LabVIEW Based Monitoring the Building in wireless communication

IJMEIT// Vol. 2 Issue 4 //April 2014 //Page No: 180-186//e-ISSN: 2348-196x 2014
Labview Based Wireless Sensor for Monitoring the Building
Authors
Mr.Sathish Kumar.M1
Department of Electronics and Communication Engineering
Saveetha University
Email: sathishas4u@gmail.com
Mr.Reji.M2
Assistant Professor, ECE
Saveetha University
Abstract:
The presented wireless system for building monitoring takes advantage of the unique features of
custom-developed MEMS sensors and read-out ASIC combined with an optimized network and module
architecture, to realize a solution which offers long battery lifetime and potentially low cost in
manufacturing, installation and maintenance, while providing high-quality sensor data at the right
time which can be proposed for monitoring building to assess earthquake damage. Low power network
architecture was implemented over an 802.15.4 MAC in the 900-MHz band.A custom patchantenna
was designed in thisfrequency band to obtain robustlinks in real-worldconditions. The modules have
been validatedin a full-scale laboratory setup with simulated earthquakes. This will be illustrated via
LABVIEW software which shows the Temperature level in the time of Earthquake and which helps in
preventing the human life.
INTRODUCTION
Due to the Natural calamity, Material aging,
Design error the buildings can get damage
during their lifetime, to eradicate this kind of
problem a continuous monitoring on the
building should be maintained. It’s very
difficult to monitor manually,
Hence automatic system should be proposed
for safety and serviceability of the buildings
and humans.The emergence of wireless
sensor networks has enabled new classes of
applications for distributed systems that
filter into very many interdisciplinary fields.
Mr.Sathish Kumar.M IJMEIT Vol 2 Issue 4 April 2014 www.igmpublication.org/ijmeit Page 180

These networks have been used for solving
problems in the fields of distributed control,
tracking and inventory, structural
monitoring, fire-safety, habitat monitoring
etc.However, in order for the installation of
a permanently installed sensing system in
buildings to be economically viable so a
wireless sensor should be made in low cost
that can be mass produced such as MEMS
sensors. The capability of MEMS and
wireless networking for monitoring civil
structures is well documented.
LABVIEW
LabVIEW (short for Laboratory Virtual
Instrumentation Engineering Workbench) is
a platform and development environment for
a visual programming language from
National Instruments. The purpose of
suchprogramming is automating the usage
of processing and measuring equipment in
any laboratory setup.
The graphical language is named "G" (not to
be confused with G-code). Originally
released for the Apple Macintosh in 1986,
LabVIEW is commonly used for data
acquisition, instrument control, and
industrial automation on a variety of
platforms including Microsoft Windows,
various versions of UNIX, Linux, and Mac
OS X. The latest version of LabVIEW is
version LabVIEW 2010, released in August
2010.
System Architecture:
Two types of sensor modules have been
developed in the monitoring system i.e.,
Strain sensing modules and Acceleration
sensing modules. They are placed in the
building as the lowest level of the building
the strain sensor modules are mounted for
the estimating the vertical column loads and
to measure the settlement and the plastic
hinge activation of the building after an
earthquake. Horizontal acceleration is
measured by two 3D acceleration sensing
modules (where only the two horizontal axes
are really required) at each level during an
earthquake, allowing analysis of the seismic
response of the whole structure. To monitor
a building for e.g. a 7-story, 24-Column
building requires approximately 72 strain
sensors (3 per column) and 14 accelerometer
modules (2 per floor).
The data received by the sensor
system is wirelessly transmitted by the base
station using a line of sight link with a range
of less than 1 km. The line of sight link uses
directional antennas to improve the link
budget, but not so directional that alignment
is required, which could pose a problem
during seismic events. The receiver base
station can store and process the data or
forward them, immediately or later, using
classical wide area network connection
technology.
The modules and the receiver base station
will have the battery back-up power, which
records the data acquired during seismic
events even in case of outages of the electric
power and communication networks. Multi
hop network architecture is used to form a
robust wireless link from all modules,
including the strain sensor modules at the
basement of the building towards the
receiver the base station. A router module
(without sensor) is placed at the roof of the
building to forward the data between the
sensor network and the receiver base station.
Some accelerometer modules on
intermediate floors can be configured as
additional intermediate routers when
required to obtain a robust link from all
sensor modules in the building towards the
roof router module. It is recommended to
place the router modules in or close to the
stairwell for improved vertical floor-to-floor
propagation through the building.
In the sensor modules to consume low
power the network is implemented using
indirect data transfer using polling on top of
a standard 802.15.4 MAC. In this way, the
end nodes’ radio is powered down most of

