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Digital Heart Beat Counter
[Type the document subtitle]
3/13/2012
Deevanshu Swani
CONTENTS
I nt rod uct io n …… … …… … … … … … … … ……… … … … … … … … …1
Ab s tr ac t …… … … … …… … … … … … … … ……… … … … … … … … …. 2
C ir c uit di a gr a m … … … … … … … … ……… … … … … … … … …… . 3
1 . Construction……………………………………………………………………........4
1.1 CA 3140 OPAMP……………………………………………………5
1.2 uA 741 OPAMP……………………………………………………...6
1.3 CD 4071 OR GATE………………………………………………….6
1.4 NE555 TIMER……………………………………………………... 7
1.5 CD 4026B COUNTER………………………………………………10
1.6 REGULATORS……………………………………………………..11.
1.7 LT543 COMMON CATHODE, SEVEN SEGMENT DISPLAY …12
1.8 5mm L.E.Ds…………………………………………………………14
1.9 TRIMPOTS AND PRESETS……………………………………….15
1.10 STEP DOWN TRANSFORMER………………………………….16
1.11 PIEZOELECTRIC SENSOR……………………………………...17
1.12 POWER SUPPLY…………………………………………………19
2. Working………………………………………………………………………….20
2.1 PIEZO ELECTRIC ACCELEROMETER …………………………21
2.2 PRE AMPLIFIER…………………………………………………...21
2.3 LOW PASS FILTER………………………………………………..21
2.4 PULSE MONITOR ………………………………………………...22
2.5 PULSE COUNTER AND DIGITAL READOUT …………………22
Conclusion & Future scope ………………………………………………………….23
Bibliography …………………………………………………………………………25
LIST OF FIGURES
1. CIRCUIT DIAGRAM 3
1.4.1 555 TIMER IC 7
1.4.2 PIN DIAGRAM 8
1.4.3 555 CIRCUIT DIAGRAM 8
1.6.1 REGULATORS 11
1.7.1 SEVEN SEGMENT DISPLAY 12
1.8.1.LED BASIC DIAGRAM 14
1.9.1 TRIMPOTS AND PRESETS 15
1.10.1 TRANSFORMER 16
1.11.1 PIEZOELECTRIC SENSOR 17
1.12.1 POWER SUPPLY CIRCUIT 19
2. SNAPSHOT OF HARDWARE CIRCUIT 24
INTRODUCTION
Objective of the Project
The objective of the project is to count the heart beat of human body accurately and then display it on a LED screen.
Overview of the project
The heart beat rate, also known as the pulse rate, is the number of times the persons heart beat in one minute .It is
one of the vital signs that are often taken by doctors to access the most basic functions of the patient‘s body.
So counting of heartbeat sometimes become essentially for proper treatment.
Although the pulse rate can be measured manually by ourselves, an electronic digital
heart beat counter gives the opportunity to measure it automatically and continuously.
Here is a digital heart beat counter that has the following features –
1. A piezoelectric accelerometer used as a sensor .
2. A blinking LED for visual indication of heart beat.
3. Counts are automatic and displayed on a 2-digit, 7-segment display.
4. Continuous monitoring can be done.
ABSTRACT
A person‘s heart forces his blood to flow through the arteries .As a result, the arteries
throb in synchronization with the beating of the heart . This throbbing can be felt at the
person‘s wrist and other places over the body.
Electronically, this throbbing can be sensed with an accelerometer that generates
electrical signals against the vibration-resulted processing of the signals. The counter is
configured such that it counts the pulses for 10 seconds and then displays the same for
the next five seconds. The process repeats as long as the accelerometer sensor is tied
tightly around the person‘s wrist.
CIRCUIT DIAGRAM
FIG 1. HARDWARE CIRCUIT DIAGRAM
CHAPTER 1
CONSTRUCTION
This circuit consists of various components such as:-
1. CA 3140 OPAMP.
2. uA 741 OPAMP.
3. CD 4071 OR GATE.
4. NE555 TIMER.
5. CD 4026B COUNTER.
6. +5V 7805 REGULATOR.
7. -5V 7905 REGULATOR.
8. LT543 COMMON CATHODE,SEVEN SEGMENT DISPLAY.
9. 5mm L.E.Ds.
10. TRIMPOTS AND PRESETS.
11. STEP DOWN TRANSFORMER.
12. PIEZOELECTRIC SENSOR.
13. POWER SUPPLY
Now we would like to give the detailed description about the components listed above:
1.1 CA3140 OPERATIONAL AMPLIFIER
The CA3140 is integrated circuit op amp that combines the advantage of high voltage PMOS transistors with high
voltage bipolar transistors on a single monolithic chip.
The CA3140 BiMOS op amp features gate protected MOSFET transistors in the input circuit to provide very high
input impedance, very low input current and high speed performance.
The CA3140 operate at supply voltage from 4V to 36V.these op amp are internally phase compensated to achieve
stable operation in unity gain follower operation and additionally have access terminal for a supplementary external
capacitor if additional frequency roll off is desired. Terminals are also provided for use in applications requiring
input offset voltage manning. The use of PMOS FET in the input stage results in common mode input voltage
capability down to 0.5 volts below the negative supply terminal. The output stage uses bipolar transistors and
includes built in protection against damage from load terminal short circuiting to either supply rail or to ground.
The CA3140 Series has the same 8 lead pin out used for the ―741‖ and other industry standard s op amps.
The CA 3140 op amp work as an instrumentation amplifier.
1.2 uA741 OPAMP
The uA741 is a high performance monolithic operational constructed on a single silicon chip .It is intended for a
wide range of analog applications .
Applications include summing amplifier, voltage follower, integrator, active filters, function generators.
The high gain and wide range of operating voltages provide superior performance integrator, summing amplifier and
general feedback applications. The internal compensated network insures stability in close loop applications
The two 741 op amp ICs together combine and operate as a low pass filter.
1.3 CD 4071 OPAMP
These quad gates are monolithic complementary CMOS integrated circuits constructed with N- and P- channel
enhancement mode transistors. They have equal source and sink current capabilities and conform to standard B
series out put drive. The devices also have buffered outputs which improve transfer characteristics by providing very
high gain.
This IC is used to implement logical OR function in the circuit
All inputs protected against static discharge with diodes to Vdd and Vss.
1.4 555 TIMER IC
The 555 Timer IC is an integrated circuit (chip) implementing a
variety of timer and multivibrator applications. It includes over
20 transistors, 2 diodes and 15 resistors on a silicon chip installed in
an 8-pin mini dual-in-line package (DIP-8).
