final file of comp hrdwr 8 practicls.doc

8/14/2019 final file of comp hrdwr 8 practicls.doc

1/21

PRACTICAL NO 1

AIM:~ To study soldering and desoldering of various components.

INTRODUTION:

Once a defective component needs to be isolated from the given faulty equipment, it isrequired to remove the defective component from the PCB & all this require a good practice of

soldering & desoldering.

!O"D#RIN$ %RO#!!:Soldering is the process of joining to or more metals at temperature belo there melting

points using filler metal !solder" having melting point belo #$%c. 'he solder binds the metal

together by chemical & physical processes. Chemically solder reacts ith small part of each metal to

be joined or soldered, thus forming a ne compound. Physically the liquid solder alloy then enters

the e(posed pores of the metals. Solder on cooling solidifies and forms a continuous metallic bond.

)f the metals are not heated properly, solder ill not penetrate into the metal pores. *s a result solderill solidify over the top of the pores in the metal & this result in defective joint +non as cold

solder joint

.

!O"D#R :ost of the soldering in electronics is done using tin lead alloy. Pure lead melts at -/c

here as tin melts at -c and their mi(ture at 011c hen ratio of tin & lead is 2%3#%.

'he tin lead ratio at hich the solder alloy goes directly to liquid stage is called

#"#TRNONI OM%OI!ITION& resultant alloy is +non as #UT#TI A""O&. 'his alloy

is generally referred to as 2-3-/ .'he addition of antimony to this alloy increases the strength. 'he

tin lead alloy is dran into hollo ire hose centre is fi(ed ith flu(. 'his is +non as RO!IN

OR# !O"D#R. 4or general soldering 01 gauge ire solder is used.

'"U(#!:'he soldering process requires that the surface should be totally clear so that metal to metal

contact can be established. ost of the metals in the air form an o(ide layer hich prevents etting.

'o maintain a clean surface flu( is used. )t dissolves o(ides and allos good soldering. 'he flu( ill

also assist in the transfer of heat from the soldering iron tip t the joint area. 4lu( is imbedded in

solder !rosin core solder". )t is also available in paste or liquid form .

A flu) s*ould *ave t*e follo+ing properties:

0 )t must be sufficiently active at room temperature to remove o(ides. )t must be mobile enough to allo the solder to flo at this temperature.

- )t must remove fingerprints, dirt, grease etc.

0


2/21

Traditionally flu)es can ,e grouped as:

0. 5osin based flu(es.

. 6ater soluble flu(es.

-. Solvent removable synthetic flu(es.

#. 7o solid flu(es.

Of these rosin based flu(es are generally used for repair or+. 'hese consist of rosin

dissolved in some solvent.

TINNIN$:'he component leads may get rusted during storage. )t ill be difficult t solder such leaded

components. 'hus leads of such components or ires need to be tinned.

'inning consist of the application of the thin layer of solder to the surface of metal hich

could be lead of a component or copper trac+ on PCB.

T*e t+o c*ief met*ods are8

0. 9ot dip tinning.

. :sing soldering iron.

Before tinning a ire, the insulation must be removed ith ire strippers. 'he first method

consists of immersing the metal surface to be tinning in to hot solder bath, after application of flu(.

'his method is not used for repair or+.

;uring repair or reor+, tinning is done using soldering iron. 4irst of all flu( is applied to the

surface to be tinned.

!O"D#RIN$ IRON!:Soldering iron is used during soldering process to supply sufficient heat to melt solder by

transfer of heat from soldering iron tip. 'he tip of the soldering iron is applied to a connection hichis to be soldered

.

T*ere are generally t*ree classes or types of soldering irons:

0. 5esistive soldering irons.

. Soldering gun.

-. 'emperature controlled soldering gun.

R#!I!TI-# !O"D#RIN$ IRON:)t is cheapest soldering iron. 'hese can not be used for precision or+ as heat produced is in

e(cess then required to melt solder. 'he e(cessive heat can be very damaging PCB,S andsemiconductor devices. 'his should be used in emergency and hen used should be applied for

minimum of time to prevent damage of devices due to overheating.

'his consists of a copper tip hich is heated electrically by resistive coil. 'his tip acts a heat

store and heat conductor.

!O"D#RIN$ $UNSoldering gun is used for soldering heavy iring. )t is not recommended for use on PCB


3/21

T#M%#RATUR# ONTRO""#D !O"D#RIN$ $UN'he soldering irons are most suited to maintenance purposes especially hen dealing ith

semiconductors components hich are li+ely to be damaged by overheating. 'his iron operates

much sloly as compared to uncontrolled iron.

