Abstract:
An RF based state indicator for indicating the state of a control device is provided. The RF-based state indicator indicates the position of a control mechanism by using the position of the control mechanism to enable or disable an RF tag. An RF reader acquires RF transmitted data from enabled RF tags and uses the data to indicate or control an operation aspect of a device.

Description:
BACKGROUND 
       [0001]    The invention relates generally to the field of switches and similar devices used to control application of power to electrical loads. More particularly, the invention relates to the use of radio frequency identification (RFID) tags to indicate the state of an input device, such as a pushbutton, an electrical contact, a relay or contactor, and so forth. 
         [0002]    In the field of electronics, a wide range of control devices is used for controlling the delivery of power to a load. Such control devices may include various switches, relays, contactors and disconnects to control load power, circuit breakers to protect electrical circuits from overload, and pushbuttons and selector switches to facilitate user control of power circuit operation. Additionally, a variety of electrical devices are known and currently available for indicating the state of a control device. For example, an auxiliary contact is often coupled to a contactor so that the auxiliary contact produces an auxiliary signal, a low power electrical signal that indicates whether the contactor is open or closed. The auxiliary signal may be coupled, as an input signal, to other components within a power control or monitoring system. For example, the auxiliary signal may be used to turn on or off an indicator light, or some other component within the power electronics system. 
         [0003]    As power control systems and the logic required to control these systems become more complex, the number of state indicators increases, and the wiring coupled to the state indicators also increases. The increased wiring, in turn, leads to increased costs due to hardware requirements, connection labor and wiring maintenance. For example, control devices are often disposed within and on the doors of metal enclosures for load control purposes, with wires running between the door-mounted devices and internal devices. An increase in the number of wires increases maintenance problems due to wiring failure and inconvenient tethering of door-mounted devices with internal devices. Additionally, because there is a limit to how many wires can be placed under the common screw-terminal connectors, hardware is often added to control devices in the form of additional contacts driven by a mechanical or electromechanical shaft called an operator. Furthermore, each electrical connection creates the potential for vibration induced failure. Therefore, labor, maintenance and material costs could be reduced if the discrete wired state indicators could be replaced with wireless state indicators. 
         [0004]    The use of wireless state indicators, however, presents the difficulty of finding a suitable power supply. Often times a power supply is not available from the control device. Even when power is available, in the form of load power, the conversion from high voltage to low voltage adds additional cost. Batteries, on the other hand, incur additional maintenance costs due to the need for frequent replacement, and large batteries may interfere with control devices housed within the limited space of the metal enclosures. Furthermore, power scavenging techniques (based on vibration, or light or thermal gradients) typically provide too little power to achieve suitable control update rates, are too large, or depend on unreliable sources. 
         [0005]    Therefore, it may be advantageous to provide an improved state selection or indicator device. In particular, it may be advantageous to provide a state selection or indicator device that communicates wirelessly and employs a power supply that is reliable, maintenance free, and allows acceptable control update rates. 
       BRIEF DESCRIPTION 
       [0006]    Embodiments of the present invention use RFID tags as binary state indicators to indicate the state of power control devices and user input indications. An embodiment of an RFID tag, in accordance with the present invention, includes an RFID chip, which contains identification information and an RF antenna that is selectively coupled to or decoupled from the RFID chip to indicate the binary state of a power control device. An embodiment of a control system, in accordance with the present invention, includes one or more RFID tag readers electrically coupled to load control circuitry and one or more RFID tags in wireless communication with the RFID tag readers to effect changes in the state of the loads. 
     
    
     
       DRAWINGS 
         [0007]    These and other features, aspects, and advantages of the present invention will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein: 
           [0008]      FIG. 1  is a block diagram of an exemplary control system having a plurality of components, e.g. RFID tag reader, RFID state indicators, motors, etc. 
           [0009]      FIG. 2  is a schematic of an exemplary RFID state selector or indicator with a pushbutton actuator. 
           [0010]      FIG. 3  is a schematic of an exemplary RFID state selector or indicator with a pushbutton actuator, wherein the pushbutton is pushed into contact with RFID tag. 
