Stress Meter Report

8/3/2019 Stress Meter Report

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ABSTRACT

Stress is a term that refers to the sum of the physical, mental, and emotional strains

or tensions on a person. Feelings of stress in humans result from

interactions between pe rson s a nd thei r e nvir onme nt that are

perceived as s t ra in ing or exceeding the i r adapt ive capaci t ies and

threaten ing their w ell-bei ng. The element o f percept i onindicates

that human stress responses reflect differences in personality as well

asdifferences in physical strength or health.

This Stress meter allows to assess ones emotional pain. If the stress is very high,itgives visual indication through LED display along with a warning yellow light.

Stress meter is based on the principle that the resistance of the skin

varies inaccordance with your emotional states. Resistance varies inversely

proportional to thes t re s s . I f th e s t re s s l ev el i s h i gh th e s k i n

o f f e r s l e s s r e s i s t a n c e , a n d i f r e l a x e d , resistance is high.In an article

Stress and Mind Control, 21/03/2008,Roberto Bonomistated thatWhen we

speak of the fabulous relaxation capacity that mind control gives us,

thefirst thing that comes to our mind, is that we will be able to take off,

the excesses of nervous tension, the stress; and this is a great benefit. Because

suppose that you couldmeasure stress in inches, and that you have stress

zero when the meter is located inzero. Based on this our project isaimed to give a visual indication of ones stress through a light-emitting

diode display along with a warning light.
http://www.articlesbase.com/authors/roberto-bonomi/51803.htmhttp://www.articlesbase.com/authors/roberto-bonomi/51803.htmhttp://www.articlesbase.com/authors/roberto-bonomi/51803.htm


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LIST OF TABLES

1. Table : LED Color Vs. Potential difference...

2. Table : LED Vs. Threshold voltage...


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LIST OF FIGURES

1)Fig 2.1: Block diagram of stress meter. .. 6

2)Fig 3.1: Dot/Bar display driver.. ..... 8

3)Fig 3.2: The piez o element . .9

4)Fig 3.3: Piezo elec tric diaphragm.. ..10

5)Fig 3.4: Touch pad.. .10

6)Fig 3.5: Light emitting diode ...11

7)Fig 3.6: Inside a light emitting diode. ..12

8)Fig 3.7: Regulated po wer supply... ..14

9)Fig 3.8: Voltage re gulator 14

10)Fig 3.9: Circuit diagram of Stress meter. .15

11)Fig 4.1: Basicblock diagram showing the operation of the circuit .17

12)Fig 4.2: Role played by touch pads. 18

13)Fig 4.3: Bridge Rectifier Circuit.. 20

14)Fig 4.4: The Power supply generation..213


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Chapter1

Introdution

1.1Stress MeterStress is very common condition of every human being . stress is nothing more

than socially acceptable from of mental illness .This stress meter allow to access

the emotional pain . If stress is high, it gives visual indication on LED display

along with a warning light.

Stress meter is based on principle that the resistance of the skin varies in

accordance with your emotional states. If stress level is high the skin offers low

resistance, and if relaxed resistance is high .

The low resistance is of skin during high stress due to increase in blood supply of

skin. This increases the permeability of skin and hence the conductivity for electric

current. This property of skin is use here to measure stress. Using suitable circuitry

we can convert the amount of stress a human being feels to a varying along

voltage.

The LM3915 is monolithic integrated circuit that sense along voltage level and

drives five LEDs, LCDs or vacuumed fluorescent displays, providing a

logarithmic 3dB/step analog display.

The touch pad of stress meter sense the voltage variation across the touch pad and

convey the same to the circuit. The circuit is very sensitive and detect even a

minute voltage variation across the touch pad


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1.2EVOLUTIONIn an article Stress and Mind Control, 21/03/2008, Roberto Bonomi

stated thatWhen we speak of the fabulous relaxation capacity that mind

control gives us, thefirst thing that comes to our mind, is that we will beable to take off, the excesses of nervous tension, the stress; and this is a great

benefit. Because suppose that you couldmeasure stress in inches, and that you

have stress zero when the meter is located inzero.

