U.S. patent application number 12/459585 was filed with the patent office on 2010-09-16 for rfid power control and monitoring system.
This patent application is currently assigned to New Jersey Microsystems, Inc.. Invention is credited to William N. Carr.
Application Number | 20100231407 12/459585 |
Document ID | / |
Family ID | 42730242 |
Filed Date | 2010-09-16 |
United States Patent
Application |
20100231407 |
Kind Code |
A1 |
Carr; William N. |
September 16, 2010 |
RFID power control and monitoring system
Abstract
A system for monitoring parameters associated with a device,
such as current, voltage, power, temperature, energy consumed,
moisture, fluid levels and flow, wind speed, identification
parameters, and repair history. The system includes the use of
hybrid RFID sensor tags including a combination of active,
semi-passive, and passive RFID circuits. Hybrid tags are attached
to electrical system components. Standalone electrical components
and generators and those connected to the electrical grid may be
monitored. Data collected and stored in the hybrid tags may be
accessed via a wireless communication link between hybrid tags and
either active scanners or a passive interrogators. The data
collected and processed from the hybrid tags may be provided to a
user via the Internet or another wired or wireless communication
network.
Inventors: |
Carr; William N.;
(Montclair, NJ) |
Correspondence
Address: |
DARBY & DARBY P.C.
P.O. BOX 770, Church Street Station
New York
NY
10008-0770
US
|
Assignee: |
New Jersey Microsystems,
Inc.
|
Family ID: |
42730242 |
Appl. No.: |
12/459585 |
Filed: |
July 2, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61209897 |
Mar 13, 2009 |
|
|
|
Current U.S.
Class: |
340/691.1 ;
340/10.1; 340/10.3; 340/10.51 |
Current CPC
Class: |
H04Q 2209/883 20130101;
H04Q 2209/47 20130101; H04Q 9/00 20130101; Y02B 10/30 20130101;
H04Q 2209/60 20130101; G06K 19/0723 20130101; H04Q 2209/25
20130101 |
Class at
Publication: |
340/691.1 ;
340/10.1; 340/10.3; 340/10.51 |
International
Class: |
G06K 7/00 20060101
G06K007/00 |
Claims
1. An RFID system comprising: a hybrid sensor tag, comprising an
active RFID circuit and a passive RFID circuit, the active RFID
circuit being communicatively coupled to the passive RFID circuit;
an interrogator, operative to wirelessly communicate with the
passive RFID circuit; and a scanner, operative to wirelessly
communicate with the active RFID circuit, wherein the passive RFID
circuit is operative to enable the active RFID circuit when the
active RFID circuit is in a sleep mode.
2. The system of claim 1, wherein the scanner is operative to
exchange data with the active RFID circuit across a star or mesh
network.
3. The system of claim 1, wherein the interrogator is a mobile
device.
4. The system of claim 1, wherein the hybrid sensor tag further
comprises a sensor that is communicatively linked to the active
RFID circuit and operative to monitor a parameter associated with a
component.
5. The system of claim 4, wherein the sensor is operative to
monitor energy delivered to a load.
6. The system of claim 4, wherein the parameter is an environmental
parameter.
7. The system of claim 6, wherein the environmental parameter
includes at least one of temperature, humidity, and sound.
8. The system of claim 7, wherein the component is one of a
building, electrical equipment, a solar panel, and a wind turbine
electrical generator.
9. The system of claim 4, wherein the parameter is fluid flow and
the component is a pipe.
10. The system of claim 1, wherein the passive circuit is operative
to: store information; report wirelessly the information to the
interrogator.
11. The system of claim 10, wherein the information includes at
least one of identification information, installation detail
information, and repair history information.
12. The system of claim 1, wherein the hybrid sensor tag is
attached to at least one of a solar panel, an inverter, an
electrical transformer, a streetlamp, a power pole, a supply bin, a
vehicle, a person, and a tool.
13. The system of claim 1, wherein the interrogator and scanner are
connected via a communications link to at least one of a local area
network, a wide area network, and a telephone network.
14. The system of claim 5, wherein the active RFID circuit is
operative to report energy usage data to the scanner.