!#"#TION O' !O"D#RION$ IRON :

Soldering irons are available in variety of si=es, shapes and attages. )n standard iron, theinput voltage is fi(ed> this resulting temperature depends on capacity of the heating unit and si=e of

the tip. ?enerally, soldering irons are selected on the basis of the input attage or the tip, idling,

temperature neither of these is valid criterion for matching the right to iron to the job. )deal tip

or+ing temperature is defined as the temperature range beteen appo( 2%% to /%% for most

electronic assembly.

!O"D#RIN$ IRON TI% "#ANIN$8)ron plated tips should be cleaned hile hot ith metal brush or ith cellulose sponge !et"

and hile cold ith a ire brush to remove o(ide film. 'hese should not be cleaned ith files, sand

paper or emery cloth.

D#!O"D#RIN$:'his operation is frequently required during maintenance for replacing a component. )t

consists of removal of solder from a previously soldered joint.

The following techniques are often used for this purpose.

. U!# O' D#!O"D#RIN$ %UM%;esoldering pump is a mechanically operated, hand held desoldering tool,. 'his tool consist

of a outer shaft, piston handle and release pin and 'eflon pin. )t is designed to be held andoperated in one hand. 'he pump can be disassembled and cleaned as required

.

The step by step procedure for desoldering is8

7oad the pump

9eat the solder connected ith soldering iron until solder melts.

9old desoldering pump lightly against the melted solder.

Press the pin to vacuum solder from connection.

5eload and repeat as necessary to clean the area of solder.

/. U!# O' D#!O"D#RIN$ 0RAID ;esoldering braid is loosely oven, flu( impregnated, stranded braid of copper ire. 'he

joint to be desoldered is not heated using soldering iron. 'he braid !ic+" is heated first. 'he solder

is suc+ed into the braid due to capillary action hen it is brought near joint. 'he used portion is cut

and thron aay. )n this method soldering iron never touches the solder so prevents over heating of

components.

1. U!# O' D#!O"D#RIN$ 0U"0'his also operates on vacuum principle. 'he rubber is simply a hollo rubber ball ith heat

resistant 'eflon tip. )t can be used ith any soldering iron.'he iron is held in one hand and used to melt the solder. 'he bulb held in second hand is then

squee=ed to create vacuum. 'he tip is ne(t applied to the reheated solder. Connection action that

suc+s the solder up through hollo tip into bulb.

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4/21

2. U!# O' D#!O"D#RIN$ TI% AND DI% #(TRATOR3 'his method is used fordesoldering )C


5/21

PRACTICAL NO 2

AIM: To c*ec6 and measure various po+er supply voltages of pc.

T*eory:'he PC poer supply is primarily designed simply to ta+e *C from the all outlet & convert

into the much loer ;C voltages needed by the system. 6hen system shut don, it must prevent

any voltage overshoot & fluctuations so that none of sensitive circuits are e(posed to any damaging

voltage fluctuation .)t must include some ay of providing cooling air flo, because of the

conversion process alays has some heat by product.

onverting A to D po+er:'he sitching mode poer supply used in a PC is much lighter & more efficient then the

more common linear mode poer supplies. Often used in the past systems, & therefore is a good

choice for a poer supply. 'he first part of PC sitching poer supply is rectifier. e(t is thesitches circuit hich chops up .the input voltage at a frequency much higher than the *C supply.

4urther more, any load fluctuation are fed bac+ to the input in such aay as to cause sitcher circuit

to adjust the input poer to the transformer so that it can maintain the output voltage to final

regulator. 'he sitcher circuitry it self generate @), hich can feed bac+ into the building *C

poer & contribute to problems elsehere.

Output voltage supply voltage lines:

'he voltages delivered by the poer supply to the motherboard must remain stable in spite ofa ide range of input *C voltage and varying load conditions

$


6/21

78 volt supply:'his is the basic supply voltage for nearly allFelectronic components. 'he $D supply is no

sometimes used by motors, but usually only in smaller drives, such as G.$inchH & some -.$inch

drive. 'he I$D supply ires should alays be red in any standard PC system.)f regulated voltage is

adjustable, the jumpers or sitches ill probably be found near regulator circuit.

7/- po+er supply:

'his line supplies most if not all, motors in the system, from drive motor to cooling fans.Because motors often used up to $%J more poer on start up then hile running ,the I0D supply

may sho adequate operation hile running , but be in an over loaded condition during the $

seconds or so immediately .after the system or a particular drive is turned on .

3/ - po+er supply:'his supply line is usually used for some of the same communications circuits that use I0

D line.

38 - po+er supply:'his voltage is no longer used by any device and is retained only the purpose of bac+ard

compatibility ith the older )S* slots. Originally, this voltage as used by some ;5* memory

chips in original PC design. icro channel system omitted this voltage from the poer supply

entirely

71.1- po+er supply: Starting ith the *'A designed in 0KK$ any system ith *'A compatible poer supplies

include a -.- volt supply line from the poer supply to the motherboard. Currently most CP:s &

;5* used -.-D as ell as some PC) adapter cards.