Based on this, our project is aimed to give a visual indication of onesstressthrough a light-emitting diode display along with a warning yellow light.

1.3PURPOSE OF THE PROJECTThe purpose of stress meter is to assess the emotional pain of human

being. Thestress can cause h air to fal l , a cne to break o ut and many

ot he r pr ob le ms . Th es e manifestations of stress can cause even more

anxiety. Stress causes cortical levels toin c r e a s e w i t h i n t h e b o d y ,

w h i c h i n c r e a s e s o i l p r o d u c t i o n , w h i c h c a u s e s a c n e breakouts.

So this stress meter is to so lve all the problems caused due to stress by

checkingthe stress of an individual and taking care before any serious problem

occurs.


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Chapter 2

Block diagram and project over view

2.1: The principle of stress meterThe stress meter is based on the principle that the variation in resistance of skin

due to blood pressure of ones. Body can converted and transmitted into along

voltage level give to visual indication of human stress using proper circuitry.

regulated

power supplytransformer touchpad

integratedcircuit

buzzer LED


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2.3 BLOCK DIAGRAM DESCRIPTION

The 230 volts ac power supply is given to the transformer.Th e t ransformer

st ep s do wn th e in pu t vo lt ag e li ne an d isolates the power supply from the

power line. A full wave bri dg e re ct if ie r ci rc ui t al on g wi th a vo lt ag e

re gu la to r is used to give a regulated power supply to the circuit

.Theinput touch pads are used to sense the resistance of our skinand this input is

fed to the dot/bar display driver.

The dot/bar display driver accepts the input through thetouch pads which sense

the small change in resistance thedo t / b a r d r i v e r g i v e s t h e o u t p u t

s t r e s s l e v e l i n d i c a t i o n a c c o r d i n g t h e i n p u t . T h e o u t p u t i s

i n d i c a t e d o n a l e d display .The ten leds ac t l ike the s t ress levelindicatorsform zero stress level to high stress level on a scale of ten.The high

stress detected from the dot/ bar display driver isindicated through a warning

yellow light.

2.4 APPLICATION:Each LED in stress meter operates with a 3dB differencefrom the

previous one, and a jumper is provided to allowdot or ba r mo de . Th is


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project is an essential part of theexpandable analyzer and one meter

circuit is used for eachfr eq ue nc y ba nd . Th er e ar e ma ny ot he r us es fo r

a si mp le LED meter. They are ideal as power meters on amplifiers,can be

used with mixers (including the high quality mixer), preamps and any other

application where it is important toknow the signal level.

The LM3915s 3dB step display is suited for signals with

wide dynamic range, such as audio level ,power, light, intensity

or vibration. Audio application include average or peak value

level indicator, power meters and RF signals strength meters ,

replacing conventional meter with an LED bar graph result in

a faster responding ,more rugged display with high visibility

that retains ease of interpretation of analog display.

Chapter 3

COMPONENTS OVERVIEW

3.1 DOT/BAR DISPLAY DRIVER

The LM3915 is monolithic integrated circuit that sense analog voltage and drive

five LEDs. One pin changes the display from a bar graph to moving dot display.


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LED current drive is regulated and programmable eliminating the need for current

limiting resistor. The input buffer drive 10 individual comparators referenced to

the precision divider. Accuracyis typically better than 1 dB.

3.2 THE PIEZO ELEMENT:

P i e z o e l e c t r i c d i a p h r a g m i s a b a s i c e l e c t r o n i c

s o u n d component . I t has the advantages of s imple s t ruc ture ,s tab le

performance and high reliability. It is not only thecore element of

piezoelectric buzzers and the alarms, but also used as shock sensors in many

sensitive equipments.