15. The system of claim 1, wherein the active RFID circuit is
operative to communicate using at least one of IEEE 801.15.4,
ZigBee, and 802.11 communication protocol and the passive RFID
circuit is operative to communicate using at least one of ISO 18000
and EPC Gen2.
16. The system of claim 4, wherein the hybrid tag further comprises
an alarm indicator, operative to signal a status of the monitored
parameter.
17. The system of claim 1 where the hybrid tag is further operative
to control a light intensity of a light source connected to the
hybrid tag.
18. The system of claim 17, wherein the scanner is operative to
remotely control the intensity of the light source connected to the
hybrid tag.
19. The system of claim 17, wherein the interrogator is operative
to remotely control the intensity of the light source connected to
the hybrid tag.
20. A hybrid sensor tag comprising: an active RFID circuit, powered
by an energy source located within the tag; and a passive RFID
circuit, communicatively coupled to the active RFID circuit;
wherein the passive RFID circuit is operative to enable the active
RFID circuit when the active RFID circuit is in a sleep mode, and
wherein the hybrid sensor tag is operative to communicate with RFID
nodes.
21. The hybrid sensor tag of claim 20, further comprising an
integral power source that powers the active RFID circuit if power
from the external energy source is insufficient.
22. The hybrid sensor tag of claim 21, wherein the external energy
source is a photovoltaic solar panel.
23. The hybrid sensor tag of claim 21, wherein the external energy
source is an AC power grid.
24. The hybrid sensor tag of claim 20, further comprising a memory,
and wherein the active RFID circuit and the passive RFID circuit
are operative to store data in the memory and retrieve data from
the memory.
25. The hybrid sensor tag of claim 24, wherein the active RFID
circuit and the passive RFID circuit are operative to access and
modify data stored in the memory via a common bus.
26. The hybrid sensor tag of claim 24, wherein the memory is a
dual-port digital memory that provides separate data bus
connections to the active RFID circuit and the passive RFID
circuit.
27. The hybrid sensor tag of claim 20 further comprising a sensor
that is communicatively coupled to the active RFID circuit and is
operative to monitor an amount of energy delivered to a load.
28. The hybrid sensor tag of claim 20 further comprising a sensor
that is communicatively coupled to the active RFID circuit and is
operative to monitor an environmental parameter.
29. The hybrid sensor tag of claim 28, wherein the environmental
parameter is at least one of temperature, humidity, and sound.
30. The hybrid sensor tag of claim 20 further comprising a sensor
that is communicatively coupled to the active RFID circuit and is
operative to generate slow scan video images.
31. The hybrid sensor tag of claim 20 further comprising an RF
antenna that is electrically coupled to both the passive RFID
circuit and the active RFID circuit.
32. The hybrid sensor tag of claim 20, wherein the active RFID
circuit and the passive RFID circuit are operative to communicate
wirelessly using a frequency in the range of 300 MHz to 10 GHz.
33. A hybrid sensor tag comprising: an active RFID circuit, powered
by an energy source located within the tag; and a passive RFID
circuit, communicatively coupled to the active RFID circuit;
wherein the hybrid sensor tag is operative to communicate with RFID
nodes, wherein the passive RFID circuit is operative to
repetitively enable the active RFID circuit when the active RFID
circuit is in a sleep mode with a predetermined period, and wherein
the active RFID circuit is operative to enter the sleep mode after
a predetermined period of time elapses after the active circuit is
enabled.
34. The hybrid sensor tag of claim 33 further comprising a sensor
that is communicatively coupled to the active RFID circuit and is
operative to monitor an amount of energy delivered to an electrical
power generation device.
35. The hybrid sensor tag of claim 33 further comprising a sensor
that is communicatively coupled to the active RFID circuit and is
operative to control an electrical power generation device.
36. The hybrid sensor tag of claim 33 further comprising a sensor
that is communicatively coupled to the active RFID circuit and is
operative to monitor at least one of temperature, humidity,
pressure, inclination, a status of a door, and material strain.
37. The hybrid sensor tag of claim 33 further comprising a sensor
that is communicatively coupled to the active RFID circuit and is
operative to identify and track at least one vehicle.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] The present application claims priority under 35 U.S.C.
