Experiments.docx1

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Experiment No. 1

AIM :To study and measure various supply voltages of PC(ATX Power supply for PCs.)

TOOLS/LIABILITIES/SOFTWARE USED:

HARDWARE USED: SMPS , LMPS , Voltmeter.

PRE CONDITION/INPUT: Measure voltage of various components through voltmeter

POST CONDITION: Various supply voltages of PC successfully checked.

THEORY: The pc power supply is mainly designed to convert AC from wall outlet and convert it

into DC voltage needed by the system. However it must do this conversion efficiently and

reliably, and must be able to shut down the system if it is over loaded, short circuits and over

heats.

When the PC power starts up, it must do it in proper sequence.

When it shuts down it must prevent any voltage overshoot or fluctuations .it must check itself

regularly,so that any detected failure can cause an immediate and safe shutdown.

FUNCTIONS OF POWER SUPPLY:

1. Convert AC into DC power ,to supply clean electric power to system.

2. To interact with motherboard to perform various other operations like CPU startup ,shutdown ,voltage and temperature detection.

3. Supply control signals and clean power to each component.

TYPES OF POWER SUPPLY:

1. LMPS (Linear Mode Power Supply)

2. SMPS (Switch Mode Power Supply)

1. LMPS POWER SUPPLY:The term linear means straight.The linear supply essentially operates

in a straight line from AC input to DC output.This type of supplies are transformer based and

are less used in computers or peripherals.


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The voltage produced by an unregulated power supply will vary depending on the load and on

variations in the AC supply voltage. For critical electronics applications alinear regulatormay be

used to set the voltage to a precise value, stabilized against fluctuations in input voltage and

load. The regulator also greatly reduces the ripple and noise in the output direct current. Linear

regulators often provide current limiting, protecting the power supply and attached circuit from

over current.

For example, a bench power supply used by circuit designers may be adjustable up to 30 volts

and up to 5 amperes output. Some can be driven by an external signal, for example, for

applications requiring a pulsed output.

Linear power supplies were the mainstay of power conversion until the late 1970s when the

first commercial switch-mode became available. Now apart from very low power wall mount

linear power supplies used for powering consumer items like cell phones and toys, switch-mode

power supplies are dominant.

2. SMPS POWER SUPPLY:

The SMPS is digital in nature and is used with most of the PCs.

The name switching mode is given to them because they step down voltage essentially by

switching the supply ON and OFF.
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A switched-mode power supply (switching-mode power supply, SMPS, or switcher) is an

electronicpower supplythat incorporates a switching regulator to convert electrical power

efficiently. Like other power supplies, an SMPS transfers power from a source like the

electricalpower gridto a load (such as apersonal computer) while

convertingvoltageandcurrentcharacteristics. An SMPS is usually employed to efficiently

provide a regulated output voltage, typically at a level different from the input voltage.

The major drawback of the LMPS is the wastage of power in the form of heat.In SMPS instead

of throwing this extra energy in form of heat,it was arranged to create a feed backloop.Thefeedback circuit senses the output voltage provided to the load and then switches the output

voltage ON/OFF according to the requirement.

This is done in order to maintain steady level of output.

In the case of the high load the voltage at the output drops,which is sensed by the switching

circuit results in increased chopped DC duty cycle also known as long duty cycles.It increases

the voltage at the secondary winding.

In case of thesmall load the output voltage increases which is sensed by the switching circuit

hence it decreasas the chopped dc cycles resulting in the decrease of the voltage provided by

the secondary windings.

Thus in both the cases the output voltage comes back to the designed value .the regulated

output voltage is then fed to the load.
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Switching regulators are used as replacements for the linear regulators when higher efficiency,

smaller size or lighter weight are required. They are, however, more complicated, their

switching currents can cause electrical noise problems if not carefully suppressed, and simple

designs may have a poorpower factor.

ATX POWER SUPPLY FOR PCS:

OUTPUT SUPPLY VOLTAGE LINE:

+5 volt: (red color)

for all electrical components.

+12 volt: yellow color

For spindal and steeper motors.

-12 volt: blue color

Used by some communication circuits(serial ports).

-5 volts: white color

Used only for backward copatipility with older ISA slots.

+3.3 volts: orange color

Used to provide power to motherboard.