           [0011]      FIG. 4  is a schematic of an exemplary selector switch, wherein the selector switch can optionally make contact with one of three normally-open RFID tags. 
           [0012]      FIG. 5  is a schematic of an auxiliary signal device, wherein an actuator makes contact with one of two normally-open RFID tags. 
           [0013]      FIG. 6  is a schematic of a short circuiting RFID tag in a transmitting configuration. 
           [0014]      FIG. 7  is a schematic of a short circuiting RFID tag in a short circuited configuration. 
       
    
    
     DETAILED DESCRIPTION 
       [0015]    Turning now to the drawings, and referring first to  FIG. 1 , an exemplary control system is illustrated and designated generally by reference numeral  10 . The control system  10  may include a plurality of RFID state selectors or indicators  12  (referred to herein simply as state indictors). Although  FIG. 1  depicts two RFID state indicators, it should be noted that the present invention is not limited to any particular number of RFID state indicators. In embodiments of the present invention, the RFID state indicators  12  are input devices used to facilitate user control of some operational aspect of the control system  10 , as will be explained below. In other embodiments, the RFID state indicators  12  are coupled to components within the control system  10  such as to provide an indication of the operational state of the control system  10 . 
         [0016]    Also included in the control system  10  is a reader  16 . The reader  16  may be any device known to those of ordinary skill in the art for communicating with, or “reading,” RFID tags. Readers are also commonly known as interrogators. The reader  16  iteratively acquires data from the RFID state indicators  12 , by transmitting a power/interrogation signal  18 . As described below, the RFID state indicators  12  may or may not emit a return signal  14  to the reader  16  in response to the power/interrogation signal  18 . The detection or non-detection of a return signal  14  corresponding with each RFID state indicator  12  informs the reader  16  of the binary state of each RFID state indicator  12 . 
         [0017]    The RFID state indicator  12  includes an RFID tag  22 . The RFID tag  22  includes an antenna  24  and a circuit  26 . The antenna  24  is both a receiving antenna and a transmitting antenna, designed to resonate at a particular frequency that corresponds with the communication frequency or frequencies of the reader  18 . The electrical energy received by the antenna  24  from the reader  16  through the power/interrogation signal  18  serves to power the circuit  26 . In certain embodiments of the present invention, the circuit  26  that holds a small amount of coded information, such as, for example, identification data, make and model, year of manufacture, etc. The circuit  26  is considered “passive” in that it does not have an independent power source and it does not initiate transfer of the information except in response to the signals from reader  16 . If the circuit  26  is coupled to the antenna  24 , the power/interrogation signal  18  from the reader  16  will power the circuit  26  and cause the circuit  26  to generate a control signal encoded with the data stored on the circuit  26 . 
         [0018]    The RFID state indicator  12  also includes an operator  30 , which selectively couples or decouples the antenna  24  from the circuit  26  (or that completes a circuit required to define the antenna). Whether the RFID tag  22  emits a return signal in response to the power/interrogation signal  18  depends on the state of the operator  30 . In certain embodiments of the present invention, the RFID tag  22  is normally open, as shown in  FIG. 1 . As such, the antenna  24  is decoupled from the circuit  26  by an interruption  28 , a small insulative gap on one side of the circuit  26 . The interruption  28  causes the circuit  26  to be inoperative. In the embodiment illustrated, the interruption actually opens the loop required to form the antenna. If the operator  30  is brought into contact with the RFID tag  22 , however, the interruption  28  is bridged by an electrical conductor, causing the circuit  26  to become operative. The operator  30  may be coupled to a control device, such as, for example, a pushbutton or a switch, thereby allowing a user to enable or disable a particular RFID tag  22 . Alternatively, the operator  30  may be coupled to a contactor so as to provide an indication of whether a particular circuit within the system is powered, or more generally, to indicate the operative state of the system. 