The 556 is a 14-pin DIP that combines two 555s on a single chip.
The 558 is a 16-pin DIP that combines four slightly modified 555s
on a single chip (DIS & THR are connected internally, TR is falling
edge sensitive instead of level sensitive).
Also available are ultra-low power versions of the 555 such as the
7555 and TLC555. The 7555 requires slightly different wiring using
fewer external components and less power.
The 555 has three operating modes:
1.4.1 MONOSTABLE MODE: In this mode, the 555
functions as a "one-shot". Applications include timers, missing
pulse detection, bouncefree switches, touch switches, frequency
divider, capacitance measurement, pulse-width modulation (PWM) etc
1.4.2 ASTABLE FREE RUNNING MODE: The 555 can operate as an oscillator. Uses
include LED and lamp flashers, pulse generation, logic clocks, tone generation, security alarms, pulse position
modulation, etc.
1.4.3 BISTABLE MODE OR SCHMITT TRIGGER: the 555 can operate as a flip-flop, if the DIS
pin is not connected and no capacitor is used. Uses include bounce free latched switches, etc.
555 TIMER IC
FIGURE:1.4.1
The connection of the pins is as follows:
Figure1.4.2
Sr. Name Purpose
1 GND Ground, low level (0V)
2 TRIG A short pulse high-to-low on the trigger starts the timer
3 OUT During a timing interval, the output stays at +VCC
4 RESET A timing interval can be interrupted by applying a reset pulse to low (0V)
5 CTRL Control voltage allows access to the internal voltage divider (2/3 VCC)
6 THR The threshold at which the interval ends (it ends if U.thr → 2/3 VCC)
7 DIS Connected to a capacitor whose discharge time will influence the timing
interval.
8 V+, VCC The positive supply voltage which must be between 3 and 15 V
figure 1.4.3
MONOSTABLE MODE
In the monostable mode, the 555 timer acts as a ―one-shot‖ pulse generator. The pulse begins when the 555 timer
receives a trigger signal. The width of the pulse is determined by the time constant of an RC network, which consists
of a capacitor (C) and a resistor (R). The pulse ends when the charge on the C equals 2/3 of the supply voltage. The
pulse width can be lengthened or shortened to the need of the specific application by adjusting the values of R and
C.
The pulse width of time t is given by
which is the time it takes to charge C to 2/3 of the supply voltage. See RC circuit for an explanation of this
effect.
SPECIFICATIONS
These specifications apply to the NE555. Other 555 timers can have better specifications depending on the grade
(military, medical, etc).
Supply voltage (VCC) 4.5 to 15 V
Supply current (VCC = +5 V) 3 to 6 mA
Supply current (VCC = +15 V) 10 to 15 mA
Output current (maximum) 200 mA
Power dissipation 600 mW
Operating temperature 0 to 70 °C
1.5 CD 4026 /4033 DECADE COUNTER
CD4026 and CD4033 each consist of a 5-stage Johnson decade counter and an output decoder which converts the
Johnson code to a 7-segment decoded output for driving one stage in a numerical display. These devices are
particularly advantageous in display applications where low power dissipation are important. Inputs common to both
types are CLOCK, RESET & CLOCK INHIBIT. Common outputs are CARRY OUT and seven decoded outputs (a,
b, c, d, e, f, g).Additional inputs and outputs for the IC include DISPLAY ENABLE input .Signals peculiar to the IC
are RIPPLE BLANKING INPUT AND LAMP TEST INPUT and a RIPPLE BLANKING OUTPUT.
A high RESET signal clears the decade counter to its zero count. The counter is advanced one count at the positive
clock signal transition if the CLOCK INHIBIT signal is low. Counter advancement via the clock line is inhibited
when the CLOCK INHIBIT signal is high. The CLOCK inhibit signal can be used as a negative-edge clock if the
clock line is held high. Anti clock gating is provided on the JOHNSON counter, thus assuring proper counting
sequence. The CARRY-OUT signal completes one cycle every ten CLOCK INPUT cycles and is used to clock the
succeeding decade directly in a multi-decade counting chain .The seven decoded outputs illuminate the proper
segments in a seven segment display device used for representing the decimal numbers 0 to 9.The 7-segment
outputs go high on selection in the IC, these outputs go high only when the DISPLAY ENABLE IN is high.
1.6 7805,7905 REGULATOR
The 78xx (also sometimes known as LM78xx) series of devices is a
family of self-contained fixed linear voltage regulator integrated
circuits. The 78xx family is a very popular choice for many
electronic circuits which require a regulated power supply, due to
their ease of use and relative cheapness. When specifying individual
ICs within this family, the xx is replaced with a two-digit number,
which indicates the output voltage the particular device is designed
to provide (for example, the 7805 has a 5 volt output, while the 7812
produces 12 volts). The 78xx line are positive voltage regulators,
meaning that they are designed to produce a voltage that is positive
relative to a common ground. There is a related line of 79xx devices
which are complementary negative voltage regulators. 78xx and
79xx ICs can be used in combination to provide both positive and
negative supply voltages in the same circuit, if necessary.
78xx ICs have three terminals and are most commonly found in the
TO220 form factor, although smaller surface-mount and larger TO3 packages are also available from some
manufacturers. These devices typically support an input voltage which can be anywhere from a couple of volts over
the intended output voltage, up to a maximum of 35 or 40 volts, and can typically provide up to around 1 or 1.5
amps of current (though smaller or larger packages may have a lower or higher current rating)
REGULATORS
FIGURE:1.6.1
1.7 COMMON CATHODE SEVEN SEGMENT LED DISPLAY
A popular type consists of seven small, bar-shaped LED segment arranged so that depending on which combinations
are energized, the numbers 0 to 9 light up. All the LED cathodes (or sometimes anodes) are joined to form a
common connection. Current limiting resistors are required (e.g. 270 ohms), preferably one per segment.
Figure 1.7.1
The main requirements for a suitable LED material are:-
1) It must have on energy gap of appropriate width.
2) Both P and N types must exist, preferably with low resistivity.
3) Efficient radioactive pathways must be present.
Generally, energy gaps greater than or equal to about 2 are required.