The Piezo Element


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Basically, the sound source of a piezoelectric soundcomponent is a

piezoelectric diaphragm. A piezoelectricdiaphragm consists of a

piezoelectric ceramic plate whichhas ele ct rod es on bot h si des and a

m et al p la t e ( br as s o r s t a i n l e s s s t e e l , e t c . ) . A p i e z o e l e c t r i c

ce ra mi c p l a t e i s a t t ached to a meta l p l a t e wi th adhesives .Applying D.C.voltage between electrodes of a piezoelectric

diaphragmcauses mechanical distortion due to the piezoelectric effect.

Design Considerations :

These devices contain no electronics, and require externalc ir cu it ry to

produce an audib le tone . Presence of thefeedback tab enables the

des ign er to s imp l i fy the d ri ve circuit. Voltage applied to the device

produces mechanical


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distortions which are usable, among other applications, inalarms and

sensors.

Piezo electric buzzer

The Touch Pad:

The Touch Pad is two tinned pads on the PC board. Whentouched them with a

finger, the resistance of the finger isreduced by a factor of about 100 -

400 by the gain of theemitt er-f ollo wer tran sis tor and this puts a

HI GH on th e input pin of the chip. The input impedance of the chip

isfa i r ly h igh (about 50k) but when you add a pul l -downres is tor

(to prev ent s tray sign als b eing dete cted by t he chip), the impedance

decreases . The answer is to add the emitter-follower transistor.

Touch pad


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3.3 LIGHT EMITTING DIODES:

A l i g h t e m i t t i n g d i o d e ( L E D ) i s a P N

j u n c t i o n semiconductor diode that emits photons whenelectricalc u r r e n t p a s s e s t h r o u g h t h e j u n c t i o n i n t h e

f o r w a r d direction, the electrical carriers give up energy proportionalto the

forward voltage drop across the diode junct ion, this energy is emitted in the

form of light.

Construction of LED

LEDs are used in numerical displays such as those one l e c t r o n i c

d i g i t a l w a t c h e s a n d p o c k e t c a l c u l a t o r s . B y d ef in it io n, i t i s a

so l id-s ta te device tha t cont ro ls cur rentwi thout heated f i laments

and i s therefore very re l iab le .LEDs are highly monochromatic, emitting a

pure color ina narrow frequency range. The color emitted from an LEDi s

i d e n t i f i e d b y p e a k w a v e l e n g t h a n d m e a s u r e d

i n nanometers. LEDs are made from gallium-based crystalst h a t

c o n t a i n o n e o r m o r e a d d i t i o n a l m a t e r i a l s su c h a s phosphorousto produce a distinct color. LED light outputvaries with the type of chip,

encapsulation, efficiency of indiv idual wafer lo ts and o ther

var iables . Several LEDmanufacturers use terms such as "super-bright," and

"ultra- bright" to describe LED intensity.


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Because LEDs are solid-state devices they are not subjectto c a t a s t r o p h i c

f a i l u r e w h e n o p e r a t e d w i t h i n d e s i g n parameters. LEDs are current-

driven devices, not voltagedriven. Although drive current and light output are

directlyr e l a t e d , e x c e e d i n g t h e m a x i m u m c u r r e n t r a t i n g

w i l l p r o d u c e e x c e s s i v e h e a t w i t h i n t h e L E D c h i p d u et o e x c e s s i v e p o w e r d i s s i p a t i o n . T h e c o l o r o f a n L E D

i s d e t e r m i n e d b y t h e s e m i c o n d u c t o r m a t e r i a l , n o t b y

thecolor ing of the 'package ' ( the plast ic body) . LEDs areavai lable

in red, orange, amber, yellow, green, and bluea n d w h i t e c o l o r s .

L E D s a r e sp ec i a l ly co ns t r uc te d to release a large number of

photons outward. Additionally,they are housed in a plastic bulb that

concentrates the lightin a particular direction


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Design Parameters:

Never an LED should be connected directly to a battery or power supply. It will

be destroyed almost instantly becauseto o mu ch cu r re nt wi l l pass thro ugh

an d bu rn it ou t. An LED must have a resistor connected in series tolimit thecurrent through the LED; otherwise it will burn out almostinstantly and

try to avoid connecting them in parallel.

