Digital Heart-beat Counter1

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RAKI K CHANDRANRINIL M GROSHNI VARGHEESE

SHINI NARAYANANSUJITHRA K R


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

Digital heart beat counter count the pulse continuouslyand automatically.

It have the following features:-1. A piezoelectric accelerometer as sensor.

2. A blinking LED for visual indication of persons pulse.

3.

Counts are automatic and displayed on a 2 sevensegment display.

4. Continuous monitoring can be done.

5. Counting can be done from remote place.

6. Works off AC mains or batteries.


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A persons heart forces his blood to flow throw the arteries.

Arteries throb in synchronization 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.


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The function of heart is to maintain a constant

circulation of blood throughout the body.

This is achieved by rhythmic contraction of its muscle.

It is the sequence of events which occur in the heartduring a single beat.

The rate of heart is 72 beats per minute .

Time taken for 1 beat is 0.8 seconds. It appears in two phases

1. Systole - A period of contraction.

2. DiastoleA period of relaxation.


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Pulse is the throbbing sensation felt over the wallof arteries.

Pulse rate is almost the same as heart rate .

The wrist is the common site where pulse isusually felt, which is referred as radial pulse.

Bradycardia occurs when the pulse rate is below

60. Tachycardia occurs when pulse rate is above 100

During sleep pulse rate is 40 BPM.


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BLOCK DIAGRAM


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-

An accelerometer measures the instantaneousacceleration of the object on which accelerometer isbounded.

It transduce the acceleration which results from thevibration to corresponding analog signal.

Here we use piezoelectric type accelerometer is used.


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PREAMPLIFIER

Here we usehigh input impedance pre-amplifier.

An instrumentation amplifier is used as a pre-amplifier.

Three CA3140 op-amp ICs unitedly act as an

instrumentation amplifier. Instrumentation amplifier is used because it greatly

enhanced CMRR .


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LOW PASS FILTER

The output signal from the instrumentationamplifier gets adulterated with some harmonicsof 50 Hz AC power frequency, along with some

other frequency components from surroundings.

A sallen key low pass filter is used to reduce allthese interferences.


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AMPLIFIER & PULSE INDICATOR

This amplifier section is used to drive the LEDs.

The LEDs blink in synchronization with heart

beat pulse.

One LED blink at the time of systole and anotherLED blink at the time of diastole.


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PULSE AMPLIFIER & MONOSTABLE

MULTIVIBRATOR

Pulse amplifier amplifies the LPF output.

In two monostable multivibrators, one designed for 15seconds and the other with time delay 10seconds.

The monostable multivibrator helps to stay the displayfor 5 seconds.


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INVERTER & 2-INPUT OR GATE

The inverter, inverts the output of monostablemultivibrator and is used to enable the counterICs.

The OR gate prevent the triggering ofmonostable multivibrator, while the displaystays constant.


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DIGITAL COUNTER & SEVEN SEGMENT

DISPLAY

Digital counter count the number of pulses for10seconds.

The counter IC here used is CD4033.

The counter gets incremented with each pulse.

The seven segment display displays the numberof pulses of 10 seconds.


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CIRCUIT DIAGRAM


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

1. Pre-amplifier2. Low Pass Filter

3. Pulse Monitor

4. Pulse Counter with digital readouts


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PREAMPLIFIER

The heart of the circuit is a piezo-electric accelerometer.

The sensor outputs an electrical charge, directlyproportional to magnitude of throbbing of artries.


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This charge gives a voltage of order of fewmillivolts across very high impedance of thepiezo-electric crystal.

Hence a high input impedance pre-amplifier isused.

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


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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.


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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.


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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 LPFoutput.

The output of first monostable multivibrator IC8,

( whose pulse width is 10 seconds) is given to clock enablepin of IC10.

Pulse from the LPF, trigger both IC8 and IC9

simultaneously. The output of IC8 remains high for 10 seconds and

output of IC9 for 15 seconds.


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The counter counts for 10 seconds.

After 10 seconds output of IC8 goes low, henceoutput counter stops countings and will high fornext 5 seconds.

During this 5 seconds, OR gate prevent any otherpulse on triggering IC8.

Hence the counter output stay on last count.


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POWER SUPPLY


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Here we use a center tapped transformer (9-0-9,500mA).

The transformer is rectified by a full wave bridge rectifiercomprising 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.


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THE PIEZO-ELECTRIC

ACCELEROMETER SENSOR


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CONSTRUCTION OF THE SENSOR

Instead of commercial accelerometer, self constructedaccelerometer is used.

It is constructed by using a ceramic piezo buzzer element.

The diameter of the brass plate and silver layer of the

piezo buzzer plate is used in this project are around 27mmand 18mm respectively.

One of the two wire of 2 core shielded earphone cable is

connected to white silver layer sprayed over the piezoelement, and other wire to brass plate.

Mount the mass centrally over the white silver layer.


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ADVANTAGES & DISADVANTAGES


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CONCLUSION


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TH

AN

K

S


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THANKS

Documents

Digital Heart-beat Counter1