Commercial LED materials::
Gallium arsenide (Ga As) doped with Si
Gallium Phosphide (GaP) doped with N & Bi
Gallium arsenide Phosphide (Ga As1-x Px)
Gallium aluminium arsenide (Gax Al1-x As)
1.8 LIGHT EMITTING DIODE
LED STRUCTURE
Light emitting diode (LED) is basically a P-N junction semiconductor diode particularly designed to emit visible
light. There are infrared emitting LEDs which emit invisible light. The LEDs are now available in many colours red,
green and yellow. A normal LED emits at 2.4V and consumes MA of current. The LEDs are made in the form of flat
tiny P-N junction enclosed in a semi-spherical dome made up of clear coloured epoxy resin. The dome of a LED
acts as a lens and diffuser of light. The diameter of the base is less than a quarter of an inch. The actual diameter
varies somewhat with different makes. The common circuit symbols for the LED are shown in Fig. It is similar to
the conventional rectifier diode symbol with two arrows pointing out. There are two leads- one for anode and the
other for cathode.
LEDs often have leads of dissimilar length and the shorter one is the cathode. All manufacturers do not strictly
adhere this to. Sometimes the cathode side has a flat base. If there is doubt, the polarity of the diode should be
identified. A simple bench method is to use the ohmmeter incorporating 3-volt cells for ohmmeter function. When
connected with the ohmmeter: one way there will be no deflection and when connected the other way round there
will be a large deflection of a pointer. When this occurs the anode lead is connected to the negative of test lead and
cathode to the positive test lead of the ohmmeter.
Figure: 1.8.1 L.E.D BASIC DIAGARM
If low range (Rxl) of the ohmmeter is used the LED would light up in most cases because the low range of
ohmmeter can pass sufficient current to light up the LED.
Another safe method is to connect the test circuit shown in Fig. 2. Use any two dry cells in series with a current
limiting resistor of 68 to 100 ohms. The resistor limits the forward diode current of the LED under test to a safe
value. When the LED under test is connected to the test terminals in any way: if it does not light up, reverse the test
leads. The LED will now light up. The anode of the LED is that which is connected to the ―A‖ terminal (positive
pole of the battery). This method is safe, as reverse voltage can never exceed 3 volts in this test.
1.9 TRIMPOTS AND PRESETS
A trimmer is a miniature adjustable electrical component. It is meant to be set correctly
when installed in some device, and never seen or adjusted by the device's user. Trimmer
can be variable resistors or variable capacitors.
They are common in precision circuitry like A/V components, and may need to be adjusted when the equipment is
serviced. Unlike other variable controls, trimmers are mounted directly on circuit boards, turned with a small
screwdriver and rated for many fewer adjustments over their lifetime. In 1952, Marlan Bourns patented the world's
first trimming potentiometer, trademarked "Trimpot".
TRIMPOTS AND PRESETS
Figure 1.9.1
1.10 TRANSFORMER
A transformer is a device that transfers electrical energy from one
circuit to another through inductively coupled conductors — the
transformer's coils. Except for air-core transformers, the conductors
are commonly wound around a single iron-rich core, or around
separate but magnetically-coupled cores. A varying current in the
first or "primary" winding creates a varying magnetic field in the
core (or cores) of the transformer. This varying magnetic field
induces a varying electromotive force (EMF) or "voltage" in the
"secondary" winding. This effect is called mutual induction.
If a load is connected to the secondary, an electric current will flow
in the secondary winding and electrical energy will flow from the
primary circuit through the transformer to the load. In an ideal
transformer, the induced voltage in the secondary winding (VS) is in
proportion to the primary voltage (VP), and is given by the ratio of
the number of turns in the secondary to the number of turns in the primary as follows:
By appropriate selection of the ratio of turns, a transformer thus allows an alternating current (AC) voltage to be
"stepped up" by making NS greater than NP, or "stepped down" by making NS less than NP.
Transformers are essentially of two types:
1.STEPUP TRANSFORMER
2.STEPDOWN TRANSFORMER.
They come in a range of sizes from a thumbnail-sized coupling transformer hidden inside a stage microphone to
huge units weighing hundreds of tons used to interconnect portions of national power grids. All operate with the
same basic principles, although the range of designs is wide. While new technologies have eliminated the need for
transformers in some electronic circuits, transformers are still found in nearly all electronic devices designed for
household ("mains") voltage. Transformers are essential for high voltage power transmission, which makes long
distance transmission economically practical.
TRANSFORMER
Figure:1.10.1
1.11 PIEZOELECTRIC SENSOR
A piezoelectric sensor is a device that uses the piezoelectric effect to measure pressure, acceleration, strain or force
by converting them to an electrical signal.
Figure 1.11.1 PIEZOELECTRIC ACCLEROMETER
Piezoelectric sensors have proven to be versatile tools for the measurement of various processes. They are used for
quality assurance, process control and for research and development in many different industries.
Based on piezoelectric technology various physical quantities can be measured; the most common are pressure and
acceleration. For pressure sensors, a thin membrane and a massive base is used, ensuring that an applied pressure
specifically loads the elements in one direction. For accelerometers, a seismic mass is attached to the crystal
elements. When the accelerometer experiences a motion, the invariant seismic mass loads the elements according to
Newton‘s second law of motion F = ma.
1.11.1 CONSTRUCTION OF THE SENSOR
A self constructed piezoelectric accelerometer is used in this project .It is constructed by using a ceramic piezo
buzzer element. These elements are widely used in landline telephones sets to produce ring tones. The diameters of
the brass plate and silver layer of piezo buzzer used in this project are around 27 mm and 18 mm respectively.
Firstly top cover of the plastic case is removed. One of the two wires of a 2-core shielded earphone cable to the
white silver layer sprayed over the piezo element .Connect the other wire of a 2-core cable to the brass plate of the
element. The shielded part of the cable should be keep open but it should not touch the element. Mount the mass (1
cm long piece of solid cylindrical brass rod having 1 cm diameter) centrally over the white silver layer with some
adhesive like quick fix. Add adhesive to the sides of the mass to fix it over the crystal.
Allow sufficient time for drying up. Generally the cases have mounting holes diametrically opposite sides. Attach
length of Velcro belts hooks with the help of a small nut bolt through one of the mounting holes. Similarly attach
another length of Velcro belt at the other mounting hole of the case. Bridge the two holes with a small piece of
Velcro belt. The piece should be short enough to put some pressure on the top surface of the brass rod. Too low or
too high pressure would hamper the sensitivity of the accelerometer.