+5VSB: purple color

Used to power stand by circuit such as PC ON circuit ,wake ON LAN and remote ring ON

circuitry as well as intrusion detection circuit.
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POWER SUPPLY CONTROL SIGNALS:

1) Powergood signal:-green color (output signal)

Power good is the signal from power supply to motherboard to indicate that power supply is

working properly and it tell the CPU circuitry to start the CPU running.2) Power-ON :-green color (input signal)

Power signal is from motherboard to power supply it tells when to turn off or on the input or

power supply.

3) 3.3 sense: brown (input signal)

This signal is used to sense the actual voltage of the 3.3 volt supply after it has reached the

motherboard which allow the power supply to actively adjust the 3.3 volt output to

compensate for line losses b/w the power supply and mother board.

POWER SUPPLY CONNECTORS:

The connectors themselves come in two basic styles:

1. The large size, often called a Molex connector is keyed by virtue of the connector

itself being D-shaped. It is used on most internal drives including HDD, CD/DVD, ZIP and other

removable media drives and older FDD (5.25).

2. The smaller size typically called a mini-plugis use for the newer style of 3.5 FDDs.

COMPARISON OF LMPS & SMPS:


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Experiment No. 2

AIM: To Study Floppy Disk And its working.

APPARATUS REQUIRED: floppy disk and floppy disk drive

THEORY:

FLOPPY DISK

A floppy disk is a disk storage medium composed of a disk of thin and flexible magnetic storage

medium, sealed in a rectangular plastic carrier lined with fabric that removes dust particles.

They are read and written by a floppy disk drive (FDD).

PARTS: Common Internal parts of floppy disk.

1. A hole that indicates a high-capacity disk.

2. The hub that engages with the drive motor.

3. A shutter that protects the surface when removed from the drive.

4. The plastic housing.

5. A polyester sheet reducing friction against the disk media as it rotates within the housing.

6. The magnetic coated plastic disk.

7. A schematic representation of one sector of data on the disk; the tracks and sectors are not

visible on actual disks.

INTERNAL STRUCTURE:

The 514-inch disk has a large circular hole in the

center for the drive's spindle and a small oval

aperture in both sides of the plastic to allow the

drive's heads to read and write data; the

magnetic medium can be spun by rotating it

from the middle hole. A small notch on the right

of the disk identifies that it is writable, detected

by a mechanical switch or phototransistor above

it; if it is not present, the disk is read-only. Punch

devices were sold to convert read-only disks to

writable ones and enable writing on the unused


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side of single sided disks; such modified disks became known as floppy disks.

Fig.1. Floppy Disk

COMPONENTS

Tape may be used over the notch to protect writable disks from unwanted writing. Oddly: this

arrangement was the converse of the system used on 8 inch floppy discs where the notch had

to be covered before the disc could be written to.

TYPES/SIZES:

8-inch floppy disk:

The first floppy disk was 8 inches in diameter, and was protected by a

flexible plastic jacket. IBM used this size as a way of loading microcode into

mainframe processors, and the original 8 inch disk was not field-

writeable. Rewriteable disks and drives became useful. Early

microcomputers used for engineering, business, or word processing

often used one or more 8 inch disk drives for removable storage; the O.S

was developed for microcomputers with 8 inch drives. Fig.2. 8-inch Floppy Disk

514-inch floppy disk:

The head gap of an 80-track high-density 514-inch drive is shorter

than that of a 40-track double-density (360 kB) drive but can format,

read and write 40-track disks well provided the controller supports

double stepping or has a switch to do such a process. A blank 40-

track disk formatted and written on an 80-track drive can be taken to

its native drive without problems, and a disk formatted on a 40-track

drive can be used on an 80-track drive

Fig.3. 51/

4-inch Floppy Disk

312-inch floppy disk ("Microfloppy"):

A 312-inch 2.88 MB floppy disk drive. This capacity was never

common, but the more common 1.44 MB drives looked almost
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identical.312-inch floppy disk were produced with a capacity of 720 KB, followed by what

became the most common format, 1.44 MB. All disks had a rectangular hole which, if

obstructed, write-enabled the disk. 1.44 MB disks had another hole which identified them as

being of that capacity.

Fig.4.31/2inch FD

OPERATION:

A spindle motor in the drive rotates the magnetic medium at a certain speed, while a stepper

motor-operated mechanism moves the magnetic read/write head(s) along the surface of the

disk. Both read and write operations require the media to be rotating and the head to contact

the disk media, an action accomplished by a "disk load" solenoid.

