Chapter 1 INTRODUCTION
1.1 STRESS METER Stress is the very common condition of every human being. Stress is nothing more than a socially acceptable form of mental illness. illness . This Stress meter allows to assess the emotional pain. If the stress is very high, it gives visual indication on a LED display along with a beep. This stress monitor lets you assess your emotional pain. If the stress is very high, it gives visual indication through a light-emitting diode LED! display along with warning beep. The gadget is small enough to be worn around the wrist. The L"#$%& is a monolithic integrated circuit that senses analog voltage levels and drives ten LED's, L(D's or vacuum fluorescent displays, providing a logarithmic #d)*step analog a nalog display. The gadget is based on the principle that the resistance of the s+in varies in accordance with your emotional states. If the stress level is high the s+in offers less resistance, and if the body is relaed the s+in resistance is high. The low resistance of the s+in
During high stress is due to an increase in the blood supply to the s+in. This increases the permeability of the s+in s +in and hence the conductivity for electric current. This property of the s+in is used
ere e re to me measu asure re th thee st stres resss le leve vel, l, th thee to touc uch h pa pads ds of th thee st stre ress ss me meter ter se sens nsee th thee vo volt ltag agee variations across the touch pads and convey the same to the circuit. The circuit is very sensitive and detects even a minute voltage variation across the touch pads.
1.2 EVOLUTION In an article Stress and "ind (ontrol/, 0%*1#*0112, 3oberto )onomi stated that 4hen we spea+ of the fabulous relaation capacity that mind control gives us, the first thing that comes to our mind, is that we will be able to ta+e off, the ecesses of nervous tension, the stress5 and
1
this is a great benefit. )ecause suppose that you could measure stress in inches, and that you have stress 6ero when the meter is located in 6ero./
7euroscientists have begun to learn that even acute, everyday stress can turn off the brain's brain's command-and-control center, the prefrontal corte. 4ithout 4ithout our mental eecutive, we feel helpless and out of control.The more we learn about stress, the more we reali6e that monitoring stress and ta+ing steps to +eep it under control is an important preventive health measure.
1.3 PURPOSE OF THE PROJECT The purpose of stress meter is to assess the emotional pain of human being. The stress can cause hair to fall, acne to brea+ out and many other problems. These manifestations of stress can cause even more aniety. Stress causes cortical levels to increase within the body, which increases oil production, which causes acne brea+outs. So this stress meter is to solve all the problems caused due to stress by chec+ing the stress of an individual and ta+ing care before any serious problem occurs.
2
Chapter 2 BLOCK DIARAM AND PROJECT OVERVIE!
2.1 PRINCIPLE OF STRESS METER" The stress meter is based on the principle that the variations in the resistance of the s+in due to blood pressure of one's body can be directly converted and transmitted into analog voltage levels to give the visual indication of human stress using a proper circuitry.
2.2 BLOCK DIARAM" INPUT #FROM FINERS
TRANSISTOR
TOUCH PADS
#BC%&'$
LED(S #OUTPUT$
IC LM3)1%
Fig: 2.1 Block diagram of stress stress meter
3
2.2.1 BLOCK DIARAM DESCRIPTION" 8igure above shows a bloc+ diagram of the Stress Indicator device. The touch pads of the stress meter sense the voltage variations across the touch pads and convey it to the signal amplifier, followed by LED display for visual indication and a warning beep. The circuit is very sensitive and detects even a minute voltage variation across the touch pads. • •
•
•
Touch pad- detects the changes on the s+in resistance. resistance. Transistor )(&92- amplify the signal produced at s+in surface obtain from the touch pad. I( L"#$%&- is use to sense the analogue voltage level at pin & obtain from the transistor. LED- indicates the level of pain produce from the galvanic s+in response.
2.3 APPLICATION" Each LED in stress meter operates with a #d) difference from the previous one, and a :umper is provided to allow dot or bar mode. This pro:ect is an essential part of the epandable analy6er and one meter circuit is used for each fre;uency band. There are many other uses for a simple LED meter. They are ideal as power meters on amplifiers, can be used with miers including the high ;uality mier!, preamps and any other application where it is important to +now the signal level. L"#$%&
Chapter 3
4
COMPONENTS OVERVIE! The components re;uired for stress meter are as follows>
1. I( L"#$%& % nos.! 2. Touch ?ads 3. $@ )attery % nos.! &. LEDs & red! %. Transistor )(&92 % nos.! *. Aener Diode &.%@, 1.&4 % nos.! +. Switch % nos.! '. ?ie6o )u66er % nos.! ). Diode %79%92 % nos.! @ariable 3esistor %"B, 9CB! 1,. @ariable 9CB,%.0B,&1B,%B,9C1B,9C1B! 11. 11. 3esistors 9CB,%.0B,&1B,%B,9C1B,9C1B! 12. (apacitor %11u8, %v 0 nos.! 13. (apacitor %1u8,%v % nos.! 1&. Aero ?()
3.1 IC LM3)1%" The L"#$%& is a monolithic integrated circuit that senses analog voltage levels and drives ten LEDs, L(Ds or vacuum fluorescent displays, providing a logarithmic # d)*step analog display. Fne pin changes the display from a bar graph to a moving dot display. LED current drive is regulated and programmable, eliminating the need for current limiting resistors. The whole display system can operate from a single supply as low as #@ or as high as 0&@ .