%o+er !upply ontrol !ignals:*lthough the primary function of the poer supply is indeed to supply clean electrical poer

to systems, the poer supply also interacts ith the motherboard to perform an increasing number of

functions, including CP: startup, system poer don, voltage and temperature detection and other

functions.

%o+er $ood !ignal:'he signal is actually a logic level signal designed as a poer supply output signal to the

CP: circuitry, to start the CP: running.

%o+er On:Prior to the *'A standard, *' compatible poer supplies either had the poer sitch

mounted on the bac+ or side of poer supply itself ,or had a remote sitch mounted on the front

panel.

'he poer on signal ire is apart of *'A standard and carries only a lo voltage logic level

signal from the motherboard to the poer supply, telling it hen to turn on and hen to turn off.

2


7/21

PRACTICAL NO 3

AIM: To study various cards used in a system.

DI!%"A& ARD :3

T*ree components in a video card

'he video card is just as important as the screen L and more often overloo+ed. ;uring the years

0KKKF%%0 the overall quality of video adapters has been improved. @arlier there ere some very

lousy products in the mar+et. 4ollo my articles to +no more of the video adapter. * video card is

typically an adapter, a removable e(pansion card in the PC. 'hus, it can be replaced. 'he video card

can also be an integral part of the system board this is the case in certain brands of PCs and is alays

the case in lap tops. ) have a clear preference for a replaceable video card in my stationary PC.

9oever modern motherboard may include good integrated video chip sets. ou just have to +no

hich onesM

5egardless of hether it is replaceable or integrated, the video adapter consists of three components8

* video chip set of some brand !*'), atro(, vidia, S-, )ntel, to name some of the

better +non". 'he video chip creates the signals, hich the screen must receive to form

an image.

Some +ind of RAM !@;O, S?5*, or D5*, hich are all variations of the regular

5*". emory is necessary, since the video card must be able to remember a complete

screen image at any time. :sing *?P, the video card may use the main memory of the

motherboard.

* RAMA!F a chip converting digital3analog signals. :sing 4lat panel monitors, you do

not need a the function of a 5*;*C. Dideo cards alays have a certain amount of 5*. 'his 5* is also called t*e frame

,uffer. 'oday video cards hold plenty of 5*, but before it as more important8

9o much 5*N 'hat is significant for color depth at the highest resolutions.

6hich type 5*N 'his is significant for card speed.

Dideo card 5* is necessary to +eep the entire screen image in memory. 'he CP: sends

its data to the video card. 'he video processor forms a picture of the screen image and

stores it in the frame buffer. 'his picture is a large bit map. )t is used to continually update

the screen image.

T*e Amount of RAMOlder video cards ere typically available ith 0, , # or more B 5*. 9o much is necessaryN

'hat depends primarily on ho fine a resolution you ant on your screen. 4or ordinary ; use, 02

bit colors are good enough. 7et us loo+ at 5* needs for different resolutions8

ote that the video 5* is not utili"ed 1##$for the bit map. 'herefore, 1 M%is not enough to

sho a # ' (##picture ith 1( bit colors, as the above calculation could lead you to believe.

'oday video cards come ith ) M%* & M%or +ore RAM.

:sing ordinary 5*, you sa speed improvements of the graphics card using ) M%instead of 2

M%*if the resolution only as # ' (## or 1#2) ' ,(&. )n this case data can be ritten to and read

/


8/21


9/21

PRACTICAL NO )

AIM: To remove; study and replace 5ard dis6 drive.

T*eory:9ard dis+s ere invented in the 0K$%s. 9ard dis+s have a hard platter that holds the magnetic

medium, as opposed to the fle(ible plastic film found in tapes and floppies. *t the simplest level, a

hard dis+ is not that different from a cassette tape. Both hard dis+s and cassette tapes use the samemagnetic recording techniques. 9ard dis+s and cassette tapes also share the major benefits of

magnetic storage FF the magnetic medium can be easily erased and reritten, and it ill remember

the magnetic flu( patterns stored onto the medium for many years.

* modern hard dis+ is able to store an ama=ing amount of information in a small space. * hard dis+

can also access any of its information in a fraction of a second. * typical des+top machine ill have

a hard dis+ ith a capacity of beteen 0% and #% gigabytes. ;ata is stored onto the dis+ in the form

of files. * file is simply a named collection of bytes. 'he bytes might be the *SC)) codes for the

characters of a te(t file, or they could be the instructions of a softare application for the computer

to e(ecute, or they could be the records of a data base, or they could be the pi(el colors for a ?)4

image. o matter hat it contains, hoever, a file is simply a string of bytes. 6hen a program

running on the computer requests a file, the hard dis+ retrieves its bytes and sends them to the CP:

one at a time.