To write data, current is sent through a coil in the head as the media rotates. The

head's magnetic field aligns the magnetic particles directly below the head on the media. Whenthe current is reversed the particles align in the opposite direction encoding the data digitally.

To read data, the magnetic particles in the media induce a tiny voltage in the head coil as they

pass under it. This small signal is amplified and sent to the floppy disk controller, which converts

the streams of pulses from the media into data, checks it for errors, and sends it to the host

computer system.

FLOPPY DISK DRIVE

A floppy disk drive is a hardware device that reads one of

the first types of portable data storage media-floppy

diskettes, also known as floppy disks. The floppy disk drive

has many parts that are needed in order for it to work

properly. Among the most important of these are the read

and write heads.

Fig.5. Floppy Disk Drive

COMPONENTS

The floppy disk drive consists of different parts. These parts interact with each other and

perform the functions of reading and writing data on the floppy disk. It is important to know

the different components of the floppy disk drive before servicing the drive, and to understand
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the working of the floppy disk drive.

Fig.6. Floppy Disk Drive components

READ WRITE HEAD:

The floppy disk drive has a read write head. It performs the work of reading and writing data on

the floppy disk by converting the binary signals to electromagnetic signals.

The double-sided floppy disk drive has two heads on both the sides of the floppy disk drive to

read and write data on both sides of the floppy disk. The position of the read writes head on|

both sides of the drive is such that they are not opposed to each other. This positioning

prevents any interruption between the heads while writing data on the floppy disk.

The floppy disk drive uses the same head to perform both reading and writing data on the

floppy disk. The floppy disk head consists of two parts. The first part reads and writes head on

the floppy disk. The second part is a set of two heads that erases the data from a track before

the read write head writes the data on the track.

HEAD ACTUATOR:

The head actuator enables the read write head to access all the tracks on one side of the floppy

The head actuator moves the read write head forward, from the center of the floppy outwards

and backward to place the head over the required track. The head actuator is connected to a

motor that moves the head forward and backward. This motor is the stepper motor.

SPINDLE MOTOR:

The spindle motor spins the floppy disk in the floppy disk drive. The spindle motor has a clamp

that catches the floppy disk when the floppy disk enters the floppy disk drive. The spindle

motor rotates at a speed of 300 rotations per minute.


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CIRCUIT BOARD

The circuit board connects all the parts of the floppy disk drive together. It consists of the

circuits that send the data signals to the different parts of the floppy disk drive. The function

used to runthe floppy disk drive is built into the circuit board. It controls the speed of the

motors and manages the positions of the read write head over the required track

FDD CANTROLLER

The floppy Disk Drive (FDD) controller forms the interface between the floppy disk drive and

the system. It is a card that controls the floppy disk drive. The FDD controller is affixed on the

motherboard.

POWER SUPPLY:- D.C. power to the 2 internal FDD is supplied via a single 4 pin converter The

electronic ckt. present in the drive need +5V and motor need +12 V.

CABLE: the internal FDDs are connected to the FD controller board through a 34 pin flat cable.

the signal cable for the internal FDDs has a significant partial twist in it. In case of two FDDs if a

FDD is connected after the twist it acts as A drive and if is connected before the twist it act as B

drive. In case of single FDD the drive will act as A drive whether it is connected before or after

the twist.

FLOPPY DISK CONTROLLER: The FDC can support up to 4 disk drives. The FDC is connected to

the system bus &DMA controller. The FDC has the capacity to support different sector format.

It can handle FDD of different speed

TROUBLESHOOTING:

Bad floppy diskette:


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Verify that the floppy diskette that you are attempting to read from is not write protected or

bad. Verify that the diskette is not write protected by sliding the tab into the position not

allowing light to shine through it. If you do not have a tab place tape over this hole.

Because of the technology of floppy diskette drives, it is likely for a floppy diskettes to easily

become bad. Verify that other floppy diskettes are not exhibiting the same issue.

Not setup in CMOS:

Verify that the floppy drive is properly setup in CMOS Setup. If the floppy drive is not setup

properly you may experience read / write errors or the floppy may not work at all. Most

computers need to have the floppy setup as a 3.5, 1.44MB.

Confliction with other hardware:

If you have recently physically installed any new hardware such as a tape drive or other backup

medium, temporarily disconnect that new hardware to ensure that it is not the cause of your

floppy drive not working.

