pulse counting project

Mini project 2013 Heart rate measurement through finger tipCHAPTER 1

INTRODUCTION

This project is based on the principle of photoplethysmography (PPG) which is a non-invasive method of measuring the variation in blood volume in tissues using a light source and a detector. Since the change in blood volume is synchronous to the heart beat, this technique can be used to calculate the heart rate. Transmittance and reflectance are two basic types of photoplethysmography. For the transmittance PPG, a light source is emitted in to the tissue and a light detector is placed in the opposite side of the tissue to measure the resultant light. Because of the limited penetration depth of the light through organ tissue, the transmittance PPG is applicable to a restricted body part, such as the finger or the ear lobe. However, in the reflectance PPG, the light source and the light detector are both placed on the same side of a body part. The light is emitted into the tissue and the reflected light is measured by the detector. As the light doesn’t have to penetrate the body, the reflectance PPG can be applied to any parts of human body. In either case, the detected light reflected from or transmitted through the body part will fluctuate according to the pulsatile blood flow caused by the beating of the heart.

There is a reflectance PPG probe to extract the pulse signal from the fingertip. A subject’s finger is illuminated by an infrared light-emitting diode. More or less light is absorbed, depending on the tissue blood volume. Consequently, the reflected light intensity varies with the pulsing of the blood with heart beat. A plot for this variation against time is referred to be a photoplethysmographic or PPG signal.

The PPG signal has two components, frequently referred to as AC and DC. The AC component is mainly caused by pulsatile changes in arterial blood volume, which is synchronous with the heart beat. So, the AC component can be used as a source of heart rate information. This AC component is superimposed onto a large DC component that relates to the tissues and to the average blood volume. The DC component must be removed to measure the AC waveform with a high signal-to-noise ratio. Since the useful AC signal is only a very small portion of the whole signal, an effective amplification circuit is also required to extract desired information from it.

The use of TCRT100 simplifies the build process of the sensor part of the project as both the infrared light emitter diode and the detector are arranged side by side in a leaded package, thus blocking the surrounding ambient light, which could otherwise affect the sensor performance. The output pulse can be fed to either an ADC channel or a digital input pin of a microcontroller for further processing and retrieving the heart rate in beats per minute (BPM).

Department of ECE 1 Al - Ameen Engineering College

Mini project 2013 Heart rate measurement through finger tip

CHAPTER 2

LITERATURE SURVEY

The Heart rate measurement through fingertip project, the infrared LED and photodiode

used for finger photoplethysmography were actually from salvaged parts, and therefore,

could not provide specifications for them in the article. As a result of that it takes quite a

bit of time to replicate that project with a different set of IR LED and photodiode as the

values of the current limiting and biasing resistors may have to be changed for the new

sensor to work properly. This is a revised version of the same project but with all the

components specified this time. The new version uses the TCRT1000 reflective optical

sensor for photoplethysmography. The use of TCRT100 simplifies the build process of

the sensor part of the project as both the infrared light emitter diode and the detector are

arranged side by side in a leaded package, thus blocking the surrounding ambient light,

which could otherwise affect the sensor performance.


http://embedded-lab.com/blog/?p=1671


CHAPTER 3

BLOCK DIAGRAM

3.1 Amplifier and Counter section

Fig 3.1 Block diagram of Amplifier and Counter section


Mini project 2013 Heart rate measurement through finger tip3.2 Power Supply

Fig. 3.2 Block diagram of Power supply


Mini project 2013 Heart rate measurement through finger tipCHAPTER 4

BLOCK DIAGRAM DESCRIPTION

4.1. AMPLIFIER AND COUNTER

The sensor used in this project is TCRT1000, which is a reflective optical

sensor with both the infrared light emitter and phototransistor placed side by side and

are enclosed inside a leaded package so that there is minimum effect of surrounding

visible light. Pulling the enable pin high will turn the IR emitter LED on and activate

the sensor. A fingertip placed over the sensor will act as a reflector of the incident light.