Feat-re •
# d)*step, #1 d) 3ange
•
Drives LEDs, L(Ds, or @acuum @acuum 8luorescents
•
)ar or Dot Display "ode Eternally Selectable by
•
Epandable to Displays of $1 Db
•
Internal @oltage @oltage 3eference from %.0@ to %0@
3.2 TOUCH PADS" PADS"
5
Gser
FIG 3.1 IC LM3915
The touch pads are the two copper strips tied on two fingers of the left hand. This provides the input in terms of s+in resistance. S+in resistance is primarily affected by sweat, as salty water is an ecellent conductor. So So essentially the machine is measuring how sweaty your palms are.
FIG 3.4 Toc! Toc! "ads
3.3 BATTER/" It has a rectangular prism shape with rounded edges and a polari6ed snap connector at the top. The battery has both terminals terminals in in a snap connector on one end. The smaller circular male! terminal is positive, and the larger heagonal or octagonal female! terminal is the negative contact. The connectors on the battery are the same as on the connector itself5 the smaller one connects to the larger one and vice versa. FIG 3.3 9# $atter%
3.& LED #0ht ett4 565e$" = light emitting diode LED! is a ?7 :unction semiconducto semiconductorr diode that emits photons when electrical current passes through the :unction in the forward direction, the electrical carriers give give up energy energy proportio proportional nal to the forward forward voltag voltagee drop drop across across the diode diode :unctio :unction, n, this this energy is emitted in the form of light. Fig 3.4 Light Emitting LED's are used in numerical displays such as those on electronic digital watches and poc+et
calculat calculators ors.. )y defini definitio tion, n, it is a solid-s solid-state tate device device that that contro controls ls current current withou withoutt heated heated filaments and is therefore very reliable. LED's are highly monochromatic, emitting a pure 6
color in a narrow fre;uency range. The color
emitted
from an LED is identified by pea+ wavelength and measure measured d in nanometer nanometers. s. LEDs LEDs are made from galliu gallium-b m-based ased crystal crystalss that that contain contain one or more more additional materials such as phosphorous to produce a distinct color. LED LED ligh lightt outp output ut varie variess with with the the type type of chip chip,, encapsulation,
LED Color
efficiency
Potential
of
Diference
Fig 3.5 Fig 3.5 inside a Light and other variables.
individual wafer lots Several
LED
such to
as
Infrared
1 .6 V
manufacturers use terms
red
1.8 to 2.1V
bright,H and Hultra-brightH
orange
2 .2 V
yellow
2 .4 V
green
2 .6 V
solid-state devices they
blue
3.0V to 3.5V
catastrophic failure when
white
3.0V to 3.5V
design parameters. LED's
ultraviolet
3 .5 V
Hsuper-
describe
LED
)ecause LED's are are
not
operated are driven.
sub:ect
to
within
current-driven =lthough
intensity.
devices,
no not
vo voltage
drive current and light
output are directly related, eceeding the maimum current rating will produce ecessive heat within the LED chip due to ecessive power dissipation. The color of an LED is determined by the semiconductor material, materia l, not by the coloring of the
LED's are specially constructed to release a large number of photons outward. =dditionally, they are housed in a plastic bulb that concentrates the light in a particular direction. Table 3.1: LED color vs. potential
3.% TRANSISTOR #BC%&'$" gene nera rall pu purp rpos osee si sili lico con, n, 7? 7?7, 7, bi bipo pola larr :u :unc ncti tion on tr tran ansi sist stor or.. It is us used ed fo for r BC%&' is ge amplification and switching purposes. The current gain may vary between %%1 and 211. The maimum D( current gain is 211.
7
Its e;u e;uiva ivalent lent tran transist sistors ors are 07# 07#$19 $19 and 0S(% 0S (%2% 2%&. &.
The hese se
e;ui e; uiva vale lent nt
tran tr ansi sist stor orss
howeve how everr hav havee dif differ ferent ent lead ass assign ignmen ments. ts. The variants of )(&92 are &92=, &92) and &92( which vary in range of current gain and other characteristics.