1.12 POWER SUPPLY
The 230V AC mains is stepped down by transformer to deliver a secondary output of 9v-0-9v, 500mA. The
transformer output is rectified by a full-wave rectifier comprising diodes D3 through D6. The output of rectifier is
filtered by using a capacitor filter. This filtered output is given to fixed voltage regulators 7805(+5V) and 7905(-
5V).Regulators 7805, 7905 provide +5V and -5V regulated supply to circuit. Capacitors C16 and C17 bypasses any
ripple present in regulated supply.
Figure:1.12.1 Power supply circuit
CHAPTER 2
WORKING
The whole working of Digital heart beat counter can be divided into various parts which are following:
2.1. Piezoelectric accelerometer
2.2. Preamplifier
2.3. Low pass filter
2.4. Pulse monitor
2.5. Pulse counter and digital readout
2.1 PIEZOELECTRIC ACCLEROMETER
An accelerometer measures the instantaneous acceleration of the object on which accelerometer is bounded. It
transduces the acceleration which results from the vibration to corresponding analog signal. Here we use
piezoelectric type accelerometer .When such an accelerometer is tightly coupled to one‘s wrist ,throbbing of arteries
supplies this acceleration .Due to temporary deformation of the crystal by the exerted force , the piezoelectric crystal
develops a charge across the electrodes attached to its lower and upper faces. The crystal regains its original
dimensions as soon as the acceleration disappears .
2.2 PREAMPLIFIER
Here we use high input impedance pre-amplifier. An instrumentation amplifier is used as a pre-amplifier. Three
CA3140 op-amp IC‘s unitedly act as an instrumentation amplifier. Instrumentation amplifier is used because it
greatly enhanced CMRR . CMRR refers to common mode rejection ratio. A high CMRR considerably reduces the
ground noises from the surrounding environment.
2.3 LOW PASS FILTER
The output signal from the instrumentation amplifier gets adulterated with some harmonics of 50 Hz AC power
frequency, along with some other frequency components from surroundings .A sallen key low pass filter is used to
reduce all these interferences. The amplified output voltage from IC3 of the 3-op-amp instrumentation amplifier is
fed to op-amp IC4 through resistor R10. Op-amp IC4 along with resistor R10 and R12 and capacitors C4 and C5
forms the unity – gain Sallen key low pass filter. Although the presence of R11 and VR3 reduces the output voltage
slightly , the upper cutoff frequency of the filter is 1.5 Hz .All frequencies above 10 Hz would be greatly filtered out.
2.4 PULSE MONITOR
Apart of IC4 output is fed through a one stage RC low pass filter comprising R14 and C7 to pin 3 of op-amp IC5.
The RC filter enhance the steepness of previous filter response. The additional stage amplification is required for
driving LED1 and LED2. The LEDs blink in synchronization with heart beat pulses coming from the accelerometer
.These pulses are fed through diodes D1 and D2 such that while one LED blinks during diastoles , the other one
blinks during systoles . The gain of this stage is approximately 22.
2.5 PULSE COUNTER & DIGITAL READ OUT
CMOS decade counters IC9 (CD4033/CD4026) and IC10(CD4033/CD4026) in tandem form the two digit decimal
counter. The counters, count the heart beat pulses coming from Sallen key low pass filter. If pin 2 of IC 10 is at
logic 0 ,each pulse from the LPF advances the counter by ‗1‘. The logic condition of pin 2 is dependent upon the
logic condition of the monoshot configured around IC8 (NE555). The time period of the monoshot is governed by
the combination of resistor R22 , preset VR5 and capacitor C12 and can be set for 10 seconds. Another monoshot
configured around IC7(NE555) can be set by varying preset VR6 to give a time period of 15 seconds . The two
monoshots are triggered simultaneously whenever low going pulse from the LPF reaches the common input(pin 2 of
each NE555).As soon as they are triggered respective output goes low the same time .While the output of IC7 is
designed to stay low for additional five seconds .Transistor T2 inverts the output of IC8 (logic 1) to drag CE of IC10
(pin2) to logic 0 .As soon as IC8 is triggered , the leading edge of the positive going output pulse resets decade
counters IC9 and IC10 via capacitor C 13.
The two 7-segment display DIS1 and DIS2 now show the count as ‘00‘. The counter is now enabled to count for 10
seconds. Since the output of the monoshot IC7 is triggered at the same time ,pin 9 of the OR gate IC6 goes high . It
remains high for the time equal to time period of IC7, i.e 15 seconds . During the last period , no further beat pulses
is allowed to trigger monoshot IC7 or IC8 .This is because the output of OR gate holds the common trigger input
high .However the beating pulses are allowed to reach counter IC10 via inverter T2.So the components goes on
counting the pulses as long as the output of IC8 remains high.At the end of 10 seconds the output of IC8 goes low.
This disables IC10 and no further counting is allowed .The so far counted result is now displayed on 7-segment
display DIS1 and DIS2 connected to the output of decade counters IC9 and IC10 respectively. At the end of 15
seconds the output of monoshot IC7 again goes low allowing the incoming pulses to trigger the monoshots to repeat
cycle. The process continues as long as the accelerometer is tied to one‘s wrist.
CONCLUSION AND FUTURE SCOPE
CONCLUSION
The project has been completed successfully and the heart beat count is measured and displayed by sensing the
pulses through a piezoelectric accelerometer.
Electronics digital heart-beat counter gives the opportunity to measure it automatically, continuously and precisely
which is very important aspect for health diagnostics in medical science.
FUTURE SCOPE
In Digital heart beat counter counts are automatic and displayed on a 2-digit, 7-segment display. Continuous
monitoring can be done .And the processed signal can be fed to a data-acquisition system (DAS) to observe or save
the nature of the pulse.
