Note: Descriptions are shown in the official language in which they were submitted.
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WIRELESS SENSOR SYSTEM
Backy--ound of the Invention
Field of the Invention
[0001] The present invention relates to a wireless sensor system for
monitoring
potentially dangerous or costly conditions such as, for example, smoke,
temperature, water,
gas and the like in a building or vehicle, and/or for monitoring energy usage
or efficiency of
water heaters and the like.
Description of the Related Art
[0002] Maintaining and protecting a building or complex is difficult and
costly.
Some conditions, such as fires, gas leaks, etc. are a danger to the occupants
and the structure.
Other malfunctions, such as water leaks in roofs, plumbing, etc. are not
necessarily dangerous
for the occupants, but can nevertheless cause considerable damage. In many
cases, an adverse
condition such as water leakage, fire, etc. is not detected in the early
stages when the damage
and/or danger is relatively small. Sensors can be used to detect such adverse
conditions, but
sensors present their own set of problems. For example, adding sensors, such
as, for example,
smoke detectors, water sensors, and the like in an existing structure can be
prohibitively
expensive due to the cost of installing wiring between the remote sensors and
a centralized
monitoring device used to monitor the sensors. Adding wiring to provide power
to the
sensors further increases the cost. Moreover, with regard to fire sensors,
most fire
departments will not allow automatic notification of the fire department based
on the data
from a smoke detector alone. Most fire departments require that a specific
temperature rate-
of-rise be detected before an automatic fire alarm system can notify the fire
department.
Unfortunately, detecting fire by temperature rate-of-rise generally means that
the fire is not
detected until it is too late to prevent major damage.
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Summarv
[0003] The present invention.solves these and other problems by providing a
relatively low cost, robust, wireless sensor system that provides an extended
period of
operability without maintenance. The system includes one or more intelligent
sensor units
and a base unit that can communicate with a the sensor units. When one or more
of the sensor
units detects an anomalous condition (e.g., smoke, fire, water, etc.) the
sensor unit
communicates with the base unit and provides data regarding the anomalous
condition. The
base unit can contact a supervisor or other responsible person by a plurality
of techniques,
such as, telephone, pager, cellular telephone, Internet (and/or local area
network), etc. In one
embodiment, one or more wireless repeaters are used between the sensor units
and the base
unit to extend the range of the system and to allow the base unit to
communicate with a larger
number of sensors.
[0004] In one embodiment, the sensor system includes a number of sensor units
located throughout a building that sense conditions and report anomalous
results back to a
central reporting station. The sensor units measure conditions that might
indicate a fire, water
leak, etc. The sensor units report the measured data to the base unit whenever
the sensor unit
determines that the measured data is sufficiently anomalous to be reported.
The base unit can
notify a responsible person such as, for example a building manager, building
owner, private
security service, etc. In one embodiment, the sensor units do not send an
alarm signal to the
central location. Rather, the sensors send quantitative measured data (e.g.,
smoke density,
temperature rate of rise, etc.) to the central reporting station.
[0005] In one embodiment, the sensor system includes a battery-operated sensor
unit that detects a condition, such as, for example, smoke, temperature,
humidity, moisture,
water, water temperature, carbon monoxide, natural gas, propane gas, other
flammable gases,
radon, poison gasses, etc. The sensor unit is placed in a building, apartment,
office, residence,
etc. In order to conserve battery power, the sensor is normally placed in a
low-power mode.
In one embodiment, while in the low power mode, the sensor unit takes regular
sensor
readings and evaluates the readings to determine if an anomalous condition
exists. If an
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anomalous condition is detected, then the sensor unit "wakes up" and begins
communicating
with the base unit or with a repeater. At programmed intervals, the sensor
also "wakes up"
and sends status information to the base unit (or repeater) and then listens
for commands for a
period of time.
[0006] In one embodiment, the sensor unit is bi-directional and configured to
receive instructions from the central reporting station (or repeater). Thus,
for example, the
central reporting station can instruct the sensor to: perform additional
measurements; go to a
standby mode; wake up; report battery status; change wake-up interval; run
self-diagnostics
and report results; etc. In one embodiment, the sensor unit also includes a
tamper switch.
When tampering with the sensor is detected, tlie sensor reports such tampering
to the base
unit. In one embodiment, the sensor reports its general health and status to
the central
reporting station on a regular basis (e.g., results of self-diagnostics,
battery health, etc.).
[0007] In one embodiment, the sensor unit provides two wake-up modes, a first
wake-up mode for taking measurements (and reporting such measurements if
deemed
necessary), and a second wake-up mode for listening for commands from the
central
reporting station. The two wake-up modes, or combinations thereof, can occur
at different
intervals.
[0008] In one embodiment, the sensor units use spread-spectrum techniques to
communicate with the base unit and/or the repeater units. In one embodiment,
the sensor
units use frequency-hopping spread-spectrum. In one embodiment, each sensor
unit has an
Identification code (ID) and the sensor units attaches its ID to outgoing
communication
packets. In one embodiment, when receiving wireless data, each sensor unit
ignores data that
is addressed to other sensor units.
[0009] The repeater unit is configured to relay coinmunications traffic
between a
number of sensor units and the base unit. The repeater units typically operate
in an
environment with several other repeater units and thus each repeater unit
contains a database
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(e.g., a lookup table) of sensor IDs. During normal operation, the repeater
only communicates
with designated wireless sensor units whose IDs appears in the repeater's
database. In one
embodiment, the repeater is battery-operated and conserves power by
maintaining an internal
TM
schedule of when it's designated sensors are expected to transmit and going to
a low-power
mode when none of its designated sensor units is scheduled to transmit. In one
embodiment,
the repeater uses spread-spectrum to communicate with the base unit and the
sensor units. In
one embodiment, the repeater uses frequency-hopping spread-spectrum to
communicate with
the base unit and the sensor units. In one embodiment, each repeater unit has
an ID and the
repeater unit attaches its ID to outgoing communication packets that originate
in the repeater
unit. In one embodiment, each repeater unit ignores data that is addressed to
other repeater
units or to sensor units not serviced by the repeater. -
[0010] In one embodiment, the repeater is configured to provide bi-directional
communication between one or more sensors and a base unit. In one embodiment,
the
repeater is configured to receive instructions from the central reporting
station (or repeater).
Thus, for example, the central reporting station can instruct the repeater to:
send commands
to one or more sensors; go to standby mode; "wake up"; report battery status;
change wake-
up interval; run self-diagnostics and report results; etc.