The transistor terminals re;uire a fied D( Fig 3.6 ins sho!ing the
voltage to operate
in
the
desired
region
of
its
characteristic curves. This is +nown as the biasing. 8or amplification applications, the transistor is biased such that it is partly on for all input conditions. The input signal at base is amplified
and
at the emi emitter tter.. BC%&' is used in common emitter amplifiers. The voltage divider is the commonly swiitch sw chiing ap app plica cattions, tra ran nsi sist sto or is biased so that
used
ta+en
configuration
for
biasing
8or
mode.
it rem emaains fully on if there is a
signal at its base. In the absence of base signal, it gets completely off. Fig 3." #ct$al vie! o%
3.* 7ENER DIODE " The 7e4er 565e is li+e a general-purpose signal diode
consisting of a silicon ?7
:unction. 4hen biased in the forward direction it behaves
:ust li+e a normal signal
diode passing the rated current, but as soon as a reverse
voltage applied across
the Aener Diod Diodee eceeds th t he ra r ated vo voltage of of th t he de d evice, th t he
diodes
brea+down voltage is reached at which point a process called &# called &#ala'c!e i n th t he se s emiconductor de d epletion ala'c!e Breakdo(' occurs in
layer and
a current starts to flow through the diode to limit this increase in voltage.
8
Fig 3.( )ener Diode
The current now flowing through the 6ener diode increases dramatically to the maimum circuit value which is usually limited by a series resistor! and once achieved this reverse saturation current remains fairly constant over a wide range of applied voltages. The voltage point at which the voltage across the 6ener diode becomes stable sta ble is called the 6ener voltage/ for 6ener diodes this voltage can range from less than one volt to hundreds of volts. The point at which the 6ener voltage triggers the current to flow through the diode can be very accurately controlled to less than % tolerance! in the doping stage of the diodes semiconductor construction giving the diode a specific )e'er specific )e'er $reakdo(' #oltage #ol tage,, @6 @6 ! ! for eample, 9.#@ or C.&@. This 6ener brea+down voltage on the I-@ curve is almost a vertical straight line.
fig 3.9 *I c!aracteristics of )e'er diode
3.' S!ITCH" The The swit switch ch used used is a sing single le pole pole doub double le thro throw w type type swit switch ch.. It perfo perform rmss the the F7*F F7*F88 88 operation.
fig 3.1+ ,"-T s(itc!
9
3.) PIE7O8BU77ER" PIE7O8BU77ER" Pe96 :-99er is an electronic device commonly used to produce sound. Light weight, simple construction
and
low
price ma+e it usable in
various applications li+e
car*truc+
indicator, computers, call
bells etc. ?ie6o bu66er
is based on the inverse
principle
electricity discovered in
%221 by Jac;ues and
?ierre
phenomena
(urie. It is the
generating
electricity
when
reversing
of
pie6o
of mechanical
pressure is applied to
certain materials and
the vice versa is also true.
Such
called
materials.
pie6o
electric
materials
are ?ie6o
electric elec tric mate material rialss are eith either er nat natura urally lly avai availab lable le or man manmad made. e. ?ie ?ie6oc 6oceram eramic ic is clas classs of manmade material, which poses pie6o electric effect and is widely used to ma+e disc, the heart of pie6o bu66er. 4hen sub:ected to an alternating electric field they stretch or compress, compress , in accordance with the fre;uency of the signal thereby producing sound.
3.1, DIODE 1N&1&'"
fig 3.11"ie)o$))er 3.11"ie)o$))er
10
Switching diodes are a single p-n diode in a discrete pac+age. = switching diode provides the same functionality as a switch. It has high resistance below the specified applied voltage similar to an open switch, whereas above that voltage it changes in a sudden way to the low resistance of a closed switch. Switching diodes are used in
devices such as ring
modulation.
The 1N&1&' is a standard silicon switching diode diode.. It is one of the most popular and long fig 3.12 -iode 1414/
lived switching diodes because of its dependable specifications and low cost. Its name follows the JEDE( JEDE( nomenclature. nomenclature. The %79%92 is useful in switching applications up to about %11 "6 with a reverse-recovery time of time of no more than 9 ns. The %79%92 comes in a DF-#& DF-#& glass glass pac+age for throughfor throughhole mounting. hole mounting. This is useful for bread for bread boarding of boarding of circuits.
SPECIFICATIONS" •
@33" K C&-%11 @ maimum repetitive reverse voltage
•
IF K C&-011 m= average rectified forward current
•
I8 K #11 m= maimum direct forward current
•
@8 K %.1 @ at %1 m=.
