1. Smart Home System using a Wireless Sensor
Network for Elderly care
1
R.Gnanavel, 2
P.Anjana,3
K.S.Nappinnai,4
N.Pavithra Sahari
1
Assistant Professor, Department of Computer Science and Engineering, Rajalakshmi Institute of Technology, Chennai, India.
2,3,4
UG Students, Department of Computer Science and Engineering, Rajalakshmi Institute of Technology, Chennai, India.
1
rgvelu22@gmail.com, 2
anjuprasan@gmail.com, 3
nappinnaikalaivanan@gmail.com, 4
pavithrasahari@gmail.com
Abstract—Elderly people who are staying alone require some
form of assistance since they might forget minor things which
could lead to a major security threats. Aged people can easily get
sick and if they are alone at these situations they cannot get help
in time. This project proposes a Wireless Sensor Network based
smart home monitoring system for such elderly people to monitor
their health and provide them with a safe and secure living. The
Wireless Sensor Network deploys various sensors to identify the
occurrence of specific events. By placing wearable sensors on the
waist of the person, the sensor values are computed and assessed.
Temperature, Heartbeat and Pressure sensors are used to
determine the health parameters of the person. The contact
sensors are used to determine if a door is open or not. The
fall detection system consisting of an inertial unit includes a tri-
axial accelerometer and a gyroscope for efficient data fusion.
The fall detection algorithm is used to monitor the activities of
the elderly people and determine whether or not a fall has
occurred. Starting with raw data, the implemented orientation
filter provides the correct orientation of the subject in terms of
yaw, pitch, and roll angles. In case of any emergency, SMS will be
sent to the caregiver and the nearby hospitals using GSM modem
to take preventive action.
Keywords—Wireless Sensor Network, Smart home, GSM
modem
I. INTRODUCTION
Wireless Sensor Networks have become an attractive field
for research as well as scientific and technological
developments. Wireless Sensor Networks can be easily
installed and maintained. They comprise of a large number of
tiny devices equipped with a few sensors, along with some
processing circuits and a wireless transceiver. Such devices
are called sensor nodes and these nodes can be deployed either
inside the phenomenon to be sensed or very close to it.
Parameters such as temperature, pressure, humidity and
chemical activity are constantly detected and reported by these
nodes.
As the age of people increases over time, they generally
tend to forget everyday activities like switching off the
lights/fans. They might be forgetful and not remember to
switch off the gas cylinder which may in turn cause a LPG
gas leakage, or closing the doors leading to thefts in home.
Thus a Wireless Sensor Network based smart home system is
developed for such elder people to help them ease their work
and provide them a safe, sound and secure living.
Many devices are combined and integrated to create a
smart home system which is used to sense the required
parameters and control some of those characteristics. Sensors
like temperature sensor, heartbeat sensor and pressure sensor
are deployed to monitor the health of elder people. An inertial
unit that includes a tri-axial accelerometer and a gyroscope are
also used for fall detection. In case of any emergency an SMS
will be sent to the caregiver and the nearby hospitals using a
GSM modem to take action for helping the person.
The LM35 sensor used in this system is implemented to
detect the person’s body temperature. The person’s body
temperature corresponds to the output voltage produced by the
sensor. This sensor provides the centigrade reading by sensing
the variation in temperature. It provides us with a more
accurate reading than a thermostat. One of its major
advantages is that it is of low cost, low self heating and apt for
remote sensing applications. The heart beat sensors generates
the number of heartbeat as its output when a finger is placed
on it. The heartbeat sensor can be connected to the
microcontroller to estimate the actual number of heart beats
per minute (BPM). It works based on the principal of
modulations that occur in the blood flow through the finger
tip, which is placed on the sensor. This is mainly used in
applications such as patient monitoring systems.
Accelerometers are used to measure acceleration due to
gravity and its orientation. Accelerometers are utilized by the
autopilot systems present in ships and airplanes. The can be
used in applications such as guidance, navigation systems and
automobile that eject airbags. Gyroscope, on the other hand, is
used to measure rotational motion. It has a better accuracy and
efficiency than its predecessors. Gyroscope works on the
principle of conservation of angular momentum. It is used in
applications such as magnetic compass, telescopes, unmanned
aerial vehicles, commercial ships, recreational boats, etc. The
door sensor works on the principle of magnetic attraction.
When the magnet which is placed in the door is pulled away,

2. then it breaks the circuit. On the other hand, when the door is
closed the magnet pulls the magnetic contact switch together
thereby closing the circuit. These sensors can be used to sense
when a door or window is opened and closed.
II. LITERATURE REVIEW
In a smart home [1], monitoring of the house is performed
by sensors like LPG sensor, room temperature sensor and a
contact sensor. These sensors are used to detect gas leakage,
fire detection and checking whether a door is closed or not. It
uses ZigBee protocol to transfer information from one module
to another. Though ZigBee is of low cost and consumes less
power the overall range of the system is restricted within a few
meters. The development in the field of wearable
physiological monitoring devices has been reported in [2]. The
system consists of a device that can be worn on the wrist and
finger to check for the person’s temperature and heartbeat. An
impact sensor is used to detect a fall. If the person is medically
stressed then an alarm is raised by a receiver unit of the
computer. A general smart home concept is presented in [3]
which shows a system directed towards a sensor based and
ontology modeled approach. It implements a Service Oriented
Approach (SOA) which comprises of real heterogeneity of the
information presented in it.