There are two ways to +easure the perfor+ance of a hard dis:

ata rateF 'he data rate is the number of bytes per second that the drive can deliver to the

CP:. 5ates beteen $ and #% megabytes per second are common.

/ee ti+eF 'he see+ time is the amount of time beteen hen the CP: requests a file and

hen the first byte of the file is sent to the CP:. 'imes beteen 0% and % milliseconds are

common.

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10/21

'he platters typically spin at -2%% or /%% rpm hen the drive is operating. 'hese platters are

manufactured to ama=ing tolerances and are mirrorFsmooth. )n order to increase the amount of

information the drive can store, most hard dis+s have multiple platters.

*nnotated illustration of a typical PC actuator assembly, shoing the major

components. 'he platters have been removed from the drive to provide a better vie of the actuator

arms and heads. 'here are four sliders but only

one of each pair is visible. 'he spindle motor is visible at the top right.

'he arm that holds the read3rite heads is controlled by the mechanism in the upperFleft corner, and

is able to move the heads from the hub to the edge of the drive. 'he arm and its movement

mechanism are e(tremely light and fast. 'he arm on a typical hardFdis+ drive can move from hub to

edge and bac+ up to $% times per second.

;ata is stored on the surface of a platter in sectors and trac+s. 'rac+s are concentric circles, and

sectors are pieFshaped edges on a trac+. * sector contains a fi(ed number of bytes FF for e(ample,

$2 or $0. @ither at the drive or the operating system level, sectors are often grouped together intoclusters.

'he process of loFlevel formatting a drive establishes the trac+s and sectors on the platter. 'he

starting and ending points of each sector are ritten onto the platter. 'his process prepares the drive

to hold bloc+s of bytes. 9ighFlevel formatting then rites the fileFstorage structures, li+e the fileF

allocation table, into the sectors. 'his process prepares the drive to hold files.

'he data bus connecting hard dis+ to the motherboard is of - bits & -K pins. 'he poer supplyfrom the SPS is a # pin supply that goes into the hard dis+. Eumper settings for the various

configurations of the hard dis+ are shon belo8


11/21

'he most common interface for PC hard dis+s is called ID#, hich in fact stands forIntegrated

Drive #lectronics.'his name is something of a misnomer today. 6hen it as introduced, );@ as

distinguished from the other interfaces of the day by having the integrated electronics on the drive,

instead of on the controller card plugged into the system bus li+e older interfaces. 9oever, the term

really refers to here the control logic is and not the interface itself, and since all hard dis+s today

use integrated electronics the name doesnQt mean anything any more, despite the fact that everyone

continues to use it. 'he other popular PC hard dis+ interface today, /!/*also uses drives that have

integrated controllers. 'he more correct name for the );@ interface isAT Attac*mentorATA. %rocedure:

0. Sitch off the main poer supply.

. 'a+e out the data bus & the poer supply from the hard dis+, gently.

-. :nscre the hard dis+ & ta+e it out ith e(treme care.

#. o put the hard dis+ bac+ in & scre up.

$. Plug in the data bus & poer supply & ma+e sure that the connections are precise.

'itting t*e 5ard Dis6 Drive

:npac+ the 9;;. a+e sure at this stage that you have your antiFstatic measures in place, and even

briefly ma+e contact ith both hands on the metal of the case to ma+e sure.

7ocate the );@ Configuration Pins on the 9;;. 'hese can usually be found ne(t to the poer and

data connections, and ill be a group of si( or eight small pins ith a small plastic QjumperQ attached

beteen to of the pins. )f this is to be the only 9;; in your PC, then set this to aster.

*lternatively, if this is to be an additional 9;; then it must be set to Slave.'he 9ard ;rive differs from the 4loppy ;rive in that it is usually inserted from ithin the PC case.

On one end of the 9ard ;rive ill be the soc+ets for connecting the cables. 'his end must point into

the case such that the cables can be connected later on. ?ently slide the 9ard ;rive into the bay that

no holds the floppy drive above. ove the drive around until you find the fi(ing points and use the

standard scres to secure it. Clear any obstructions to this insertion from inside the case if necessary.

00


12/21

PRACTICAL NO 5

AIM: To remove; study and replace D ROM drive.

T*eory:

T*e Optic Medias =D ROM>s and D-D?