•
I8S" K %.1 = pulse width K % s!, 9.1 = pulse width K % Ms! non-repetitive pea+ forward surge current
•
?D K &11 m4 power dissipation
•
T33 N N 9 ns reverse-recovery time
11
3.11 VARIABLE RESISTOR #1M;< RESISTOR #1M;< &+K;$" = p6te4t6eter , informally a p6t, is a threeterminal resistor with with a sliding or rotating contact that forms an ad:ustable voltage divider . If only two terminals are used, one end and the wiper, it acts as a =ara:0e ret6r or rhe6tat . fig 3.14 "ote'tiometer
The measuring instrument called a potentiometer a potentiometer is is essentially a voltage divider used for measuring electric potential voltage!5 the component is an implementation of the same principle, hence its name. ?otentiometers are commonly used to control electrical devices such as volume controls on audio e;uipment. ?otentiometers operated by a mechanism can be used as position transducers transducers,, for eample, in a :oystic+ a :oystic+ . ?otentiometers are rarely used to directly control significant power more than a watt watt!, !, since the power dissipated in the potentiometer would be comparable to the power in the controlled load.
3.12 RESISTORS #&+K;< 1.2K;< %*,;< 1K;< &+,;< &+,;$" = ret6r is a passive a passive two-terminal electrical component that component that implements electrical resistance as a circuit element. 3esistors act to reduce current flow, and, at the fig 3.15 46 ,I,T
same time, act to lower voltage levels within circuits. In electronic circuits, resistors are used to limit current flow, to ad:ust signal levels, bias levels, bias active active elements,
fig 3.10 1.2 ,I,T
and terminate transmission lines among lines among other uses. igh-power resistors, 12
that can dissipate many watts watts of of electrical power as heat, may be used as part of motor controls, in power distribution systems, or as test loads for generators generators..
fig 3.16 50+ ,I,T
8ied resistors have resistances that only change slightly with temperature, time or operating voltage.
fig 3.1/ 1 ,I,T
@ariable resistors can be used to ad:ust circuit elements such as a volume control or a lamp dimmer!, or as sensing devices for heat, light, humidity, fig 3.19 46+ ,I,T force, or chemical activity. 3esistors are common elements of electrical networ+s and electronic circuits and are ubi;uitous in electronic e;uipment. e;uipment. ?ractical resistors as discrete components can be composed of various compounds and forms. 3esistors are also implemented within integrated circuits.. circuits The electrical function of a resistor is specified by its resistance> common commercial resistors are manufactured over a range of more than nine orders of magnitude. magnitude . The nominal value of the resistance will fall within a manufacturing tolerance. tolerance.
3.13 CAPACITOR 1,,-F< 1,->"
13
= ?apa?t6r is a passive a passive two-terminal electrical component used component used to store electrical energy energy temporarily temporarily in an electric field. field. The forms of practical capacitors vary widely, but all contain at least two electrical conductors plates! conductors plates! separated by a dielectric dielectric i.e. i.e. an insulator that that can store energy by becoming
polari6ed!. polari6ed !.
The conductors can be thin films, foils or
sintered beads
of metal or conductive electrolyte, etc. The non conducting dielectric acts to increase the
capacitor
capacity. = dielectric can be glass, ceramic, cera mic, plastic film, air, a ir, vacuum, paper, mica, oide layer etc. (apacitors are widely used as parts of electrical circuits in many common electrical devices. Gnli+e a resistor , an ideal capacitor does not dissipate energy. Instead, a capacitor stores energy energy in in the form of an electrostatic field between field between its plates. 4hen there is a potential a potential difference across difference across the conductors e.g., when a capacitor is attached across a battery!, an electric field develops across the dielectric, causing positive charge charge O O7 7 to collect on one plate and negative charge P7 P 7 to collect on the other plate. If a battery has been attached to a capacitor for a sufficient amount of time, no current can flow through the capacitor. owever, if a time-varying voltage is applied across the leads of the capacitor, a displacement current can current can flow. =n ideal capacitor is characteri6ed by a single constant value, its capacitance capacitance.. (apacitance is defined as the ratio of the electric charge 7 on each conductor to the potential difference * between between them. The SI SI unit unit of capacitance is the farad farad 8!, 8!, which is e;ual to one coulomb coulomb per per volt volt % % (*@!. Typical Typical capacitance values range from about a bout % p8 %1 P%0 8! to about % m8 %1 P# 8!. The larger the surface area of the HplatesH conductors! and the narrower the gap between them, the greater the capacitance is. In practice, the dielectric between the plates passes a small amount of lea+age current and current and also has an electric field strength limit, +nown as the brea+down the brea+down voltage. voltage. The conductors and leads leads introduce introduce an undesired inductance inductance and and resistance resistance.. (apacitors are widely used in electronic circuits for circuits for bloc+ing direct current while current while allowing alternating current to pass. In analog filter networ+s, networ+s, they smooth the output 14
of power supplies. supplies. In resonant circuits they tune radios radios to to particular fre;uencies fre;uencies.. In electric power transmission systems, transmission systems, they stabili6e voltage and power flow.