Not connected properly:

a. Bad drivers:

If you are not able to read or write to a floppy diskette from Windows, verify that the computer

is not exhibiting floppy drivers issues by testing the floppy drive from MS-DOS.

b. Bad hardware:

If you continue to experience issues after following the above steps it is likely that hardware

with in the computer is bad. Replace the following hardware in the computer in the below

order.


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Experiment No. 3

AIM OF EXPERIMENT :TO MAKE COMPARATIVE STUDY OF MOTHERBOARDS: 386, 486, P1, P2,

P3.

HARDWARE USED: VARIOUS MOTHERBOARDS.

THEORY:

The main circuit board of a microcomputer. The motherboard contains the connectors for

attaching additional boards. Typically, the motherboard contains the CPU, BIOS, memory, mass

storage interfaces, serial and parallel ports, expansion slots, and all the controllers required to

control standard peripheral devices, such as the display screen, keyboard, and disk drive.

Collectively, all these chips that reside on the motherboard are known as the motherboard's

chipset.

The motherboard is the primary component of the entire system. In addition to hardware the

motherboard also contains some software .The system ROM actually contains three small but

very critical programs these are post, the BIOS and the setup program. This device provides,

even the C.P.U is enabled to function. In addition to hardware the motherboard also contain

some software. The following is the picture of motherboard:


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The important constituent components of an ATX Motherboard are given below:

1. Mouse and keyboard2. USB3. Parallel port4. CPU Chip5. RAM slots6. Floppy Controller7. IDE controller8. PCI slot9. ISA slot10.CMOS Battery11.

AGP Slot12.CPU

13.Power supply plug in

1. Mouse & keyboard: Keyboard Connectors are two types basically. All PCs have a Key board

port connected directly to the motherboard. The oldest, but still quite common type, is a

special DIN, and most PCs until recently retained this style connector. The AT-style keyboard

connector is quickly disappearing, being replaced by the smaller mini DIN PS/2-style keyboard

connector. You can use an AT-style keyboard with a PS/2-style socket (or the other way

around) by using a converter. Although the AT connector is unique in PCs, the PS/2-style mini-DIN is also used in more modern PCs for the mouse. Fortunately, most PCs that use the mini-

DIN for both the keyboard and mouse clearly mark each mini-DIN socket as to its correct use.

Some keyboards have a USB connection, but these are fairly rare compared to the PS/2

connection keyboards.

2. USB (Universal serial bus): USB is the General-purpose connection for PC. You can find USB


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versions of many different devices, such as mice, keyboards, scanners, cameras, and even

printers. A USB connector's distinctive rectangular shape makes it easily recognizable. USB has

a number of features that makes it particularly popular on PCs. First, USB devices are hot

swappable. You can insert or remove them without restarting your system.

3. Parallel port: Most printers use a special connector called a parallel port. Parallel portcarries data on more than one wire, as opposed to the serial port, which uses only one wire.

Parallel ports use a 25-pin female DB connector. Parallel ports are directly supported by the

motherboard through a direct connection or through a dangle.

4. CPU Chip: The central processing unit, also called the microprocessorperforms all the

calculations that take place inside a pc. CPUs come in Variety of shapes and sizes. Modern

CPUs generate a lot of heat and thus require a cooling fan or heat sink. The cooling device

(such as a cooling fan) is removable, although some CPU manufactures sell the CPU with a fan

permanently attached.

5. RAM slots: Random-Access Memory (RAM) stores programs and data currently being used

by the CPU. RAM is measured in units called bytes. RAM has been packaged in many different

ways. The most current package is called a 168-pin DIMM (Dual Inline Memory module).

6. Floppy controller: The floppy drive connects to the computer via a 34-pin ribbon cable,

which in turn connects to the motherboard. A floppy controller is one that is used to control

the floppy drive.

7. IDE controller: Industry standards define two common types of hard drives: EIDE and SCSI.

Majority of the PCs use EIDE drives. SCSI drives show up in high end PCs such as network

servers or graphical workstations. The EIDE drive connects to the hard drive via a 2-inch-wide,40-pin ribbon cable,which in turn connects to the motherboard. IDEcontrolleris responsible

for controlling the hard drive.

8. PCI slot: Intel introduced the Peripheral component interconnect bus protocol. The PCI bus

is used to connect I/O devices (such as NIC or RAID controllers) to the main logic of the

computer. PCI bus has replaced the ISA bus.

