Eg24842846

Shukla, Vandana Pandya / International Journal of Engineering Research and Applications
(IJERA) ISSN: 2248-9622 www.ijera.com
Vol. 2, Issue 4, June-July 2012, pp.842-846
Open Hardware Platform For Reconstruction Of ECG Signal
Deepali Shukla1 (Asst.Professor), Vandana Pandya2 (Asst.Professor)
Medicaps Institute of Technology & Management, Indore (M.P.), India

Abstract
At present the heart disease is one of the heart that depicts the cardiac cycle. It is routinely
serious disease that may threaten human life. The used as a first course of choice in diagnosing many
electrocardiogram is important role in the cardiovascular diseases [7].
prevention, diagnosis the abnormality of patients
& rescue of heart disease. An ECG is used to A. ECG Measurement
measure the electrical activity of the heart treated The potential created by the heart wall
as a vector quantity. It measures the rate and contraction spreads electrical currents from the heart
regularity of heartbeats. The goal of this project is throughout the body. The spreading electrical
to develop a device classified as a “Open hardware currents create different potentials at different points
platform for reconstruction of ECG signal ”.A on the body. Leads are placed on the body in several
remote device is attached to the person being pre-determined locations to provide information
monitored. The remote device acquires the raw about heart conditions. The cardiac signal, typically 5
ECG data from the Leads which are placed in mV peak to peak, is an AC signal with a bandwidth
predefined areas of the body. In this paper three of 0.05 Hz to 50 Hz
lead ECG monitor system is present, which can be .
used for measurement & recording of human The Three Lead ECG
electrocardiogram. ATMEL Atmega8 AVR series The electrical activity can be represented as
microcontroller is the heart of system which is in a dipole (a vector between two point charges). The
the Severnio board. The ECG signal from the placement of the electrodes on the body determines
body is amplified and filtered by the the view of the vector as a function of time[1]. Figure
instrumentation amplifier. Sevrenio is an open 1 represents the most basic form of the electrode
hardware, Bluetooth wireless communication, placement which is based on Einthoven’s triangle.
single microcontroller, multiple I/O platforms, This theoretical triangle is drawn around the heart
used in this project to interface our with each apex of the triangle representing where the
electrocardiogram Signal conditioning circuit to fluids.
the PC. Necessary filter requirements (for ECG Around the heart connect electrically with
frequency band selection) and formatting of the limbs. Lead I measure the differential potential
filtered ECG data (for transmission) both occur in between the right and left arms, Lead II between the
the Severnio board in which AVR microcontroller right arm and left leg, and Lead III between the left
is present. A second Data acquisition unit is arm and left leg.
connected to Serial port of a P.C. The data is then
transmitted via the serial port to the P.C for
display. A user friendly graphical interface (GUI)
was constructed using Visual Basic 6.0 enterprise
edition. The GUI allows for the monitoring of real
time ECG data. A database was implemented
using MS Access 2000. This allowed for storage of
the ECG data.

Key Words: Open Hardware ECG, Electrodes,
Severnio Board, Serial cable, PC.

INTRODUCTION
Cardiac disease is one of the most dangerous Figure 1: The Three Leads
threats to human health. Moreover, due to the Einthoven’s law also states that the value of any point
problem of aging of population is getting worse and of the triangle can be computed as long as values for
worse, the number of cardiac deaths is sustained the other two points are known [1]. The Einthoven
increasing [6]. ECG diagnosis has the advantages of limb leads (standard leads) are defined in the Figure
convenience, precision and low-cost, and therefore
ECG diagnosis has been widely used nowadays. An
electrocardiogram (ECG) is an electrical recording of

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SYSTEM FUNCTIONALITY into three sections. The section A works as a voltage
ECG Design follower of the two input signals, the circuit has a
The heart electric signal has a very small high input impedance and can be connected to other
amplitude (around1mV) and is immersed into other devices or human signals without changing the shape
greater signals produced by the body. To be able to of the signal to be measured. The section B is a
measure the heart signals, first they must be differential amplifier, it takes the difference between
amplified and filtered form those we are not the two input signals and multiplies it times a factor.
interested in. If the goal is to digitize the ECG signal Basically this ECG system takes the difference
the frequencies of the heart signal goes from 0.05Hz between the two voltages measured in both arms
to 100Hz, first the frequencies out of that range must having as a reference voltage that measured in one
be minimized and then they should pass through a leg. In the figure, the inputs labeled as VRA and
stage of amplification, later, the resulting signal has VLA represent the Voltage of the Right Arm and the
to be Manipulated so it can be in the range of 0-5V in Voltage of the Left Arm, respectively, while the VLL
order to be digitized. input represents the Voltage of the Left Leg acting as
A. Signal Acquisition a reference of the bioelectric potentials. The ECG
The circuit used for acquire the heart signal is an electrodes should be connected in the inner part of
instrumentation amplifier (figure 3) which is divided the left ankle and both wrists.