C; 5O and ;D; are optic readable media, contrary to hard dis+s, floppy dis+s and tapes, hichare magnetic. 'he optic storage media are read ith a very thin and very precisely aimed laser beam.'hey supplement the magnetic media. 'hey have clear advantages in the areas of data density and

stability8 ;ata can be pac+ed much more densely in an optic media than in a magnetic media. *nd

they have much longer life span. )t is presumed that a magnetic media, such as a hard dis+ or ;*'

!digital audio tape" can maintain their data for a ma(imum of five years. 'he magnetism simply

fades aay in time. Conversely, the life span of optic media is counted in tens of years.

T*e ompact Dis6'he compact dis+ !C;" as introduced by Philips and Sony in 0K1% to replace 7P records. )t is a

small plastic dis+ ith a reflecting metal coating, usually aluminum. yriadQs of tiny indentationsare burned into this coating. 'hese indentations contain the music in millions of bits. 'he C; is

organi=ed in trac+s. @ach trac+ is assigned a number.

'he big advantage of the C; is its highFquality music reproduction and total absence of bac+ ground

noise as ell as a great dynamic. ;uring operation, the softare in the drive can correct errors

caused by such things as finger mar+s on the dis+. *ll in all, the C; is an e(cellent music storage

media.

T*e D3ROM'he C;F5O !5ead Only emory" came as an e(tension of the C; in 0K1#. )n principle, the media

and the drives are the same. 'he difference is in the data storage organi=ation. )n a C;F5O, thedata are stored in sectors, hich can be read independently F

7i+e from a hard dis+.

'he C;F5O has become an important media in the PC orld. )t can hold 2$% B of data, and it is

very ine(pensive to produce. 'oday, there are three types of C; drives and ;D; drives are on their

ay8

7et us start by loo+ at the C;F5O construction. 'o facilitate understanding, it ill be easiest to

compare it ith other dis+ types, especially the hard dis+. 'he C;F5O is a plastic dis+ of #.2

diameter. )t is placed in a C;F5O drive, hich is li+e a draer in the PC cabinet 8

6hen the C;F5O dis+ is placed in the drive, it starts to spin the dis+. )t reaches operating speed in

one to to seconds. 'hen the drive is ready to read from the dis+.

0


13/21

A,out Optic Data !torage'he C;F5O can be compared to a floppy drive, because the dis+s are removable. )t can also be

compared ith a hard drive, because of similar data storage capacity. *ctually, a C;F5O dis+ can

hold up to 21% B of data. 'his equals the capacity of #/% floppy dis+s. 9oever, the C; 5O is

neither a floppy nor a hard dis+M 6hile floppy and hard dis+s are magnetic media, the C;F5O is

an optic media. 'he magnetic media or+ in principle li+e an audio cassette tape player. 'hey havea read3rite head, hich reads or rites magnetic impressions on the dis+. 'he magnetic media

contains myriads of microscopic magnets, hich can be polari=ed to represent a =ero or numeral one!one bit".

)n the optic readable C;F5O, the data storage consists of millions of indentations burnt into the

lacquerFcoated, lightFreflecting silver surface. 'he burnt dents reflect less light than the shiny

surface. * ea+ laser beam is sent to the dis+ through a toFay mirror and the sensor registers the

difference in light reflection from the burnt and shiny areas as =eroQs and oneQs.

Rotation speed and data transmission'here are different generations of C;F5O drives. 9ere you see their data.

C;F5O 'ype ;ata 'ransfer Speed 5P OutmostFinnermost 'rac+

0A 0$%+b3sec %%F$-%

A -%% +b3sec #%%F0%2%

#A 2%% +b3sec 1%%F0%

1A 0.B3Sec 02%%F##%

0AF#A 0.1 L -.2 B3Sec #%%F2-2%

'he ne drives are #A and -A spin. 6hen you see their rotation speeds, you onder ho muchfurther this technology can be advanced. 'he hard dis+ can spin at high speeds, because it operates

in sealed bo(. 'he C; does not.

%rocedure:0. Sitch off the main poer supply.

. 'a+e out the data bus & the poer supply from the drive, gently.

-. :nscre the C; 5O & ta+e it out ith e(treme care.

#. o put it bac+ in the cabinet from the front & scre up.


0-


14/21

PRACTICAL NO - (

AIM: To o,serve and study various ca,les; connections used in computer communication.

4*at is Net+or6 a,ling@ Cable is the medium through hich information usually movesfrom one netor+ device to another. 'here are several types of cable hich are commonly

used ith 7*s. )n some cases, a netor+ ill utili=e only one type of cable, other netor+s

ill use a variety of cable types. 'he type of cable chosen for a netor+ is related to the

netor+Qs topology, protocol, and si=e. :nderstanding the characteristics of different types of

cable and ho they relate to other aspects of a netor+ is necessary for the development of a

successful netor+.