9. ISA slot: (Industry Standard Architecture) It is the standard architecture of the Expansion

bus. Motherboard may contain some slots to connect ISA compatible cards. The memory

address bus is to 32 bits .The bus speed is 8.33 MHZ and the bandwidth is 16 bits.

10. CMOS Battery: To provide CMOS with the power when the computer is turned off all

motherboards comes with a battery. These batteries mount on the motherboard in one of

three ways: the obsolete external battery, the most common onboard battery, and built-in

battery.

11. AGP slot: If you have a modern motherboard, you will almost certainly notice a single


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connector that looks like a PCI slot, but is slightly shorter and usually brown. You also probably

have a video card inserted into this slot. This is an Advanced Graphics Port (AGP) slot

12. CPU slot: To install the CPU, just slide it straight down into the slot. Special notches in the

slot make it impossible to install them incorrectly. So remember if it does not go easily, it is

probably not correct. Be sure to plug in the CPU fan's power.

13. Power supply plug in: The Power supply, as its name implies, provides the necessary

electrical power to make the pc operate. The power supply takes standard 110-V AC power

and converts into +/-12-Volt, +/-5-Volt, and 3.3-Volt DC power.

The power supply connector has 20-pins, and the connector can go in only one direction.

386 MOTHERBOARD:

FEATURES OF 386 M.B.

SYSTEM ARCHITECTURE:

1. Microprocessor 80386

2. Clock speed 15,16,20,25 MHz

3. Bus type MCA

4. Bus width 32-bit

5. Interrupt level 16-bit

6. Sharable yes

7. DMA channels 15

8. DMA burst mode support yes


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9. Upgradable processor complex yes

MEMORY:

1. Standard on sys board 4MB

2. Max on system board 6MB, 8MB

3. Max total memory 16 MB4. Memory speed and type 80ns dynamic RAM

5. System board memory socket type 36 bit SIMM

6. number of memory module socket 3

7. Paged memory logic yes

8. Memory cache controller yes

9. Cache memory speed and type 25 ns static RAM

STANDARD FEATURES:

1. ROM size 128KB

2. ROM shadowing yes

3. Optimal math co-processor 80387DX

4. Co-processor speed 16,20,25 MHz

5. Standard graphics VGA

6. Video RAM 256 KB

7. Max. No. of ports 8

8. Mouse supported 1

9. Parallel ports 1

DISK STORAGE:

1. Standard FDD 1.2, 1.44MB

2. HDD included yes, IDE controller3. Automatic heat parking yes

4. Expansion slots yes

SECURITY FEATURES:

1. Lock covers yes

2. KBD password yes

3. Power on password yes

PHYSICAL SPECIFICATIONS:

1. Height 5.52. Width 14.2

3. Depth 16.5

4. Weight 21 lbs

ENVIRONMENT SPECIFICATIONS:

1. Power supply output 132 watt

2. Temperature operating range 16-90 degree


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3. Max operating altitude 7000 ft.

486 Motherboard

FEATURES OF 486 M.B.:


1. Microprocessor 80486

2. Clock speed 25 MHz

3. Bus type MCA, ISA4. Bus width 32-bit

5. Interrupt level 16-bit

MEMORY:

1. Standard on sys board 2MB

2. Max on system board 8MB

3. Max total memory 16 MB

4. Memory speed and type 80ns dynamic RAM

5. System board memory socket type 36 bit SIMM

6. number of memory module socket 4

7. Paged memory logic yes8. Memory cache controller yes


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STANDARD FEATURES:

1. ROM size 128KB

2. ROM shadowing yes

3. Optimal math co-processor Built-in

4. Co-processor speed 25 MHz

5. Standard graphics VGA6. Video RAM 256 KB

7. Max. No. of ports 5

8. Mouse supported 1

9. Parallel ports

1

DISK STORAGE:

1. Standard FDD 1.2, 1.44MB

2. HDD included yes, IO controller

SECURITY FEATURES:

1. Lock covers yes

2. KBD password yes

3. Power on password yes


1. Height 5.5

2. Width 14.2

3. Depth 16.5

4. Weight 21 lbs

ENVIRONMENT SPECIFICATIONS:

1. Power supply output 132 watt

2. Temperature operating range 16-90 degree

3. Max operating altitude 7000 ft.


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Pentium 1 Motherboard

FEATURES OF PENTIUM-I M.B.:

Support Intel Pentium/P-MMX,AMD K5/K6-2/K6-3 and many more WAKEUP-LINK interface header supporting Intel wake-on-LAN supports modems ring on on board crystal 3-d audio chip 1 line out,1 line in,1 mic in,2 CD in,1 game port two DIMM slots supporting up to 512 MB memory capacity

4 PCI slots,2 ISA slots 2 USB ports,1 PS2 mouse port,1 IrDA port 1 FDD port, 1 LPT port, 2 COM ports Dual IDE channels supporting 4 ultra DMA 33 IDE devices dual AT/ATX power supply interface slim baby AT Flash BIOS full S/W configurable



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FEATURES OF PENTIUM-II M.B.:


1. Microprocessor PII

2. Clock speed 366,300,266,233 MHz


1. Height 21/2

2. Width and length 220*240 mm

3. Depth 4 layers, 0.05

4. Weight 18 ounces

ENVIRONMENTAL SPECIFICATIONS:Required airflow 50 linear feet per min across

Temp. Operating range 10-40 degree C

Max operating altitude 0 to 10000 feet

MEMORY SUPPORT:

Three DIMM slots for DRAM 168 pin memory modules

Max installed memory 256 MB

Cache 512KB pipelined built in

BIOS:

1. AWARD system BIOS

2.128*8 flash ROM

3. Supports plug and play, ACIP, DMI and green functions

HARDWARE MONITORING:

When CPU is over heated the system BIOS will tell board to give a series of beeping alarm and slow

down CPU speed


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EXPANSION SLOTS:

AGP slots 32 bit*1

PCI slots 32 bit*3

ISA slots 16 bit*3

ON BOARD FLASH ROM:

Provides P&P functions for automatic CPU and board config.


FEATRURES OF PENTIUM III M.B.:

SLOT-1 PROCESSOR SUPPORT

1. P-3 support for 450,550 MHz clock rates

2. P-2 support 233 MHz to 450 MHz clock rates3. Support for 66,100 MHz

4. All processors config. By CPU plug and play.

SOCKET370 PROCESSOR SUPPORT:

1. The PPGA celeron provides P-2 performance with integrated level 1and level 2 caches.

2. Supports 66 MHz FSB system bus.

All celerons are automatically config. Using firmware

MEMORY SUPPORT:

1. Three DIMM slots for SDRAM 168 pin memory modules2. Support 66 MHz memory bus and 100 MHz memory bus.

3. Max installed memory can be 3*256 MB.

EXPANSION SLOTS:

1. One 32 bit PCI slots

2. One 8/16 bit ISA slots


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ON BOARD IDE CHANNEL:

1. Primary and secondary IDE and PCI channels

2. Support for PIO modes

3. Support for bus mastering and ultra DMA 33/6 modes

POWER SUPPLY AND POWER MANAGEMENT:1. Dual connector for either an AT/ATX power supply.

1. Support for green PC std, suspends which keyboard on/off

BUILT-IN GRAPHIC SYSTEM

1. Supports high resolution up to 1600*1200 pixels

ON BOARD I/O PORTS:

1. FDD port 1MB/s transfer rate

2. One serial ports with 16550 compatible fast UART

3. One parallel port with support for ECP and EPP

4. Two USB ports

5. One PS/2 ports

One infrared port

HARDWARE MONITORING:

Build in hardware monitoring for CPU temp. And fan speed


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Experiment No. 4

AIM: To study, replace and install the hard disk.

Fig. 1 HARD DISK

A hard disk drive is a non-volatile storage device which stores digitally encoded data on rapidly

rotating platters with magnetic surfaces. The hard disk drive in your system is the "data center"

of the PC. It is here that all of your programs and data are stored between the occasions that

you use the computer.

HARD DISK FEATURES:

Areal Density: Densities in the lab are now exceeding 35 Gbits/in2, and modern disks are now

packing as much as 20 GB of data onto a single 3.5" platter

Capacity: Hard disk capacity continues to not only increase, but increase at an accelerating rate.

From 10 MB in 1981, we are now well over 10 GB in 2000 and will probably hit 100 GB within a

year for consumer drives

Spindle Speed: 7200 RPM spindles are now standard on mainstream IDE/ATA drives. A 15,000RPM SCSI drive was announced by Seagate in early 2000.

Form Factor: Desktop and server drives are likely to transition to the 2.5" form factor as well.