.sctn.119(e) from the following patent application which is
incorporated herein by reference in its entirety: U.S. Provisional
Patent Application Ser. No. 61/209,897, filed Mar. 13, 2009,
entitled RFID Power Monitoring and Control System.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to Radio-frequency
identification (RFID).
[0004] 2. Description of the Related Art
[0005] RFID is the use of an object, which is typically referred to
as an RFID tag, for the purpose of identification and tracking
using radio waves. Generally, the RFID tag is physically attached
to a product, person, or other object. RFID tags can be categorized
into three basic types: active, passive, and semi-passive.
[0006] An active RFID tag is a wireless device that is powered
locally and contains a local radio frequency (RF) receiver and a
source of RF power that actively transmits to a remotely located
network node. An active RFID tag can be powered from a local
battery or from an external source, such as the AC power grid or a
photovoltaic solar panel. The present state of the art for a
wireless network consisting of active RFID tags permits the network
to be extended over many miles. For example, the current state of
the art for an active ZigBee circuit transponder operating at 915
MHz operating within the US FCC Part 15 RF emission limits with an
appropriate antenna is approximately 10 miles. ZigBee is a
low-cost, low-power, wireless mesh networking standard.
[0007] A passive RFID tag is a wireless device that is powered by
RF power received from a nearby interrogator. A passive RFID tag
contains a local radio receiver but it communicates with the
interrogator only by modulating and reflecting the RF radiation
provided by the interrogator. This method is sometimes referred to
as modulated backscatter.
[0008] The passive RFID tag receives wireless data from the
interrogator by demodulating an RF carrier received from the
interrogator and decoding the data from the demodulated signal. The
passive RFID tag transmits data to the interrogator by reflecting
the RF radiation provided by the interrogator and modulating data
onto the reflected radiation by adjusting the load impedance of the
tag antenna. The interrogator decodes the data from the reflected
radiation.
[0009] In a fully passive RFID tag there are no local power sources
such as batteries, solar cells, solar panels, piezoelectric
generators, or the power grid. A fully passive RFID tag can be
powered by a circuit that scavenges power from incident RF
originating from an interrogator. The present state of the art for
a passive RFID network permits a separation between the passive
RFID tag and a wireless interrogator of up to 60 meters.
[0010] A semi-passive RFID tag provides the passive tag function as
a subset of its total function. However, a semi-passive RFID tag
also receives power locally. During normal operation the
semi-passive RFID tag does scavenge power from the remote
interrogator. The semi-passive RFID tag is usually powered locally
from a battery, the power grid, solar cells, solar panels, wind
generation source, vibration scavenging source, piezoelectric power
source, or some other power source. The local power supply is given
priority in supplying power to the tag by a local prioritizing
power control circuit. When the local power supply is not adequate
the prioritizing power-control circuit gates in power to the
passive tag by scavenging from the RF incident energy supplied by
the remote interrogator device.
[0011] Traditional RFID systems use tags containing digital memory.
The digital memory within the tag can be read from or written to by
an interrogator. These traditional systems do not include sensors
to determine the state or condition of other devices, and are thus
limited to applications that require only storage and retrieval of
data, such as inventory control systems. Additionally, traditional
RFID tags include only one type of RFID circuit, and thus, must
either include a power source to constantly supply power to an
active RFID circuit, or are limited to applications requiring only
a passive RFID circuit.
[0012] Therefore, there is need in the art for a more complex RFID
system. Specifically, there is a need for a system including an
RFID tag that contains both an active and a passive circuit.
Additionally, there is a need for an RFID tag that can sense,
control, log, and monitor electrical and identification parameters
from a power source or a power load device. The present invention
satisfies these and other needs.
BRIEF SUMMARY OF THE INVENTION
[0013] According to a first aspect of the present invention, a
hybrid RFID tag is described. The hybrid RFID tag contains both an
active RFID circuit and a passive RFID circuit. The Active RFID
circuit is typically powered by an external source such as the AC
power grid or a solar panel. If this power source becomes
unavailable or is degraded, e.g., during a brown-out, the active
RFID circuit enters a sleep mode, which reduces the power required
by the active RFID circuit. The passive RFID circuit, which does
not require local power, but instead scavenges power from received
radio frequency transmissions, can direct the active RFID circuit
to exit the sleep mode. The passive RFID circuit may be directed to
wake up the active RFID circuit by an interrogator. An interrogator
is a device, which is typically handheld, that can communicate with
passive RFID circuits.