3.1& PERFORATED CIRCUIT BOARD #PCB$" = circuit in 6ero ?() ?rinted (ircuit )oard! is one that uses individual components on a breadboard or circuit board rather than a ?() to design an electronic circuit. This This method is cheaper compared to the use use of ?(). The procedure used is>
Q ?lace the components on the circuit board Q ?lan the board's wiring using the ?erfboard layout planning sheet. Q Gse the ynar wire to connect the components.
Sp0>e5 pr6?e5-re %! (omponent list> ynar wire, wire cutter, wire stripper, 3osin core solder, twee6ers and reading glasses or manual deterity.
0! ?lace the components on the circuit board> ?lace the components to minimi6e the lengths of wires re;uired to reduce stray capacitance. )end the pins to hold all the components place. #! "a+e the wiring plan > Gse a fine pencil in the holes for a soc+et pin and components wires. (hec+ the placement of the wires to ensure they are correctly placed. =lways use the circuit schematic. 9! Gse the ynar wire to connect the components> This procedure is repeated several times until all the wires are connected. Se;uentially, circuit board is placed to the helping hands tool ready for soldering. &! "easure and cut> Every wire is cut after referring to the planning sheet the loops are made around the ends of wires. It is crucial to strip the insulation by 0mm from its end before cutting a wire. ! (rimps all the loops over pins and solder them > (rimping is done by twee6ers and the connection should last until the solder is applied. C! Test Test the circuit circ uit board 15
Fig 3.21 8erforated circit $oard $oard
Chapter & CIRCUIT DIARAM AND OPERATION
&.1 CIRCUIT DIARAM Fig 4.1 "I -I&G&M F ,T,, MT MT
16
&.2 CIRCUIT OPERATION" This stress monitor lets you assess your emotional pain. If the stress is very high, it gives visual indication through a light-emitting diode LED! display along with a warning beep. The gadget is small enough to be worn on the fingers. The gadget is based on the principle that the resistance of the s+in varies in accordance with your emotional states. If the stress level is high the s+in offers less resistance, and if the body is relaed the s+in resistance is high. The low resistance of the s+in during high stress is due to an increase in the blood supply to the s+in. This increases the permeability of the s+in and hence the conductivity for electric current. This property of the s+in is used here to measure the stress level. The touch pads of the stress meter sense he voltage variations across the touch pads and convey the same to the circuit. The The circ circui uitt is very very sens sensiti itive ve and and dete detects cts even even a minut minutee volt voltag agee varia variati tion on acros acrosss the the touchpads.
17
Fig 4.2 -is8la% 8a'el
The circuit circuit compris comprises es signal signal amplif amplifier ier and analog analogue ue display sections. @oltage @oltage variations variations from the sensing sensing pads are amplified by transistor )(&92 T%!, which is configured as a common-emitter amplifier. The base of T% is conn connect ected ed to one one of the the touc touch h pads pads thro throug ugh h resistor 3% and to the ground rail through potentiometer @3%. )y varying @3%, the sensitivity of T% can be ad:usted to the desired level. Diode D% maintains proper biasing of T% and capacitor (% +eeps the voltage
from
the
emitter
ofT%
steady.
The amplified signal from transistor T% is given to the input of I( L"#$%& I(%! through @30. I( L"#$%& is a monolithic integrated circuit that senses analogue voltage levels at its pin & and displays them through LEDs L EDs providing a logarithmic analogue display. It can drive up to ten LEDs one by one in the dot*bar mode for each increment of %0& m@ in the input. ere, we've used only five LEDs connected at pins %9 through %2 of I(%. LED% glows when input pin & of I(% receives rece ives %&1 m@. m@. LED& glows glows when the voltage rises ris es to &1 m@ and LED& flashes and pie6obu66er ?A% beeps when the stress level is high. 3esistors 39 and 3& and capacitor (0 form the flashing elements. 3esistor 3# maintains the LED current at around 01 m=. (apacitor (# should be placed close to pin # for proper functioning of the I(. Aener diode AD% in series with resistor 3 provides regulated &@ to the circuit.
The circuit can be assembled on a small piece of perforated board. Gse transparent #mm LEDs and a small pie6obu66er for audio-visual indications. Enclose the circuit in a small plastic case with touch pads on the bac+ side. s ide. Two self-loc+ing straps can be used to tie the unit around your wrist.