         [0019]    Information regarding the state of the RFID state indicator  12  is collected electronically by the reader  16  by sending out a power/interrogation signal  18 . If the power/interrogation signal  18  causes the antenna  24  to resonate, and if the antenna  24  is electrically coupled to the circuit  26 , the electrical energy received by the antenna  24  will power the circuit  26 , thereby inducing the circuit  26  to modulate its antenna with its coded information creating a reflected return signal  14  back to the reader  16 . In response to each power/interrogation signal, therefore, all of the operative RFID state indicators  12  within communications range follow protocol instructions encoded in the power/interrogation signal and if requested send a return signal  14  that carries, among other things, identification information. If an RFID state indicator  12  responds with a return signal  14 , the reader  16  is thereby informed that the particular RFID tag  22  corresponding with the transmitted identification information is operative, meaning that the particular input device coupled to the RFID tag  22 , e.g. pushbutton, switch, etc., has been engaged. The information thus gained by the reader  16  can then be used to control some part of the control system  10 . In other words, the detection of a return signal  14  with a particular identification code may indicate that a particular part of the control system  10 , which corresponds with the identification code, should be engaged or disengaged (e.g., turned on or off.) It should be noted that, in embodiments of the present invention, the “on” state is signified by the detection of a return signal  14  from the RFID state indicator  12 . In alternate embodiments, the “on” state is signified by the non-detection of a return signal  14  from the RFID state indicator  12 . 
         [0020]    Also included in the control system  10  is processing circuitry  36 . In one embodiment, the processing circuitry  36  is used to control the reader  16 . For example, the processing circuitry  36  may be used to adjust the frequency or intensity of the power/interrogation signal  18 , to control a read-cycle rate of reader  16 , or to trigger individual read cycles. Furthermore, processing circuitry may also be used to process the RFID state data received by the reader  16 . For example, the reader  16  may send RFID state data to the processing circuitry  36  after each read cycle. The processing circuitry  36  may then respond to the RFID state data by initiating an electronic output that manipulates the control system  10  in accordance with the desired operational state as represented by the RFID state data received. The processing circuitry  36 , therefore, includes a means of interpreting the RFID state data and associating the RFID state data with a desired operational state of control system  10 . In this regard, the control system  10  may optionally include a memory  38  coupled to the processing circuitry  36 . The memory  38  may, for example, contain a database that associates the identification information encoded in each RFID tag  22  with a particular controlled load  42 . Additionally, although some or all of the programming logic by which the processing circuitry  36  operates could be hardwired into the processing circuitry  36 , the memory  38  could also be used to hold a software program which determines, at least in part, how the processing circuitry  36  operates. 
         [0021]    Also included in the control system  10  is driver circuitry  40 . The driver circuitry  40  can include any means known in the art for powering components of a control or monitoring system. The driver circuitry  40  is electronically coupled to the processing circuitry  36 , the load  42  and a state indicator  48 , in this case an indicator light. The driver circuitry  40  receives an input signal from the processing circuitry  36  and optionally delivers a control signal to the load  42  and/or the indicator light  48 , thereby powering the load  42  and/or the indicator light  48 , depending on the state of the RFID state indicators  12 . In the embodiment shown in  FIG. 1 , the load  42  includes a motor  46  and switch gear  44 , such as, for example, a contactor. As stated above, however, the present invention is not limited to a particular type or combination of load components. 
         [0022]    Embodiments of the present invention also include a network  34 . The network  34  may include any type of communications network such as a local computer network. The network  34  can be used in conjunction with the processing circuitry  36 , or as an alternate technique, for controlling the control system  10 . For example, according to one embodiment, the reader  16  may send RFID state data to the network  34  through the interface  32 . Some or all of the acquired RFID state data may then be routed to the processing circuitry  36  or to the processor  50 . If the RFID state data is routed to the processor  50 , the processor  50  then processes the state data and sends control signals to the driver  52 , which, in turn, delivers load power or a control signal to the load  54 , thereby turning the power supplied to the load  54  on or off depending on the user desire and the system programming, as indicated by the RFID state data. According to another embodiment of the present invention, software and configuration data can also be downloaded from the network  34  to the processing circuitry  36  or the processor  50 . According to another embodiment, the network  34  is coupled to a computer system or other electronic device that includes a display, and RFID state data is used to display the current operational configuration of the control system  10 . 