[0014] In accordance with another aspect of the present invention,
the active RFID circuit is communicatively coupled to a plurality
of sensors. The sensors may measure properties associated with a
device or object. For example, the voltage, current, or power
provided to a load or the rate of fluid flow through a pipe may be
measured. The sensors may also be used to measure environmental
parameters such as temperature, wind speed, and humidity. Sensors
may also record audio, still images, and video images, including
slow scan video. The active RFID circuit may log data retrieved
from the sensors in a non-volatile memory such as ferroelectric
memory, magnetoresistive memory, flash memory, static ram provided
with a battery backup, or a hard disk drive. The passive circuit
may also have access to the non-volatile memory.
[0015] In accordance with yet another aspect of the present
invention, an RFID system comprising hybrid tags and one or more
network interrogators and scanners is described. The system may
include a network of active nodes configured in a star or mesh
network. A network scanner communicates with the hybrid tags via
this network of active nodes. The network scanner can communicate
with the active RFID circuit to control the active RFID circuit and
to retrieve sensor data or other information from the active RFID
circuit.
[0016] The system also includes at least one interrogator, which
communicates with the passive circuit in each of the hybrid tags.
The interrogator may direct the passive circuit in the hybrid tag
to take the active circuit in the hybrid tag out of sleep mode. The
interrogator may also download previously stored sensor data by
directing the passive circuit to retrieve this data from the shared
non-volatile memory.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
[0017] The foregoing and other features of the present invention
will be more readily apparent from the following detailed
description and drawings of illustrative embodiments of the
invention in which:
[0018] FIG. 1 is a schematic block diagram of an RFID hybrid tag
according to an embodiment of the present invention;
[0019] FIG. 2 is a functional diagram of an RFID hybrid system
according to an embodiment of the present invention; and
[0020] FIG. 3 is a functional diagram of an RFID hybrid system tag
and its immediate interfaces according to an embodiment of the
present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0021] Aspects of the invention are disclosed in the following
description and related drawings directed to specific embodiments
of the invention. Alternate embodiments may be devised without
departing from the spirit or the scope of the invention.
Additionally, well-known elements of exemplary embodiments of the
invention will not be described in detail or will be omitted so as
not to obscure the relevant details of the invention. Further, to
facilitate an understanding of the description, discussion of
several terms used herein follows.
[0022] The word "exemplary" is used herein to mean "serving as an
example, instance, or illustration." Any embodiment described
herein as "exemplary" is not necessarily to be construed as
preferred or advantageous over other embodiments. Likewise, the
term "embodiments of the invention" does not require that all
embodiments of the invention include the discussed feature,
advantage, or mode of operation.
[0023] FIG. 1 is a schematic block diagram of a hybrid tag 105
according to an embodiment of the present invention. The hybrid tag
includes both an active RFID circuit ("active circuit") 60 and
either a fully passive or a semi-passive RFID circuit ("passive
circuit") 80. In the following description, semi-passive RFID
circuits and fully passive RFID circuits are referred to
generically as passive circuits.
[0024] As illustrated in FIG. 1, the hybrid tag 105 may include
separate antennas for the active and passive circuits 60, 80. For
example, the active circuit 60 may use a single quarter wavelength
whip antenna 100. The passive circuit 80 may use a resonant antenna
130 that contains cavities that are each tuned to a frequency of
interest. Alternatively, the active circuit 60 and the passive
circuit 80 may share a single antenna.
[0025] Sensors 50, which may be connected to components of interest
with wired or wireless connections, are also included. For example,
a sensor 50 may be connected to a DC solar panel, DC-to-AC solar
panel inverter, or an AC power grid. Each sensor 50 may be located
in its entirety on the hybrid tag 105. Alternatively, a sensor 50
may be distributed between the tag 105 and the component of
interest.
