J Med Syst (2006) 30:205–209
DOI 10.1007/s10916-005-7989-6
R E S E A R C H PAP E R
Low-Cost Compact ECG With Graphic LCD and
Phonocardiogram System Design
Sadık Kara · Semra Kemaloğlu · Şamil Kirbaş
Received: 11 March 2005 / Accepted: 18 April 2005
C Springer Science+Business Media, Inc. 2006
Abstract Till today, many different ECG devices are made
in developing countries. In this study, low cost, small size,
portable LCD screen ECG device, and phonocardiograph
were designed. With designed system, heart sounds that take
synchronously with ECG signal are heard as sensitive. Improved system consist three units; Unit 1, ECG circuit, filter
and amplifier structure. Unit 2, heart sound acquisition circuit. Unit 3, microcontroller, graphic LCD and ECG signal
sending unit to computer. Our system can be used easily in
different departments of the hospital, health institution and
clinics, village clinic and also in houses because of its small
size structure and other benefits. In this way, it is possible that
to see ECG signal and hear heart sounds as synchronously
and sensitively. In conclusion, heart sounds are heard on the
part of both doctor and patient because sounds are given to
environment with a tiny speaker. Thus, the patient knows and
hears heart sounds him/herself and is acquainted by doctor
about healthy condition.
Keywords Compact ECG . Phonocardiograph and graphic
LCD
S. Kara () · Ş. Kirbaş
Erciyes University, Department of Electronics Engineering,
38039, Kayseri/Turkey
e-mail: kara@erciyes.edu.tr
S. Kemaloğlu
Erciyes University, Department of Biomedical
Devices Technology, 38039,
Kayseri/Turkey
e-mail: ksemra@erciyes.edu.tr
Introduction
There are a great number of fatalities due to cardiovascular
problems in the world. One of the most useful diagnostic
tools for heart patients is the electrocardiogram (ECG) which
operates by measuring the tiny electrical signals emitted by
heart through chest electrodes [1].
The first of ECG measurement devices is materialized in
the 1946. Until to these days, many different ECG devices
are produced in during developing.
Some of these devices that collect ECG data from locations other than the external surface of the body (typically
ECG), devices for interpretation or pattern recognition (e.g.,
QRS detectors, alarm circuits, rate meters, diagnostic algorithms), fetal ECG monitors, ambulatory monitoring electrocardiographic devices, including ECG recorders and associated scanning and readout devices devices for fetal heart
rate monitoring, vectorcardiographs that is the display of
loops pulse plethysomographic devices electrocardiographs
used in other medical devices (e.g., patient monitors, defibrillators, stress testing devices). Also telemetry systems and
Holter monitor that recording ECG during long period.
In our literature study, very much compact ECG devices
with LCD screen were researched. These systems that is
shows ECG signals, connected to computer, have print feature and in small dimensions [2–5].
While making its physiological activity, the heart produces sounds having low frequency, large dynamic range
and fastly changing content. Expert physicians listen to the
heart sounds by using stethoscope to make a decision on
heart defects. By the way, the diagnosis of the heart defects
would be possible in a large range from aortic regurgitation and mitral regurgitation to ejection click and systolic
murmur.
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One of the most common method used for listening and
tracking the heart sounds is to record it with a special devices. First heart sound recording had done by K. Huerthle
in the 1893. In recording the heart sounds, the PCG (Phonocardiography) is a particularly useful diagnostic tool because
the graphic recordings show timings and relative intensities
of heart beat sounds [6–8].
The sounds produced during a cycle of normal cardiac activity occur principally in two groups, known as
the first and second heart sounds. These two bursts of
sound correspond to the familiar lub-dub sound one hears
through the stethoscope. The time of the first sound corresponds to the end of atrial contraction and the beginning of
ventricular contraction. Closure of the mitral and tricuspid
valve (between the atria and ventricles) contributes significantly to this sound. Frequency band and duration are 30–
100 Hz and 50–100 ms respectively. The second heart sound
is produced initially by a slight backflow of blood into the
ventricles, just preceding closure of the outflow valves (aortic and pulmonic valves), and then by closure of these valves
a short time later. Frequency band and duration are 100–
200 Hz and 25–50 ms respectively [9].
Aim of this study, designing low-cost compact ECG and
PCG that have small dimensions and it is heard heart sounds
as synchronous and sensitively. Also, ECG signal should be
transferred to computer due to apply signal processing tools.
The designed compact system should be used hospital, clinic,
and village clinic, even in houses.
Material and method
The block diagram of system seen in Fig. 1 was designed as
three units.