         [0023]    It should be recognized that a control system in accordance with the present invention may take on a variety of configurations and include a wide variety of electrical devices, many of which are not depicted. For example, embodiments of the present invention may include several motors, switches, valves, pumps, indicator lights, alarms, breakers, etc. Additionally, some of the components depicted in  FIG. 1  may not be necessary, such as the interface  32  or the network  34 . The present invention is not intended, therefore, to be limited to the embodiment depicted in  FIG. 1 . In fact, RFID state indicators in accordance with the present invention can be adapted for use in any system that uses binary inputs or outputs. 
         [0024]    Turning now to  FIG. 2 and 3 , an exemplary embodiment of an RFID state indicator is shown.  FIG. 2  depicts an RFID state indicator  12  that includes a housing  20  an operator  30 , and an RFID tag  22 . The operator  30  is a pushbutton-style operator that includes a body  64 , conductive extensions  66  and  68 , and a biasing member  70 , such as a spring, that biases the actuator  30  away from the RFID tag  22 . The RFID tag  22  includes an antenna  24 , electrical contact pads  56  and  68  separated by interruptions  28 , and a circuit  26 . In the embodiment shown in  FIG. 2 , the RFID tag  22  is inoperative because the interruption  28  prevents the antenna  24  from electrically coupling to the circuit  26 . Because the RFID tag  22  is inoperative, the circuit  26  will not power up or send a return signal in response to a power/interrogation signal sent by an RFID tag reader. In the embodiment shown in  FIG. 3 , however, the operator  30  has been depressed, and the conductive extensions  66  and  68  have bridged the interruptions  28  between the electrical contact pads  56  and  58 . Thus, the RFID tag  22  shown in  FIG. 3  has become operative. Therefore, if an RFID reader sends a power/interrogation signal of the proper frequency, circuit  26  will send a return signal containing at least the identification information stored on the chip. 
         [0025]    It should be recognized that in the embodiment shown in  FIGS. 2 and 3 , the lack of a return signal could indicate a disengaged pushbutton or a failure of the RFID tag  22  to operate properly. Therefore, depending on the specific application, it may be desirable to include a second RFID tag that will indicate the normal or disengaged position of the actuator  30 . In this regard, an embodiment of the present invention may include a second RFID tag that is enabled when the actuator  30  is in the disengaged position shown in  FIG. 2 . With two RFID tags, a return signal will be expected whether the pushbutton is engaged or disengaged, and a failure to detect a return signal indicates a failure of an RFID tag or a failure to read an RFID tag, facilitating detection of failures. 
         [0026]    RFID tags in accordance with the present invention may include various embodiments not depicted by  FIGS. 2 and 3 . Regarding the antenna  24 , embodiments of the present invention may include any form of antenna known by those of ordinary skill in the art. For example, antenna  24  could be electrically and/or magnetically excited and may include one or more conductive loops, a conductive spiral, a conductive dipole or monopole, an inductor, a capacitor, or some combination thereof. The antenna  24  may also be printed or etched onto a substrate material or may be comprised of conductive wire. Additionally, the antenna  24  may include a material designed to alter the resonance characteristics of the antenna such as a ferromagnetic material. The design of the antenna  24  will be an ordinary engineering task involving the selection of a particular substrate, substance, geometry, etc. that is optimal for the particular design requirements that are chosen for a particular implementation of the present invention such as frequency, directionality, gain and power handling. 
         [0027]    Additionally, embodiments of the present invention may include several alternative configurations for isolating the circuit  26  from the antenna  24 . For example, in some embodiments, an electrical interruption is included on only one side of the circuit  26 . Alternatively, one or more electrical interruptions may be placed at any position along the length of antenna  24 . Additionally, in some embodiments, the interruptions  28  will be as close as possible to circuit  26  to lessen the degree of residual coupling that may occur due to the short conductive segments that may protrude from the circuit  26  depending on the location of the interruptions. 