SNAPSHOT OF THE HARDWARE CIRCUIT
FIG 2.DIGITAL HEART BEAT COUNTER
BIBLIOGRAPHY
BOOKS REFERRED:
1. Electronic devices and circuits by J.B.Gupta,VOL-2,KATSON BOOKS.
2. Electronics devices and circuits by S. Salivahnan, TMH Publications,16 reprint
WEBSITES REFERRED:
1. www.electronicsforu.com
2. www.datasheetcatalog.com

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DIGITAL HEART BEAT COUNTER

  • 1. 0 | P a g e qwertyuiopasdfghjklzxcvbnmqw ertyuiopasdfghjklzxcvbnmqwert yuiopasdfghjklzxcvbnmqwertyui opasdfghjklzxcvbnmqwertyuiopa sdfghjklzxcvbnmqwertyuiopasdf ghjklzxcvbnmqwertyuiopasdfghj klzxcvbnmqwertyuiopasdfghjklz xcvbnmqwertyuiopasdfghjklzxcv bnmqwertyuiopasdfghjklzxcvbn mqwertyuiopasdfghjklzxcvbnmq wertyuiopasdfghjklzxcvbnmqwe rtyuiopasdfghjklzxcvbnmqwerty uiopasdfghjklzxcvbnmqwertyuio pasdfghjklzxcvbnmqwertyuiopas dfghjklzxcvbnmqwertyuiopasdfg hjklzxcvbnmqwertyuiopasdfghjk Digital Heart Beat Counter [Type the document subtitle] 3/13/2012 Deevanshu Swani
  • 2. CONTENTS I nt rod uct io n …… … …… … … … … … … … ……… … … … … … … … …1 Ab s tr ac t …… … … … …… … … … … … … … ……… … … … … … … … …. 2 C ir c uit di a gr a m … … … … … … … … ……… … … … … … … … …… . 3 1 . Construction……………………………………………………………………........4 1.1 CA 3140 OPAMP……………………………………………………5 1.2 uA 741 OPAMP……………………………………………………...6 1.3 CD 4071 OR GATE………………………………………………….6 1.4 NE555 TIMER……………………………………………………... 7 1.5 CD 4026B COUNTER………………………………………………10 1.6 REGULATORS……………………………………………………..11. 1.7 LT543 COMMON CATHODE, SEVEN SEGMENT DISPLAY …12 1.8 5mm L.E.Ds…………………………………………………………14 1.9 TRIMPOTS AND PRESETS……………………………………….15 1.10 STEP DOWN TRANSFORMER………………………………….16 1.11 PIEZOELECTRIC SENSOR……………………………………...17 1.12 POWER SUPPLY…………………………………………………19 2. Working………………………………………………………………………….20 2.1 PIEZO ELECTRIC ACCELEROMETER …………………………21 2.2 PRE AMPLIFIER…………………………………………………...21 2.3 LOW PASS FILTER………………………………………………..21 2.4 PULSE MONITOR ………………………………………………...22 2.5 PULSE COUNTER AND DIGITAL READOUT …………………22 Conclusion & Future scope ………………………………………………………….23 Bibliography …………………………………………………………………………25
  • 3. LIST OF FIGURES 1. CIRCUIT DIAGRAM 3 1.4.1 555 TIMER IC 7 1.4.2 PIN DIAGRAM 8 1.4.3 555 CIRCUIT DIAGRAM 8 1.6.1 REGULATORS 11 1.7.1 SEVEN SEGMENT DISPLAY 12 1.8.1.LED BASIC DIAGRAM 14 1.9.1 TRIMPOTS AND PRESETS 15 1.10.1 TRANSFORMER 16 1.11.1 PIEZOELECTRIC SENSOR 17 1.12.1 POWER SUPPLY CIRCUIT 19 2. SNAPSHOT OF HARDWARE CIRCUIT 24
  • 4. INTRODUCTION Objective of the Project The objective of the project is to count the heart beat of human body accurately and then display it on a LED screen. Overview of the project The heart beat rate, also known as the pulse rate, is the number of times the persons heart beat in one minute .It is one of the vital signs that are often taken by doctors to access the most basic functions of the patient‘s body. So counting of heartbeat sometimes become essentially for proper treatment. Although the pulse rate can be measured manually by ourselves, an electronic digital heart beat counter gives the opportunity to measure it automatically and continuously. Here is a digital heart beat counter that has the following features – 1. A piezoelectric accelerometer used as a sensor . 2. A blinking LED for visual indication of heart beat. 3. Counts are automatic and displayed on a 2-digit, 7-segment display. 4. Continuous monitoring can be done.
  • 5. ABSTRACT A person‘s heart forces his blood to flow through the arteries .As a result, the arteries throb in synchronization with the beating of the heart . This throbbing can be felt at the person‘s wrist and other places over the body. Electronically, this throbbing can be sensed with an accelerometer that generates electrical signals against the vibration-resulted processing of the signals. The counter is configured such that it counts the pulses for 10 seconds and then displays the same for the next five seconds. The process repeats as long as the accelerometer sensor is tied tightly around the person‘s wrist.
  • 6. CIRCUIT DIAGRAM FIG 1. HARDWARE CIRCUIT DIAGRAM
  • 7. CHAPTER 1 CONSTRUCTION This circuit consists of various components such as:- 1. CA 3140 OPAMP. 2. uA 741 OPAMP. 3. CD 4071 OR GATE. 4. NE555 TIMER. 5. CD 4026B COUNTER. 6. +5V 7805 REGULATOR. 7. -5V 7905 REGULATOR. 8. LT543 COMMON CATHODE,SEVEN SEGMENT DISPLAY. 9. 5mm L.E.Ds. 10. TRIMPOTS AND PRESETS. 11. STEP DOWN TRANSFORMER. 12. PIEZOELECTRIC SENSOR. 13. POWER SUPPLY Now we would like to give the detailed description about the components listed above:
  • 8. 1.1 CA3140 OPERATIONAL AMPLIFIER The CA3140 is integrated circuit op amp that combines the advantage of high voltage PMOS transistors with high voltage bipolar transistors on a single monolithic chip. The CA3140 BiMOS op amp features gate protected MOSFET transistors in the input circuit to provide very high input impedance, very low input current and high speed performance. The CA3140 operate at supply voltage from 4V to 36V.these op amp are internally phase compensated to achieve stable operation in unity gain follower operation and additionally have access terminal for a supplementary external capacitor if additional frequency roll off is desired. Terminals are also provided for use in applications requiring input offset voltage manning. The use of PMOS FET in the input stage results in common mode input voltage capability down to 0.5 volts below the negative supply terminal. The output stage uses bipolar transistors and includes built in protection against damage from load terminal short circuiting to either supply rail or to ground. The CA3140 Series has the same 8 lead pin out used for the ―741‖ and other industry standard s op amps. The CA 3140 op amp work as an instrumentation amplifier.