The amount of light reflected back from the fingertip is monitored by the

phototransistor.

The output (VSENSOR) from the sensor is a periodic physiological

waveform attributed to small variations in the reflected IR light which is caused by the

pulsatile tissue blood volume inside the finger. The waveform is, therefore, synchronous

with the heartbeat. The AC signal is amplified by the transistor BC548.

Output of monostable 555 multivibrator remains in its stable state until it

gets a trigger. Primarily the transistor and capacitor are shorted to ground, this state is

considered as the stable state of monostable 555 multivibrator.As we know that, when

the voltage at the second pin of 555 IC goes below 1/3 Vcc, the output becomes high.

The high state is known as ‘Quasi stable’. The trigger causes the transition from stable

state to Quasi stable state. So when we press the button (Trigger), the voltage at 2nd pin

become less than 1/3 Vcc (Disconnected from Vcc), hence the output is high. Then the

discharge transistor is cut off and capacitor starts charging towards Vcc (refer internal

circuit) internal Charging of capacitor is through the resistor R1 with a time constant

R1C1. As the capacitor voltage increases and finally exceeds 2/3 Vcc, it will reset the

internal control flip flop, there by turning off the 555 timer IC. (more than 2/3



voltage at the threshold pin (6th pin) causes IC to reset).Thus the output goes back to its

stable state from Quasi stable state.

The CD54/74HC190 are asynchronously presettable BCD decade

counters, whereas the CD54/74HC191 and CD54/74HCT191 are asynchronously

presettable binary counters. Presetting the counter to the number on preset data inputs

(A−D) is accomplished by a low asynchronous parallel load (LOAD) input. Counting

occurs when LOAD is high, count enable (CTEN) is low, and the down/up (D/U) input

is either high for down counting or low for up counting. The counter is decremented or

incremented synchronously with the low-to-high transition of the clock. When an

overflow or underflow of the counter occurs, the MAX/MIN output, which is low

during counting, goes high and remains high for one clock cycle. This output can be

used for look-ahead carry in high-speed cascading. The MAX/MIN output also initiates

the ripple clock (RCO) output, which normally is high, goes low, and remains low for

the low-level portion of the clock pulse. These counters can be cascaded using RCO.

The decoder converts BCD input data into control signals. The output form the control

signals for the 7 segment display

Display is the machine man interface in every unit. This section displays

information from the microcontroller. We are planning to use alpha numeric display

since it can display both alphabets and numerals. The display units are incorporated to

perform the machine man interface through which the machine interacts with the user.

The user is first of all advised to enter his / her card in the socket and remove it once the

system read the data. Also other commands to the user are conveyed through this.



4.2. POWER SUPPLY

The correct voltage is of almost important for the proper functioning of

IC’s used in the system. Power supply in the circuit is built by using centre tapped full

wave rectifier, filter and regulator. 7812 and 7805 is used for 12V and 5V respectively.

In the receiver with a transformer 230V AC source is stepped for 24V peak to peak. The

down converter is then passed through a bridge rectifier to be converted to 12V DC

supply. Capacitor keeps the voltage to be constant, but as expected, the wave form

contain a lot of ripples. Therefore voltage regulator is needed to correct the imperfection

of the transformer. A 12V 7812 is used to generate 12V and 5V regulator 7805 is used

to generate 5V that is needed. In addition, large capacitors are coupled with the

regulator to offset any ripples or imperfection generated by the transformer.

The rectifier and filter circuit, which are used in the initial stages of a DC

power supply is essential for the operation of almost all electronic devices. A rectifier

circuit is a circuit which convert AC voltage to pulsating DC. There are 2 type of

rectifier circuit are half wave rectifier and full Wave rectifier

Now in the case of full wave rectifier circuit, this allows a unidirectional

current to flow through the load during the entire input cycle. As a result of this, output

voltage that pulsates every half cycle of the input.