[0011] The base unit is configured to receive measured sensor data from a
number
of sensor units. In one embodiment, the sensor information is relayed through
the repeater
units. The base unit also sends commands to the repeater units and/or sensor
units. In one
embodiment, the base unit includes a diskless PC that runs off of a CD-ROM,
flash memory,
DVD, or other read-only device, etc. When the base unit receives data from a
wireless sensor
indicating that there may be an emergency condition (e.g., a fire or excess
smoke,
temperature, water, flammable gas, etc.) the base unit will attempt to notify
a responsible
party (e.g., a building manager) by several communication channels (e.g.,
telephone, Internet,
pager, cell phone, etc.). In one embodiment, the base unit sends instructions
to place the
wireless sensor in an alert mode (inhibiting the wireless sensor's low-power
mode). In one
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embodiment, the base unit sends instructions to activate one or more
additional sensors near
the first sensor.
[0012] In one embodiment, the base unit maintains a database of the health,
battery status, signal strength, and current operating status of all of the
sensor units and
repeater units in the wireless sensor system. In one embodiment, the base unit
automatically
performs routine maintenance by sending commands to each sensor to run a self-
diagnostic
and report the results. The bases unit collects such diagnostic results. In
one embodiment, the
base unit sends instructions to each sensor telling the sensor how long to
wait between
"wakeup" intervals. In one embodiment, the base unit schedules different
wakeup intervals to
different sensors based on the sensor's health, battery health, location, etc.
In one
embodiment, the base unit sends instructions to repeaters to route sensor
information around
a failed repeater.
Brief Description of the Drawings
[0013] Figure 1 shows an sensor system that includes a plurality of sensor
units
that communicate with a base unit through a number of repeater units.
[0014] Figure 2 is a block diagram of a sensor unit.
[0015] Figure 3 is a block diagram of a repeater unit.
[0016] Figure 4 is a block diagram of the base unit.
[0017] Figure 5 shows one embodiment a network communication packet used by
the sensor units, repeater units, and the base unit.
[0018] Figure 6 is a flowchart showing operation of a sensor unit that
provides
relatively continuous monitoring.
[0019] Figure 7 is a flowchart showing operation of a sensor unit that
provides
periodic monitoring.
[0020] Figure 8 shows how the sensor system can be used to detected water
leaks.
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Detailed Description
[0021] The entire contents of Applicant's co-pending application, Application
No.
, titled "WIRELESS SENSOR SYSTEM," filed May 27, 2004 is hereby
incorporated by reference.
100221 The entire contents of Applicant's co-pending application, Application
No.
titled "WIRELESS SENSOR UNIT," filed May 27, 2004 is hereby
incorporated by reference.
[0023] The entire contents of Applicant's co-pending application, Application
No.
, titled "WIRELESS REPEATER FOR SENSOR SYSTEM," filed May
27, 2004 is hereby incorporated by reference.
[0024] The eritire contents of Applicant's co-pending application, Application
No.
titled "WIRELESS SENSOR MONITORING UNIT," filed May 27,
2004 is hereby incorporated by reference.
[0025] The entire contents of Applicant's co-pending application, Application
No.
, titled "METHOD AND APPARATUS FOR DETECTING
CONDITIONS FAVORABLE FOR GROWTH OF FUNGUS," filed May 27, 2004 is hereby
incorporated by reference.
[0026] The entire contents of Applicant's co-pending application, Application
No.
, titled "METHOD AND APPARATUS FOR DETECTING WATER
LEAKS," filed May 27, 2004 is hereby incorporated by reference.
[0027] Figure 1 shows an sensor system 100 that includes a plurality of sensor
units 102-106 that communicate with a base unit 112 through a number of
repeater units 110-
111. The sensor units 102-106 are located throughout a building 101. Sensor
units 102-104
communicate with the repeater 110. Sensor units 105-105 communicate with the
repeater
111. The repeaters 110-111 communicate with the base unit 112. The base unit
112
communicates with a monitoring computer system 113 through a computer network
connection such as, for example, Ethernet, wireless Ethernet, firewire port,
Universal Serial
Bus (USB) port, bluetooth, etc. The computer system 113 contacts a building
manager,
maintenance service, alarm service, or other responsible personnel 120 using
one or more of
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several communication systems such as, for example, telephone 121, pager 122,
cellular
telephone 123 (e.g., direct contact, voicemail, text, etc.), and/or through
the Internet and/or
local area network 124 (e.g., through email, instant messaging, network
communications,
etc.). In one embodiment, multiple base units 112 are provided to the
monitoring computer
113. In one embodiment, the monitoring computer 113 is provided to more than
one compute
monitor, thus allowing more data to be displayed than can conveniently be
displayed on a
single monitor. In one embodiment, the monitoring computer 113 is provided to
multiple
monitors located in different locations, thus allowing the data form the
monitoring computer
113 to be displayed in multiple locations.
[0028] The sensor units 102-106 include sensors to measure conditions, such
as,
for example, smoke, temperature, moisture, water, water temperature, humidity,
carbon
monoxide, natural gas, propane gas, security alarms, intrusion alarms (e.g.,
open doors,
broken windows, open windows, and the like), other flammable gases, radon,
poison gasses,
etc. Different sensor units can be configured with different sensors or with
combinations of
sensors. Thus, for example, in one installation the sensor units 102 and 104
could be
configured with smoke and/or temperature seinsors while the sensor unit 103
could be
configured with a humidity sensor.
[0029] The discussion that follows generally refers to the sensor unit 102 as
an
example of a sensor unit, with the understanding that the description of the
sensor unit 102
can be applied to many sensor units. Similarly, the discussion generally
refers to the repeater
I 10 by way of example, and not limitation. It will also be understood by one
of ordinary skill
in the art that repeaters are useful for extending the range of the sensor
units 102-106 but are
not required in all embodiments. Thus, for example in one embodiment, one or
more of the
sensor units 102-106 can communicate directly with the bast unit 112 without
going through
a repeater. It will also be understood by one of ordinary skill in the art
that Figure 1 shows
only five sensor units (102-106) and two repeater units (110-111) for purposes
of illustration
and not by way of limitation. An installation in a large apartment building or
complex would
typically involve many sensor units and repeater units. Moreover, one of
ordinary skill in the
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art will recognize that one repeater unit can service relatively many sensor
units. In one
embodiment, the sensor units 102 can communicate directly with the base unit
112 without
going through a repeater 111.
