the chamber, closing the open box with a lid so that the chamber is fully closed, placing a pressure sensitive layer on the lid, placing a humidity sensitive layer on the pressure sensitive layer, and placing a second plate on the humidity sensitive layer, so that the first plate and the second plate form a parallel plate capacitor. A dielectric multi-layer of the parallel plate capacitor includes the pressure sensitive layer and the humidity sensitive layer.
For a more complete understanding of the present invention, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which:
The following description of the embodiments refers to the accompanying drawings. The same reference numbers in different drawings identify the same or similar elements. The following detailed description does not limit the invention. Instead, the scope of the invention is defined by the appended claims. The following embodiments are discussed, for simplicity, with regard to a three-sensory integrated system that can be home made, with only materials available around the house. However, the embodiments to be discussed next are not limited to such a homemade device or to three sensors, but may be applied to industrially manufactured devices that use the same principles as the home made sensor and can include more than three sensors.
Reference throughout the specification to “one embodiment” or “an embodiment” means that a particular feature, structure or characteristic described in connection with an embodiment is included in at least one embodiment of the subject matter disclosed. Thus, the appearance of the phrases “in one embodiment” or “in an embodiment” in various places throughout the specification is not necessarily referring to the same embodiment. Further, the particular features, structures or characteristics may be combined in any suitable manner in one or more embodiments.
According to an embodiment, a small-sized multi-function sensor 100 is equipped with a liquid (humidity) detection capability, a heat (temperature) detection capability, and a touch (pressure) capability, all embedded in a single device/tag in the form of a single parallel plate capacitive structure, as illustrated in
In one application, the sensor can be attached in the form of a tag to an asset 200, for example, a picture in a museum as illustrated in
The sensor 100 is show in
One of these layers is a layer of air 132 formed inside the chamber 140, which is located between the first plate 110 and the lid 134. Thus, the dielectric multi-layer 130 also includes (a) the lid 134, which is made from, for example, a polymer, (b) a pressure sensitive layer 136, which is made from, for example, a sponge, and (c) a liquid sensitive layer 137, which is made from, for example, a microfiber wipe. Other materials may be used for any of these components as long as they comply with their functionalities noted above.
To hold in place these layers of the dielectric multi-layer 130, it is possible, in one embodiment, to make the second metal plate 120 from a flexible material, for example, copper tape, and to use additional material for the second metal plate 120 to extend it, as shown in
The parallel plate capacitive structure or capacitor 111 thus includes, in the embodiment of
Still with regard to
Returning to
Still with regard to
As shown in
The effective capacitance of the parallel plate capacitor 111 depends upon the overlapping area of the two metal plates 110 and 120. If the sensor 100 has the fixes plate 120 shaped as illustrated in
The two plates 110 and 120 are each connected to a corresponding electrical terminal 114, and 124, respectively, as shown in
If one of the desired parameters to be measured by the sensor 100 is the tilt angle of the housing 101 relative to the gravity, a mathematical relation is used by the processor 320 to convert the value of the capacitance of the parallel plate capacitor 111 into the angle of inclination of the housing relative to the gravity axis. Thus, it is possible to directly relate the change in the capacitance of the sensor 111 to the angle of tilt. In this regard,
The sensor 100 discussed in the embodiments illustrated in
For the pressure and liquid sensing capabilities, the dielectric multi-layer 130 is made up of a sponge and a microfiber wipe stacked on top of each other. Those skilled in the art would understand that other materials may be used for the pressure and humidity layers 136 and 137. The thickness of the sponge changes in response to the applied pressure, resulting in a reduction of the gap between the parallel plates 110 and 120, which in turn changes the capacitance of the sensor 100. When the microfiber wipe 137 makes contact with any form of a liquid, its dielectric value changes, and thus, the capacitance of the sensor 100 changes. Thus, by calibrating these changes in the capacitance due to the various changes in the pressure, humidity, and temperature that are present around the sensor, the processor 320 of the sensor system 300 can measure these parameters. These three capabilities are now discussed in turn.