[0026] Sensors 50 may be configured to measure voltage, current,
power, fluid flow, or any other measureable property associated
with the component of interest. If an AC circuit is monitored,
separate sensors 50 may be used for each phase of the AC circuit.
The neutral wire of the AC circuit may also be monitored. For
example, electrical current may be measured with a Hall sensor for
AC and DC current flow, a Rogowski coil for sensing AC current
levels, or a shunt resistor. Power measurements may be obtained by
integrating the current-voltage product over time. Cumulative
energy may be determined by integrating the power over a lapsed
time period. Specific circuits for sensing current, voltage, power,
and temperature are currently included in the function of ICs
including the Texas Instruments MSP430FE4232 and the ST
Microelectronics STM01FTR.
[0027] Sensors 50 may also be configured to monitor environmental
parameters. For example, a sensor 50 may monitor parameters such as
temperature, pressure, wind speed, and humidity. Sensors may
monitor other parameters associated with an object, such as
inclination, the status of door openings, or material strain.
Sensors 50 may also record audio, still images, and video images.
Due to the limited bandwidth generally available to RFID tags, slow
scan video may be used instead of full rate video. Slow scan video
provides multiple still images at a rate that is generally lower
than full rate video, but still effectively represents
environmental change over time.
[0028] A memory 120 may also be included in the hybrid tag 105. The
memory 120 may be a semiconductor integrated circuit (IC) that
includes EEPROM and ferroelectric memory. Alternatively, the memory
120 can be a magnetoresistive memory, flash memory, static ram
provided with a battery backup, a hard disk drive, or any other
type of memory element known in the art. The memory 120 may be
connected to the active and passive circuits 60, 80. Both the
active circuit 60 and the passive circuit 80 may be able to write
to and read from the memory 120. The connection to the memory 120
may be shared between the active circuit 60 and the passive circuit
80. Alternatively, the memory 120 may be a multiport device having
separate connections to each of the active circuit 60 and the
passive circuit 80.
[0029] The active and passive circuits 60, 80 may also include a
control component. For example, the control component may be a
microprocessor, a microcontroller, or a programmable device, such
as a field programmable gate array (FPGA) or a complex programmable
logic device (CPLD). In the active circuit 60, the control
component is operative to process information retrieved from the
sensors 50. In both the active circuit 60 and the passive circuit
80, the control component may implement software that is operative
to perform functions such as communicating with the memory 120 and
other devices. In accordance with an embodiment of the present
invention, it is possible for new software to be downloaded into
the active and passive circuits 60, 80 from another device.
[0030] The active and passive circuits 60, 80 may also be capable
of controlling components of interest. For example, the active and
passive circuits 60, 80 may be connected to switches or other
control circuitry associated with a component of interest. The
component of interest can thereby be controlled or influenced by
the active and passive circuits 60, 80.
[0031] The active circuit 60 is normally powered externally from
the AC power grid or from a source such as a photovoltaic solar
panel. A battery 110 or other local source may be included to power
the active circuit 60 when external power is not available.
[0032] The passive circuit 80 is normally powered by scaveriging
transmitted RF power from an interrogator 90. The hybrid tag 105
contains an RF micropower scavenging circuit 85 for providing DC
power to the passive tag circuit 80. The scavenging circuit 85 may
also provide power to the memory 120. This allows for access to the
passive circuit 80 and the memory 120 when a separate power source
is not available. In the case where a single antenna is shared by
the active circuit 60 and the passive circuit 80, the RF micropower
scavenging circuit 85 is isolated from the transmit port of the
active circuit 60 by a directional coupler to reduce the loss of
transmit power from the active circuit 60.
[0033] In the case of a hybrid tag that includes a semi-passive
circuit, the onboard RF micropower scavenging circuit 85 is
supplemented variously by another source of power available to the
hybrid tag 105, such as a battery, the power grid, a solar panel, a
wind power generator, or a piezoelectric source. The separate
source of power permits the semi-passive circuit to operate without
requiring scavenged RF power from an interrogator 90. A
semi-passive hybrid tag also provides increased range as compared
with a hybrid tag 105 that contains only a fully passive
circuit.