[0030] When the sensor unit 102 detects an anomalous condition (e.g., smoke,
fire, water, etc.) the sensor unit communicates with the appropriate repeater
unit 110 and
provides data regarding the anomalous condition. The repeater unit 110
forwards the data to
the base unit 112, and the base unit 112 forwards the information to the
computer 113. The
computer 113 evaluates the data and takes appropriate action. If the computer
113 determines
that the condition is an emergency (e.g., fire, smoke, large quantities of
water), then the
computer 113 contacts the appropriate personnel 120. If the computer 113
determines that a
the situation warrants reporting, but is not an emergency, then the computer
113 logs the data
for later reporting. In this way, the sensor system 100 can monitor the
conditions in and
around the building 101.
[0031] In one embodiment, the sensor unit 102 has an internal power source
(e.g.,
battery, solar cell, fuel cell, etc.). In order to conserve power, the sensor
unit 102 is normally
placed in a low-power mode. In one embodiment, using sensors that require
relatively little
power, while in the low power mode the sensor unit 102 takes regular sensor
readings and
evaluates the readings to determine if an anomalous condition exists. In one
embodiment,
using sensors that require relatively more power, while in the low power mode
the sensor unit
102 takes and evaluates sensor readings at periodic intervals. If an anomalous
condition is
detected, then the sensor unit 102 "wakes up" and begins communicating with
the base unit
112 through the repeater 110. At programmed intervals, the sensor unit 102
also "wakes up"
and sends status information (e.g., power levels, self diagnostic information,
etc.) to the base
unit (or repeater) and then listens for commands for a period of time. In one
embodiment, the
sensor unit 102 also includes a tamper detector. When tampering with the
sensor unit 102 is
detected, the sensor unit 102 reports such tampering to the base unit 112.
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[0032] In one embodiment, the sensor unit 102 provides bi-directional
communication and is configured to receive data and/or instructions from the
base unit 112..
Thus, for example, the base unit 112 can instruct the sensor unit 102 to
perform additional
measurements, to go to a standby mode, to wake up, to report battery status,
to change wake-
up interval, to run self-diagnostics and report results, etc. In one
embodiment, the sensor unit
102 reports its general health and status on a regular basis (e.g., results of
self-diagnostics,
battery health, etc.)
[0033] In one embodiment, the sensor unit 102 provides two wake-up modes, a
first wake-up mode for taking measurements (and reporting such measurements if
deemed
necessary), and a second wake-up mode for listening for commands from the
central
reporting station. The two wake-up modes, or combinations thereof, can occur
at different
intervals.
[0034] In one embodiment, the sensor unit 102 use spread-spectrum techniques
to
communicate with the repeater unit 110. In one embodiment, the sensor unit 102
use
frequency-hopping spread-spectrum. In one embodiment, the sensor unit 102 has
an address
or identification (ID) code that distinguishes the sensor unit 102 from the
other sensor units.
The sensor unit 102 attaches its ID to outgoing communication packets so that
transmissions
from the sensor unit 102 can be identified by the repeater 110. The repeater
110 attaches the
ID of the sensor unit 102 to data and/or instructions that are transmitted to
the sensor unit
102. In one embodiment, the sensor unit 102 ignores data and/or instructions
that are
addressed to other sensor units.
[0035] In one embodiment, the sensor unit 102 includes a reset function. In
one
embodiment, the reset function is activated by the reset switch 208. In one
embodiment, the
reset function is active for a prescribed interval of time. During the reset
interval, the
transceiver 203 is in a receiving mode and can receive the identification code
from an
external programmer. In one embodiment, the external programmer wirelessly
transmits a
desired identification code. In one embodiment, the identification code is
programmed by an
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external programmer that is connected to the sensor unit 102 through an
electrical connector.
In one embodiment, the electrical connection to the sensor unit 102 is
provided by sending
modulated control signals (power line carrier signals) through a connector
used to connect the
power source 206. In one embodiment, the external programmer provides power
and control
signals. In one embodiment, the external programmer also programs the type of
sensor(s)
installed in the sensor unit. In one embodiment, the identification code
includes an area code
(e.g., apartment number, zone number, floor number, etc.) and a unit number
(e.g., unit 1, 2,
3, etc.).
[0036] In one embodiment, the sensor communicates with the repeater on the 900
MHz band. This band provides good transmission through walls and
other=obstacles normally
found in and around a building structure. In one embodiment, the sensor
communicates with
the repeater on bands above and/or below the 900 MHz band. In one embodiment,
the sensor,
repeater, and/or base unit listen to a radio frequency channel before
transmitting on that
channel or before beginning transmission. If the channel is in use, (e.g., by
another devise
such as another repeater, a cordless telephone, etc.) then the sensor,
repeater, and/or base unit
changes to a different channel. In one embodiment, the sensor, repeater,
and/or base unit
coordinate frequency hopping by listening to radio frequency channels for
interference and
using an algorithm to select a next channel for transmission that avoids the
interference.
Thus, for example, in one embodiment, if a sensor senses a dangerous condition
and goes
into a continuous transmission mode, the sensor will test (e.g., listen to)
the channel before
transmission to avoid channels that are blocked, in use, or jammed. In one
embodiment, the
sensor continues to transmit data until it receives an acknowledgement from
the base unit that
the message has been received. In one embodiment, the sensor transmits data
having a normal
priority (e.g., status information) and does not look for an acknowledgement,
and the sensor
transmits data having elevated priority (e.g., excess smoke, temperature,
etc.) until an
acknowledgement is received.
[0037] The repeater unit 110 is configured to relay communications traffic
between the sensor 102 (and, similarly, the sensor units 103-104) and the base
unit 112. The
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repeater unit 110 typically operates in an environment with several other
repeater units (such
as the repeater unit 111 in Figure 1) and thus the repeater unit 110 contains
a database (e.g., a
lookup table) of sensor unit IDs. In Figure 1, the repeater 110 has database
entries for the Ids
of the sensors 102-104, and thus the sensor 110 will only communicate with
sensor units 102-
104. In one embodiment, the repeater 110 has an internal power source (e.g.,
battery, solar
cell, fuel cell, etc.) and conserves power by maintaining an internal schedule
of when the
sensor units 102-104 are expected to transmit. In one embodiment, the repeater
unit 110 goes
to a low-power mode when none of its designated sensor units is scheduled to
transmit. In
one embodiment, the repeater 110 uses spread-spectrum techniques to
communicate with the
base unit 112 and with the sensor units 102-104. In one embodiment, the
repeater 110 uses
frequency-hopping spread-spectrum to communicate with the base unit 112 -and
the sensor
units 102-104. In one embodiment, the repeater unit 110 has an address or
identification
(ID) code and the repeater unit 110 attaches its address to outgoing
communication packets
that originate in the repeater (that is, packets that are not being
forwarded). In one
embodiment, the repeater unit 110 ignores data and/or instructions that are
addressed to other
repeater units or to sensor units not serviced by the repeater 110.