  • 9. 1.2 uA741 OPAMP The uA741 is a high performance monolithic operational constructed on a single silicon chip .It is intended for a wide range of analog applications . Applications include summing amplifier, voltage follower, integrator, active filters, function generators. The high gain and wide range of operating voltages provide superior performance integrator, summing amplifier and general feedback applications. The internal compensated network insures stability in close loop applications The two 741 op amp ICs together combine and operate as a low pass filter. 1.3 CD 4071 OPAMP These quad gates are monolithic complementary CMOS integrated circuits constructed with N- and P- channel enhancement mode transistors. They have equal source and sink current capabilities and conform to standard B series out put drive. The devices also have buffered outputs which improve transfer characteristics by providing very high gain. This IC is used to implement logical OR function in the circuit All inputs protected against static discharge with diodes to Vdd and Vss.
  • 10. 1.4 555 TIMER IC The 555 Timer IC is an integrated circuit (chip) implementing a variety of timer and multivibrator applications. It includes over 20 transistors, 2 diodes and 15 resistors on a silicon chip installed in an 8-pin mini dual-in-line package (DIP-8). The 556 is a 14-pin DIP that combines two 555s on a single chip. The 558 is a 16-pin DIP that combines four slightly modified 555s on a single chip (DIS & THR are connected internally, TR is falling edge sensitive instead of level sensitive). Also available are ultra-low power versions of the 555 such as the 7555 and TLC555. The 7555 requires slightly different wiring using fewer external components and less power. The 555 has three operating modes: 1.4.1 MONOSTABLE MODE: In this mode, the 555 functions as a "one-shot". Applications include timers, missing pulse detection, bouncefree switches, touch switches, frequency divider, capacitance measurement, pulse-width modulation (PWM) etc 1.4.2 ASTABLE FREE RUNNING MODE: The 555 can operate as an oscillator. Uses include LED and lamp flashers, pulse generation, logic clocks, tone generation, security alarms, pulse position modulation, etc. 1.4.3 BISTABLE MODE OR SCHMITT TRIGGER: the 555 can operate as a flip-flop, if the DIS pin is not connected and no capacitor is used. Uses include bounce free latched switches, etc. 555 TIMER IC FIGURE:1.4.1
  • 11. The connection of the pins is as follows: Figure1.4.2 Sr. Name Purpose 1 GND Ground, low level (0V) 2 TRIG A short pulse high-to-low on the trigger starts the timer 3 OUT During a timing interval, the output stays at +VCC 4 RESET A timing interval can be interrupted by applying a reset pulse to low (0V) 5 CTRL Control voltage allows access to the internal voltage divider (2/3 VCC) 6 THR The threshold at which the interval ends (it ends if U.thr → 2/3 VCC) 7 DIS Connected to a capacitor whose discharge time will influence the timing interval. 8 V+, VCC The positive supply voltage which must be between 3 and 15 V figure 1.4.3
  • 12. MONOSTABLE MODE In the monostable mode, the 555 timer acts as a ―one-shot‖ pulse generator. The pulse begins when the 555 timer receives a trigger signal. The width of the pulse is determined by the time constant of an RC network, which consists of a capacitor (C) and a resistor (R). The pulse ends when the charge on the C equals 2/3 of the supply voltage. The pulse width can be lengthened or shortened to the need of the specific application by adjusting the values of R and C. The pulse width of time t is given by which is the time it takes to charge C to 2/3 of the supply voltage. See RC circuit for an explanation of this effect. SPECIFICATIONS These specifications apply to the NE555. Other 555 timers can have better specifications depending on the grade (military, medical, etc). Supply voltage (VCC) 4.5 to 15 V Supply current (VCC = +5 V) 3 to 6 mA Supply current (VCC = +15 V) 10 to 15 mA Output current (maximum) 200 mA Power dissipation 600 mW Operating temperature 0 to 70 °C
  • 13. 1.5 CD 4026 /4033 DECADE COUNTER CD4026 and CD4033 each consist of a 5-stage Johnson decade counter and an output decoder which converts the Johnson code to a 7-segment decoded output for driving one stage in a numerical display. These devices are particularly advantageous in display applications where low power dissipation are important. Inputs common to both types are CLOCK, RESET & CLOCK INHIBIT. Common outputs are CARRY OUT and seven decoded outputs (a, b, c, d, e, f, g).Additional inputs and outputs for the IC include DISPLAY ENABLE input .Signals peculiar to the IC are RIPPLE BLANKING INPUT AND LAMP TEST INPUT and a RIPPLE BLANKING OUTPUT. A high RESET signal clears the decade counter to its zero count. The counter is advanced one count at the positive clock signal transition if the CLOCK INHIBIT signal is low. Counter advancement via the clock line is inhibited when the CLOCK INHIBIT signal is high. The CLOCK inhibit signal can be used as a negative-edge clock if the clock line is held high. Anti clock gating is provided on the JOHNSON counter, thus assuring proper counting sequence. The CARRY-OUT signal completes one cycle every ten CLOCK INPUT cycles and is used to clock the succeeding decade directly in a multi-decade counting chain .The seven decoded outputs illuminate the proper segments in a seven segment display device used for representing the decimal numbers 0 to 9.The 7-segment outputs go high on selection in the IC, these outputs go high only when the DISPLAY ENABLE IN is high.