[0034] The active circuit 60, passive circuit 80, sensors 50, and
other components of the hybrid tag 105 may all be located on a
single printed circuit board (PCB). Alternatively, the components
of the hybrid tag 105 may be distributed across multiple PCBs that
are connected to each other. The antennas 100, 130 may be separate
components or, alternatively, the antennas 100, 130 may be formed
using metallic circuit traces on the PCB, as is well known in the
art.
[0035] FIG. 2 illustrates an exemplary embodiment of an energy
metering system according to the present invention. In this
embodiment, the metering system includes at least one RFID hybrid
tag 105 with an active RFID circuit 60 connected to a passive RFID
circuit 80.
[0036] Hybrid tags 105 within the system may communicate with other
devices and with one another using wireless protocols. The active
circuits 60 may communicate with protocols such as the
international communications standard 802.15.4, ZigBee, 802.11, and
Bluetooth. The passive circuits 80 may communicate via
international communications standards such as ISO 18000 and EPC
Gen2. The practical frequency range for these wireless operations
operating at low and micro power levels is from 300 MHz to 20 GHz
with the current state of the art.
[0037] A network scanner 210 may be used to monitor the status of
the components of interest by accessing the active circuit 60.
Typically, the scanner 210 is permanently interfaced via program
control into a local area network (LAN) 260, the Internet 240, the
telephone network, or some other communications network. In one
embodiment, external active RFID nodes 200, 220, 230 communicate
with the active circuit 60. The external nodes 200, 220, 230
comprise a star or mesh network with multiple communication paths
linking the active circuit 60 to the network scanner 210. The
network scanner 210 is programmed to scan the network and retrieve
sensor data selectively from the sensors 50.
[0038] Similarly, an interrogator 90 may be used to retrieve
information from the passive circuit 80. Typically, the
interrogator 90 is a mobile device which interfaces to a PC or PDA
through a USB port. The interrogator 90 may also access a LAN 260,
the Internet 240, or the telephone network. The interrogator 90 may
be able to retrieve data from the tag when the power source for the
tag is unavailable if the data stored on memory 120 in the tag can
be read from and written to by the passive circuit 80 when the
source of power for the hybrid tag 105 is not available.
[0039] Although typically a handheld device, the interrogator 90
can be located in a fixed location. Alternatively, the interrogator
90 may be mounted in or on a vehicle.
[0040] The interrogator 90 contains circuitry that enables it to
access the passive circuit 80. The interrogator 90 may also include
an active RFID circuit. This feature permits the interrogator 90 to
access both the active and passive circuits 60, 80 of the hybrid
tag 105.
[0041] The active circuit 60 can be controlled from external wired
and wireless network nodes, such as a PC based LAN node 270 or for
programming in manufacturing through a JTAG bus. The active circuit
60 may have a wireless connection into the mesh or star network of
RFID nodes 200, 220, 230 and the network scanner 210 in addition to
the wired local connection to the passive circuit 80. Communication
including control of the active RFID circuit is obtained variously
through the RFID nodes 200, 220, 230; directly through the
interrogator 90; or indirectly from the interrogator 90 through the
passive circuit 80. Data, including sensor data, may be
communicated to and from the hybrid tag 105 through the network
scanner 210 and a concentrator 250 to the Internet 240, a telephone
network, a local LAN 260, a proprietary network, or any combination
thereof by methods well known in the art.
[0042] The interrogator 90 can control the active circuit 60 via
the passive circuit 80. The interrogator 90 may communicate with
the PC Based LAN Node 270 via a wireless network, a LAN 260, a wide
area network(WAN) 240, such as the Internet, or some other
communications network. The PC based LAN Node 270 can thereby
control the interrogator 90. The concentrator 250 may also be used
to connect multiple interrogators 90 to a communications
network.
[0043] Applications for the system of the present invention include
monitoring and control of photovoltaic solar panels and windmill
power generation in a network that also includes ancillary devices
such as light sources, environmental sensors, moisture sensors,
water level sensors, and slow scan video imaging equipment. The
interface of each of these sensors to the control component in the
active circuit 60 is a technology well known to those in the field
of sensor systems. Applications are not limited to energy metering
systems. For example, hybrid tags 105 could be used for
identification of logs in a timber operation, containers in a
storage or transportation network, railcars, and vehicles.