[0038] In one embodiment, the base unit 112 communicates with the sensor unit
102 by transmitting a communication packet addressed to the sensor unit 102.
The repeaters
110 and 111 both receive the communication packet addressed to the sensor unit
102. The
repeater unit 111 ignores the communication packet addressed to the sensor
unit 102. The
repeater unit 110 transmits the communication packet addressed to the sensor
unit 102 to the
sensor unit 102. In one embodiment, the sensor unit 102, the repeater unit
110, and the base
unit 112 communicate using Frequency-Hopping Spread Spectrum (FHSS), also.
known as
channel-hopping.
[0039] Frequency-hopping wireless systems offer the advantage of avoiding
other
interfering signals and avoiding collisions. Moreover, there are regulatory
advantages given
to systems that do not transmit continuously at one frequency. Channel-hopping
transmitters
change frequencies after a period of continuous transmission, or when
interference is
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encountered. These systems may have higher transmit power and relaxed
limitations on in-
band spurs. FCC regulations limit transmission time on one channel to 400
milliseconds
(averaged over 10-20 seconds depending on channel bandwidth) before the
transmitter must
change frequency. There is a minimum frequency step when changing channels to
resume
transmission. If there are 25 to 49 frequency channels, regulations allow
effective radiated
power of 24 dBm, spurs must be -20 dBc, and harmonics must be -41.2 dBc. With
50 or
more channels, regulations allow effective radiated power to be up to 30 dBm.
[0040] In one embodiment, the sensor unit 102, the repeater unit 110, and the
base
unit 112 communicate using FHSS wherein the frequency hopping of the sensor
unit 102, the
repeater unit 110, and the base unit 112 are not synchronized such that at any
given moment,
the sensor unit 102 and the repeater unit I 10 are on different channels. In
such a system, the
base unit 112 communicates with the sensor unit 102 using the hop frequencies
synchronized
to the repeater unit 110 rather than the sensor unit 102. The repeater unit
110 then forwards
the data to the sensor unit using hop frequencies synchronized to the sensor
unit 102. Such a
system largely avoids collisions between the transmissions by the base unit
112 and the
repeater unit 110.
[0041] In one embodiment, the sensor units 102-106 all use FHSS and the sensor
units 102-106 are not synchronized. Thus, at any given moment, it is unlikely
that any two or
more of the sensor units 102-106 will transmit on the same frequency. In this
manner,
collisions are largely avoided. In one embodiment, collisions are not detected
but are
tolerated by the system 100. If a collisions does occur, data lost due to the
collision is
effectively re-transmitted the next time the sensor units transmit sensor
data. When the sensor
units 102-106 and repeater units 110-111 operate in asynchronous mode, then a
second
collision is highly unlikely because the units causing the collisions have
hopped to different
channels. In one embodiment, the sensor units 102-106, repeater units 110-110,
and the base
unit 112 use the same hop rate. In one embodiment, the sensor units 102-106,
repeater units
110-110, and the base unit 112 use the same pseudo-random algorithm to control
channel
hopping, but with different starting seeds. In one embodiment, the starting
seed for the hop
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algorithm is calculated from the ID of the sensor units 102-106, repeater
units 110-110, or the
base unit 112.
[0042] In an alternative embodiment, the base unit communicates with the
sensor
unit 102 by sending a communication packet addressed to the repeater unit 110,
where the
packet sent to the repeater unit 110 includes the address of the sensor unit
102. The repeater
unit 102 extracts the address of the sensor unit 102 from the packet and
creates and transmits
a packet addressed to the sensor unit 102.
[0043] In one embodiment, the repeater unit 110 is configured to provide bi-
directional communication between its sensors and the base unit 112. In one
embodiment, the
repeater 110 is configured to receive instructions from the base unit 110.
Thus, for example,
the base unit 112 can instruct the repeater to: send commands to one or more
sensors; go to
standby mode; "wake up"; report battery status; change wake-up interval; run
self-diagnostics
and report results; etc.
[0044] The base unit 112 is configured to receive measured sensor data from a
number of sensor units either directly, or through the repeaters 110-111. The
base unit 112
also sends commands to the repeater units 110-111 and/or to the sensor units
110-111. In one
embodiment, the base unit 112 communicates with a diskless computer 113 that
runs off of a
CD-ROM. When the base unit 112 receives data from a sensor unit 102-111
indicating that
there may be ari emergency condition (e.g., a fire or excess smoke,
temperature, water, etc.)
the computer 113 will attempt to notify the responsible party 120.
[0045] In one embodiment, the computer 112 maintains a database of the health,
power status (e.g., battery charge), and current operating status of all of
the sensor units 102-
106 and the repeater units 110-111. In one embodiment, the computer 113
automatically
performs routine maintenance by sending commands to each sensor unit 102-106
to run a
self-diagnostic and report the results. The computer 113 collects and logs
such diagnostic
results. In one embodiment, the computer 113 sends instructions to each sensor
unit 102-106.
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telling the sensor how long to wait between "wakeup" intervals. In one
embodiment, the
computer 113 schedules different wakeup intervals to different sensor unit 102-
106 based on
the sensor unit's health, power status, location, etc. In one embodiment, the
computer 113
schedules different wakeup intervals to different sensor unit 102-106 based on
the type of
data and urgency of the data collected by the sensor unit (e.g., sensor units
that have smoke
and/or temperature sensors produce data that should be checked relatively more
often than
sensor units that have humidity or moisture sensors). In one embodiment, the
base unit sends
instructions to repeaters to route sensor information around a failed
repeater.
[0046] In one embodiment, the computer 113 produces a display that tells
maintenance personnel which sensor units 102-106 need repair or maintenance.
In one
embodiment, the computer 113 maintains a list showing the status and/or
location of each
sensor according to the ID of each sensor.
[0047] In one embodiment, the sensor units 102-106 and /or the repeater units
110-111 measure the signal strength of the wireless signals received (e.g.,
the sensor unit 102
measures the signal strength of the signals received from the repeater unit
110, the repeater
unit 110 measures the signal strength received from the sensor unit 102 and/or
the base unit
112). The sensor units 102-106 and /or the repeater units 110-111 report such
signal strength
measurement back to the computer 113. The computer 113 evaluates the signal
strength
measurements to ascertain the health and robustness of the sensor system 100.