A transformer is static piece of apparatus by means of which electric

power in 1 circuit is transformed in to electrical power of the same frequency in another

circuit. It can raise or lower the voltage in a circuit but with corresponding decrease or

increase in current



CHAPTER 5

CIRCUIT DIAGRAM

5.1 SENSOR AND AMPLIFIER

Fig: 5.1 Circuit diagram of Sensor and Amplifier



5.2 COUNTER AND DISPLAY

Fig : 5.2 Circuit diagram of Counter and Display



5.3 POWER SUPPLY

Fig: 5.3 Circuit diagram of Power Supply



CHAPTER 6

CIRCUIT DIAGRAM DESCRIPTION

6.1 Amplifier and Counter section

The sensor used in this project is TCRT1000, which is a reflective optical

sensor with both the infrared light emitter and phototransistor placed side by side and

are enclosed inside a leaded package so that there is minimum effect of surrounding

visible light. The circuit diagram below shows the external biasing circuit for the

TCRT1000 sensor. Pulling the enable pin high will turn the IR emitter LED on and

activate the sensor. A fingertip placed over the sensor will act as a reflector of the

incident light. The amount of light reflected back from the fingertip is monitored by the

phototransistor.TCRT1000 used for sensing pulse from fingertip



Fig 6.1: Sensor circuit

The output (VSENSOR) from the sensor is a periodic physiological

waveform attributed to small variations in the reflected IR light which is caused by the

pulsatile tissue blood volume inside the finger. The waveform is, therefore, synchronous

with the heartbeat. The following circuit diagram describes the first stage of the signal

conditioning which will suppress the large DC component and boost the weak pulsatile

AC component, which carries the required information. The AC signal is amplified by

the transistor BC548.



Fig 6.2: BC548

6.1.1 Monostable Multivibrator

Output of monostable 555 multivibrator remains in its stable state until it

gets a trigger. Primarily the transistor and capacitor are shorted to ground, this state is

considered as the stable state of monostable 555 multivibrator. As we know that, when

the voltage at the second pin of 555 IC goes below 1/3 Vcc, the output becomes high.

The high state is known as ‘Quasi stable’. The trigger causes the transition from stable

state to Quasi stable state. So when we press the button (Trigger), the voltage at 2nd pin

become less than 1/3 Vcc (Disconnected from Vcc), hence the output is high. Then the

discharge transistor is cut off and capacitor starts charging towards Vcc (refer internal

circuit) internal Charging of capacitor is through the resistor R1 with a time constant

R1C1. As the capacitor voltage increases and finally exceeds 2/3 Vcc, it will reset the

internal control flip flop, there by turning off the 555 timer IC. (more than 2/3 voltage at


Mini project 2013 Heart rate measurement through finger tipthe threshold pin (6th pin) causes IC to reset).Thus the output goes back to its stable

state from Quasi stable state.

Design equation for monostable multivibrator

On time, T=1.1 R1 C1 For time period : 30 seconds

Assuming C=470µF, we get R=56kΩ

For time period: 20 seconds

Assuming C=470µF, we get R=39kΩ

For time period: 3 minutes

Assuming C=470µF, we get R=330Kω

6.1.2 555 Timer IC Working Principle

Comparator 1 has a threshold input (pin 6) and a control input (pin 5). In

most applications, the control input is not used, so that the control voltage equals +2/3

VCC. Output of this comparator is applied to set (S) input of the flip-flop. Whenever the

threshold voltage exceeds the control voltage, comparator 1 will set the flip-flop and its

output is high. A high output from the flip-flop saturates the discharge transistor and

discharge the capacitor connected externally to pin 7. The complementary signal out of

the flip-flop goes to pin 3, the output. The output available at pin 3 is low . These

conditions will prevail until comparator 2 triggers the flip-flop. Even if the voltage at

the threshold input falls below 2/3 VCC, that is comparator 1 cannot cause the flip-flop to

change again. It means that the comparator 1 can only force the flip-flop’s output

high.To change the output of flip-flop to low, the voltage at the trigger input must fall

below + 1/3 Vcc. When this occurs, comparator 2 triggers the flip-flop, forcing its

output low. The low output from the flip-flop turns the discharge transistor off and

forces the power amplifier to output a high. These conditions will continue independent

of the voltage on the trigger input. Comparator 2 can only cause the flip-flop to output

low.