[0044] The hybrid tag 105 is typically mounted on electrical
components or electrical equipment. The active circuit 60 is
connected to sensors 50 that the active circuit 60 uses to monitor
electrical power and energy. As illustrated in FIG. 2, voltage and
current measuring wire leads are connected to components of
interest such as a DC solar panel 10, a DC-to-AC solar panel
inverter 40, the AC power grid 30, or a street lamp 20. It should
be understood that street lamp 20 may represent other loads in
place of, or in addition to, a street lamp.
[0045] For example, as illustrated in FIG. 2, the sensor 50
connected to the streetlamp may be monitored to determine if the
light is on or off. This status information may be accessed from
the active circuit 60 through the wireless network by the scanner
210 and also with the interrogator 90.
[0046] In addition, the hybrid tag 105, may include control
functionality. For example, a solenoid-controlled power switch may
be included in the hybrid tag 105. The switch can be enabled or
disabled under program control by the active circuit 60. An
external device or user can direct the active circuit 60 to change
the state of the switch by communicating with the active circuit 60
via a wired or wireless communication network. The state of traffic
and street lights can thereby be controlled via the hybrid tag 105
by the user.
[0047] The hybrid tag 105 permits connection to more than one
electrical source or load. For example, a single hybrid tag 105 can
be configured to monitor a single solar panel 10, a group of solar
panels, a single DC-to-AC inverter 40, and the external AC power
grid 30. Parameters of interest including current, voltage, phase
angle, and instantaneous power can be monitored.
[0048] Additionally, a history of measurements can be recorded in
the memory 120. The hybrid tag 105 can be configured to log sensor
data at predetermined time intervals. The hybrid tag 105 may
monitor the energy dissipated or delivered to the AC power grid 30
at specific time intervals to thereby determine the cumulative
energy dissipated or delivered. For example, current and voltage
may be determined for a multi-phase local generation device at 15
minute intervals with power and energy data recorded in memory 120
for readout at a later time.
[0049] Both the scanner 210 and the interrogator 90 may interface
into a processing device, such as a PC, Personal Digital Assistant
(PDA), or a mobile telephone. Users can use such devices to read
data stored in the tags, such as data recorded from the sensors 50.
Additionally, the tag's 105 operational information, such as the
sampling rate for logging operations, the temperature of the tag,
and other identification and digital history information located in
the tag memory 120 can be retrieved, analyzed, and modified.
[0050] The hybrid tag 105, interrogator 90, scanner 210 and the
other devices in the system may each include an alarm indicator.
The alarm indicator may be used to indicate that a sensor 50 has
acquired a measurement that is unexpected or out of specification.
A user can thereby be warned of potential problems within the
system.
[0051] The sensor data obtained from this system can be used by a
utility company or an interested business. For instance, a utility
company could use the data retrieved from the hybrid tag 105 for
billing or crediting purposes relating to power sold or delivered
to the utility.
[0052] In one exemplary embodiment, the energy metering system may
have only minimal passive tag features. In this embodiment, the
passive circuit 80 in each hybrid tag 105 is used to wake-up the
active circuit 60 under control from the remote interrogator 90.
The active circuit 60 is normally powered externally from the AC
power grid 30 or from a local source such as a solar panel 10.
During brownout or blackout periods, the active circuit 60
automatically enters a sleep mode in order to reduce the energy
drain from a small integrally mounted battery 110. The active
circuit 60 can be awakened to perform normal sensor operations by
the passive circuit 80.
[0053] The passive circuit 80 may wake the active circuit 60 from
its sleep mode by setting an interrupt that the active circuit 60
monitors. For example, the passive circuit 80 may set the level of
a dedicated interrupt input pin on the control component of the
active circuit 60 to a level that would cause the active circuit 60
to recognize that an interrupt has been requested. The active
circuit 60 then wakes itself up when the available power level is
adequate. The data collected from the sensors 50 cannot be readout
by the passive circuit 80 in this embodiment. Consequently, sensor
data cannot be retrieved when the source of power for the active
circuit 60 is not available.