In one
embodiment, the computer 113 uses the signal strength information to re-route
wireless
communications traffic in the sensor system 100. Thus, for example, if the
repeater unit 110
goes offline or is having difficulty communicating with the sensor unit 102,
the computer 113
can send instructions to the repeater unit 111 to add the ID of the sensor
unit 102 to the
database of the repeater unit 111 (and similarly, send instructions to the
repeater unit 110 to
remove the ID of the sensor unit 102), thereby routing the traffic for the
sensor unit 102
through the router unit 111 instead of the router unit 110.
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[0048] Figure 2 is a block diagram of the sensor unit 102. In the sensor unit
102,
one or more sensors 201 and a transceiver 203 are provided to a controller
202. The
controller 202 typically provides power, data, and control information to the
sensor(s) 201
and the transceiver 202. A power source 206 is provided to the controller 202.
An optional
tamper sensor 205 is also provided to the controller 202. A reset device
(e.g., a switch) 208
is proved to the controller 202. In one embodiment, an optional audio output
device 209 is
provided. In one embodiment, the sensor 201 is configured as a plug-in module
that can be
replaced relatively easily.
[0049] In one embodiment, the transceiver 203 is based on a TRF 6901
transceiver chip from Texas Instruments. Inc. In one embodiment, the
controller 202 is a-
conventional programmable microcontroller. In one embodiment, the controller
202 is based
on a Field Programmable Gate Array (FPGA), such as, for example, provided by
Xilinx
Corp. In one embodiment, the sensor 201 includes an optoelectric smoke sensor
with a smoke
chamber. In one embodiment, the sensor 201 includes a thermistor. In one
embodiment, the
sensor 201 includes a humidity sensor. In one embodiment, the sensor 201
includes an
sensor, such as, for example, a water level sensor, a water temperature
sensor, a carbon
monoxide sensor, a moisture sensor, a water flow sensor, natural gas sensor,
propane sensor,
etc.
[0050] The controller 202 receives sensor data from the sensor(s) 201. Some
sensors 201 produce digital data. However, for many types of sensors 201, the
sensor data is
analog data. Analog sensor data is converted to digital format by the
controller 202. In one
embodiment, the controller evaluates the data received from the sensor(s) 201
and determines
whether the data is to be transmitted to the base unit 112. The sensor unit
102 generally
conserves power by not transmitting data that falls within a normal range. In
one
embodiment, the controller 202 evaluates the sensor data by comparing the data
value to a
threshold value (e.g., a high threshold, a low threshold, or a high-low
threshold). If the data is
outside the threshold (e.g., above a high threshold, below a low threshold,
outside an inner
range threshold, or inside an outer range threshold), then the data is deemed
to be anomalous
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and is transmitted to the base unit 112. In one embodiment, the data threshold
is programmed
into the controller 202. In one embodiment, the data threshold is programmed
by the base
unit 112 by sending instructions to the controller 202. In one embodiment, the
controller 202
obtains sensor data and transmits the data when commanded by the computer 113.
[0051] In one embodiment, the tamper sensor 205 is configured as a switch that
detects removal of or tampering with the sensor unit 102.
[0052] Figure 3 is a block diagram of the repeater unit 110. In the repeater
unit
110, a first transceiver 302 and a second transceiver 305 are provided to a
controller 303. The
controller 303 typically provides power, data, and control information to the
transceivers 302, -
304. A power source 306 is provided to the controller 303. An optional tamper
sensor (not
shown) is also provided to the controller 303.
[0053] When relaying sensor data to the base unit 112, the controller 303
receives
data from the first transceiver 303 and provides the data to the second
transceiver 304. When
relaying instructions from the base unit 112 to a sensor unit, the controller
303 receives data
from the second transceiver 304 and provides the data to the first transceiver
302. In one
embodiment, the controller 303 conserves power by powering-down the
transceivers 302,
304 during periods when the controller 303 is not expecting data. The
controller 303 also
monitors the power source 306 and provides status information, such as, for
example, self-
diagnostic information and/or information about the health of the power source
306, to the
base unit 112. In one embodiment, the controller 303 sends status information
to the base unit
112 at regular intervals. In one embodiment, the controller 303 sends status
information to
the base unit 112 when requested by the base unit 112. In one embodiment, the
controller
303 sends status information to the base unit 112 when a fault condition
(e.g., battery low) is
detected.
[0054] In one embodiment, the controller 303 includes a table or list of
identification codes for wireless sensor units 102. The repeater 303 forwards
packets received
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from, or sent to, sensor units 102 in the list. In one embodiment, the
repeater 110 receives
entries for the list of sensor units from the computer 113. In one embodiment,
the controller
303 determines when a transmission is expected from the sensor units 102 in
the table of
sensor units and places the repeater 110 (e.g., the transceivers 302, 304) in
a low-power mode
when no transmissions are expected from the transceivers on the list. In one
embodiment, the
controller 303 recalculates the times for low-power operation when a command
to change
reporting interval is forwarded to one of the sensor units 102 in the list
(table) of sensor units
or when a new sensor unit is added to the list (table) of sensor units.
[0055] Figure 4 is a block diagram of the base unit 112. In the base unit 112,
a
transceiver 402 and a computer interface 404 are provided to a controller 403.
The controller
303 typically provides data and control information to the transceivers 402
and to the
interface. The interface 402 is provided to a port on the monitoring computer
113. The
interface 402 can be a standard computer data interface, such as, for example,
Ethernet,
wireless Ethernet, firewire port, Universal Serial Bus (USB) port, bluetooth,
etc.
[0056] Figure 5 shows one embodiment a communication packet 500 used by the
sensor units, repeater units, and the base unit. The packet 500 includes a
preamble portion
501, an address (or ID) portion 502, a data payload portion 503, and an
integrity portion 504.
in one embodiment, the integrity portion 504 includes a checksum. In one
embodiment, the
sensor units 102-106, the repeater units 110-111, and the base unit 112
communicate using
packets such as the packet 500. In one embodiment, the packets 500 are
transmitted using
FHSS.
[0057] In one embodiment, the data packets that travel between the sensor unit
102, the repeater unit 111, and the base unit 112 are encrypted. In one
embodiment, the data
packets that travel between the sensor unit 102, the repeater unit 111, and
the base unit 112
are encrypted and an authentication code is provided in the data packet so
that the sensor unit
102, the repeater unit, and/or the base unit 112 can verify the authenticity
of the packet.