the time. Only the routers and base station
have their receivers constantly on. To avoid
the battery depletion, the modules with
router functionality are mains-powered
through an AC/DC adapter, with the battery
serving only for back-up power in case
mains power is interrupted. The end nodes
(i.e., the large majority of installed sensor
modules) are powered exclusively by their
battery.
MEMS SENSORS:
A wireless sensor network plays an
important role in such strategies and can be
connected to the internet so that this
information can be used to monitoring future
risks. Wireless sensors are easy to install,
remove, and replace at any location, and are
expected to become increasingly smaller
(i.e., “smart dust”) by using MEMS
technology.MEMS are the most appropriate
devices for motion compensation which is a
technology that in its most general form can
be defined as miniaturized mechanical and
electro-mechanical elements (i.e., devices
and structures) that are made using the
techniques of micro-fabrication. The critical
physical dimensions of MEMS devices can
vary from well below one micron on the
lower end of the dimensional spectrum, all
the way to several millimetres. They will
provide a ubiquitous, networked sensing
environment in buildings. For example, the
acceleration and strain at numerous
locations on each beam and column,
temperature and light in each room, images
and sounds in desired regions can be
obtained by the “smart dust” sensors, as
illustrated in. Additionally, a single type of
sensor such as a condenser microphone can
be used for multiple purposes, for example,
to detect earthquake, fires and intrusions.
Furthermore, a fiber optic network is not
only utilized as infrastructure for
information technology, but also as a
“wired” sensor network. Table 1 shows
various kinds of hazards, and possible
applications/combination of sensors.
Table 1 Sensor Applications
Hazard Application Sensor
Earthquake/
Wind
Observation Acceleration
Experiment Acceleration,
Strain
Structural
Control
Acceleration
Health
monitoring
Acceleration,
Strain
Damage
detection
Acceleration,
Strain,
displacement
Fire Fire
Detection
Temperature,
Smoke,
Acoustic,
Acceleration,
Olfactory
Gas leak
detection
Olfactory
Alarm
Warning
Sounder
Evacuation
Control
Temperature,
Smoke,
Acoustic,
light,
Olfactory
Crime Surveillance Acceleration,
Acoustic,
Light, Camera
Security Sounder
Sensor Module Architecture:
The block diagram of the sensor modules is
shown in Fig given below. Both the
accelerometer and strain sensing

BLOCK DIAGRAM
Variants of the module use the same core
components. For installing these
components in the building which will be
placed into a standard off-the-shelf plastic
casing that can be conveniently mounted on
the floor, wall or ceiling using screws, and
offering access for sporadic battery
replacement if needed.
The core components are:
1) A custom-developed low power
capacitive sensor read-out ASIC. This ASIC
can be matched to either MEMS-based
comb finger capacitive accelerometers or
strain sensors in a half-bridge configuration.
Its gain can be set by a number of
integration pulses N, optimizing signal-to-noise
ratio and bandwidth with power. In
addition, the architecture suppresses residual
motion artifacts. In combination with the
MEMS strain sensor, it can measure a range
of ± 20,000με with a resolution of 10με and
non- linearity <0.6%. In combination with
the MEMS accelerometer it can measure an
acceleration range of ±2.5g with a resolution
of 80dB (13-bit) for vibrations between 10-
100Hz and a non-linearity <1%.
2) A low power 16-bit successive-approximation
analog to- digital converter
(Analog Devices AD7683).
3)A low power microcontroller (TI
MSP430) to control the sensor data
acquisition and temporarily store the data in
a 64Kx16bit SRAM memory (Cypress
CY62126) .
4)A low power wireless IEEE 802.15.4-
compatible module (Atmel ATZB-900)
operating in the 900MHz band. This
frequency band was chosen in preference to
the more common 2.4GHz band because it
offers a larger propagation range for the
wireless communication. The wireless
module includes a radio chip (Atmel
AT86RF212) and a baseband
microcontroller (Atmel AVR) which needs
to be active only during wireless
communication events.
5)A custom patch antenna was designed for
the modules. The patch antenna is tuned for
868MHz operation with an efficiency of
51% using standard FR4 material as the
substrate. Its size is 5 x 5 x 1.3 cm3. Its
shape and radiation pattern is optimized for
wall-, floor- and ceiling-mounting in the
building.
6)The modules are powered by a an 8.5Ah
C-cell long operating life primary Lithium
Thionyl Chloride battery (Tadiran SL-2770),
suitable for 10 to 25 years of operation.