To detect any tampering attempts by a person with the sensor 100, i.e., removal of the sensor 100 from the asset 200, the pressure sensitive layer 136 is added as part of the dielectric multi-layer 130. In the embodiment illustrated in
where ‘E’ is the permittivity of the sponge, combined with the permittivity of the lid, the humidity sensitive layer 137, and the air layer 132. As a person applies pressure on the top metal plate 120 of the sensor 100, the sponge compresses and the distance ‘D’ between the parallel plates 110 and 120 decreases, resulting in an increase in the capacitance C of the capacitor 111.
This response can be correlated to any touch or tampering event with the sensor 100 using a prior calibration, so that if anyone tries to remove the sensor 100 from the asset 200, the change in pressure can be detected and a notification can immediately be sent out to the external device 350 alerting it that this tampering event is taking place. In one application, the external device 350 is located in the control room of a security company, which based on the received warning from the sensor 100, can dispatch personnel for checking the integrity of the asset 200.
The humidity functionality of the sensor 100 is useful because the sensor is an add-on device, i.e., it needs to be bonded to any asset 200 using an adhesive. There are various kinds of adhesives with different bonding strengths. The type of adhesive will vary depending upon the asset in question. If the sensor 100 needs to be attached to human skin, skin-friendly adhesives may be used while in case of actual objects, heat curable adhesives can be used. The advantage of using adhesives is that the add-on sensor 100 can be easily attached to any object without affecting its form factor and can be removed from the object with little effort when desired.
One of the ways of removing adhesives is using organic solvents or volatile fluids. Thus, a person may use a volatile fluid on the sensor in an effort to remove the sensor from the asset, which endangers the safety of the asset monitored by the sensor 100. Generally, fluids are easily detected by using potentiometric sensors. In these sensors, a voltage is applied across electrodes and if there is a liquid in between them, a current passes through the liquid. The amount of passing current depends upon the salinity of the liquid. However, such techniques are unable to detect organic solvents which do not have ions to pass current through the solvent. Thus, as illustrated in the embodiment of
A third capability of the sensor 100 is now discussed. There is another possible way of removing the sensor 100 from its asset 200, for example, by using heat. Some adhesives are sensitive to temperature. Heat, on one hand, can be used to cure some adhesives while heat can also be used to debond certain kinds of adhesives. Thus, the temperature plays a critical role in the bonding strength of any adhesive. Because an adhesive will be required to attach the sensor 100 to any asset 200, there arises a vulnerability that someone can attempt to remove the sensor without touching it, for example, by using a heat source. For this purpose, a heat capability is also incorporated in the sensor 100, albeit in the same parallel plate structure 111, by using a heat sensitive metal for the top plate 120, which is outside the housing 101. The top metal plate 120 is continuously exposed to the surrounding temperature and thus, any change in the ambient temperature, which is not correlated to the change in the weather, could be associated with an attempt to remove the sensor from the asset 200. Copper, like most conductors, has a temperature dependent resistance governed by the equation (2):
R=R
ref(1+ζ(T−Tref)), (2)
where ‘R’ is the resistance at a given temperature ‘T’ and Tref is a reference temperature at which the resistance Rref of that material is known. ‘ζ’ is the temperature coefficient of resistance, which for copper is 0.004041. Thus, it means that with changes in the temperature, the resistance R of the copper will change. The metal plate used as the top plate 120 of the capacitor 111 acts like a resistor in series with the capacitor forming an RC circuit. The capacitance ‘C’ of a capacitor can be measured by applying a fixed amount of voltage ‘V’ across the capacitor and then measuring the time ‘t’ taken for the capacitor to fully charge to a charge level ‘Q’ as governed by equation (3):
By the application of heat, the resistance R (also called Equivalent Series Resistance) of the copper plate will rise as a result of which the time constant RC increases. Thus, it takes longer for the capacitor to charge or discharge. Due to the increased time is taken to charge the capacitor, the capacitance appears to be increased for the capacitance measured by the digital converter circuitry of the processor 320. Thus, increasing the electrode resistance causes an increase in the calculated capacitance of the parallel plate capacitive structure 111. This phenomenon is used herein to detect when heat is applied to the top metal plate 120 of the sensor 100. Some capacitors are designed such that they are not affected by temperature by using non-metallic electrodes. However, the capacitor 111 has metal plates to sense the heat applied to the sensor.
