Biometric Based Heart Beat Monitoring System
Richa Gupta
Department of Electronics and Commmunication
Maharaja Surajmal Institute of Technology
Delhi,India
[email protected]
Abstract—There has been exponential increase in health care
cost in last decade. This paper describes the development of
reliable, cheap and accurate heart beat monitor system through
heart beat sensor. This paper deals with signal conditioning and
data acquition of heart rate signal. The hardware and software
designed are oriented towards microcontroller based system,
minimizing the complexity of system. The important feature of
this paper is to use fingertip sensor to monitor and compute
heart rate &displayed on LCD monitor
fingertip heartbeat sensor. Result and Conclusion are given in
Section IV, while future advancements are given at the end
II. HARDWARE SYSTEM
The hardware Design is based on an embedded system
implementation using PIC16FA778 microcontroller from
microchip. The block diagram of hardware system is shown in
Fig 1.
Keywords:Heart beat Sensor, microcontroller, heart beat
monitoring
I.
INTRODUCTION
Technology is being used everywhere in our daily life to fulfill
our requirements[1]. One of the ideal ways of using
technology is to employ it to sense serious health problems so
that efficient medical services can be provided to the patient in
correct time. Changes in lifestyle and unhealthy lifestyles have
resulted in incidents of heart disease. Coronary heart disease is
the measure cause of death. Hence there is a need that patient
is able to measure the hearth rate in home environment as
well.
The heart rate of a healthy adult at rest is around 72 bpm.
Athletes normally have lower heart rates than less active
people. Babies have a much higher heart rate at around 120
bpm, while older children have heart rates at around 90 bpm.
Heart beat monitor and display system is a portable and a best
replacement for the old model stethoscope which is less
efficient. The heart beat rate is calculated manually using
stethoscope where the probability of error is high because the
heart beat rate lies in the range of 70 to 90 per minute whose
occurrence is less than 1 sec, so this device can be considered
as a very good alternative instead of a stethoscope. The
functioning of this device is based on the truth that the blood
circulates for every heart beat which can be sensed by using a
circuit formed by the combination of an LDR and LED.
Depending upon the rate of circulation of blood per second the
heart beat rate per minute is calculated. This device consists of
a micro controller [2] which takes the input from the fingertip
sensor and calculates the heart rate of the patient. The micro
controller also takes the responsibility to display the same on
LCD, which is interfaced to it through LCD drivers.
The next Section gives, Hardware system overview, SectionIII
introduces software used for implementation of prototype
Fig 1: Block diagram of Microcontroller based heartbeat monitor
with display on LCD
The block diagram consists of Microcontroller
PIC16FA778, Heart Beat Sensor, Reset, Crystal
Oscillator,LCD Driver,LCD Display,LCD Intensity Control
and LED Indicators.
2.1 Microcontroller 16FA778
A Microchip Microcontroller PIC 16FA778 [3] is used to
collect and process data. It has 256 bytes of EEPROM data
memory, 2 camparator, 8 channels 10 bit Analog to Digital
Convertor. It has on chip 3 timers and 8k flash program
memory. The Heart beat Sensor is interfaced to
microcontroller via port pins. The Output of Sensor is fed to
microcontroller via ADC (Analog to Digital Convertor).An
LCD is used to display data.
2.2 Heart Bear Sensor
3.1 Microcontroller Software
Heart beat Sensor consists of super bright LED and LDR. It
works on the principle of light modulation by the blood flow
through finger at each pulse. The finger is inserted in probe,
shown in Fig 2 and red light from high intensity LED is
allowed to fall on the finger. The amount of red light absorbed
by finger varies according to the pulsatile blood flow in the
finger. Therefore the amount of light transmitted varies
according to the blood flow. The LDR placed on opposite side
of LED detects the transmitted light. With increase in
transmitted light its resistance decreases and vice-versa. A
voltage divider circuit is employed to get a voltage signal
proportional to the resistance of the LDR. This voltage signal
consists of AC and DC components. Non-moving structures
(veins, blood capillaries, bones, soft tissues, non-pulsatile
blood) absorb constant amount of light and hence contribute to
the DC component of voltage signal. As it provides no
information about the blood pulses, DC components are not
needed. Pulsatile blood absorbs varying amount of light and
hence contributes to AC component of voltage signal. AC
components are our required signal. The magnitude of the DC
components is almost 100-1000 times higher than the AC
components. Hence they need to be removed in order for the
AC components to be conditioned properly further on.
Therefore, a high pass filter circuit is employed after the
voltage divider network to block the DC components of the
signal. The AC signal is now amplified from mV range to V
range. The amplified signal is given to a comparator where it is
compared against a set threshold value. The comparator output
consists of positive pulses corresponding to blood pulses. The
comparator output is given to the microcontroller. The
microcontroller calculates the time duration between 2
successive pulses and then computes the instantaneous heart
rate. The microcontroller then proceeds to display the
calculated heart rate on the LCD display,as shown in Fig 3.
Fig 2: Placing the finger on heart beat sensor
III. SOFTWARE SYSTEM
This work is implemented using the following software,
Proteus – for designing circuit and simulation, MPlab - for
compilation ,Embedded C – for programming code , Pickit2 –
for dumping the programming code into the microcontroller
(Burner)
In this case, the method consists of computing the heart rate of
the person each minute. A pre-processing step is needed to
perform an amplification of the signal and hardware filtering to
remove unwanted components. The programming language
used to program the microcontroller is Embedded C. Many
algorithms have been investigated to choose the best fit method
for the microcontroller. The micro controller is programmed in
such a way that it takes input from the heart beat sensor when a
finger is inserted into it and displays the value on the LCD
continuously.
Fig 3: Hardware Design
IV. RESULT AND CONCLUSION
In this paper, the implementation of an embedded system,
based on microcontroller for real time analysis of heart beat
rate has been investigated. The system has been tested
successfully on subjects of different age group. The heart beat
sensor which detects heart beat is interfaced to microcontroller
along with LCD, which display the heart beat rate. The goal of
the paper is to reduce the hospitalization and assistance cost.
The pulse rate can be used to check overall heart health and
fitness level. Besides it can prove to be a boon for senior
citizen people who won’t have to travel distances or wait in
long queues at the hospitals and clinics to get a measure of
their heart beat. They can themselves handle this device easily
by sitting at home. The low cost factor associated with this
device can make it a household name.
V. FUTURE SCOPE
The work can be extended to improve health care system
by transmitting patient’s physiological signals wirelessly.
Wireless technology like Zigbee can be used to eliminate the
wired mechanism [4]. Also, GSM module can be used to send
the monitored heart beat values for doctor reference. The work
can also be extending to measure other vital body signals like
Blood pressure and transmit them wirelessly.
REFERENCES
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[2]
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Microcontrollers, Microchip Technology Inc., 2001.
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