Appliance monitoring is an integral part in a smart home.
[4] telecasts a smart home system which integrates the sensors
to monitor the working of the appliances at home. It uses a
light cube with 512 lights to make the person aware of the
situation. When an exception condition occurs, then the owner
is sent a GSM message. Home monitoring is performed using
an Android based Smart phone app in [5]. It presents a flexible
home control and monitoring system using a web server, IP
connectivity for controlling the devices and appliances
remotely. Since the connectivity is made over the Web, it does
not require a dedicated server PC to offer a novel
communication protocol to monitor and control the home
environment.
III. EXISTING MODEL
The existing model consists of a temperature sensor which
is used for sensing the temperature of the environment, a LPG
leakage sensor for sensing LPG concentration and a contact
sensor to sense whether any door is left open or not. The
sensors generate analog voltage which is fed to the ADC
inputs of the microcontroller. The digital value is then given to
the XBee module to transmit wirelessly. Another XBee
module receives the data and transmits it to the host computer.
The data is processed in LABVIEW. It displays the values
received from each sensor. Each value is compared to a
respective threshold. If the measured value is greater than the
threshold a warning alarm is played through a loudspeaker. A
warning SMS is also sent to the care giver using GSM
modem.
The hardware components include LM35 Precision
centigrade Sensor, MQ-6 Gas sensor, Magnetic contact
switch, Arduino mega 2560,XBee series 2 module. The LM35
sensor is an accurate integrated circuit temperature sensor. The
output voltage of LM35 is linearly proportional to centigrade
temperature. It measures temperature within the range of -55
C TO +150C and detects fire. MQ-6 gas sensor is highly
sensitive to LPG, iso-butane and propane. It can be used to
detect LPG gases concentration of 200-1000ppm. The
Magnetic Contact Switch is a door sensor which is used to
detect whether a door is open or closed. The Xbee
microcontroller follows ZigBee protocol. GSM modem can be
used to send and receive SMS. Software components include
Arduino programming and LABVIEW. The Arduino
environment is used to write the code and upload it in the I/O
board and LABVIEW is a development environment for
visual programming language.
IV. PROPOSED SYSTEM
The proposed system aims at constantly monitoring the health
condition of elderly people and detecting a fall caused by
abnormal conditions. The proposed fall detection system
consists of an inertial unit that includes a tri-axial
accelerometer and a gyroscope. Sensors such as heartbeat
sensor, pressure sensor and temperature sensor are use to
determine the health and wellness of the elderly people based
on their daily activities. By placing the wearable sensor on the
waist of the subject a functional assessment can be done. In
case of any emergency, SMS will be sent to the caregiver
using the GSM modem architecture to take preventive action
or help the person by any means necessary.The sensor data is
procured and sent to the PIC microcontroller. The PIC
compares the data to a pre-existing threshold value to
determine if an event has occurred or not. If a life threatening
event has occurred then a message is sent to the caretaker and
the hospital via the GSM module.
Fig 1: Block diagram of the proposed system

3. A. LM35 Sensor
The LM35 sensor is an accurate integrated circuit temperature
sensor. The output voltage of LM35 is linearly proportional to
centigrade temperature. It measures temperature within the
range of -55 C TO +150C and detects fire. This sealed
precision centigrade sensor circuit provides protection from
oxidation. Since it produces a higher output voltage it does not
require any amplification process. This sensor is used to detect
the body temperature of the person wearing it. Once it
completes the detection process it sends the detected data to
the microcontroller for processing it.
B. LM38 Sensor
Heartbeat is a vital health parameter in the human
cardiovascular system. The heartbeat sensor LM38 was
designed based on the principle of photo phlethysmography.
The volume of the blood that flows through any body organ is
measured using this sensor. The change in volume of blood
during its flow changes the light intensity though the vascular
region of that organ. In certain applications the timing of the
heart pulses is more important, for such cases the pulse rate is
monitored. The rate of heart pulses is used to determine the
flow of blood volume. The light absorbed by blood helps to
find the signal pulses for its equivalent heart beat pulses. The
pressure sensors are required to measure a very high changes
in speed of pressure. The heartbeat of the person wearing this
sensor is captured and sent to the microcontroller for
processing.
C. Pressure Sensor
Generally the pressure of liquids and gases can be
measured by using a pressure sensor. They are also called as
pressure indicators, pressure transducers, etc. Pressure sensors
can be used for applications such as altitude sensing, leak
testing, flow sensing, etc. The pressure sensor is used to
measure a person’s blood pressure. The pressure sensor and
the heartbeat sensor are integrated into the digital
sphygmomanometer.