Fig no: 6.3 Internal diagram of 555 Timer IC

6.1.3 555 timer

From the above discussion it is concluded that for the having low output

from the timer 555, the voltage on the threshold input must exceed the control voltage

or + 2/3 VCC. They also turn the discharge transistor on. To force the output from the

timer high, the voltage on the trigger input must drop below +1/3 VCC. This also turns

the discharge transistor off.

A voltage may be applied to the control input to change the levels at

which the switching occurs. When not in use, a 0.01 nanoFarad capacitor should be

connected between pin 5 and ground to prevent noise coupled onto this pin from

causing false triggering.

Connecting the reset (pin 4) to a logic low will place a high on the output

of flip-flop. The discharge transistor will go on and the power amplifier will output a

low. This condition will continue until reset is taken high. This allows synchronization

or resetting of the circuit’s operation. When not in use, reset should be tied to +VCC.


Mini project 2013 Heart rate measurement through finger tip6.1.4 Counter and Display

The CD54/74HC190 are asynchronously presettable BCD decade

counters, whereas the CD54/74HC191 and CD54/74HCT191 are asynchronously

presettable binary counters. Presetting the counter to the number on preset data inputs

(A−D) is accomplished by a low asynchronous parallel load (LOAD) input. Counting

occurs when LOAD is high, count enable (CTEN) is low, and the down/up (D/U) input

is either high for down counting or low for up counting. The counter is decremented or

incremented synchronously with the low-to-high transition of the clock. When an

overflow or underflow of the counter occurs, the MAX/MIN output, which is low

during counting, goes high and remains high for one clock cycle. This output can be

used for look-ahead carry in high-speed cascading. The MAX/MIN output also initiates

the ripple clock (RCO) output, which normally is high, goes low, and remains low for

the low-level portion of the clock pulse. These counters can be cascaded using RCO.

The decoder converts BCD input data into control signals. The output

form the control signals for the 7 segment display

.

6.2 Power Supply

The system requires a regulated +5v supply for the semiconductors and

circuit. These can be delivered from the 230V domestic supply. Before applying this to

the system we must step down this high voltage to an appropriate value. After that it

should be rectified. This will provide a unidirectional current. To achieve a +5V DC we

should regulate this. All these are done in the power supply circuitry, which is explained

below. Full-wave rectification converts both polarities of the input waveform to DC,

and is more efficient. However, in a circuit with a non-center tapped transformer, four

rectifiers are required instead of the one needed for half-wave rectification. This is due

to each output polarity requiring two rectifiers each, for example, one for when AC

terminal 'X' is positive and one for when AC terminal 'Y' is positive. The other DC


Mini project 2013 Heart rate measurement through finger tipoutput requires exactly the same, resulting in four individual junctions (See

semiconductors/diode). Four rectifiers arranged this way are called a bridge rectifier:

A full wave rectifier converts the whole of the input waveform to one of

constant polarity (positive or negative) at its output by reversing the negative (or

positive) portions of the alternating current waveform. The positive (negative) portions

thus combine with the reversed negative (positive) portions to produce an entirely

positive (negative) voltage/current waveform

Fig 6.4 Center tapped rectifier

6.2.1 Rectifier output smoothing

While half- and full-wave rectification suffices to deliver a form of DC

output, neither produces constant voltage DC. In order to produce steady DC from a

rectified AC supply, a smoothing circuit, sometimes called a filter, is required. In its

simplest form this can be what is known as a reservoir capacitor, Filter capacitor or

smoothing capacitor, placed at the DC output of the rectifier. There will still remain an

amount of AC ripple voltage where the voltage is not completely smoothed. Sizing of

the capacitor represents a tradeoff. For a given load, a larger capacitor will reduce ripple

but will cost more and will create higher peak currents in the transformer secondary and


Mini project 2013 Heart rate measurement through finger tipin the supply feeding it. In extreme cases where many rectifiers are loaded onto a power

distribution circuit, it may prove difficult for the power distribution authority to

maintain a correctly shaped sinusoidal voltage curve.