It is noted that the three capabilities of the sensor 100 discussed above, i.e., pressure, humidity and heat detection, may be implemented in the capacitor 111 independent of the tilt angle capability discussed above with regard to
A method for assembling a sensor 100 as discussed above is now discussed with regard to
In step 706, the pressure sensitive layer 136 is placed over the lid 134, and in step 708, the humidity sensitive layer 137 is placed over the pressure sensitive layer 136. Note that the order of these two steps may be reversed, so that the humidity sensitive layer 137 is formed directly over the lid, and the pressure sensitive layer 136 is formed over the humidity sensitive layer 137. As the pressure sensitive layer 136 has a porous structure, if a liquid is poured directly over the pressure sensitive layer 136, the porous structure would absorb part of the liquid, and release some of it to the humidity sensitive layer 137, so that the reverse order of these layers does not negatively impacts the sensing of the liquid.
In step 710, the fixed plate 120 is attached to the lid. In one application, the fixed plate 120 is a copper tape shaped partially like a triangle. The fixed plate is attached to the top of the lid. Other shapes may be used as previously discussed. The fixed plate can be wrapped in this embodiment around the housing 101, towards the back side of the box so that it also acts as a second electrical terminal 124 and both terminals 114 and 124 are on the same side of the housing for easier integration with the electronic interface 310. The shape of the fixed plate is made in the shape of a triangle such that it has variable area across the width of the sensory platform, if the tilt angle is desired to be measured. If the tilt angle is not desired to be measured, the fixed plate 120 may have a constant width.
Then, in step 712, a processor and a memory may be attached to the lid or the box. The processor and the memory serve to receive a signal from the parallel plate capacitor 111, to determine a change in its capacitance when the capacitor is tilted or rotated about the first electrical terminal 114, or when a pressure is applied to the sensor, or when a liquid is poured over the sensor, or when heat is applied to the fixed plate 120, or a combination of these of actions. The processor is further configured to map the calculated capacitance to a corresponding tilt angle, or pressure, or humidity, or temperature or any combination of these parameters, as the sensor has been previously calibrated to establish the correspondence between the capacitance and these variations in the capacitance of the capacitor. A communication device 340 is attached to the housing 101 in step 714 for communicating the calculated parameter when a value of such parameter is larger than a given threshold. For powering all these electronic components, a power source 330 is added to the housing 101 in step 716.
In one embodiment, the electronic components discussed in the last three steps of the method illustrated in
This PSoC chip is advantageous because its 32-bit processor is integrated with a Bluetooth Low-Energy (BLE) 4.1 technology based communication module 340, to achieve wireless communication with a smartphone 350, so that the entire system 300 has a total package size of 10×10×1.8 mm. The BLE 4.1 module 340 has a special 1.3 μA low-power mode which is configured to consume significantly less power than Bluetooth 2.0 and other communication protocols like Wi-Fi and ZigBee. This module consumes just 10 mA instantaneous power while transmitting data at the maximum lowest connection interval of 7.5 ms. By increasing the connection interval to mere 100 ms, the power consumption drops down to 0.5 mA. It operates in the 2.4 GHz ISM band with an adjustable receiver frequency of +3 to −18 dBm and a 50-meter range. By having such a large range, a single receiver node 350 in a 50-meter radius space can be used to connect to all the sensors 100. Furthermore, the chip 320 comes with 256 kB flash memory and 32 kB of RAM 322, so large amounts of data can be stored on-chip before sending a bulk transmission to the receiving device 350 after every few seconds in order to save power. Furthermore, by enabling the Over-the-Air (OTA) boot-loading functionality, the system 300 can be reprogrammed wirelessly.