The primary reasons for this "shrinking trend" include the enhanced rigidity of smaller platters,

reduction of mass to enable faster spin speeds, and improved reliability due to enhanced ease

of manufacturing.


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Performance: Both positioningandtransferperformance factors are improving. The speed with

which data can be pulled from the disk is increasing more rapidly than positioning performance

is improving, suggesting that over the next few years addressing seektime and latency will be

the areas of greatest value to hard disk engineers.

DESCRIPTION:

HDD systems consist of a hard disk drive, a disk controller, jumpers, and a cable. On some PC's

the controller is a separate expansion board that interfaces the system through an expansion

slot. Power is supplied by direct cabling to the power supply.

Hard disks are measured by their capacity, that is, how many megabytes it can store. Older

drives hold up to 20 - 500 MB. Newer models hold 1 - 6 gigabyte (GB) and more. The best drives

are physically small, spin fast, have fast seek times, have large buffers, and a long warranty.

INTERNAL STRUCTURE:

. 2 INTERNAL STRUCTURE

PHYSICAL COMPONENTS:

1.DISK PLATTERS: The platter is divided into Tracks and Sectors and isread by Zone Recording or Clusters.

TRACKS: Platters are organized into specific structures to enable the organized

storage and retrieval of data. Each platter is broken into se- Fig 3 Tracks

veral thousand tracks.
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SECTORS: Each track is further broken down into sectors. A sector is normally the smallest

individually-addressable unit of information stored on a hard disk, and in most cases holds 512

bytes of information.

BLOCK MODE: More than one sector can be transferred on each interrupt notification. Newer

drives allow you to transfer as many as 16 or 32 sectors at a time. These sectors are known as

CLUSTERS

2. HEADS

Each platter is accessed for read and write operations using two read/write heads, one

mounted on the top of the platter and another on the bottom. These heads are mounted onto

arms that allow them to be moved from the outer tracks of the hard drive

to the inner tracks and back again. The arms are controlled using a device

called an actuator that positions the arms to the appropriate track on the

disk.

3. Head Actuator

The actuator is the device used to position the headarms to different tracks on the surface of

the platter (actually, to different cylinders, since all head arms are moved as a synchronous

unit, so each arm moves to the same track number of its respective surface.

4. Spindle Motor

The spindle motor, also sometimes called the spindle shaft, is responsible for turning the hard

disk platters, allowing the harddrive to operate.

Fig. 5 Fig. 6

HDD Parts Internal components
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5.Hard Disk Connector

Several different connectors and jumpers are used to configure the hard disk and connect it to

the rest of the system like power connector, data interface connector, etc.

6.Head Sliders

Each hard disk head is therefore mounted to a special device called a head slider or just slider

for short. The function of the slider is to physically support the head and hold it in the correct

position relative to the platter as the head floats over its surface.

7.Head Arms

The head arms are thin pieces of metal, usually triangular in shape onto which the headsliders

(carrying the read/write heads) are mounted.

8. Hard Disk Logic Board

All modern hard disks are made with an intelligent circuit board integrated into the hard disk

unit.

INSTALLATION:

1. Find Pin 1 On Drive:Take a close look at the drive and determine which end of the interface

connector is pin 1. There should be some sort of a marking near pin 1 to indicate it, which may

be a small number "1", a dot, an arrow, a square around the pin where it connects to the circuit

board, or some other indication

2. Install Mounting Kit, If Necessary:Virtually all modern cases have internal 3.5" drive bays

meant specifically for hard drives. However, if you are installing into an older case or one that

has its internal 3.5" bays full, you will need to use a mounting or adapter kit.

There are two common ways of mounting a hard disk drive into the system case:

Direct Mount: The simplest and most common mounting method is the direct mount, where

the drive slides into the bay and mounts directly to the drive bay walls.
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Mounting Box: Some cases, especially desktops, use a removable metal box into which the

drive is mounted. The procedure here is similar to that for direct mount, above, except that you

have to remove the box first and insert the drive into it, then remount the box.

Double-Check Installation: Make sure the drive has been fitted properly into the case and that

there is no interference with other components. In particular, make sure that the logic board on

the bottom of the drive is not touching anything. Ensure that it is not loose in the case.

Remove and replace internal hard disk:

Turn off your computer, disconnect the power, and remove your computers cover. If you have

a mobile PC, check the information from the manufacturer to find out if there is a panel you can

remove to access the hard disk.