=fter wearing touch pads on fingers with touch pads in contact with the s+in!, slowly vary @3% until LED% glows assuming that you are in relaed state!. =d:ust @30 if the sensitivity of I(% is very high. The gadget is now ready for use. 18
Chapter % IMPLEMENTATION IMPLEMENTATION OF CIRCUIT CI RCUIT The circuit can be implemented in 0 ways>
1. )readboard 2. ?()
19
%.1 BREADBOARD"
Fig 5.1 Bread$oard Bread$oard
= :rea5:6ar5 is a construction base for prototyping for prototyping of of electronics electronics.. Friginally it was literally a bread board, a polished piece of wood used for slicing bread. In the %$C1s the 605er0e
:rea5:6ar5 available and nowadays the term HbreadboardH is commonly used to refer to these. H)readboardH is also a synonym for H prototype H prototypeH. H. )ecause the solderless breadboard does not re;uire soldering soldering,, it is reusable. This ma+es it easy to use for creating temporary prototypes and eperimenting with circuit design. 8or this reason, solderless breadboards are also etremely popular with students and in technological education. Flder breadboard types did not have this property. propert y. = stripboard stripboard veroboard! veroboard! and similar prototyping printed prototyping printed circuit boards, boards, which are used to build semi-permanent soldered prototypes or one-offs, cannot easily be reused. = variety of electronic systems may be prototyped by using breadboards, breadboards, from small analog and digital circuits to complete central processing units (?Gs!. units (?Gs!.
T@p?a0 pe?>?at64 = modern solder less breadboard consists of a perforated bloc+ of plastic with numerous tin plated phosphor plated phosphor bron6e or bron6e or nic+el nic+el silver alloy alloy spring clips under the perforations. The clips are often called tie 8oi'ts or 8oi'ts or co'tact 8oi'ts. 8oi'ts. The number of tie points is often given in the specification of the breadboard. The spacing between the clips lead pitch! is typically 1.% in 0.&9 mm!. Integrated circuits I(s! in dual in-line pac+ages DI?s! can be inserted to straddle the centerline of the 20
bloc+. Interconnecting wires and the leads of discrete components such as capacitors capacitors,, resistors resistors,, and inductors inductors!! can be inserted into the remaining free holes to complete the circuit. 4here I(s are not used, discrete components and connecting wires may use any of the holes. Typically the spring clips are rated for % ampere ampere at at & volts volts and and 1.### amperes at %& volts & watts watts!. !.
B- a45 ter4a0 trp Solderless breadboards are available from several different manufacturers, but most share a similar layout. The layout of a typical solderless breadboard is made up from two types of areas, called strips. Strips consist of interconnected electrical terminals.
Fig 5.2 Termi'al Termi'al a'd $s stri8s
Ter4a0 Te r4a0 trp trp The main areas, to hold most of the electronic components. In the middle of a terminal strip of a breadboard, one typically finds a notch running in parallel to the long side. The notch is to mar+ mar+ the centerline of the terminal strip and provides limited airflow cooling! to DI? I(s straddling the centerline Rcitatio' 'eeded . The clips on the right and left of the notch are each connected in a radial way5 typically five clips i.e., beneath five holes! in a row on each side of the notch are electrically connected. The five clip columns on the left of the notch are often mar+ed as =, ), (, D, and E, while the ones on the right are mar+ed 8, , , I and J. 4hen a Hs+innyH dual in-line pin pac+age DI?! integrated circuit such as a typical DI?-%9 or DI?-%, which have a 1.#-inch C. mm! separation between the pin rows! is plugged into a breadboard, the the pins of one side of the chip are supposed to go into column E while the pins of the other side go into column 8 on the other side of the notch.
B- trp To provide provide power to the electronic e lectronic components. = bus strip usually contains two columns> one for ground and one for a supply voltage. owever, some breadboards only provide a single-column power distr ibutions bus strip on each long side. Typically the column intended for a supply voltage is mar+ed in red, while the column for ground is mar+ed in blue or blac+. Some manufacturers connect all terminals in a column. Fthers :ust connect groups of, for eample, 0& consecutive terminals in a column. 21
The latter design provides a circuit designer with some more control over crosstal+ over crosstal+ inductively inductively coupled noise! on the power supply bus. Fften the groups in a bus strip are indicated by gaps in the color mar+ing. )us strips typically run down one or both sides of a terminal strip or between terminal strips. Fn large breadboards additional bus strips can often be found on the top and bottom of terminal strips. = Hfull si6eH terminal breadboard strip typically consists of around & to & rows of connectors, each row containing the above-mentioned two sets of connected clips = to E and 8 to J!. Together with bus strips on each side this ma+es up a typical C29 to $%1 tie point solderless breadboard. HSmall si6eH strips typically come with around #1 rows. "iniature solderless breadboards as small as %C rows no bus strips, %C1 tie points! can be found, but these are only suitable for small and simple designs.