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[0058] In one embodiment the address portion 502 includes a first code and a
second code. In one embodiment, the repeater 111 only examines the first code
to determine
if the packet should be forwarded. Thus, for example, the first code can be
interpreted as a
building (or building complex) code and the second code interpreted as a
subcode (e.g., an
aparhnent code, area code, etc.). A repeater that uses the first code for
forwarding thus
forwards packets having a specified first code (e.g., corresponding to the
repeater's building
or building complex). Thus alleviates the need to program a list of sensor
units 102 into a
repeater, since a group of sensors in a building will typically all have the
same first code but
different second codes. A repeater so configured, only needs to know the first
code to forward
packets for any repeater in the building or building complex. This does,
however, raise the
possibility that two repeaters in the same building could try to forward
packets for the same
sensor unit 102. In one embodiment, each repeater waits for a programmed delay
period
before forwarding a packet. Thus reducing the chance of packet collisions at
the base unit (in
the case of sensor unit to base unit packets) and reducing the chance of
packet collisions at
the sensor unit (in the case of base unit to sensor unit packets). In one
embodiment, a delay
period is programmed into each repeater. In one embodiment, delay periods are
pre-
programmed onto the repeater units at the factory or during installation. In
one embodiment,
a delay period is programmed into each repeater by the base unit 112. In one
embodiment, a
repeater randomly chooses a delay period. In one embodiment, a repeater
randomly chooses
a delay period for each forwarded packet. In one embodiment, the first code is
at least 6
digits. In one embodiment, the second code is at least 5 digits.
[0059] In one embodiment, the first code and the second code are programmed
into each sensor unit at the factory. In one embodiment, the first code and
the second code are
programmed when the sensor unit is installed. In one embodiment, the base unit
112 can re-
program the first code and/or the second code in a sensor unit.
[0060] In one embodiment, collisions are further avoided by configuring each
repeater unit 111 to begin transmission on a different frequency channel.
Thus, if two
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repeaters attempt to begin transmission at the same time, the repeaters will
not interfere with
each other because the transmissions will begin on different channels
(frequencies).
[0061] Figure 6 is a flowchart showing one embodiment of the operation of the
sensor unit 102 wherein relatively continuous monitoring is provided. In
Figure 6, a power up
block 601 is followed by an initialization block 602. After initialization,
the sensor unit 102
checks for a fault condition (e.g., activation of the tamper sensor, low
battery, internal fault,
etc.) in a block 603. A decision block 604 checks the fault status. If a fault
has occurred, then
the process advarices to a block 605 were the fault information is transmitted
to the repeater
110 (after which, the process advances to a block 612); otherwise, the process
advances to a
block 606. In the block 606, the sensor unit 102 takes a sensor reading from
the sensor(s)
201. The sensor data is subsequently evaluated in a block 607. If the sensor
data is abnormal,
then the process advances to a transmit block 609 where the sensor data is
transmitted to the
repeater 110 (after which, the process advances to a block 612); otherwise,
the process
advances to a timeout decision block 610. If the timeout period has not
elapsed, then the
process returns to the fault-check block 603; otherwise, the process advances
to a transmit
status block 611 where normal status information is transmitted to the
repeater 110. In one
embodiment, the normal status information transmitted is analogous to a simple
"ping" which
indicates that the sensor unit 102 is functioning normally. After the block
611, the process
proceeds to a block 612 where the sensor unit 102 momentarily listens for
instructions from
the monitor computer 113. If an instruction is received, then the sensor unit
102 performs the
instructions, otherwise, the process returns to the status check block 603. In
one embodiment,
transceiver 203 is normally powered down. The controller 202 powers up the
transceiver 203
during execution of the blocks 605, 609, 611, and 612. The monitoring computer
113 can
send instructions to the sensor unit 102 to change the parameters used to
evaluate data used in
block 607, the listen period used in block 612, etc.
[0062] Relatively continuous monitoring, such as shown in Figure 6, is
appropriate for sensor units that sense relatively high-priority data (e.g.,
smoke, fire, carbon
monoxide, flammable gas, etc.). By contrast, periodic monitoring can be used
for sensors that
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sense relatively lower priority data (e.g., humidity, moisture, water usage,
etc.). Figure 7 is a
flowchart showing one embodiment of operation of the sensor unit 1.02 wherein
periodic
monitoring is provided. In Figure 7, a power up block 701 is followed by an
initialization
block 702. After initialization, the sensor unit 102 enters a low-power sleep
mode. If a fault
occurs during the sleep mode (e.g., the tamper sensor is activated), then the
process enters a
wake-up block 704 followed by a transmit fault block 705. If no fault occurs
during the sleep
period, then when the specified sleep period has expired, the process enters a
block 706
where the sensor unit 102 takes a sensor reading from the sensor(s) 201. The
sensor data is
subsequently sent to the monitoring computer 113 in a report block 707. After
reporting, the
sensor unit 102 enters a listen block 708 where the sensor unit 102 listens
for a relatively
short period of time for instructions from monitoring computer 708: If an
instruction is
received, then the sensor unit 102 performs the instructions, otherwise, the
process returns to
the sleep block 703. In one embodiment, the sensor 201 and transceiver 203 are
normally
powered down. The controller 202 powers up the sensor 201 during execution of
the block
706. The controller 202 powers up the transceiver during execution of the
blocks 705, 707,
and 708. The monitoring computer 113 can send instructions to the sensor unit
102 to change
the sleep period used in block 703, the listen period used in block 708, etc.
[0063] In one embodiment, the sensor unit transmits sensor data until a
handshaking-type acknowledgement is received. Thus, rather than sleep of no
instructions or
acknowledgements are received after transmission (e.g., after the decision
block 613 or 709)
the sensor unit 102 retransmits its data and waits for an acknowledgement. The
sensor unit
102 continues to transmit data and wait for an acknowledgement until an
acknowledgement
is received. In one embodiment, the sensor unit accepts an acknowledgement
from a repeater
unit 111 and it then becomes the responsibility of the repeater unit 111 to
make sure that the
data is forwarded to the base unit 112. In one embodiment, the repeater unit
111 does not
generate the acknowledgement, but rather forwards an acknowledgement from the
base unit
112 to the sensor unit 102. The two-way communication ability of the sensor
unit 102
provides the capability for the base unit 112 to control the operation of the
sensor unit 102
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and also provides the capability for robust handshaking-type communication
between the
sensor unit 102 and the base unit 112.