For a given tolerable ripple the required capacitor size is proportional to

the load current and inversely proportional to the supply frequency and the number of

output peaks of the rectifier per input cycle. The load current and the supply frequency

are generally outside the control of the designer of the rectifier system but the number

of peaks per input cycle can be effected by the choice of rectifier design.

A half wave rectifier will only give one peak per cycle and for this and

other reasons is only used in very small power supplies. A full wave rectifier achieves

two peaks per cycle and this is the best that can be done with single phase input. For

three phase inputs a three phase bridge will give six peaks per cycle and even higher

numbers of peaks can be achieved by using transformer networks placed before the

rectifier to convert to a higher phase order. To further reduce this ripple, a capacitor-

input filter can be used.

This complements the reservoir capacitor with a choke and a second filter

capacitor, so that a steadier DC output can be obtained across the terminals of the filter

capacitor. The choke presents a high impedance to the ripple current. If the DC load is

very demanding of a smooth supply voltage, a voltage regulator will be used either

instead of or in addition to the capacitor-input filter, both to remove the last of the ripple

and to deal with variations in supply and load characteristics.

6.2.2 3 terminal voltage regulator for ± 5 v

The L7800 series of three-terminal positive regulators is available in TO-

220 ISOWATT220 TO-3 and D2PAK packages and several fixed output voltages,

making it useful in a wide range of applications. These regulators can provide local on-

card regulation, eliminating the distribution problems associated with single point

regulation. Each type employs internal current limiting, thermal shut-down and safe

area protection, making it essentially indestructible. If adequate heat sinking is


Mini project 2013 Heart rate measurement through finger tipprovided, they can deliver over 1A output current. Although designed primarily as fixed

voltage regulators, these devices can be used with external components to obtain

adjustable voltages and currents.

Fig no: 6.5 Voltage regulator

Three-terminal IC power regulators include on-chip overload protection

against virtually any normal fault condition. Current limiting protects against short

circuits fusing the aluminum interconnects on the chip. Safe-area protection decreases

the available output current at high input voltages to insure that the internal power

transistor operates within its safe area.

Finally, thermal overload protection turns off the regulator at chip

temperatures of about 170°C, preventing destruction due to excessive heating. Even

though the IC is fully protected against normal overloads, careful design must be used

to insure reliable operation in the system.

FEATURES

1. Output current up to 1.5 A

2. Output voltages of 5; 5.2; 6; 8; 8.5; 9;12; 15; 18; 24V

3. Thermal overload protection


Mini project 2013 Heart rate measurement through finger tip4. Short circuit protection

5. Output transition safe operating area protection

R11KU1

L7805/TO220

1

3

2VIN

GND

VOUT

C3CAP NP

D2

LED

GND

+C12200MFD

230V

D1

1n4007

1 2

+12V VCC

230V

+ C210MFD

T1

12 - 0-12V / 1AD3

1n4007

1 2

Fig 6.2.3 5V Power supply

This ac supply goes to a center tap rectifier, which converts the ac into a

unidirectional voltage. The ripples in the resulting supply is filtered and smoothed by a

2200FD/25V capacitor. The 0.1F capacitor bypasses any high frequency noises. The

resulting supply has the magnitude above 17V. This voltage is fed to the regulator IC

7805. This IC provides a regulated 5V positive supply at its 3rd pin. The required input

for this is more than 7.5V. Also there is an LED in series with a 1K resistor. This

will act as a power ON indicator.



