4. Abstract
This paper describes a Heart monitoring system. This heart monitoring system consists
of ECG monitoring.Electrocardiography (ECG or EKG) is a interpretation of the electrical
activity of the heart over time captured and externally recorded by skin electrodes.
5. HEART MONITORING SYSTEM
Sagar Shah
Mihir Shah
Amit Sheth
SE Electronics, S.P.I.T.
under the guidance of: Prof. Y. S. Rao
Sardar Patel Institute of Technology
Munshi Nagar, Andheri (West), Mumbai-400058
6. Chapter 1
Introduction
Heart rate measurement is one of the very important parameters of the human cardiovascular
system. The heart rate of a healthy adult at rest is around 72 beats per minute (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.
The heart rate rises gradually during exercises and returns slowly to the rest value after
exercise. The rate when the pulse returns to normal is an indication of the fitness of the
person. Lower than normal heart rates are usually an indication of a condition known as
bradycardia, while higher than normal heart rates are known as tachycardia. Heart rate is
simply and traditionally measured by placing the thumb over the subject’s arterial pulsation,
and feeling, timing and counting the pulses usually in a 30 second period. Heart rate (bpm)
of the subject is then found by multiplying the obtained number by 2. This method although
simple, is not accurate and can give errors when the rate is high. More sophisticated methods
to measure the heart rate utilize electronic techniques. Plenty of noninvasive methods exist
for electronically sensing the human heartbeat. The job can be done acoustically (stethoscope
or Doppler), mechanically (sphygmomanometer), electrically (EKG), and optically [1].
1
7. Chapter 2
Circuit Implementations
The following methods describe the circuit design of a heart rate monitoring in 2 ways:
2.1 Method 1: ECG(Electrocardiogram)
In ECG, The electrical waves can be measured at electrodes placed at specific points on
the skin. Electrodes on different sides of the heart measure the activity of different parts
of the heart muscle. An ECG displays the voltage between pairs of these electrodes, and
the muscle activity that they measure, from different directions, can also be understood as
vectors. This display indicates the overall rhythm of the heart and weaknesses in different
parts of the heart muscle. It is the best way to measure and diagnose abnormal rhythms
of the heart, particularly abnormal rhythms caused by damage to the conductive tissue
that carries electrical signals, or abnormal rhythms caused by electrolyte imbalances. In
a myocardial infarction (MI), the ECG can identify if the heart muscle has been damaged
in specific areas, though not all areas of the heart are covered. The ECG cannot reliably
measure the pumping ability of the heart, for which ultrasound-based (echocardiography) or
nuclear medicine tests are used[2].
2.2 Method 2
In the heart beat measurement using optical sensor the changes in the reflectivity of the
tissue is measured. The basic principle behind using an optical sensor for measurement
of heart rate is that whenever the heart beats, it pumps the blood through the limbs and
tissues. Thus blood volume in the tissues changes and hence the reflectivity of the skin to
the infrared rays changes. This transducer works with the principle of light reflection,in this
case the light is infrared. The skin is used as a reflective surface for infrared light. The
density of blood in the skin will affect on the IR reflectivity. The pumping action of heart
causes the blood density rises and falls. So that we can calculate the heart rate based on
the rise and fall of intensity of infrared that reflected by skin[3].
2
8. Chapter 3
Components and Software
The following discrete components and supporting software has been used.
3.1 Components
• Resistors
1. R1 - 220K 1/4 W
2. R2 - 10K 1/4 W
3. R3 - 220K 1/4 W
4. R4 - 100 1/4 W
5. R5 - 100K 1/4 W
6. R6 - 10K 1/4 W
7. R7 - 220K 1/4 W
8. R8 - 100K 1/4 W
9. R9 - 10K 1/4 W
10. R10 - 10K 1/4 W
11. R11 - 100 1/4 W
12. R12 - 1M 1/4 W
13. R13 - 1M 1/4 W
14. R14 - 1K 1/4 W
15. R15 - 22K 1/4 W
• Capacitors
1. C1 - 0.022uf
2. C2 - 0.022uf
3. C3 - 0.01uf
4. C4 - 0.01uf
5. C5 - 1uf
3
9. 6. C6 - 0.022uf
• TL084 Instrumentation Amplifier IC.
3.2 Software
• For Simulation: Livewire 1.11 Pro Unlimited
• For Layout: Eagle 5.4.0 Light
4
10. Chapter 4
Circuit Description
Figure 4.1: Electrocardiogram
The circuit shown in Fig.1(a) is for developing ECG waveforms. There are in all 3 elec-
trodes to be connected to the patients body. The ground terminal electrode to the leg.
Remaining terminals on the either of the hands and the signal from electrode to the respec-
tive two inputs. The input signal is fed to intrumentation amplifier and the signal from
instrumentation amplifier is fed to difference amplifier and then to filtering and output cir-
cuitry. The IC used for the purpose is IC TLO84. Accordingly we get the ECG waveform[4].
5
11. Chapter 5
PCB Layout And Schematic
The schematic is made in Livewire 1.11 Pro. The layout has been designed using Eagle 5.4.0.
The general purpose board is used to further elaborate the simplicity of the circuit.
Figure 5.1: Livewire Schematic
6
13. Chapter 6
Troubleshooting
• Removal of power supply hum: Use DC battery directly instead of giving supply with
the help of transformer and rectifier circuit.
• Improving CMRR: Use instrumentation amplifier IC TL08 instead of making it with
the help of OP-AMP.
• Decreasing the distortion at the output: Use Notch filter of 60 Hz at the output.
• Output ECG is not proper: Apply proper gel to the limbs where electrodes are placed.
8
14. Chapter 7
Conclusion
The design of a Low cost device for measuring the heart pulse rate has been described.
The device has the advantage that it can be used by non-professional people at home
to measure the heart rate easily and safely. The device can be improved in certain
areas with the help of microcontroller as listed below:
o A graphical LCD can be used to display a graph of the change of heart rate over
time o Sound can be added to the device so that a sound is output each time a pulse
is received. o The maximum and minimum heart rates over a period of time can be
displayed. o Serial output can be attached to the device so that the heart rates can be
sent to a PC for further online or offline analysis. o Warning or abnormalities (such
as very high or very low heart rates) can be displayed on the LCD or indicated by an
LED or a buzzer.
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15. Chapter 8
Bibliography
[1]Paper on ”HEART RATE MEASUREMENT FROM THE FINGER USING A
LOW-COST MICROCONTROLLER” by Dogan Ibrahim and Kadri Buruncuk.
[2]Biotech instruments.
[3]http://www.emo.org.tr/ekler/a568a2aa8c19a31 ek.pdf
[4]Op-Amps and Linear Integrated Circuits by Ramakant Gayakwad
[5]www.alldatasheets.com
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