         [0028]    Furthermore, in addition to electrically isolating the circuit  26  from the antenna  24 , embodiments of the present invention include an RFID tag  22  that is made inoperative by preventing the antenna  24  from resonating in response to the power/interrogation signal emitted by the reader  16 . For example, the operator  30  may bring one or more additional conductors into proximity or contact with the antenna  24 , thereby altering the resonant characteristics of the antenna  24  such that it will not effectively resonate at the frequency transmitted by the reader  16 . In this way, the RFID tag  22  is disabled because the antenna  24  will not transmit electrical power to the circuit  26 . 
         [0029]    Additionally, RFID tags in accordance with the present invention may be normally operative or normally inoperative. In other words, if an RFID tag is normally operative, the circuit  26  and the antenna  24  will be electrically coupled and operative without the interposition of the operator  30 , and the engagement of the operator  30  will disable the RFID tag in some way. On the other hand, if an RFID tag is normally inoperative, the circuit  26  and the antenna  24  will be electrically decoupled or, in some other way, disabled without the interposition of the operator  30 , and the engagement of the operator  30  will enable the RFID tag. 
         [0030]    Regarding the circuit  26 , the circuit  26  can be any type of semiconductor circuit known in the art, such as, for example, a CMOS integrated circuit. Although the circuit  26  will ideally be passive, i.e. not requiring a power source other than the power/interrogation signal, the circuit  26  could optionally be active, or semi-passive. In other words, the circuit  26  could be fully or partially powered by a battery or some other power source other than the reader  16 . Additionally, the circuit  26  may hold and transmit a range of useful information, such as, for example, RFID tag model, style, serial number, date of manufacture, physical location, etc. This data may then be used to maintain the RFID tags or replace RFID tags. For example, the data may be used to indicate the location of a particular RFID tag and whether a particular RFID tag is old or outdated or may need to be replaced as part of regular maintenance. To hold the data, the circuit  26  may include any form of electronic memory known in the art including read-only memory, writable memory or some combination of both. 
         [0031]    Turning now to  FIG. 4 , an exemplary embodiment of a rotary device  72 , in accordance with the present invention, is depicted. The rotary device  72  comprises three normally inoperative RFID tags  74 ,  76  and  78  aligned along an arc  80 , and a rotary operator  82  anchored at the radial center of the arc  80 . The operator  82  is rotatable, such that the conductive portions of the operator  82  selectively enable one of the RFID tags  74 ,  76 , or  78 . The operator  82 , may be human operated, or may be mechanically coupled to another rotating element (not depicted) whose position is to be determined by the rotary device  72 . The operator  82  may also include one or more detent mechanisms to hold the operator  82  more securely in contact with one of the RFID tags  74 ,  76  or  78 . Additionally, the rotary device  72  may include any number of RFID tags aligned along the arc  80 . In embodiments of the present invention, the rotary device  72  includes one or more additional arcs, not depicted, along which additional RFID tags are aligned. The additional RFID tags may be staggered radially so that only one RFID tag is enabled for any position of operator  82 , or the additional RFID tags may be radially aligned so that more than one RFID tag is enabled for a particular position of operator  82 . 
         [0032]    Turning now to  FIG. 5 , an exemplary embodiment of an auxiliary signal device  84  is depicted. The auxiliary signal device  84  may be a relay, contactor, disconnect switch or any other device that controls a primary current path via an input signal. The auxiliary signal device  84  includes a control terminal  88  coupled to a controller  96 , which controls the position of an operator  92  by inducing a current flow in a coil  94 . The auxiliary signal device  84  also includes a moveable contact  100  connected to an operator  92  through a linkage  98 , such that movement of the operator  92 , will bring the moveable contact  100  into contact with a stationary contact  102 , thereby completing an electrical path between a set of output terminals  90 . 
