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LOVELY PROFESSIONALUNIVERSITY

2010

 TERMPAPERANALOG CIRCUITS AND LINEAR IC

 TOPIC:-555 TIMER BISTABLE OPERATION AS IN INDUSTRIAL

APPLICATION

 

SUB TO: -MR. SHAKTI RAJ CHOPRA

S U B B Y : - V I S H A L C H U D H A R Y , R O L L . N O : -D ! 0 " A 1 2 , B . T E C H - M . T E C H

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  Acknowledgement

I am grateful to MR SHAKTI RAJ CHOPRA teacher for asking me to prepare

the topic

I woul like to thank him for e!plaining the "asics of the presentation an for

answering m# e$er# ou"t with a smile% I woul like to thank m# classmate an

m# eler "rother who ha$e helpe me in arrange the information a"out m#

topic%

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Contents

• Introduction

•

Development of 555 timer

• Variants

• Usage

• Monostable mode

•  Bistable Mode

•  Astable mode

•  Dual timer 556

• uad timer 55!

• Bistable Multivibrators

• Bistable Multivibrator Circuit

• ""#$CM%& Bistable Multivibrators

• 'A'D (ate Bistable

• "&%)* An application of 555 timer IC 

• +eferences

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Introduction 

The &&& Timer IC is an integrate circuit 'chip( implementing a $ariet#

of timer an multi$i"rator applications% The IC was esigne "# Hans R%

Camen)in in *+,- an "rought to market in *+,* "# Signetics 'later ac.uire "# Philips(%

The original name was the S/&&& 'metal can(01/&&&'plastic 2IP( an the part was escri"e

as 3The IC Time Machine3% It has "een claime that the &&& gets its name from the three

& k4 resistors use in t#pical earl# implementations5 "ut Hans Camen)in has state that the

num"er was ar"itrar#% The part is still in wie use5 thanks to its ease of use5 low price an

goo sta"ilit#% As of 6--75 it is estimate that * "illion units are manufacture e$er# #ear%

2epening on the manufacturer5 the stanar &&& package inclues o$er 6- transistors5

6 ioes an *& resistors on a silicon chip installe in an 89pin mini ual9in9line package

'2IP98(% :ariants a$aila"le inclue the &&; 'a *<9pin 2IP com"ining two &&&s on one chip(5

an the &&8 'a *;9pin 2IP com"ining four slightl# moifie &&&s with 2IS = THR connecte

internall#5 an TR falling ege sensiti$e instea of le$el sensiti$e(%

>ltra9low power $ersions of the &&& are also a$aila"le5 such as the ,&&& an T?C&&&% The

,&&& re.uires slightl# ifferent wiring using fewer e!ternal components an less power%

",e 555 ,as t,ree operating modes*

Monostable mode@ in this moe5 the &&& functions as a 3one9shot3% Applications

inclue timers5 missing pulse etection5 "ouncefree switches5 touch switches5 fre.uenc#

i$ier5 capacitance measurement5 pulse9with moulation 'PM( etc Astable 9 free running moe@ the &&& can operate as an oscillator % >ses

inclue ?/2 an lamp flashers5 pulse generation5 logic clocks5 tone generation5 securit#

alarms5 pulse position moulation5 etc%

Bistable mode or &c,mitt trigger@ the &&& can operate as a flip9flop5 if the 2IS pin is

not connecte an no capacitor is use% >ses inclue "ouncefree latche switches5 etc%

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Development of t,e 555 timer

The &&& timer was in$ente "# Swiss esign consultant Hans Camen)in% It was esigne in

*+,- an introuce in the market "# Signetics Corporation in *+,*% Signetics was laterac.uire "# Philips% Originall# calle the S/&&&01/&&&5 this e$ice was referre to as BThe

IC Time Machine% As electronic technolog# flourishe o$er the #ears5 the IC timer e$ice

 "ecame an important part of man# electronic s#stems%

The use of the &&& timer has risen "ecause of the numerous a$antages it has to offer% The

Korean compan# Samsung toa# manufactures o$er a "illion such chips e$er# #ear to "e sol

in the glo"al electronics market%

 Variants

The &&& timer essentiall# consists of 67 transistors5 6 ioes an *; resistors integrate on a

silicon chip% This chip is installe in an 89pin ual9in9line package '2IP(% The timer ma# also