LED color Potential difference

Infrared 1.6v

Red 1.8v to 2.1v

Orange 2.2v

Yellow 2.4v

Green 2.6v

Blue 3.0vto 3.5v

white 3.0v to 3.5v

LED color vs. potentialdifference

Equation to determine the required resistance:

R e s i s t a n c e = ( S o u r c e V o l t a g e LE D Vo l t ag e Dr op ) / desired

current

To drive an LED from a system, the following values are used:

Source voltage = 13.4 volts (approximately)

Voltage drop = 3.6 volts (typical for a blue or white LED)

Desired current = 30 milliamps (typical value)


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So the resistor we need is:

(13.43.6) / (30 / 1000) = 327 ohms (Approximately 330ohms).

3.4 REGULATED POWER SUPPLY:

In a typical linear power supply, AC line voltage is firstdown-converted to a

smaller peak voltage using atransformer which is then rectified using a full wave

bridgerectifier circuit. A capacitor filter is then used to smoothenthe obtained

sinusoidal signal. The residual periodicvariation or ripple in this filtered signal is

eliminated usingan active regulator.

Regulated power supply

To obtain a DC power supply with both positive andnegative output voltages, a

center-tapped transformer isused, where a third wire is attached to the middle of

thesecondary winding and it is taken as the common ground point. Then voltages

from the opposite ends of the windingwill be positive or negative with respect to

this pointCare should be taken while connecting 78XX and 79XXICs.

Voltage Regulator:The 7805 takes in a voltage between 7 and 30 volts andregulates it down to exactly

5 volts. The first capacitor takes out any ripple coming from the transformer so

thatthe 7805 is receiving a smooth input voltage, and thesecond capacitor acts as a

load balancer to ensureconsistent output from the 7805.


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Voltage regulator

The 78 05 ha s th re eleads. If the 7805

is seenf r o m t he f r on t ( th e s id e wi th pr in t ing on i t ) , the three leads

are, from leftto right, input voltage (7to 30 volts), ground, andoutput

voltage (5 volts).


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Circuit diagram of stress meter


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CIRCUIT OPERATION

4.1 OPERATION OF THE CIRCUIT:

This stress meter circuit uses just one IC and a very few number of externalcomponents. It displays the input levelin terms of 10 LEDs. The suggested input

voltage can varyfrom 12V to 20V.

The LM3915 IC conta ins an adjus table

vol tagereference and an accura te ten-

s t ep vo l t age d iv ider . Theh i gh -

i m p e d a n c e i n p u t b u f f e r a c c e p t s s i g n a l s d o w n t o g r o u n d a n d

u p t o w i t h i n 1 . 5 V o f t h e p o s i t i v e su p p l y . F urther, it needs no

protection against inputs of 35V. The input buffer drives 10 individualcomparators referenced tothe precision divider. Accuracy is typically better

than 1dB.

A high input impedance buffer operates with signalsfrom ground to 12V,

and is protected against reverse andover voltage signals. The signal is

then applied to a seriesof 10 comparators; each of which is biased to a

differentcomparison level by the resistor string.

The LM3915 is extremely easy to apply. A 1.2V full -scale meter requires

only one resistor in addition to the tenLEDs. One more resistor programs the full-scale anywherefro m 1 .2V to 12V ind epe nde nt of su ppl y v olt age .

LED brightness is easily controlled with a single pot.

The following relations can be used to know theapproximate values of

current and reference voltages.

V ref = 1.25 (1+R2/R1) + R2* 80UA

I (LED) = (12.5V/R1) + (Vref/2.2K)18


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The output is indicated on a LED display .The ten LEDsact like the

stress level indicators form zero stress level tohigh stress level on a scale of

ten. The high stress detectedfro m th e do t/ ba r di sp la y dr iv er is

indicated by a yellowlight.