Uns*ielded T+isted %air =UT%? a,le 'isted pair cabling comes in to varieties8shielded and unshielded. :nshielded tisted pair !:'P" is the most popular and is generally

the best option for school netor+s .'he quality of :'P may vary from telephoneFgrade ire

to e(tremely highFspeed cable. 'he cable has four pairs of ires inside the jac+et. @ach pair is

tisted ith a different number of tists per inch to help eliminate interference from adjacentpairs and other electrical devices. 'he tighter the tisting, the higher the supported

transmission rate and the greater the cost per foot. 'he @)*3')* !@lectronic )ndustry

*ssociation3'elecommunication )ndustry *ssociation" has established standards of :'P and

rated five categories of ire. Buy the best cable you can afford> most schools purchase

Category - or Category $. )f you are designing a 0% bps @thernet netor+ and are

considering the cost savings of buying Category - ire instead of Category $, remember that

the Category $ cable ill provide more room to gro as transmission technologies increase.Both Category - and Category $ :'P have a ma(imum segment length of 0%% meters. )n

4lorida, Category $ cable is required for retrofit grants. 0%Base' refers to the specifications

for unshielded tisted pair cable !Category -, #, or $" carrying @thernet signals. Category 2 isrelatively ne and is used for gigabit connections.

Uns*ielded T+isted %air onnector

'he standard connector for unshielded tisted pair cabling is an 5EF#$ connector. 'his is a plastic

connector that loo+s li+e a large telephoneFstyle connector !See fig. ". * slot allos the 5EF#$ to be

inserted only one ay. 5E stands for 5egistered Eac+, implying that the connector follos a standard

borroed from the telephone industry. 'his standard designates hich ire goes ith each pin

inside the connector.

!*ielded T+isted %air =!T%? a,le

* disadvantage of :'P is that it may be susceptible to radio and electrical frequency interference.

Shielded tisted pair !S'P" is suitable for environments ith electrical interference> hoever, the

e(tra shielding can ma+e the cables quite bul+y. Shielded tisted pair is often used on netor+s

using 'o+en 5ing topology.

oa)ial a,le

Coa(ial cabling has a single copper conductor at its center. * plastic layer provides insulation

beteen the center conductor and a braided metal shield !See fig. -". 'he metal shield helps to bloc+any outside interference from fluorescent lights, motors, and other computers.

0#


15/21

*lthough coa(ial cabling is difficult to install, it is highly resistant to signal interference. )n addition,

it can support greater cable lengths beteen netor+ devices than tisted pair cable. 'he to types

of coa(ial cabling are thic+ coa(ial and thin coa(ial.'hin coa(ial cable is also referred to as thinnet.

0%Base refers to the specifications for thin coa(ial cable carrying @thernet signals. 'he refers to

the appro(imate ma(imum segment length being %% meters. )n actual fact the ma(imum segment

length is 01$ meters. 'hin coa(ial cable is popular in school netor+s, especially linear bus

netor+s.'hic+ coa(ial cable is also referred to as thic+net. 0%Base$ refers to the specifications for

thic+ coa(ial cable carrying @thernet signals. 'he $ refers to the ma(imum segment length being $%%meters. 'hic+ coa(ial cable has an e(tra protective plastic cover that helps +eep moisture aay from

the center conductor. 'his ma+es thic+ coa(ial a great choice hen running longer lengths in a linear

bus netor+. One disadvantage of thic+ coa(ial is that it does not bend easily and is difficult to

install.

oa)ial a,le onnectors

'he most common type of connector used ith coa(ial cables is the BayoneFeillFConcelman

!BC" connector !See fig. #". ;ifferent types of adapters are available for BC connectors,

including a 'Fconnector, barrel connector, and terminator. Connectors on the cable are the ea+estpoints in any netor+. 'o help avoid problems ith your netor+, alays use the BC connectors

that crimp, rather than scre, onto the cable.

'i,er Optic a,lefiber optic cabling consists of a center glass core surrounded by several layers of protective materials

!See fig. $". )t transmits light rather than electronic signals eliminating the problem of electrical

interference. 'his ma+es it ideal for certain environments that contain a large amount of electrical

interference4acts about fiber optic cables8

Outer insulating jac+et is made of 'eflon or PDC.

evlar fiber helps to strengthen the cable and prevent brea+age. * plastic coating is used to cushion the fiber center.

Center !core" is made of glass or plastic fibers.

'i,er Optic onnector

'he most common connector used ith fiber optic cable is an S' connector. )t is barrel shaped,

similar to a BC connector. * neer connector, the SC, is becoming more popular. )t has a squared

face and is easier to connect in a confined space.

Installing a,le 3 !ome $uidelines

6hen running cable, it is best to follo a fe simple rules8

*lays use more cable than you need. 7eave plenty of slac+.

