DIGITAL HEART-BEAT

COUNTER

INTRODUCTION

The heart beat rate is the number of times the persons heart beat in one minute.

Digital heart beat counter count the pulse continuously and automatically.

It have the following features:- A piezoelectric accelerometer as sensor. A blinking LED for visual indication of

persons pulse.

PRINCIPLE A persons heart forces his blood to flow

throw the arteries. Arteries throb in synchronisation with the

beating of heart. Throbbing can be felt at wrist. Electronically this throbbing is sensed with

an accelerometer, which convert it in to electrical signal.

Counter section count the number of pulses for 10 seconds and display it for 5 seconds

PULSE The wrist is the common site where pulse is

usually felt, which is referred as radial pulse. Pulse is the throbbing sensation felt over the

walls of arteries. Pulse rate is almost the same as heart rate . Bradycardia occurs when the pulse rate is

below 60. Tachycardiaoccurs when pulse rate is above

100. During sleep pulse rate is 40 BPM.

BLOCK DIAGRAM

CIRCUIT DIAGRAM

CIRCUIT DIAGRAM

The total circuit can be divided in to 4 sections as follows:-

Pre-amplifier Low Pass Filter Pulse Monitor Pulse Counter with digital readouts

PREAMPLIFIER The heart of the circuit is a piezo-electric

accelerometer . The sensor outputs an electrical charge,

directly proportional to magnitude of throbbing of artries.

This charge gives a voltage of order of few millivolts across very high impedance of the piezo-electric crystal.

Hence a high input impedance pre-amplifier is used.

The IC1,IC2,IC3 together act as pre-amplifier

LOW PASS FILTER

The amplified output voltage from IC3(CA3140) of instrumentation amplifier is given to IC4 through resistor R10.

The op-amp IC4 along with resistors R10 and R12 and capacitors C4 and C5 forms unity gain Sallen key LPF.

The upper cut frequency is approximately 1.5Hz.

PULSE MONITOR

Apart ofIC4 output is fed to a RC LPF comparing 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 for drive LED1 and LED2.

The gain of this stage is approximately 22.

PULSE COUNTER & DIGITAL READ OUT CMOS decade counters IC9(CD4033)

and IC10(CD4033) in tandem form the two digit decimal counter.

The counters, count the number of pulses from LPF output.

The output of first monostable multivibrator IC8, ( whose pulse width is 10 seconds) is given to clock enable pin of IC10.

POWER SUPPLY

POWER SUPPLY Here we use a center tapped transformer (9-0-

9,500mA) The transformer is rectified by a full wave bridge

rectifier comprising diodes D3 through D6. The output of rectifier is filtered by using a capacitor

filter . Thisfiltered 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

ADVANTAGES It count the pulses automatically and continuously. Monitoring of the heart beat rate of a person from

a remote place is also possible . Besides its rate, some other qualities of the pulse

reflect the state of the cardiovascular system. These are its rhythm, fullness and shape of the pulse wave. The signal out from the LPF/amplifier IC5 maybe fed to a DAS system for monitoring all these characteristic.

Low cost. Simplicity of the circuit.

DISADVANTAGES

Due to the absence of desired value of resistors, the time on which the counter, counts the pulse, can’t be accurately set for 10 seconds.

Due to large number of discrete components, it is very difficult to troubleshoot in case of any failure.

CONCLUSION In this fast moving world even wasting one

minute is not imaginable . This is how we came to the idea of DIGITAL HEART BEAT COUNTER which gives the opportunity to count heart beat pulse automatically. As time moves we can find digital heart beat counter in every house, as heart diseases are common among the people. And digital heart beat counter helps in detecting small variations in heart rate.

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