J-p re Jump wires also wires also called :umper wires! for solderless breadboarding can be obtained in ready-to-use :ump wire sets or can be manually manufactured. The latter can become tedious wor+ for larger circuits. 3eady-touse :ump wires come in different ;ualities, some even with tiny plugs attached to the wire ends. Jump wire
Fig 5.3 m8 (ires
material for ready-made or homemade wires should usually be 00 =4 =4 1.## mm0! solid copper, tin-plated wire - assuming no tiny plugs are to be attached to the wire ends. The wire & ends should be stripped # U % % to U % % in 9.2 to C.$ mm!. Shorter stripped wires might result in
bad contact with the board
e.g., red, blue, blac+!, some are reserved for main signals, and the rest are simply used where convenient. Some ready-to-use :ump wire sets use the color to indicate the length of the wires, but these sets do not allow a meaningful color-coding schema.
%.2 PERFORATED CIRCUIT BOARD #PCB$" for prototyping electronic Per>:6ar5 is a material for prototyping circuits also called DFT ?()!. It is a thin, rigid sheet with holes pre-drilled at standard intervals across a grid, usually a s;uare grid of 0.&9 mm 1.% in! spacing. These holes are ringed by round or s;uare copper pads. Inepensive perfboard may have pads on only one side of the board, while better ;uality perfboard can have pads on both sides 4plate-through Fig 5.4 5. plate-through ,tress meter o' $read$oard Fig 5.5 "CB
holes!. holes !.
Since each pad is electrically isolated, the builder ma+es all connections with either wire wrap or wrap or miniature point miniature point to point wiring techni;ues. wiring techni;ues. Discrete components are soldered to the prototype board such as resistors resistors,, capacitors capacitors,, and integrated circuits. circuits. The substrate is typically 23
made of paper laminated with phenolic with phenolic resin such resin such as 83-0 83-0!! or a fiberglass-reinforced epoy laminate 83-9 83-9!. !. The 1.% in grid system accommodates integrated circuits in DI? DI? pac+ages pac+ages and many other types of through-hole of through-hole components. components. ?erfboard is not designed for prototyping surface mount devices.. devices )efore building a circuit on perfboard, the locations of the components and connections are typically planned in detail on paper or with software tools. tools. Small scale prototypes, however, are often built ad hoc, using an oversi6ed perfboard. Software for ?() for ?() layout layout can often be used to generate perfboard layouts as well. In this case, the designer positions the components so all leads fall on intersections of a 1.% in grid. 4hen routing the connections more than 0 copper layers can be used, as multiple overlaps are not a problem for insulated wires. Fnce the layout is finali6ed, the components are soldered in their designated locations, paying attention to orientation of polari6ed parts such as electrolytic capacitors, diodes, and integrated circuits. 7et, electrical connections are made as called for in the layout. Fne school of thought is to ma+e as many connections as possible without adding etra wire. This is done by bending the eisting leads on resistors, capacitors, etc. into position, trimming off etra length, and soldering the lead to ma+e the re;uired electrical connection. =nother school of thought refuses to bend the ecessive leads of components and use them for wiring, on the ground that this ma+es removing a component later hard or impossible, e.g. when a repair is needed. If etra wires need to be used, or are used for principle reasons, they are typically routed entirely on the copper side of perfboards. )ecause, as opposite to strip boards, nearby holes aren
used, incorporating a thin steel blade with a slit that the wire is simply inserted into and then pulled loose, leaving a clean stripped end. This This wire was developed initially for circuit assembly by the wire wrap techni;ue wrap techni;ue but also serves well for miniature point-to-point wiring on perfboard. )are copper wire is useful when merging a number of connections to form an electrical bus such bus such as the circuit
%.3 SOLDERIN PROCESS" ,olderi'g / is defined as the S605er4 - a must s+ill for all electrical and electronic wor+s. ,olderi'g process of :oining two pieces of metals using a filler metal, +nown as solder, having a low melting point below the melting point of the wor+ piece. It is often confused with welding but the difference between them is, in soldering the wor+ piece is not melted, they are :oined using a filler metal, but in welding wor+ piece is :oined by melting.
Ht6r@
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Soldering was practiced as far bac+ as &111 years ago in Egypt. Soldering was widely performed around 9111 years ago when tin was discovered as soldering metal. The process of soldering solder ing was introd introduced uced in "edite "editerranean rranean region, and was follo followed wed in the 3oman Empire, Swiss and ungaria. Soldering Soldering has impro improved ved a lot from culture to cultur culturee and generation generation to generation and in today's scenario it is the best method for fabrication and assembly of microelectronics.
T@pe 6> S605er4 Soldering is classified as shown in the image below>
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Fig 5./ ,L-IG "CB
%.& FINAL DESIN OF STRESS METER ON PCB"
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Fig 5.9 ,T,, MT "CB FI&L FI&L -,IG;
Chapter *
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CONCLUSIONS *.1 RESULT" The stress meter thus detects the resistance of s+in which is according to one's mental stress and gives a visual indication on a LED display. The LED's on the stress meter can be observed observed as stress level indicators indicators from 6ero to & stress levels on a scale of 8I@E. The high stress of a person is indicated through a warning beep.