LED THRESHODE

1 60mv

2 80mv

3 110mv

4 160mv

5 220mv

6 320mv


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4.5 POWER SUPPLY GENERATION:

The 230 volts ac power supply is fed to the transformer and the transformer in turn

is connected to a bridgerectifier circuit.When four diodes are connected as shown

in figure, thecircuit is called a BRIDGE RECTIFIER. The input to the22circuitis applied to the diagonally opposite corners of thenetwork, and the output is taken

from the remaining twocorners.On the positive half cycle of transformer

secondarysupply voltage, diodes Da n d D conduct, supplying thisvoltage to

the load. On the negative half cycle of supply voltage, diodes Dand Dconduct

supplying this voltage tothe load.It can be seen from the waveforms

thatthepeakinversev o l t a g e o f t h e d i o d e s i s o n l y V m.The averag

e outputv o l t a g e i s t h e s a m e a s t h a t f o r t h e c e n t e r -

t a p p e d transformer full-wave rectifier.With a res istive load, the load

current is identical inshape to the output voltage. Most loads are

inductive andthe load current with these loads depends on the value

of load resistance and load inductance so they do not conductany current.D u r i n g t h e n e g a t i v e h a l f -

c y c l e , t h e t o p e n d o f t h e t ransformer winding i s negat ive .

Now, D1 and D4 a ref o r w a r d b i a s e d , a n d D 2 a n d D 3 a r e r e

v e r s e b i a s e d . Therefore, electrons move through D1, the resistor, and D4in

the d i rec t ion shown by the b lue ar rows. As wi th the posi t ive hal f -

cy cl e, el ec tr on s mo ve th ro ug h th e re si st or from left to right. In this

manner, the diodes keep switchingthe transformer connections to the resistor

so that currentalways flows in only one direction through the

r es is to r. T h e r e s i s t o r s c a n b e r e p l a c e d w i t h a n y o t h e r c i r c u i t ,

including more power supply circuitry (such as the fi lter),and still see the

same behavior from the bridge rectifier.

The output from the bridge rectifier is thus connected tovoltage regulator 7805 to

generate 5 volts regulated power supply to the circuit. The capacitors are

used as filters tosmoothen the sinusoidal signals


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4.6 THE STRESS METER:


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5.1 RESULTS:

The stress meter thus detects the resistance of skin which

i s a c c o r d i n g t o o n e s m e n t a l s t r e s s a n d g i v e s a v i s u a l i nd

ica t ion on a LED disp lay . The LEDs on the st res smeter can beobserved as stress level indicators form zeroto ten stress levels on a scale

of ten. The high stress of a person is indicated through a warning yellow light.

5.2 ANALYSIS:

Resistance varies inverse proportional to the stress. If thestress level is

high the ski n o ffe rs less resi stan ce, and if relaxed resistance is high.

The low resistance of the skinduring high stress is due to an increase in the

blood supplyto the skin. This increases the permeability of the skin andhence the

conductivity for electric current.The LED 1 glows by defaul t when the circui t

is on.When a person touches the touch pad of the stress meter with his

finger, it senses the skin resistance and hence thestress. On a scale of ten,

stress levels from 0 to 10 can beobs erv ed , whe re th e LE D 10 whe n on

gives a warning yellow light high stress indication.


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Conclusion

6.1 Summary

In this project , is proposed a stress meter indicate the stress level of human being

based on ones skin resistance on scale of ten.The ckt uses IC LM3915 which is dot

display driver which can easily drive five LED with suggested input voltage

The touch pad which is piezoelectric substance senses the skin resistance when the

touch with a finger act like as input to the ckt . the output stress level is indicated

on the led display. The high stress level indicated by a warning of yellow led.

A regulated power supply is used in project give an input voltage of 5 voltage forthe ckt to operate.

Applications

Stress meter is widely applicable in the various meters and indicators.