  • 14. 1.6 7805,7905 REGULATOR The 78xx (also sometimes known as LM78xx) series of devices is a family of self-contained fixed linear voltage regulator integrated circuits. The 78xx family is a very popular choice for many electronic circuits which require a regulated power supply, due to their ease of use and relative cheapness. When specifying individual ICs within this family, the xx is replaced with a two-digit number, which indicates the output voltage the particular device is designed to provide (for example, the 7805 has a 5 volt output, while the 7812 produces 12 volts). The 78xx line are positive voltage regulators, meaning that they are designed to produce a voltage that is positive relative to a common ground. There is a related line of 79xx devices which are complementary negative voltage regulators. 78xx and 79xx ICs can be used in combination to provide both positive and negative supply voltages in the same circuit, if necessary. 78xx ICs have three terminals and are most commonly found in the TO220 form factor, although smaller surface-mount and larger TO3 packages are also available from some manufacturers. These devices typically support an input voltage which can be anywhere from a couple of volts over the intended output voltage, up to a maximum of 35 or 40 volts, and can typically provide up to around 1 or 1.5 amps of current (though smaller or larger packages may have a lower or higher current rating) REGULATORS FIGURE:1.6.1
  • 15. 1.7 COMMON CATHODE SEVEN SEGMENT LED DISPLAY A popular type consists of seven small, bar-shaped LED segment arranged so that depending on which combinations are energized, the numbers 0 to 9 light up. All the LED cathodes (or sometimes anodes) are joined to form a common connection. Current limiting resistors are required (e.g. 270 ohms), preferably one per segment. Figure 1.7.1
  • 16. The main requirements for a suitable LED material are:- 1) It must have on energy gap of appropriate width. 2) Both P and N types must exist, preferably with low resistivity. 3) Efficient radioactive pathways must be present. Generally, energy gaps greater than or equal to about 2 are required. Commercial LED materials:: Gallium arsenide (Ga As) doped with Si Gallium Phosphide (GaP) doped with N & Bi Gallium arsenide Phosphide (Ga As1-x Px) Gallium aluminium arsenide (Gax Al1-x As)
  • 17. 1.8 LIGHT EMITTING DIODE LED STRUCTURE Light emitting diode (LED) is basically a P-N junction semiconductor diode particularly designed to emit visible light. There are infrared emitting LEDs which emit invisible light. The LEDs are now available in many colours red, green and yellow. A normal LED emits at 2.4V and consumes MA of current. The LEDs are made in the form of flat tiny P-N junction enclosed in a semi-spherical dome made up of clear coloured epoxy resin. The dome of a LED acts as a lens and diffuser of light. The diameter of the base is less than a quarter of an inch. The actual diameter varies somewhat with different makes. The common circuit symbols for the LED are shown in Fig. It is similar to the conventional rectifier diode symbol with two arrows pointing out. There are two leads- one for anode and the other for cathode. LEDs often have leads of dissimilar length and the shorter one is the cathode. All manufacturers do not strictly adhere this to. Sometimes the cathode side has a flat base. If there is doubt, the polarity of the diode should be identified. A simple bench method is to use the ohmmeter incorporating 3-volt cells for ohmmeter function. When connected with the ohmmeter: one way there will be no deflection and when connected the other way round there will be a large deflection of a pointer. When this occurs the anode lead is connected to the negative of test lead and cathode to the positive test lead of the ohmmeter. Figure: 1.8.1 L.E.D BASIC DIAGARM If low range (Rxl) of the ohmmeter is used the LED would light up in most cases because the low range of ohmmeter can pass sufficient current to light up the LED. Another safe method is to connect the test circuit shown in Fig. 2. Use any two dry cells in series with a current limiting resistor of 68 to 100 ohms. The resistor limits the forward diode current of the LED under test to a safe value. When the LED under test is connected to the test terminals in any way: if it does not light up, reverse the test leads. The LED will now light up. The anode of the LED is that which is connected to the ―A‖ terminal (positive pole of the battery). This method is safe, as reverse voltage can never exceed 3 volts in this test.
  • 18. 1.9 TRIMPOTS AND PRESETS A trimmer is a miniature adjustable electrical component. It is meant to be set correctly when installed in some device, and never seen or adjusted by the device's user. Trimmer can be variable resistors or variable capacitors. They are common in precision circuitry like A/V components, and may need to be adjusted when the equipment is serviced. Unlike other variable controls, trimmers are mounted directly on circuit boards, turned with a small screwdriver and rated for many fewer adjustments over their lifetime. In 1952, Marlan Bourns patented the world's first trimming potentiometer, trademarked "Trimpot". TRIMPOTS AND PRESETS Figure 1.9.1
  • 19. 1.10 TRANSFORMER A transformer is a device that transfers electrical energy from one circuit to another through inductively coupled conductors — the transformer's coils. Except for air-core transformers, the conductors are commonly wound around a single iron-rich core, or around separate but magnetically-coupled cores. A varying current in the first or "primary" winding creates a varying magnetic field in the core (or cores) of the transformer. This varying magnetic field induces a varying electromotive force (EMF) or "voltage" in the "secondary" winding. This effect is called mutual induction. If a load is connected to the secondary, an electric current will flow in the secondary winding and electrical energy will flow from the primary circuit through the transformer to the load. In an ideal transformer, the induced voltage in the secondary winding (VS) is in proportion to the primary voltage (VP), and is given by the ratio of the number of turns in the secondary to the number of turns in the primary as follows: By appropriate selection of the ratio of turns, a transformer thus allows an alternating current (AC) voltage to be "stepped up" by making NS greater than NP, or "stepped down" by making NS less than NP. Transformers are essentially of two types: 1.STEPUP TRANSFORMER 2.STEPDOWN TRANSFORMER. They come in a range of sizes from a thumbnail-sized coupling transformer hidden inside a stage microphone to huge units weighing hundreds of tons used to interconnect portions of national power grids. All operate with the same basic principles, although the range of designs is wide. While new technologies have eliminated the need for transformers in some electronic circuits, transformers are still found in nearly all electronic devices designed for household ("mains") voltage. Transformers are essential for high voltage power transmission, which makes long distance transmission economically practical. TRANSFORMER Figure:1.10.1
  • 20. 1.11 PIEZOELECTRIC SENSOR A piezoelectric sensor is a device that uses the piezoelectric effect to measure pressure, acceleration, strain or force by converting them to an electrical signal. Figure 1.11.1 PIEZOELECTRIC ACCLEROMETER Piezoelectric sensors have proven to be versatile tools for the measurement of various processes. They are used for quality assurance, process control and for research and development in many different industries. Based on piezoelectric technology various physical quantities can be measured; the most common are pressure and acceleration. For pressure sensors, a thin membrane and a massive base is used, ensuring that an applied pressure specifically loads the elements in one direction. For accelerometers, a seismic mass is attached to the crystal elements. When the accelerometer experiences a motion, the invariant seismic mass loads the elements according to Newton‘s second law of motion F = ma. 1.11.1 CONSTRUCTION OF THE SENSOR A self constructed piezoelectric accelerometer is used in this project .It is constructed by using a ceramic piezo buzzer element. These elements are widely used in landline telephones sets to produce ring tones. The diameters of the brass plate and silver layer of piezo buzzer used in this project are around 27 mm and 18 mm respectively. Firstly top cover of the plastic case is removed. One of the two wires of a 2-core shielded earphone cable to the white silver layer sprayed over the piezo element .Connect the other wire of a 2-core cable to the brass plate of the
  • 21. element. The shielded part of the cable should be keep open but it should not touch the element. Mount the mass (1 cm long piece of solid cylindrical brass rod having 1 cm diameter) centrally over the white silver layer with some adhesive like quick fix. Add adhesive to the sides of the mass to fix it over the crystal. Allow sufficient time for drying up. Generally the cases have mounting holes diametrically opposite sides. Attach length of Velcro belts hooks with the help of a small nut bolt through one of the mounting holes. Similarly attach another length of Velcro belt at the other mounting hole of the case. Bridge the two holes with a small piece of Velcro belt. The piece should be short enough to put some pressure on the top surface of the brass rod. Too low or too high pressure would hamper the sensitivity of the accelerometer.