Figure 2: Three Leads Calculations

The Operational Amplifiers (Opamps) used greater than 100Hz do not belong to heart signals,
are built with the JFET technology (TL084), hence additionally, when the frequencies lower than 0.05Hz
they have a high input impedance and need a very are filtered, we eliminate the difference of potential
small polarization current, giving an electrical safety between the electrodes and the skin surface that can
margin for the patient. With the configuration shown reach levels up to 300mV and may saturate the
in the figure 3, the gain of amplifier is given by amplification devices. In the circuit used to
A= (1+2R1/R2)* (R7/R4) implement the Anti Aliasing low pass filter (figure
The section C is Anti aliasing low pass 3C).The filter is a simple low pass filter; its job is to
filter, its job is to remove electrical noise picked up remove electrical noise picked up from fluorescent
from fluorescent lights, computers and AC power lights, computers and AC power lines. ECG has
lines. When ECG is amplified the noise is amplified amplitude of only about mV, so to detect it an
too & after swaps the ECG signal. Luckily, the amplifier is needed. There is a problem through
noised is usually of a higher frequency than the ECG electrical noise or electromagnetic interference.
this noise can be reduced by low pass filter. The
amplifier takes input from self sticking electrodes HARDWARE DESIGN
that are attached to the body of the subject whose A. Instrumentation Amplifier
ECG is being taken. It is important for the cables The instrumentation amplifier is generally
connecting the electrodes to the inputs of the circuit used for this purpose. The instrumentation amplifier
to be as short as possible. is a type of differential amplifier that has been
outfitted with input buffers which eliminate the need
B. Anti Aliasing low pass filter for input impedance matching and thus make the
The next step is anti aliasing filter that amplifier particularly suitable for use in measurement
ensures that the resulting signal contains only and test equipment. The instrumentation amplifier is
frequencies from 0.05Hz to100Hz[1]. Frequencies useful for amplifying small differential signal which
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may be riding n high common mode voltage levels. signals in mili-volt range which is supplied from a
This amplifier is particularly useful in amplifying high

A B C

Figure 3: Circuit Diagram of ECG

impedance source. Additional characteristics includes Severnio Interfaces to digitize and introduce the ECG
very low DC offset, low drift, low noise, very high signal to the computer via a Bluetooth wireless
input impedance. connection. This system uses AVR microcontroller
AT mega 8 as its brain. Eight channel ADC receives
B. Severnio Board analog signal from ECG circuit and convert the data
The hardware design is based on an in to digital signal.
embedded system implementation using ATMega8
AVR microcontroller within Severino Board. This SOFTWARE DESIGN
was used to verify the various ideas and the The ECG signal’s bandwidth is 100Hz, so
requirements for final system design. according with the Nyquist’s theorem; the minimum
required sampling frequency is 200Hz. The program
is
sampling with at 250Hz which is a sufficiently large
frequency for acquiring the ECG signal.

The software consist of a Standard
programming language & boot loader that runs on the
board. Software for the microcontroller is designed in
C language. Before writing a program, modes of
serial communication are decided, baud rate is
selected. & Take 100samples/sec. the microcontroller
is programmed in following way:
Figure 4: Severnio Board

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Figure 5: Severnio Software

Counter can be clock internally by the prescalar.
The prescalar is set by clock select bit CS20, CS21, CS22 equal to one.
Set counter value in Timer/Counter register 2.
Mask the AS2 bit in asynchronous status register
When AS2 is written to zero, Timer/Counter 2 is clocked from the I/O clock, clkI/O.
In Timer/Counter mask register
OCIE2: Timer/Counter2 Output Compare Match Interrupt
Timer/Counter2 Compare Match interrupt is disabled.
TOIE2: Timer/Counter2 Overflow Interrupt Enable
Timer/Counter2 Overflow interrupt is enabled.

RESULT
The design was successfully dissected into various modules. Each module with has been implemented.
The integration of the individual modules was achieved successfully. All the GUI functionality discussed in the
report is operational.
The ECG signal can be sampled and analyzed in real-time.
The ECG data also can storage in SQL Database and transport the data to PC via Serial cable.
The storage of ECG data to the database has been implemented successfully.
The system consist of two section
1. Hardware Section
2. Software Section

Hardware Section:
ECG signals captured by Electrodes are processed and filtered by signal conditioning block.
Now Filtered signals are given to MCU Board.
Microcontroller has in inbuilt 10-bit analog to digital converter, which convert analog signal coming from
human body(Amplified by instrumentation amplifier) into digital signal .
Microcontroller is capturing 200 samples in one sec. from analog pin

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Figure 6: ECG graph

Software Section: REFERENCES
 Received 200 samples(contain digital values [1] Anwar Vahed ”3-Lead Wireless ECG”.
) now stored in data base. [2] Ramakant Gaikwad “Opamp and Linear
VB code used stored data from database and plot Integrated Circuits”,Pearson Education, 4th
ECG waveform. In the figures 6 the plot of the data Edition,p-p 1-247.
stored in the *.dat file after digitalizing and filtering [3] Alejandro Romero, Carely Heras, Miriam
the signal. Vega, Javier Naranjo, Carlos Vázquez, Arturo
Preciado,”Intelligent Open –Hardware ECG
CONCLUSION Platform for the heart Patients Control and
The implementation of the proposed system Diagnosis”.
is entirely feasible, especially in those developing [4] Ghongade, R. and Ghatol, A.A.; A brief
countries that have serious delays in the health performance evaluation of ECG feature
systems, because the cost of an ECG study will extraction techniques for artificial neural
inevitably decrease making the study reachable for network based classification, TENCON 2007,
most of the population. IEEE Region 10 Conference Oct. 30 2007-
As future work, one important Nov. 2 2007 p.p. 1 – 4.
characteristics of the heart disease detection system is [5] Ms. Kanwade A. B., Prof. Dr. Patil S. P., Prof.
that after some modifications, it can work as a mobile Dr. Bormane D.S. :“ Wireless ECG
device, making the patient able to be almost in every monitoring system”.
place in the planet and still know his heart status. The [6] Shi Zhang, Jinshuan Zhao, Lihuang She, and
patient would use our GSM system with a computer Guohua Wang:” A Novel Pocket Intelligent
that receives the signal and then sends the data to a One Lead ECG Monitor
web server, in which the analysis is done. Once the Based on Fingers Touching”.
web server gets the analysis results, they can be sent [7] Tanveer Syeda-Mahmood, David Beymer, and
back to the patient along with some medical Fei Wang “Shape-based Matching of ECG
recommendations. Recordings”

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