 "e a$aila"le in ifferent forms such as the *<9pin &&; 2IP that com"ines two &&&s on a single

chip5 the *;9"it &&8 that has four &&&s on a single chip an other ultra9low power $ariants

such as the ,&&&% The low power $ersions ha$e a wiring which is slightl# ifferent as

compare to the con$entional t#pes% Aitionall# the# use less e!ternal components an

hence re.uire reuce power%

Usage

Pin out iagram

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",e connection of t,e pins is as follows*

'r- 'ame )urpose

* D12 Droun5 low le$el '- :(

6 TRID A short pulse high9to9low on the trigger starts the timer 

7 O>T 2uring a timing inter$al5 the output sta#s at EV  CC

< R/S/T A timing inter$al can "e interrupte "# appl#ing a reset pulse to low '- :(

& CTR? Control $oltage allows access to the internal $oltage i$ier '607 V CC(

; THR  The threshol at which the inter$al ens 'it ens if the $oltage at THR is at least

607 V CC(

, 2IS Connecte to a capacitor whose ischarge time will influence the timing inter$al

8   V E5 V CC The positi$e suppl# $oltage which must "e "etween 7 an *& :

Monostable mode

Schematic of a &&& in monosta"le moe

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The relationships of the trigger signal5 the $oltage on C an the pulse with in monosta"le

moe

In the monosta"le moe5 the &&& timer acts as a Fone9shotG pulse generator% The pulse "egins

when the &&& timer recei$es a trigger signal% The with of the pulse is etermine "# the time

constant of an RC network5 which consists of a capacitor  'C( an a resistor  'R(% The pulse

ens when the charge on the C e.uals 607 of the suppl# $oltage% The pulse with can "e

lengthene or shortene to the nee of the specific application "# austing the $alues of R

an C%

The pulse with of time t 5 which is the time it takes to charge C to 607 of the suppl# $oltage5

is gi$en "#

where t is in secons5 R is in ohms an C is in faras% See RC circuit for an e!planation of

this effect%

Bistable Mode

In "ista"le moe5 the &&& timer acts as a "asic flip9flop% The trigger an reset inputs 'pins 6

an < respecti$el# on a &&&( are hel high $ia pull9up resisters while the threshol input 'pin

;( is simpl# groune% Thus configure5 pulling the trigger momentaril# to groun acts as a

set an transitions the output pin 'pin 7( to :cc 'high state(% Pulling the reset input to groun

acts as a reset an transitions the output pin to groun 'low state(% 1o capacitors are re.uire

in a "ista"le configuration% Pin 8 ':cc( is5 of course5 tie to :cc while pin * 'Dn( is

groune% Pins & an , 'control an ischarge( are left floating%

Astable mode

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Stanar &&& Asta"le Circuit

In asta"le moe5 the &&& timer puts out a continuous stream of rectangular pulses ha$ing a

specifie fre.uenc#% Resistor R * is connecte "etween :CC an the ischarge pin 'pin ,( ananother resistor 'R 6( is connecte "etween the ischarge pin 'pin ,(5 an the trigger 'pin 6(

an threshol 'pin ;( pins that share a common noe% Hence the capacitor is charge through

R * an R 65 an ischarge onl# through R 65 since pin , has low impeance to groun uring

output low inter$als of the c#cle5 therefore ischarging the capacitor%

In the asta"le moe5 the fre.uenc# of the pulse stream epens on the $alues of R *5 R 6 an C@

The high time from each pulse is gi$en "#

an the low time from each pulse is gi$en "#

where R * an R 6 are the $alues of the resistors in ohms an C is the $alue of the capacitor

in faras

Dual timer 556

The ual $ersion is calle &&;% It features two complete &&&s in a *< pin 2I? package%

uad timer 55!

The .ua $ersion is calle &&8 an has *; pins% To fit four &&&s into a *; pin package the

control $oltage an reset lines are share "# all four moules% Also for each moule the

ischarge an threshol are internall# wire together an calle timing %

Bistable Multivibrators

ista"le Multi$i"rators are another t#pe of two state e$ice similar to the Monosta"leMulti$i"rator .we looke at in the last tutorial "ut the ifference this time is that "oth states

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are sta"le% ista"le Multi$i"rators ha$e TO sta"le states 'hence the name@ 3i3(5 an the#

can "e switche o$er from one sta"le state to the other "# the application of a trigger pulse%