'est every part of a netor+ as you install it. @ven if it is brand ne, it may have

problems that ill be difficult to isolate later.

Stay at least - feet aay from fluorescent light bo(es and other sources of electrical

interference.

)f it is necessary to run cable across the floor, cover the cable ith cable protectors.

7abel both ends of each cable.

:se cable ties !not tape" to +eep cables in the same location together.

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Net+or6 ommunication devices

* 7* comprises of different communication devices across the netor+ such as the folloing 8

Repeater : * ;evice that amplifies and regenerates signals , so that they can travel for longer

distance on the cable.

Router : 'he basic function of the router is to route the traffic from one netor+ to another

netor+ efficiently. )t provide intelligent redundancy and security required to select theoptimum path. :sually routers are used for connecting remote netor+s.

ub :* typical hub is a multiFport repeater. 'he signals received at the bac+bone is

regenerated and transmitted to all other ports.

/witch : 'his is a device ith multiple ports hich forards pac+ets from one port to

another. )n case of 0%bps @thernet sitch, each port supports dedicated 0%bps bandidth.

@thernet sitch is fast emerging as a replacement of the traditional thic+ bac+bone and best

ay to improve performance of the netor+

02


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PRACTICAL NO 7

AIM: To remove; study and replace floppy dis6 drive.

T*eory:'he floppy dis+ drive !4;;" as the primary means of adding data to a computer until the C;F

5O drive became popular. )n fact, 4;;s have been a +ey component of most personal computersfor more than % years. Basically, a floppy dis+ drive reads and rites data to a small, circular piece

of metalFcoated plastic similar to audio cassette tape.

Dery fe PCQs are ithout a floppy drive. ;is+ettes ere developed as a lo cost alternative to hard

dis+s. )n the 2%Qs and /%Qs, hen hard dis+ prices ere e(orbitant, it as unthin+able to use them in

anything but mainframe and mini computers. 'he first dis+ettes ere introduced in 0K/0. 'hey ere

1 diameter plastic dis+s ith a magnetic coating, enclosed in a cardboard case. 'hey had a capacity

of one megabyte. 'he dis+ettes are placed in a drive, hich has read and rite heads. Conversely to

hard dis+s, the heads actually touch the dis+, li+e in a cassette or video player. 'his ears the media.

7ater, in 0K/2, $.$ dis+ettes ere introduced. 'hey had far less capacity !only 02% B to beginith". 9oever, they ere ine(pensive and easy to or+ ith. 4or many years, they ere the

standard in PCQs. 7i+e the 1 dis+ettes, the $.$ ere soft and fle(ible. 'herefore, they ere named

floppy disks.

)n 0K1/ )BQs revolutionary PS3 PCQs ere introduced and ith them the -R hard dis+ettes e

+no today. 'hese dis+ettes have a thinner magnetic coating, alloing more trac+s on a smaller

surface. 'he trac+ density is measured in 'P) !trac+s per inch". 'he 'P) has been increased from #1

to K2 and no 0-$ in the -.$ dis+ettes.

;is+ette drives turn at -%% 5P. 'hat results in an average search time !R revolutions" of 0%% ms.

T*e floppy controller

*ll dis+ette drives are governed by a controller. 'he original PC controller as named @C P;/2$.

'oday, it is included in the chip set, but functions li+e a /2$. )t is a programmable chip. )t can be

programmed to handle all the various floppy drive types8 $.$ or -.$ drives, ;; or 9; etc.

'he controller has to be programmed at each start up. )t must be told hich drives to control. 'his

programming is performed by the start up programs in 5O !read module a". So you donQt have to

identify available drive types at each start up, these drive parameters are saved in COS 5*. 'he

floppy controller reads data from the dis+ette media in serial mode !one bit at a time li+e from harddis+s". ;ata are delivered in parallel mode !02 bits at a time" to 5* via a ;* channel. 'hus, the

drives should be able to operate ithout CP: supervision. 9oever, in reality this does not alays

or+. ;ata transfer from a dis+ette drive can delay and sometimes free=e the hole PC, so no other

operations can be performed simultaneously.

%arts of a 'loppy Dis6 Drive:

T*e Dis6

1. * floppy dis+ is a thin plastic base material coated ith iron o(ide. 'his o(ide is aferromagnetic material, meaning that if it is e(posed to a magnetic field it is

permanently magneti=ed by the field.

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2.)t can record information instantly.

3. )t can be erased and reused many times.

). 'hese are very ine(pensive and easy to use.

T*e Drive:3 'he major parts of a 4;; include8

Read45rite eads:7ocated on both sides of a dis+ette, they move together on the same assembly.