The accelerometer consists of 2 transverse
comb finger structures for the X and Y axis
and a pendulating one for Z axis and was
fabricated with a surface micro-machined
process from a 85 μm thick SOI wafer. It
has 78 fingers with a total sensitivity of
2.02pF/g. The Z sensor has as area of 2.17
mm per plate. Innovative cap through
connections were used. The main trade-off
in the design of the accelerometer is the
sensitivity-bandwidth- linearity in all three
axes, a challenge for the design given the
different used structures. The XY and Z
accelerometers are packaged together with
the readout ASIC into a system- in-a-package
and then mounted onto the printed
circuit board.
The MEMS strain sensor is a longitudinal
comb finger capacitor. The strain sensor
fabrication procedure starts with a SOI
wafer with a 500휇푚 thick handle. 50 휇푚
thick fingers and 2휇푚 thick oxide layer with
400 fingers in the sensor and it has a
sensitivity of 0.133푓퐹/휇휀. Two anchors
were etched out of the surface to create the
necessary clamps to attach the sensor to the
rebar of a pillar. The fingers are protected
with a borosilicate class cap.
The MEMS strain sensor is packaged
together with the readout ASIC into a
special front-end strain sensing module
which is to be embedded inside the
reinforced concrete onto the reinforcing bar,
preferably prior to the pouring of the
concrete. The sensor is mounted on a
polyimide or steel carrier which in turn is
glued (or in case of steel, could also be
welded) onto the reinforcing bar. The
module is molded in PDMS silicone to
protect the components from the
environment during installation and pouring
of concrete, while remaining a mechanically
compliant package to avoid distorting the
strain sensor measurement. This front-end
strain sensing module is connected to the
rest of the module with a small 4-wire cable
with a maximum length of 1.5m.
The use of custom developed MEMS sensor
and read out ASIC allows to meet the
specific requirements of the building
monitoring application and differentiates the
presented system from the earlier prototype
system presented.
Measurement initiation and radio polling:
The main trigger for the recording of
an acceleration measurement is the detection
of the start of an earthquake. The detection
can happen in two ways:
a) The output of the built- in accelerometer
in a selected number of monitoring nodes
exceeds a certain minimum threshold,
during a certain minimum time; these
monitoring nodes alert the base station
which will decide whether to wake up the
entire network of acceleration sensing nodes
over the radio The monitoring nodes are
selected based on their location and amount
of environmental noise; ground level nodes
may be suitable candidates, provided they
are sufficiently far removed from
disturbance sources such as heavy traffic.
The selection of monitoring nodes can be
done dynamically from the base station.
This allows for example to disable the
monitoring function on nodes that report
unusually high numbers of false alarms. To
that purpose, the hardware and software of
the monitoring nodes are identical to that of
the non-monitoring nodes. The monitoring
function is an optional function which can
be enabled or disabled during operation by
the base station.
b) An external source of earthquake
detection can be coupled to the base station,
which can use such information in addition
to possible information from monitoring
nodes to decide whether to wake up the
entire network or not.
In both of these cases the wake-up of (most
of) the acceleration sensing nodes to initiate

measurement has to be done over the radio
link. This also implies that it is possible to
wake up the nodes via the base station over
the radio link at any chosen time
independent of the presence of an
earthquake, which is a desired functionality
for testability and monitoring of the system.
It also means that all modules in the network
will be woken up during a detected event,
even if the accelerations locally at some
modules have not (yet) reached a value
exceeding the trigger threshold. It is
required to be able to record the early onset
of an earthquake event, even before and
certainly no later than 1ms after it reaches a
pre-set trigger threshold. In order to do this,
the accelerometer is constantly running at 3
x 200Hz sample rate with the measurements
recorded in a 54-second loop buffer. This
requires an ultra-low power sensor and
readout.
The power consumption of the 3D
accelerometer and 3-channel readout
operating continuously is 125μA at 3V. The
node must be woken up within 54 seconds
after the start of the recording of interest to
avoid the loop buffer overflowing which
would lead to data loss. To respond timely
to an event triggered from the base station,
the radio polling interval of the
accelerometer modules is set to 15 seconds.
Once the event trigger is reached the loop
buffer contents are preserved and once the
buffer is full recording will continue in a
secondary 54-second buffer until the next
event trigger.
Strain Sensor Modules:
The main measurement scenario for
the strain sensor is a periodic readout.
Samples are taken at a configurable sample
rate between 2 seconds and 18 hours. The
strain sensor modules use a radio polling
interval of 60 seconds. This also allows
manual wake-up functionality from the base
station, again useful for monitoring and
testability reasons. Unlike for the
accelerometers, in the case of the strain
sensors the sensor and read-out ASIC can be
entirely shut down between measurements.
This results in a lower power consumption
and longer battery life. Since a typical
building requires many more strain sensors
than accelerometer modules, it is useful for
the strain sensors to have the longest battery
service life.
CONCLUSION
Powe r consumption
The breakdown of the power consumption
inthe sensor modules for strain sensor
andaccelerometer modules is the total
average power consumption is 0.274mWfor
the strain sensor modules and 1.73mW for
theaccelerometer modules. With the
abovementioned C-cell sizebattery this
implies a battery life of 12 years for the
strainsensor modules and 2 years for the
accelerometer modules.
Laboratory validation
A lab setup on a scale model of the
buildingused to validate the accelerometer
modules. For thistest, thecustom patch
antenna was not used, but a standard
whipantenna was used instead. The result
shows avery goodcorrelation between the
reference accelerometers and theproposed
wireless modules.The strain sensor modules
were preliminarily validated in calibration
setup and show sensitivities between 10 and
20μɛ/mV, varying from sensor to sensor.

REFERENCES:
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Department of Civil and Environmental
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USAM. Ruiz-Sandoval
Department of Civil and Geological
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LabVIEW Based Monitoring the Building in wireless communication

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