*.2 ANAL/SIS" ANAL/SIS" 3esistance varies inverse proportional to the stress. If the stress level is high the s+in offers less resistance, and if relaed resistance is high. The low resistance of the s+in during high stress is due to an increase in the blood supply to the s+in. This increases the permeability of the s+in and hence the conductivity for electric current. The LED % glows by default when the circuit is on. 4hen a person touches the touch pad of the stress meter with his finger, finger, it senses the s+in resistance and hence the stress. Fn a scale of ten, stress levels from 1 to & can be observed, observed, where the LED & when on gives a warning beep for high stress indication.
*.3 APPLICA APPLICATI TIONS" ONS" ?erson's muscle tension changes can be seen with their stress level applied by the "uscle!. The mental state of a person can be +nown based upon the changes in s+in 3esistance!. It can be used as a lie detector. It can be use used d in phy physica sicall fitn fitness ess programs programs.. The circuit is absolutely free from ambient light. It is economical and a low budget pro:ect. 7ot a comple circuit. The components are easily available in the mar+et and replaceable. 7oise pulse do not have any effect on the circuit. LED's can withstand the voltage even if no resistors are connected across. (an be used easily to regularly chec+ one's stress level.
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*.& ADVANTAES" ADVANTAES" %. Simple circuitry. circ uitry. 0. Easy to use. #. Easy to transport. 9. Less power consumption. &. Desired output.
*.% DISADVANTAES %. Futput is not measurable. 0. Futput depends upon the grip of the person.
*.* FUTURE SCOPE Stress meter can be further developed to design e;uipment li+e lie detectors5 s+in response meters5 s+in resistance meters5 fitness meters5 grip scopes etc. therefore this model, if further developed can be used in medical field, forensic department and it even helps in improving the body fitness.
APPENDI
PIN DIARAM OF LM3)1%"
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DEFINITION OF TERMS" A:60-te A??-ra?@" The difference between the observed threshold voltage and the ideal threshold voltage for each comparator. Specified and tested with %1@ across the internal voltage divider so that resistor ratio matching error predominates over comparator offset voltage.
A5-t P4 C-rre4t" (urrent flowing out of the reference ad:ust pin when the reference amplifier is in the linear region.
C6parat6r a4 > The ratio of the change in output current ILED! to the change in input voltage @I7! re;uired to produce it for a comparator in the linear region.
Dr6p6-t V60tae > The voltage measured at the current source outputs re;uired to ma+e the output current fall by %1.
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I4p-t Ba C-rre4t > (urrent flowing out of the signal input when the input buffer is in the linear region.
LED C-rre4t Re-0at64" The change in output current over the specified range of LED supply voltage @LED! as measured at the current source outputs. =s the forward voltage of an LED does not change change significa significantly ntly with a small small change change in forward forward current, current, this is e;uivalent to changing the voltage at the LED anodes by the same amount.
L4e Re-0at64" The average change in reference output voltage @3E8! over the specified range of supply voltage @O!.
L6a5 Re-0at64> The change in reference output voltage over the specified range of load current IL 3E8!!.
O>>et V60tae > The differential input voltage which must be applied to each comparator to bias the output in the linear region. "ost significant error when the voltage across the internal voltage divider is small. Specified and tested with pin voltage @3I! e;ual to pin 9 voltage @3LF!.
Re0at=e A??-ra?@" The difference between any two ad:acent threshold points. Specified and tested with %1@ across the internal voltage divider so that resistor ratio matching error predominates over comparator offset voltage.
LM3)1% OUTPUT CHARACTERISTICS"
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REFERENCES
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J6-r4a0" 3oberto )onomi, Stress and "ind (ontrol/, dated 0%*1#*0112
Re>ere4?e B66" %. Joseph Edminster and "ahmood 7ahvi, Electric Electr ic circuits, Schaum's Futline, 011# 0. Stanley Stanley )urns )urns and ?aul ?aul 3 )ond, )ond, ?rinci ?rinciple pless of Electr Electroni onicc (ircuit (ircuits, s, Intern Internatio ational nal Thomson publishing, %$$C #. 3ichard ( Jaegar and Travis 7 )laloc+, "icro electronic circuit design, Third Errata, 0112
Edition
!e:" %. 0. #. 9.
http>**www.engineersgarage.com*articles*soldering-tutorial-tips-types-processes https>**pre6i.com*hnwCyesf:spu*stress-meter* https>**en.wi+ipedia.org*wi+i*)readboard https>* https>**en *en.wi .wi+ip +ipedi edia.o a.org rg*wi *wi+i* +i*3esi 3esisto stor r
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