[0064] Regardless of the normal operating mode of the sensor unit 102 (e.g.,
using the Flowcharts of Figures 6, 7, or other modes) in one embodiment, the
monitoring
computer 113 can instruct the sensor unit 102 to operate in a relatively
continuous mode
where the sensor repeatedly takes sensor readings and transmits the readings
to the
monitoring computer 113. Such a mode would can be used, for example, when the
sensor
unit 102 (or a nearby sensor unit) has detected a potentially dangerous
condition (e.g., smoke,
rapid temperature rise, etc.)
[0065] Figure 8 shows the sensor system used to detect water leaks. In one
embodiment, the sensor unit 102 includes a water level sensor and 803 and/or a
water
temperature sensor 804. The water level sensor 803 and/or water temperature
sensor 804 are
place, for example, in a tray underneath a water heater 801 in order to detect
leaks from the
water heater 801 and thereby prevent water damage from a leaking water heater.
In one
embodiment, an temperature sensor is also provide to measure. temperature near
the water
heater. The water level sensor can also be placed under a sink, in a floor
sump, etc. In one
embodiment, the severity of a leak is ascertained by the sensor unit 102 (or
the monitoring
computer 113) by measuring the rate of rise in the water level. When placed
near the hot
water tank 801, the severity of a leak can also be ascertained at least in
part by measuring the
temperature of the water. In one embodiment, a first water flow sensor is
placed in an input
water line for the hot water tank 801 and a second water flow sensor is placed
in an output
water line for the hot water tank. Leaks in the tank can be detected by
observing a difference
between the water flowing through the two sensors.
[0066] In one embodiment, a remote shutoff valve 810 is provided, so that the
monitoring system 100 can shutoff the water supply to the water heater when a
leak is
detected. In one embodiment, the shutoff valve is controlled by the sensor
unit 102. In one
embodiment, the sensor unit 102 receives instructions from the base unit 112
to shut off the
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water supply to the heater 801. In one embodiment, the responsible party 120
sends
instructions to the monitoring computer 113 instructing the monitoring
computer 113 to send
water shut off instructions to the sensor unit 102. Similarly, in one
embodiment, the sensor
unit 102 controls a gas shutoff valve 811 to shut off the gas supply to the
water heater 801
and/or to a furnace (not shown) when dangerous conditions (such as, for
example, gas leaks,
carbon monoxide, etc.) are detected. In one embodiment, a gas detector 812 is
provided to the
sensor unit 102. In one embodiment, the gas detector 812 measures carbon
monoxide. In one
embodiment, the gas detector 812 measures flammable gas, such as, for example,
natural gas
or propane.
[0067] In one embodiment, an optional temperature sensor 818 is provided to
measure stack temperature. Using data from the temperature sensor 818, the
sensor unit 102
reports conditions, such as, for example, excess stack temperature. Excess
stack temperature
is often indicative of poor heat transfer (and thus poor efficiency) in the
water heater 818.
[0068] In one embodiment, an optional temperature sensor 819 is provided to
measure temperature of water in the water heater 810. Using data from the
temperature
sensor 819, the sensor unit 102 reports conditions, such as, for example, over-
temperature or
under-temperature of the water in the water heater.
[0069] In one embodiment, an optional current probe 821 is provided to measure
electric current provided to a heating element 820 in an electric water
heater. Using data from
the current probe 821, the sensor unit 102 reports conditions, such as, for
example, no current
(indicating a burned-out heating element 820). An over-current condition often
indicates that
the heating element 820 is encrusted with mineral deposits and needs to be
replaced or
cleaned. By measuring the current provided to the water heater, the monitoring
system can
measure the amount of energy provided to the water heater and thus the cost of
hot water, and
the efficiency of the water heater.
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[0070] In one embodiment, the sensor 803 includes a moisture sensor. Using
data
from the moisture sensor, the sensor unit 102 reports moisture conditions,
such as, for
example, excess moisture that would indicate a water leak, excess
condensation, etc.
[0071] In one embodiment, the sensor unit 102 is provided to a moisture sensor
(such as the sensor 803) located near an air conditioning unit. Using data
from the moisture
sensor, the sensor unit 102 reports moisture conditions, such as, for example,
excess moisture
that would indicate a water leak, excess condensation, etc.
[0072] In one embodiment, the sensor 201 includes a moisture sensor. The
moisture sensor cari be place under a- sink or a toilet (to detect plumbing
leaks) or in an attic
space (to detect roof leaks).
[0073] Excess humidity in a structure can cause sever problems such as
rotting,
growth of molds, mildew, and fungus, etc. (hereinafter referred to generically
as fungus). In
one embodiment, the sensor 201 includes a humidity sensor. The humidity sensor
can be
place under a sink, in an attic space, etc. to detect excess humidity (due to
leaks,
condensation, etc.). In one embodiment, the monitoring computer 113 compares
humidity
measurements taken from different sensor units in order to detect areas that
have excess
humidity. Thus for example, the monitoring computer 113 can compare the
humidity
readings from a first sensor unit 102 in a first attic area, to a humidity
reading from a second
sensor unit 102 in a second area. For example, the monitoring computer can
take humidity
readings from a number of attic areas to establish a baseline humidity reading
and then
compare the specific humidity readings from various sensor units to determine
if one or more
of the units are measuring excess humidity. The monitoring computer 113 would
flag areas of
excess humidity for further investigation by maintenance personnel. In one
embodiment, the
monitoring computer 113 maintains a history of humidity readings for various
sensor units
and flags areas that show an unexpected increase in humidity for investigation
by
maintenance personnel.
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100741 In one embodiment, the monitoring system 100 detects conditions
favorable for fungus (e.g., mold, mildew, fungus, etc.) growth by using a
first humidity
sensor located in a first building area to produce first humidity data and a
second humidity
sensor located in a second building area to piroduce second humidity data. The
building areas
can be, for example, areas near a sink drain, plumbing fixture, plumbing,
attic areas, outer
walls, a bilge area in a boat, etc.
[0075] The monitoring station 113 collects humidity readings from the first
humidity sensor and the second humidity sensor and indicates conditions
favorable for
fungus growth by comparing the first humidity data and the second humidity
data. In one
embodiment, the monitoring station 113 establishes a baseline humidity by
comparing
humidity readings from a plurality of humidity sensors and indicates possible
fungus growth
conditions in the first building area when at least a portion of the first
humidity data exceeds
the baseline humidity by a specified amount. In one embodiment, the monitoring
station 113
establishes a baseline humidity by comparing humidity readings from a
plurality of humidity
sensors and indicates possible fungus growth conditions in the first building
area when at
least a portion of the first humidity data exceeds the baseline humidity by a
specified
percentage.