D. Accelerometer
The accelerometer measures acceleration in an accurate
manner. The proper acceleration, which is being measured, is
different from coordinate acceleration. An accelerometer at
rest will measure 9.81m/sec and in free fall or when
accelerating due to gravity of earth will measure zero. The
acceleration force is used to predict whether a person’s posture
is either static or dynamic. It measures the angle at which the
person or object is titled by using the gravitational pull of the
Earth. When a person falls down then their acceleration force
shifts radically. When the sensed data corresponds to that of a
fall, then an alert message has to be sent so that proper action
can be taken to help the person.
E. Gyroscope
The gyroscope of the inertial unit is useful for measuring
rotational motion and orientation. It is used to measure the
angular velocity of an object which gives the information
about the position and the rotation of a moving object. The
gyroscope parameters are not affected by factors such as
gravitational pull or magnetic fields present in the
environment. The gyroscope provides us with a more accurate
reading than what an accelerometer can give us separately.
The combined data helps to distinguish between a person
sleeping and that of one who is falling down.
F. Magnetic Door Sensor
A magnetic contact switch is used to sense whether or not
the doors in the house are properly closed. The door sensors
consist of a pair of electrical connectors which are placed
slightly apart from each other. The sensor consists of one
magnet and one switch which are used to create the circuit.
When a door is opened the circuit is broken as the switch and
magnet is pulled apart, triggering an event to occur. The
opening of a door is explained using a circuit diagram in Fig 2.
Fig 2: Circuit Diagram for a magnetic door sensor when it is open
When a magnetic field is placed in parallel to the electrical
connectors, they are pulled together thereby closing the
circuit. This magnetic field closes the switch by using the
principal of magnetic attraction which states that the north and
south poles attracted to one another, bringing them closer.
The mechanism for closing the door is explained in Fig 3.
Fig 3: Circuit Diagram for a magnetic door sensor when it is closed
G. GSM
The GSM modem uses a SIM card given by the mobile
operator to operate over the subscription. The computer can be
connected to a GSM modem to communicate via the
subscription network or the internet. It can be used to send
SMS, MMS, etc. When a GSM modem is used in connection
with a USB or Bluetooth, it is called a dedicated modem. The
GSM modem can act as an interface between devices by
creating a modem interface. The GSM modem is an effective
and efficient way to start off with SMS since it does not
require a separate subscription to a service provider. In the
proposed system, after processing all the information the GSM
modem sends an SMS to the caregiver in case of any
emergency.
H. PIC
Programmable Interface Controller (PIC) are pre-built
circuit that can be programmed by the user to control systems

4. like alarms, phones, computers and other electrical devices.
One of the major advantages of the PIC microcontroller is that
it is cheap and easily available. It can be easily connected to a
computer by a USB cable or power supply. The errors or the
faults can be corrected easily since the software is easy to
learn and to simulate the program on screen which shows
visible results to the user. The PIC microcontroller can either
be programmed using an assembler or a high level language
but what makes it more useful is the feature to re-program it
whenever needed. Once the program has been simulated in the
computer, it can be transferred onto the PIC kit using the USB
cable which connects the computer and the programmable
circuit board. There is a wide variety of open source tools that
can be used to program the microcontroller. It provides us
with a large range of functionalities such as serial
programming, flash memory capacity, a large user base and a
extensive collection of applications where it can be used.
V. EXPERIMENTAL RESULTS
A. Energy Consumption
In the proposed system, the PIC microcontroller
board is connected to the GSM module, to make voice calls
and to send and receive SMS. In the existing model, which
uses Arduino Mega 2560, the power consumption of it comes
close to 6000mA. In comparison to the proposed system
which uses PIC which only uses less than 1000mA the
Arduino kit’s power consumption is too high. This difference
is shown using the bar graph in Fig 4.
Fig 4: Energy Consumption comparison between the existing and proposed
system
B. Security
In the existing system uses LM35 room temperature
sensor, LPG Gas sensor, contact sensor only. In the proposed
system, a digital sphygmomanometer is used along with
conatct sensor, accelerometer, gyroscope along with a body
temperature sensor. Together, this system provides a more
secure living condition for the elderly people.
C. Accuracy
In out system, we use a digital sphygmomanometer
which consists of a heartbeat sensor and a pressure sensor. The
difference in the blood pressure readings namely systolic and
diastolic are varied the least with the digital
sphygmomanometer unlike in the conventional mercury
sphygmomanometer. In the existing model, the accuracy of
the system is found to be only 65% whereas the proposed
model that uses a digital sphygmomanometer provides a more
efficient system with an accuracy of 88%.
Fig 5: Accuracy comparison between the existing and proposed system
VI. CONCLUSION
The health parameters of the person is being monitored by
the PIC microcontroller because of its features like low data
rates, low power consumption, etc. In this paper, a system for
monitoring is explored so as to avoid hazards mainly in a
compact environment like home. This system is more efficient
and less power consuming than its predecessor. The contact
sensor is used to detect security threats. Temperature,
Heartbeat and Pressure sensors are used to determine the
health parameters of the person. Gyroscope and the
accelerometer help to detect whether or not a fall has occurred.
All these elements come together to create a smart home
system to provide a safe and secure living condition for
elderly people.
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