1. Unit: ECG signals have amplitudes of a few milivolts and
must be amplified to the level of volts by an input amplifier. The filter portion, clamping unit and ECG amplifier
are seen on the Fig. 2. The amplifier converts the difference of signals between electrodes to an output voltage.
All of the circuits are used TL084 which have quartet operational amplifier. There are a couple of ECG electrodes
Fig. 1. System block diagram.
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J Med Syst (2006) 30:205–209
on the back of device. Therefore ECG electrodes are being
done direct contact to chest by physician.
ECG signals that output of instrumentation amplifier is
transferred to filter unit due to elimination of high frequency noise [10]. The cut-off frequency of filter unit is
150 Hz. ECG signal is transmitted to clamping unit by additional an amplifier circuit. Basic amplification process
is done by this additional amplifier stage due to gain of
instrumentation circuit is low.
2. Unit: This stage related to acquisition of heart sounds. In
this unit, there are the perceive unit of heart sounds, preamplifier and filter stage are given Fig. 3. Heart sounds
are taken via capacitive transducer in diaphragm which
is used to insulate from surroundings on back of device.
The capacitive transducer operation voltage is 5–12 V,
microphone bandwidth is 20–300 Hz. Acquired heart
sound signal is filtered with low pass filter which has
cut off frequency 200 Hz after pre amplifier unit. The
obtained heart sound electrical signal is transferred to
loudspeaker.
Resistance of amplifier is selected suitable with resistance of loudspeaker in accordance with max power
theorem. R39 potentiometer is ensured to adjustment
resistance for different loudspeakers. For ECG and
heart sound units are used only two TL084 IC. The
heart sounds can be heard clearly on the speaker or
headphones along with audio-visual indication by the
flashing LED indicator.
3. Unit: LCD and microcontroller units are shown with
Fig. 4. ECG signal converted to digital with PIC16F877
which has A/D converter is transferred to graphic
LCD. Digital ECG data are changed to LCD code
system since ECG signal is seen as electrical signal
on the LCD screen. Monitoring frequency of signal
can be adjusted to desired value by delay cycle. Amplitude of signal on the screen is set as manual by
button.
In this study, used graphic LCD (EL12864A) has a structure 128×64 dot matrix, this LCD is inexpensive and can be
provided easily in market. The components of KS0108 and
KS0107 that checked to graphic LCD is triggered all of the
J Med Syst (2006) 30:205–209
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Fig. 2. (a) ECG circuit, (b)
filter and amplifier structure.
process (read, write. . .) by standard codes that send to input
terminal.
RS232 protocol was used to communicate with computer.
The computer is communicated to microcontroller using
Max232C converter by 2. (rx), 3. (tx) ve 5. (gnd) terminal of
serial port. In our study, receiver program in computer prepared with visual C++ programmer language. The caution
signal that send from computer program direct to microcontroller for data transfer and so received signal data are
monitored on computer as analog signal. Also, signal and
other information can be saved to personal computer.
Electromagnetic compatibility and other tests of system
were done in calibration and research-development laboratory in local organize Industry.
Result and discussion
As a result in this study, low cost, small size, portable and
compact ECG device with LCD screen was designed. With
designed system, heart sounds that take synchronously with
ECG signal are heard as sensitive. In this way, it is possible
that to see ECG signal on graphic display and to hear heart
sounds synchronously. A device such as this is useful from a
diagnostic perspective, and stands to greatly aid the diagnosis
of heart conditions, leading to better medical treatment.
The system built in rechargeable battery independent
from network, so its usage area is extensive and problems formed from network frequency not available. System is offered electrical safety because of independent
Fig. 3. Heart sound circuit
structure.
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Fig. 4. (a) Microcontroller,
Graphic LCD and (b) circuit of
transferring to computer.
electrical network. The our system can be used easily
in different departments in hospital, other health institution and clinics, village clinic moreover in houses because of its small size structure and other benefits. Thus,
ECG device requirement [11] in the small health center is
remedied.
Conclusion
Generally, in the majority physical applications, physician
listens to unhealthy person by stethoscope during inspection.
The person that being inspection isn’t heard heart sounds
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belongs to her or his at that time inspection listen by stethoscope.
In our designed system, heart sounds are heard on the part
of both doctor and patient due to the fact that sounds are given
to environment with a tiny speaker. Thus, the patient knows
and hears heart sounds him/herself and is acquainted by
doctor about healthy condition. Because structure of system
is without cable, is prevented whatever an artifact and ensure
easy to use.
The ECG signal that seen on the LCD can be transferred to
computer and monitored on the computer. In this way, signal
process procedures can applied to ECG signal that saved in
the computer and so, methods can be developed auxiliary to
disease diagnostic.
J Med Syst (2006) 30:205–209
Fig. 5. ECG signal on the LCD screen.
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