[0054] The use of the passive circuit 80 to wake up the active
circuit 60 has very general applicability. For instance, the
interrogator 90 can be used to direct the passive circuit 80 in a
nearby hybrid tag 105 to enable the active circuit 60, to thereby
greatly extend the range of the hybrid tag 105. The active circuit
60 may be programmed to enter a sleep mode after a given period of
time or when directed to by an external device. When in the sleep
mode, the active circuit 60 may not be able to be directly awakened
by another active RFID node. However, the passive circuit 80 can be
directed by a local interrogator 90 to wake up the active circuit
60.
[0055] If the active circuit 60 is powered by the battery 110, the
battery may not supply enough energy to maintain the active circuit
60 in a powered-up mode continuously. The active circuit 60 may be
programmed to switch between an active mode an a sleep mode with a
given duty cycle. Alternatively, the passive circuit 80 may direct
the active circuit 60 to switch between an active mode and a sleep
mode with a give duty cycle. The active/sleep duty cycle of the
active circuit 60 may also be controlled through the passive
circuit 60 by the interrogator 90. In some applications, the active
circuit 60 may be in a sleep mode more than 99% of the time in
order to conserve power.
[0056] This simple implementation permits the use of a relatively
simple passive circuit 80 to wake up the active circuit 60 at any
time. In order to conserve power, the active circuit 60 senses any
brownout condition when local tag power is limited, and goes into a
sleep mode until acceptable power becomes available. The capability
to wake up a sleeping active circuit 60 is especially useful for
maintenance and repair situations when the interrogator 90 is
available.
[0057] The passive circuit 80 may also be operated in a standalone
mode without the integral wired connection to the active circuit
60. The passive circuit 80 may be used to directly sense
temperature, moisture levels, water levels, light source operation,
various identifications, installation dates, repair history,
shipment routes, etc. The passive circuit 80 permits reading and
writing of this data via a wireless link to the interrogator
90.
[0058] In another exemplary embodiment, the energy metering system
also includes the ability to log sensor data. In this embodiment,
the active and passive circuits 60, 80 in the hybrid tag 105 also
share a memory 120 that can be read from and written to through a
shared data bus. The passive circuit 80 can take control of the
memory bus by enabling an interrupt level to the active circuit 60.
Interference between the two circuits addressing the memory 120 can
thereby be avoided. Alternatively, the memory 120 may have separate
ports respectively for the active and passive circuits 60, 80. This
embodiment provides an extra measure of security in the event of a
non-recoverable failure of the active circuit 60 because all data
stored in the memory 120 can be subsequently read out by the
passive circuit 80.
[0059] In some embodiments, the system also includes standalone
passive RFID nodes. These passive RFID nodes provide
identification, installation information, repair history
information, origin, part number, and other digital information
associated with the devices in the system. The passive nodes are
accessed with the interrogator 90.
[0060] FIG. 3 illustrates an exemplary embodiment of a hybrid tag
105 and its immediate interfaces according to the present
invention. The hybrid tag 105 is usable in the hybrid system
illustrated in FIG. 2. Components of FIG. 3 numbered with like
numbers in FIG. 2 have been described in the context of FIG. 2 and
are not described again with respect to FIG. 3.
[0061] FIG. 3 illustrates an application of hybrid tag 105 adapted
for interfacing with street lamp or other load 301. A
handheld/mobile device 303 is used to retrieve information from the
passive RFID circuit 80. The function of handheld/mobile device 303
is substantially the same as the function of interrogator 90 of
FIG. 2. Network 302 is substantially the same as Internet (or WAN)
240 of FIG. 2, and network 302 interfaces with hybrid tag 105 by
use of system components illustrated in FIG. 2. It should be
understood that the links from hybrid tag 105 to network 302 and to
handheld/mobile device 303 are bidirectional RF links. In other
aspects of operation, the embodiment of FIG. 3 has been described
earlier with respect to operation of the embodiment of FIG. 2, and
is not described again.
[0062] While the invention has been particularly shown and
described with reference to exemplary embodiments thereof, it will
be understood by those skilled in the art that various changes in
form and details may be made therein without departing from the
spirit and scope of the invention.
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