It is used as :

A simple led meter Single led level indicators In peak detectors Light , power , audio meter


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6.3 BENEFITS: The circuit is absolutely free from ambient light.

It is economical and a low budget project.

Not a complex circuit. The components are easily available in the marketand replaceable. Noise pulse do not have any effect on thecircuit. L E D s c a n w i t h s t a n d t h e v o l t a g e e v e n i f n o resist

ors are connected across.

Can be used easily to regularly check ones stress level.


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APPENDIX

PIN DIAGRAM OF LM3915:


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Dropout Voltage

: Th e vo l t ag e me as ur ed a t th e cu r r en t source outputs required to

make the output current fall by10%.

Input Bias Current

: C u r r e n t f l o w i n g o u t o f t h e s i g n a l input when the input buffer is in

the linear region.

LED Current Regulation:

The change in output currentover the specified range of LED supply voltage

(VLED)asmeasured at the current source outputs. As the forwardvoltage

of an LED does not change s igni f icant ly wi th

a s m a l l c h a n g e i n f o r w a r d c u r r e n t , t h i s i s e q u i v a l e n t t o c h a n

g i n g t h e v o l t a g e a t t h e L E D a n o d e s b y t h e s a m e amount.

Line Regulation:

The average change in reference outputvoltage (VREF) over the specified

range of supply voltage(V+).

Load Regulation

: The change in reference output voltageover the specified range of load

current (IL (REF)).

Offset Voltage

: The differential input voltage which must be ap pl ie d to ea ch

comparator to b ias the output inthel inea r region. Most s i gnif icant error when the vol t ageacross the

internal voltage divider is small. Specified andtes te d wi th pi n 6

volt age (VRHI ) equ al t o pin 4 vo ltag e(VRLO).


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Relative Accuracy:

T h e d i f fe re nc e b et we en a n y t wo adjacent threshold poin ts .

Specified and tested with

10Vacross the in ternal vol tage d iv ider so tha t res is tor ra t iom a tc hi n g e r r o r p r e d o m i n a t e s o v e r c o m p a r a t o r o f f s e t voltage.


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BIBLIOGRAPHY

Journals:

1.Rober to Bonomi , St ress and Mind Control , dated21/03/2008

Reference Books:

1. Joseph Edminster and Mahmood Nahvi, Electriccircuits, Schaums

Outline, 2003

2. S tanley G Burns and Paul R Bond, Pr inc ip les

of Ele ctronic Circui ts , Interna t ional Thomson publishi ng,1997

3 . Ri ch ar d C J ae ga r an d Tr av i s N Bl a l oc k , Mi cr oelectronic circu

it design, Third Edition Errata,200834


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A report on

STRESS METER

Submitted to Department of

Electronics and Telecommunication Engineering

Dr. D. Y. Patil Polytechnic , talsande

In partital fulfillment of the Requirment of

Industrial Measurement

Submitted by

Swapnil Patil

Prashant Gade

Prakash Chougale

Uday Patil

Under the guidance of lecturer

MissSavita Shetty


Dr. D. Y. Patil Polytechnic , talsande


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Dr. D. Y. Patil Polytechnic

Talsande , Kolhapur

Department of


Acadmic Year 2011-2012

Tis is certify that , all student mention below have successfully done a project report on the given

topic to our satisfaction during the acadmicyear2011-12 . The report made was in partial

fulfillment of 3rd

semester diploma course in Electronics and Telecommunication

Engineering

Student participants :-

1) Swapnil Patil2) Prashant Gade

3) Prakash Chogale4) Uday Patil

Date :-

Guid H.O.D Principal

CERTIFICATE


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( Miss- Savita Shetty) (Mr. U. K. Patil) (Mr. M.N.Narake)


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A

PROJECT

REPORT

ON

STRESS METER

SUBMITTED BY:-

SWAPNIL PATIL

PRASHANT GADE

PRAKASH CHOUGALE

UDAY PATIL


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Documents

Stress Meter Report