  • 22. 1.12 POWER SUPPLY The 230V AC mains is stepped down by transformer to deliver a secondary output of 9v-0-9v, 500mA. The transformer output is rectified by a full-wave rectifier comprising diodes D3 through D6. The output of rectifier is filtered by using a capacitor filter. This filtered output is given to fixed voltage regulators 7805(+5V) and 7905(- 5V).Regulators 7805, 7905 provide +5V and -5V regulated supply to circuit. Capacitors C16 and C17 bypasses any ripple present in regulated supply. Figure:1.12.1 Power supply circuit
  • 23. CHAPTER 2 WORKING The whole working of Digital heart beat counter can be divided into various parts which are following: 2.1. Piezoelectric accelerometer 2.2. Preamplifier 2.3. Low pass filter 2.4. Pulse monitor 2.5. Pulse counter and digital readout
  • 24. 2.1 PIEZOELECTRIC ACCLEROMETER An accelerometer measures the instantaneous acceleration of the object on which accelerometer is bounded. It transduces the acceleration which results from the vibration to corresponding analog signal. Here we use piezoelectric type accelerometer .When such an accelerometer is tightly coupled to one‘s wrist ,throbbing of arteries supplies this acceleration .Due to temporary deformation of the crystal by the exerted force , the piezoelectric crystal develops a charge across the electrodes attached to its lower and upper faces. The crystal regains its original dimensions as soon as the acceleration disappears .
  • 25. 2.2 PREAMPLIFIER Here we use high input impedance pre-amplifier. An instrumentation amplifier is used as a pre-amplifier. Three CA3140 op-amp IC‘s unitedly act as an instrumentation amplifier. Instrumentation amplifier is used because it greatly enhanced CMRR . CMRR refers to common mode rejection ratio. A high CMRR considerably reduces the ground noises from the surrounding environment. 2.3 LOW PASS FILTER The output signal from the instrumentation amplifier gets adulterated with some harmonics of 50 Hz AC power frequency, along with some other frequency components from surroundings .A sallen key low pass filter is used to reduce all these interferences. The amplified output voltage from IC3 of the 3-op-amp instrumentation amplifier is fed to op-amp IC4 through resistor R10. Op-amp IC4 along with resistor R10 and R12 and capacitors C4 and C5 forms the unity – gain Sallen key low pass filter. Although the presence of R11 and VR3 reduces the output voltage slightly , the upper cutoff frequency of the filter is 1.5 Hz .All frequencies above 10 Hz would be greatly filtered out. 2.4 PULSE MONITOR Apart of IC4 output is fed through a one stage RC low pass filter comprising R14 and C7 to pin 3 of op-amp IC5. The RC filter enhance the steepness of previous filter response. The additional stage amplification is required for driving LED1 and LED2. The LEDs blink in synchronization with heart beat pulses coming from the accelerometer .These pulses are fed through diodes D1 and D2 such that while one LED blinks during diastoles , the other one blinks during systoles . The gain of this stage is approximately 22. 2.5 PULSE COUNTER & DIGITAL READ OUT CMOS decade counters IC9 (CD4033/CD4026) and IC10(CD4033/CD4026) in tandem form the two digit decimal counter. The counters, count the heart beat pulses coming from Sallen key low pass filter. If pin 2 of IC 10 is at logic 0 ,each pulse from the LPF advances the counter by ‗1‘. The logic condition of pin 2 is dependent upon the logic condition of the monoshot configured around IC8 (NE555). The time period of the monoshot is governed by the combination of resistor R22 , preset VR5 and capacitor C12 and can be set for 10 seconds. Another monoshot configured around IC7(NE555) can be set by varying preset VR6 to give a time period of 15 seconds . The two monoshots are triggered simultaneously whenever low going pulse from the LPF reaches the common input(pin 2 of
  • 26. each NE555).As soon as they are triggered respective output goes low the same time .While the output of IC7 is designed to stay low for additional five seconds .Transistor T2 inverts the output of IC8 (logic 1) to drag CE of IC10 (pin2) to logic 0 .As soon as IC8 is triggered , the leading edge of the positive going output pulse resets decade counters IC9 and IC10 via capacitor C 13. The two 7-segment display DIS1 and DIS2 now show the count as ‘00‘. The counter is now enabled to count for 10 seconds. Since the output of the monoshot IC7 is triggered at the same time ,pin 9 of the OR gate IC6 goes high . It remains high for the time equal to time period of IC7, i.e 15 seconds . During the last period , no further beat pulses is allowed to trigger monoshot IC7 or IC8 .This is because the output of OR gate holds the common trigger input high .However the beating pulses are allowed to reach counter IC10 via inverter T2.So the components goes on counting the pulses as long as the output of IC8 remains high.At the end of 10 seconds the output of IC8 goes low. This disables IC10 and no further counting is allowed .The so far counted result is now displayed on 7-segment display DIS1 and DIS2 connected to the output of decade counters IC9 and IC10 respectively. At the end of 15 seconds the output of monoshot IC7 again goes low allowing the incoming pulses to trigger the monoshots to repeat cycle. The process continues as long as the accelerometer is tied to one‘s wrist. CONCLUSION AND FUTURE SCOPE CONCLUSION The project has been completed successfully and the heart beat count is measured and displayed by sensing the pulses through a piezoelectric accelerometer. Electronics digital heart-beat counter gives the opportunity to measure it automatically, continuously and precisely which is very important aspect for health diagnostics in medical science. FUTURE SCOPE In Digital heart beat counter counts are automatic and displayed on a 2-digit, 7-segment display. Continuous monitoring can be done .And the processed signal can be fed to a data-acquisition system (DAS) to observe or save the nature of the pulse.
  • 27. SNAPSHOT OF THE HARDWARE CIRCUIT FIG 2.DIGITAL HEART BEAT COUNTER
  • 28. BIBLIOGRAPHY BOOKS REFERRED: 1. Electronic devices and circuits by J.B.Gupta,VOL-2,KATSON BOOKS. 2. Electronics devices and circuits by S. Salivahnan, TMH Publications,16 reprint WEBSITES REFERRED: 1. www.electronicsforu.com 2. www.datasheetcatalog.com