[0076] In one embodiment, the monitoring station 113 establishes a baseline
humidity history by comparing humidity readings from a plurality of humidity
sensors and
indicates possible fungus growth conditions in the first building area when at
least a portion
of the first humidity data exceeds the baseline humidity history by a
specified amount over a
specified period of time. In one embodiment, the monitoring station 113
establishes a
baseline humidity history by comparing humidity readings from a plurality of
humidity
sensors over a period of time and indicates possible fungus growth conditions
in the first
building area when at least a portion of the first humidity data exceeds the
baseline humidity
by a specified percentage of a specified period of time.
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[0077] In one embodiment, the sensor unit 102 transmits humidity data when it
determines that the humidity data fails a threshold test. In one embodiment,
the humidity
threshold for the threshold test is provided to the sensor unit 102 by the
monitoring station
113. In one embodiment, the humidity threshold for the threshold test is
computed by the
monitoring station from a baseline humidity established in the monitoring
station. In one
embodiment, the baseline humidity is computed at least in part as an average
of humidity
readings from a number of humidity sensors. In one embodiment, the baseline
humidity is
computed at least in part as a time average of humidity readings from a number
of humidity
sensors. In one embodiment, the baseline humidity is computed at least in part
as a time
average of humidity readings from a humidity sensor. In one embodiment, the
baseline
humidity is computed at least in part as the lesser of a maximum humidity
reading an average
of a number of humidity readings.
[0078] In one embodiment, the sensor unit 102 reports humidity readings in
response to a query by the monitoring station 113. In one embodiment, the
sensor unit 102
reports humidity readings at regular intervals. In one embodiment, a humidity
interval is
provided to the sensor unit 102 by the monitoring station 113.
[0079] In one embodiment, the calculation of conditions for fungus growth is
comparing humidity readings from one or more humidity sensors to the baseline
(or
reference) humidity. In one embodiment, the comparison is based on comparing
the humidity
readings to a percentage (e.g., typically a percentage greater than 100%) of
the baseline value.
In one embodiment, the comparison is based on comparing the humidity readings
to a
specified delta value above the reference humidity. In one embodiment, the
calculation of
likelihood of conditions for fungus growth is based on a time history of
humidity readings,
such that the longer the favorable conditions exist, the greater the
likelihood of fungus
growth. In one embodiment, relatively high humidity readings over a period of
time indicate
a higher likelihood of fungus growth than relatively high humidity readings
for short periods
of time. In one embodiment, a relatively sudden increase in humidity as
compared to a
baseline or reference humidity is reported by the monitoring station 113 as a
possibility of a
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water leak. If the relatively high humidity reading continues over time then
the relatively high
humidity is reported by the monitoring station 113 as possibly being a water
leak and/or an
area likely to have fungus growth or water damage.
[0080] Temperatures relatively more favorable to fungus growth increase the
likelihood of fungus growth. In one embodiment, temperature measurements from
the
building areas are also used in the fungus grown-likelihood calculations. In
one embodiment,
a threshold value for likelihood of fungus growth is computed at least in part
as a function of
temperature, such that temperatures relatively more favorable to fungus growth
result in a
relatively lower threshold than temperatures relatively less favorable for
fungus growth. In
one embodiment, the calculation of a likelihood of fungus growth =depends at
least in part on
temperature such that temperatures relatively more favorable to fungus growth
indicate a
relatively higher likelihood of fungus growth than temperatures relatively
less favorable for
fungus growth. Thus, in one embodiment, a maximum humidity and/or minimum
threshold
above a reference humidity is relatively lower for temperature more favorable
to fungus
growth than the maximum humidity and/or minimum threshold above a reference
humidity
for temperatures relatively less favorable to fungus growth.
[0081] In one embodiment, a water flow sensor is provided to the sensor unit
102.
The sensor unit 102 obtains water flow data from the water flow sensor and
provides the
water flow data to the monitoring computer 113. The monitoring computer 113
can then
calculate water usage. Additionally, the monitoring computer can watch for
water leaks, by,
for example, looking for water flow when there should be little or no flow.
Thus, for
example, if the monitoring computer detects water usage throughout the night,
the monitoring
computer can raise an alert indicating that a possible water leak has
occurred.
[0082] In one embodiment, the sensor 201 includes a water flow sensor is
provided to the sensor unit 102. The sensor unit 102 obtains water flow data
from the water
flow sensor and provides the water flow data to the monitoring computer 113.
The
monitoring computer 113 can then calculate water usage. Additionally, the
monitoring
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computer can watch for water leaks, by, for example, looking for water flow
when there
should be little or no flow. Thus, for example, if the monitoring computer
detects water usage
throughout the night, the monitoring computer can raise an alert indicating
that a possible
water leak has occurred.
[0083] In one embodiment, the sensor 201 includes a fire-extinguisher tamper
sensor is provided to the sensor unit 102. The fire-extinguisher tamper sensor
reports
tampering with or use of a fire-extinguisher. In one embodiment the fire-
extinguisher temper
sensor reports that the fire extinguisher has been removed from its mounting,
that a fire
extinguisher compartment has been opened, and/or that a safety lock on the
fire extinguisher
has been removed.
[0084] It will be evident to those skilled in the art that the invention is
not limited
to the details of the foregoing illustrated embodiments and that the present
invention may be
embodied in other specific forms without departing from the spirit or
essential attributed
thereof; furthermore, various omissions, substitutions and changes may be made
without
departing from the spirit of the inventions. For example, although specific
embodiments are
described in terms of the 900 MHz frequency band, one of ordinary skill in the
art will
recognize that frequency bands above and below 900 MHz can be used as well.
The wireless
system can be configured to operate on one or more frequency bands, such as,
for example,
the HF band, the VHF band, the UHF band, the Microwave band, the Millimeter
wave band,
etc. One of ordinary skill in the art will further recognize that techniques
other than spread
spectrum can also be used and/or can be use instead spread spectrum. The
modulation uses is
not limited to any particular modulation method, such that modulation scheme
used can be,
for example, frequency modulation, phase modulation, amplitude modulation,
combinations
thereof, etc. The foregoing description of the embodiments is therefore to be
considered in all
respects as illustrative and not restrictive, with the scope of the invention
being delineated by
the appended claims and their equivalents.
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