CHAPTER 7

ADVANTAGES

7.1 ADVANTAGES

The patient’s heart beat rate is monitored using a photoelectric sensor

which can sense the patients’s pulse rate.

This method of tracking the heart rate is more efficient than traditional

method By derives the same from the ECG graph.

The duty nurse or doctors can easily identify the problems. This saves

the life of the patient.

By using the system, labor work can be reduced i.e., there’s no need to

go and check the patients consistently.

It provides increased accuracy in identifying the breathing rhythm.



CHAPTER 8

FUTURE SCOPE

The information updated through these devices sent to a doctor or

medical adviser for checking the health status of the person. The device is of great

application since we are in a world of less time and space. All basic diagnosis involve

heartbeat. It provide a cost effective method to improve chronic disaster management. A

graphical LCD can be used to display a graph of the change of heart rate over time.

Sound can be added to the device so that a sound is output each time a pulse is received.

The maximum and minimum heart rates over a period of time can be displayed.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.



CHAPTER 9

CONCLUSION

A remote patient monitoring system was developed to facilitate patient

empowerment and also to provide accurate and timely data to the care provider to help

with disease management. This system has been evaluated in populations with

hypertension. It provides a cost effective method to improve chronic disease

management. Controlling a parameter such as blood pressure in complications such as

renal and cardiovascular disease can result in improved health outcomes and increased

quality of life. Acquiring biological signal and adequately amplifying biological signal.

Semi functional heart rate counter and use of low power components for battery

operation



REFERENCES

[1] Dr. A.K. GAUTAM “Antenna and Wave propagation” S.K Kataria &

Sons Publishers, Fourth Edition 2008 – 09.

[2] Dr.S.K. Sahwaney ”Electronics Measurement and instrument.

[3] Robert L. Boylestad “Electronics Device and Circuit Theory by “

[4] Communication System by: B.P. Lathi.

[5] S. Edwards., “Heart rate Monitor Book”, Leisure systems international,

Dec.1993.

[6] M. Malik and A. J. Camm., “Heart Rate Variability”., Futura Publishing

Co. Inc., sept. 1995.

[7] J. R. Hampton., “The ECG In Practice”., Churchill Livingstone., Mar. 2003.

[8] A. R. Houghton and D. Gray., “making sense of the ECG”., Hodder

Arnold Publishing.m 2003.

[9] Microchip

Web site: http://microchip.com

[10] American Heart Association. “Cardiovascular Disease Statistics”

[Online Document], 2008 [Cited 9 Dec 2008], Available HTTP:

<http://www.americanheart.org/presenter.jhtml?identifier=447


http://microchip.com/

Mini project 2013 Heart rate measurement through finger tip [11] Centers for Disease Control and Prevention. “Heart Disease Facts and

Statistics” [Online Document], 10 Sept 2008 [Cited 4 Dec 2008], Available

HTTP: < http://www.cdc.gov/heartdisease/statistics.htm>.

[12] R.S. Khandpur. Biomedical Instrumentation: Technology

and Applications, McGraw-Hill Companies, Inc., 2005.

[13] V. Virgilio. “Prototype of a Portable ECG Monitoring System

(Holter Monitor) with Real Time Detection of Beat Abnormalitie”

Master thesis, Aalborg University, 2006.

[14] J. Hailong, M. Bing. “Design of Holter ECG System Based on

MSP430 and USB Technology” IEEE (2007) 976-979.

[15] The Electricity and the Heart website. Available

from :http://www.naspe.org/library/electricity_and_the_heart.

[16] Electronics for you website.

[17] Embedded lab website. Available

from: http://www.IntroducingEasy Pulse A DIY

photoplethysmographic sensor for measuring heart rate

Embedded Lab.htm.


http://www.Introducing/

http://www.naspe.org/library/electricity_and_the_heart

http://www.cdc.gov/heartdisease/statistics.htm


APPENDIX


pulse counting project

Documents

light detector

light source

detected light

light doesnt

resultant light

reflected light intensity

ppg signal

heart beat