         [0033]    Also included in the auxiliary signal device  84  are two normally inoperative RFID tags  108  and  114 . Depending on the position of the operator  92 , RFID tag  108  is made operative by conductive extensions  104  and  106 , or RFID tag  114  is made operative by conductive extensions  110  and  112 . As depicted in  FIG. 5 , the current position of the operator  92  is such that RFID  108  is operative and RFID tag  114  is inoperative. In the embodiment depicted in  FIG. 5 , a power/interrogation signal from an RFID tag reader would power RFID tag  108 , and RFID tag  108  would send a return signal, while RFID tag  114  would remain silent. The return signal will, therefore, indicate that auxiliary signal device  84  is off, i.e. output terminals  90  are decoupled. If a control signal is applied to the control terminals  88 , the operator  92  will move downward, bringing the movable contact  100  into contact with the stationary contact  102 , completing the circuit between the terminals  90 . Furthermore, conductive extensions  104  and  106  will move out of contact with RFID tag  108 , disabling RFID tag  108 , and conductive extensions  110  and  112  will move into contact with RFID tag  114 , enabling RFID tag  114 . With this new actuator position, a power/interrogation signal from an RFID tag reader will power RFID tag  114 , and RFID tag  114  will send a return signal, while RFID tag  108  will remain silent. The return signal will, therefore, indicate that auxiliary signal device  84  is on, i.e. output terminals  90  are coupled. 
         [0034]    In certain embodiments of the present invention, the auxiliary signal device  84  includes only one RFID tag, wherein the enablement of the RFID tag indicates one actuator position and the disablement of the RFID tag indicates the opposite position. Using one RFID tag may, however, lead to uncertainty about whether the lack of a return signal was due to the disablement of the RFID tag or failure of the RFID tag to operate properly. Therefore, the use of two RFID tags, as depicted in  FIG. 5 , provides a higher level of assurance of the state of auxiliary signal device  84 , because at least one return signal will always be expected and the lack of a return signal will generally result from device failure or a failure to read either RFID tag. 
         [0035]    Turning now to  FIGS. 6 and 7 , an embodiment of a short-circuiting RFID state indicator  116  is shown. The short-circuiting RFID state indicator  116  includes an RFID tag with a circuit  120  and an antenna  118 . Because the electrical coupling between the antenna  118  and the circuit  120  is built into the RFID tag, the RFID tag is normally operative and thus does not require the interposition of a conductive element to be enabled. Also included in the short-circuiting RFID state indicator  116  is an operator  30  that includes conductive extensions  66  and  68  and a conductive link  122 . As long as the operator  30  remains disengaged, the RFID tag will remain operative and will, therefore, send a return signal  14 . If, however, the operator  30  is moved into contact with an exposed conductive portion of the antenna  118  of the RFID tag, as shown in  FIG. 7 , the conductive extensions  66  and  68  and the conductive link  122  will create a short circuit across the circuit  120 , thereby decoupling the antenna  118  from the circuit  120 . As discussed above, other means of disabling an RFID tag may be envisioned. For example, in embodiments of the present invention the interposition of an operator serves to shield the antenna  118 . In other embodiments, the interposition of an operator changes the geometry and hence the resonance characteristics of the antenna  118  such that it no longer effectively resonates at the frequency emitted by the reader. In another embodiment, the conductive elements  66  and  68  and conductive link  122  are placed permanently on the tag instead of on the operator and the conductive link  122  is composed of a magnetic reed switch that selectively enables and disables the RFID tag by movement of a magnet carried on the tag end of the operator. 
         [0036]    As described above, the device of the invention allows for altering performance of the antenna and/or of the circuit coupled or couplable to the antenna so that the reader or interrogator may read or be prevented from reading the data in the circuit, and thereby gather an indication of the state of the device (e.g., position of the operator). As noted above, this may be done in a variety of manners. For example, the operator may complete or interrupt a conductive path defining the antenna (e.g., making or breaking a loop forming the antenna), or may short or unshort the antenna (e.g., connect or disconnect the antenna with another component or conductive path). Because the antenna operates by returning a signal to the interrogator, the operator may alter an electromagnetic property of the antenna to allow or prevent such transmission, or may shield or unshield the antenna, or change a resonant frequency of the antenna. Moreover, two or more such antenna may be utilized to provide a multi-state device in which signals from one circuit available from one antenna indicate a first state, and signals from a further circuit available from another antenna indicate a second state. 
         [0037]    While only certain features of the invention have been illustrated and described herein, many modifications and changes will occur to those skilled in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the invention.