The system 300 can be powered in one application by a 3V coin cell battery (225 mAh) which can give a lifetime of 25 days based on 1-second logging intervals. In cases where the logging interval does not have to be so small, the battery life can be increased significantly while providing continuous monitoring of precious assets. The PSOC 800 is protected by an encapsulating material 900 using, for example, a glue gun, with only the antenna protruding out to prevent any damage to the electrical circuit itself as illustrated in
The performance of the sensor system 300 is now discussed. The individual performance of each sensor's capability was evaluated. The pressure sensing part gave a large range of operation from 0-22 kPa, which allows detection of hard presses to soft finger touches with a fast 320 ms response time, as illustrated in
The heat sensor capability shows in
From these experiments, it can be seen that all of the sensor's capabilities have a good linear range and performance with fast response times deeming it as a suitable anti-theft tag. Furthermore, the three in one sensor 100 or four in one sensor 100, if the plate 110 is allowed to freely move, results in the formation of a minimalist electronic interface which allows the sensor system 300 to result in a fully functional lightweight tag that can be easily attached to any asset that needs to be monitored.
As an example, the sensor system 300 was attached to a decoration object (a toy) using just a double-sided tape, as illustrated in
However, because all stimuli responses are received at a shared output node, simple thresholding techniques cannot be used to differentiate between each kind of response and thus signal processing algorithms will be required if it is desirable to identify each stimulus separately. This is a common phenomenon in the field signal processing where, for example, a microphone can be used to differentiate between unlimited number of words/sounds based on the unique pattern each word/sound makes in the microphone's analog output. However, in one embodiment it is not important to distinguish between the various stimuli applied to the sensor system 300, but only to determine if any of the three or four stimuli changes with a value larger than a given threshold.
The purpose of the sensor system 300 is to obtain a device that can detect not only touch, but other actions too, that fall in the category of attempts to tamper with the sensor or remove it from the asset itself. In order to detect tamper attempts, the sensor system has the touch sensing capability. Furthermore, if someone tries to remove the sensor by using heat or solvents to dissolve the adhesive that hold the sensor to the asset, the sensor system includes heat and liquid sensing functions for detecting such actions. In this respect,
The embodiments discussed herein demonstrate the fabrication and working principles of a multi-sensory sensory tag that can be attached, like an add-on, to existing objects to be monitored, prevent theft and unauthorized usage. The tag can be made employing DIY or industrial methods using paper-based (or common household) materials to keep the cost of the tag low while allowing for a customizable design at a reduced additional cost in comparison to its semiconductor sensor counterparts. Additionally, with a novel design of integrating three or four sensing capabilities into one structure, the sensor system exhibits a multi-stimuli response by using a single parallel plate capacitive structure. If one of the plates of the capacitor is allowed to freely rotate about an axis, the sensor system is also capable of detecting a tilt angle. This structure of the sensor results in a several folds reduction in power consumption and sensor electronic interface complexity. The tag is further integrated with a single BLE chip for achieving wireless communication.
The disclosed embodiments provide a sensor system having three or more sensing capabilities that are achieved with a single parallel plate capacitor, which is inexpensive to manufacture and uses low power. It should be understood that this description is not intended to limit the invention. On the contrary, the embodiments are intended to cover alternatives, modifications and equivalents, which are included in the spirit and scope of the invention as defined by the appended claims. Further, in the detailed description of the embodiments, numerous specific details are set forth in order to provide a comprehensive understanding of the claimed invention. However, one skilled in the art would understand that various embodiments may be practiced without such specific details.
Although the features and elements of the present embodiments are described in the embodiments in particular combinations, each feature or element can be used alone without the other features and elements of the embodiments or in various combinations with or without other features and elements disclosed herein.
This written description uses examples of the subject matter disclosed to enable any person skilled in the art to practice the same, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the subject matter is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims.
This application claims priority to U.S. Provisional Patent Application No. 63/003,522, filed on Apr. 1, 2020, entitled “A MULTI-SENSORY SECURITY DECAL WITH THREE SENSING CAPABILITIES IN A SINGLE STRUCTURE,” the disclosure of which is incorporated herein by reference in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 63003522 | Apr 2020 | US |