'he heads are not directly opposite each other in an effort to prevent interaction beteen riteoperations on each of the to media surfaces. 'he same head is used for reading and riting, hile a

second, ider head is used for erasing a trac+ just prior to it being ritten. 'his allos the data to be

ritten on a ider clean slate, ithout interfering ith the analog data on an adjacent trac+.

rive Motor:* very small spindle motor engages the metal hub at the center of the dis+ette,

spinning it at either -%% or -2% rotations per minute !5P".

/tepper Motor:'his motor ma+es a precise number of stepped revolutions to move the read3rite

head assembly to the proper trac+ position. 'he read3rite head assembly is fastened to the stepper

motor shaft.

Mechanical 6ra+e:* system of levers that opens the little protective indo on the dis+ette to

allo the read3rite heads to touch the dualFsided dis+ette media. *n e(ternal button allos the

dis+ette to be ejected, at hich point the springFloaded protective indo on the dis+ette closes.

!ircuit %oard:Contains all of the electronics to handle the data read from or ritten to the dis+ette.

)t also controls the stepperFmotor control circuits used to move the read3rite heads to each trac+, as

ell as the movement of the read3rite heads toard the dis+ette surface.

Tools &ou May Need :

;epending on the design of you computer, you may need the folloing tools to complete the

installation

* 4lat blade scredriver

* Phillips scredriver

eedleFnosed pliers

5andling t*e .22 'loppy Drive:

our 0.## drive must be handled ith care. *void applying undue force or abnormal strain to the

spindle motor, stepping motor or printed circuit board. *void placing your fingers on the printed

circuit board. )t is best to hold the 0.## drive by the diecast frame, as indicated by the arros in4igure *. ever loosen the fi(ing scre of the printed circuit board, etc.

Applications:4loppy dis+s, hile rarely used to distribute softare !as in the past", are still used in these

applications8

0. 4or softare recovery after a system crash or a virus attac+. 6hen data from one computer is needed on a second computer and the to computers are not

netor+ed.

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19/21

-. )n bootable dis+ettes used for updating the B)OS on a personal computer

#. )n highFdensity form, used in the popular ip drive.

%rocedure:

0. Sitch off the main poer supply.

. 'a+e out the data bus & the poer supply from the 4;;, gently.

-. :nscre the 4;; & ta+e it out ith e(treme care.

#. o put the 4;; bac+ in & scre up.


0K


20/21

PRACTICAL NO &

AIM: To study t*e monitor; its circuitry and various presets and some elementary fault

detection.

MONITOR A0s'he monitor is a hardare device hich physically connects to your CP:. 'he monitor allos

information and current status be be visually outputted similar to a 'D. 7i+e most 'Ds the computer

monitor has a C5' or Cathode 5ay 'ube hich found inside the computer monitor as illustrated in

the above picture. 'he C5' is the main component and most e(pensive part ithin your computer

monitor. 6ithin the C5' are three electron guns, 5ed, ?reen and Blue. @ach of these guns streams a

steady flo of electrons left to right for each line of your monitor. *s the electrons hit the phosphors

on the C5' the phosphor ill glo certain intensities. *s a ne line begins the guns ill then begin

at the left and continue right, these guns ill repeat this process sometimes thousands of time untilthe screen has been completely dran line by line. Once the phosphors on the C5' have been hit

ith an electron they ill only glo for a short period of time, because of this the C5' must berefreshed hich means the process ill be repeated as e(plained above. )f the video cards refresh

rate is not set high enough you may encounter a flic+er or a noticeable steady line scrolling from the

top to the bottom of your screen. )f you are encountering this issue, resolutions have been described

on our video card page.

DOT %IT5

'he dot pitch is a measurement> measured in millimeters hich is the amount of space beteen the

phosphors on a computer monitor screen. 'he smaller the number of dot pitches the sharper theimage.

$5O!T 0URN

)f monitors especially older C?* 3 @?* monitors are left on for long durationQs of time as the

electron beams cause the phosphors to glo. )f the electron guns continue to do this for thousands of

hours refreshing the same images this can cause the images to be burnt into the C5' surface causing

a ghost image to appear. 'his image ill become permanently displayed on your monitor for the

duration of its life.* resolution to this problem is screen savers, hich is a program hich generates

a random set of images, lines or other methods of alloing the image to not remain static hile thecomputer is not being used.6hile ne monitors !D?* 3 SD?*" do not have this issue screen savers

are still commonly used today, you can find screen savers in our screen saver donload section.

MONITOR ONTRO"!

'he folloing is additional information on the li+ely monitor controls on your monitor. :sing these

controls you can help improve the quality and layout of the picture on your monitor for better

vieing pleasure. Please +eep in mind that not all

Monitors will have all of the available buttons.

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Documents

final file of comp hrdwr 8 practicls.doc