As ista"le Multi$i"rators ha$e two sta"le states the# are more commonl# known as lip9

flops for use in se.uential t#pe circuits%

ista"le Multi$i"rators are two state non9regenerati$e e$ices an in each state one of thetransistors is cut9off while the other transistor is in saturation5 this means that the "ista"le

circuit is capa"le of remaining inefinitel# in either sta"le state% To change o$er from one

state to the other the circuit re.uires a suita"le trigger pulse an to go through a full c#cle5

two triggering pulses5 one for each stage are re.uire% Its more common name or term of

3lip9flop3 relates to the actual operation of the e$ice5 as it 3lips3 into one logic state5

remains there an then changes or 3lops3 "ack into its first original state%

Bistable Multivibrator Circuit

The ista"le Multi$i"rator circuit a"o$e is sta"le in "oth states5 either with one transistor

3O3 an the other 3O13 or with the first transistor 3O13 an the secon 3O3% Switching

 "etween the two states is achie$e "# appl#ing a trigger pulse which inturn will cause the3O13 transistor to turn 3O3% The circuit will switch se.uentiall# "# appl#ing a pulse to

each "ase in turn an this is achie$e from a single input trigger pulse using a "iase ioes

as a steering circuit% /.uall#5 we coul remo$e the ioes5 capacitors an fee"ack resistors

an appl# ini$iual trigger pulses irectl# to the transistor ases%

Then unlike Monosta"le Multi$i"rators whose output is epenent upon the RC time constant

of the fee"ack components use5 the ista"le Multi$i"rators output is epenent upon the

application of two ini$iual trigger pulses% So Monosta"le Multi$i"rators can prouce a

$er# short output pulse or a much longer rectangular shape output whose leaing ege rises

in time with the e!ternall# applie trigger pulse an whose trailing ege is epenent upon a

secon trigger pulse as shown "elow%

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Bistable Multivibrator .aveforms

ista"le Multi$i"rators ha$e man# applications such as part of a counting circuit5 or as a one9

 "it memor# e$ice in a computer5 or as fre.uenc# i$iers "ecause the output pulses ha$e a

fre.uenc# that are e!actl# one half 'f06( that of the trigger input pulse fre.uenc# ue to them

changing state from a single input pulse% In other wors the circuit prouces re.uenc#

2i$ision as it now i$ies the input fre.uenc# "# a factor of two 'an octa$e(%

""#$CM%& Bistable Multivibrators

As well as proucing ista"le Multi$i"rators from ini$iual iscrete components such as

transistors5 we can also construct ista"le circuits using commonl# a$aila"le integratecircuits% The following circuit shows how a "asic "ista"le multi$i"rator circuit can "e

constructe using ust two 69input ?ogic 31A123 Dates%

'A'D (ate Bistable

# connecting the two 1A12 gates together as shown a"o$e5 we can construct a manuall#controlle "ista"le multi$i"rator that is acti$ate "# the single9pole ou"le9throw switch to

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 prouce a logic 3*3 or a logic 3-3 output% Lou ma# notice that this circuit looks a little

familiar5 an #ou woul "e right5 as its more commonl# calle an SR 1A12 Date lip9

flop that we looke at "ack in the Se.uential ?ogic tutorials an which we saw that this t#pe

of 1A12 Date ista"le makes an e!cellent switch e"ouncing circuit%

"&%)* An application of 555 timer IC

An application of &&& timer ICs is presente here is in infra9re etection% T: remote

controls use infra9re transmittersan recie$ers% A simple IR recie$er is sensiti$e to noise5

that is it is possi"le that the recie$er picks up strat IR signals thatwere not sent "# the

transmitter% To get aroun this pro"lem5 a techni.ue calle moualation is use% The

transmitteroes not sen continous signals% Instea5 it switches the signal on an oN at a

 particular fre.uenc# '78 kH) in case ofmost IR sensors(% The recie$er is tune to recie$e

signals onl# in a small fre.uenc# "an aroun this particular fre.uenc#%This makes sure that

constant or ranoml# uctuating IR signals are not accepte "# the recie$er%TSOP *,78 is an

e!ample of such a recie$er% It gi$es a output high if a moulate IR signal at 78 kH) is

etecte5low otherwise% Hence5 it is re.uire to make a transmitter that turns itself on or oN at

this fre.uenc#% This can "eimplemente using a a simple IR le an a s.uare wa$e generate

 "# a &&& timer%

+/0/+/'C/&*

I'"/+'/" &%U+C/&*

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