Unplug all cables connected to the hard disk, and then remove the hard disk. Pay attention to

which cables you unplug, since you will plug the same cables into the new hard disk. If there areany screws holding in the hard disk, you will need a small screwdriver to unscrew them. Many

hard disks slide in and out of the case on rails. If you have questions, check the information that

came with your computer.

Insert the new hard disk and connect it to the same cables in the same places as the hard disk

you removed. One cable connects the disk to the computers power supply, and the other cable

connects the disk to the computers motherboard.

TROUBLESHOOTING:

There is various troubleshooting instruction as follows:

1.There may be some type of electrical connection problem Make sure the cable connections

are correct. Check the 4-wire connector that carries power and makes sure it is properly

plugged in.

2.There may be some problems in the cables and they might be having a small tab in the center

of the connector's edge.

3.If all the cables are connected properly, and power is applied, you should be able to hear and

feel the drive spinning.

4.A typical hard drive has a small amount of vibration and a slight whine


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5.The hard drive has failed electronically. This will be indicated by an error message during the

computer boot cycle.


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Experiment No. 5

AIM:To study the Compact Disk Drive

APPARATUS REQUIRED: Compact disk drive

THEORY:

In a few short years, the Compact Disk - Read Only Memory(CD-ROM) drive has gone from

pricey luxury to inexpensive necessity on the modern PC. The CD-ROM has opened up new

computing vistas that were never possible before, due to its high capacity and broad

applicability. In many ways, the CD-ROM has replaced the floppy disk drive, but in many ways it

has allowed us to use our computers in ways that we never used them before. In fact, the

"multimedia revolution" was largely a result of the availability of cheap CD-ROM drives.

How CD's Work?

CD-ROM stands for Compact Disc - Read Only Memory. This disk is like a "super" floppy disk

that can hold lots of information. One CD-ROM can hold the same amount of data as 500 floppy

disks. Information is permanently recorded onto it. Computer games and other programs are

considered to be CD-ROMs.

Like gramophone records, the information on optical discs is recorded on a spiral track.

However, with a CD the laser starts reading the disc from the inside ring and ends up on the


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outside. When play back starts, a laser beam shines on the ridges and lands on the data

membrane layer.

During playback, the number of revolutions of the disc decreases from 500 to 200 rpm

(revolutions per minute) to maintain a constant scanning speed. The disc data is converted into

electrical pulses (the bit stream) by reflections of the laser beam from a photoelectric cell.

When the laser beam strikes "land", the beam is reflected onto a photoelectric cell. When it

strikes a "ridge", the photocell will receive only a weak reflection. Thus the photoelectrical cell

receives series of light pulses corresponding to the ridges and lands in the disc. These light

pulses are the foundation of binary 'digital' data. A simple substitution for the weak signal "0"

and the in-focus signal "1" results in a pure digital playback without alteration, every time,

without failure or degradation.

In music playback, a D/A-Converter (digital to analogue converter; DAC) converts the series of

pulses (binary coding) from a decimal code to a waveform, which can then be processed for

amplification. The longer the decimal code, the better the sound. Current standard CD audio is

44,100 pulses per second and 16 bit (decimal places) in digital word length. Thus a 24 bit system

sounds all that much better, in fact DVD audio is set to allow 24 bit AND pulse at 97,000 times

per second!

A recent step in CD technology is called the Mini Disc. It is half the size of a regular CD and can

hold the same amount of information.

TYPES OF CDS:

"Bridge" CDs

The term bridge CD is used to refer to disks that use extensions or derivations of the CD-ROM

Extended Architecture format. These extended formats are described in the "white book"

specification. The reason for the term "bridge" is that these disks are designed to work both in

CD-ROMs that support CD-ROM XA, and also in CD-Interactive hardware, thus "bridging" the

two types of CD hardware. .

CD-Interactive (CD-I)

In 1986, Philips and Sony again joined forces to create the CD-Interactive or CD-I format. This

concept was quite ambitious, with the goal to develop both a format and a special new type of

hardware to use it. In some ways this was the first serious attempt at what we now call

"multimedia", with authors creating disks including text, graphics, audio, video, and computer


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programs, and hardware sold to handle all of these and connect to a television screen for

output.

Video CD (VCD)

Support for a special CD format for the storing of compressed video information is defined aspart of the "white book" specification. Through the use of MPEG compression it is possible to

store 74 minutes of full-motion video in the same space that uncompressed "red book" audio

uses! This format is called video CD or sometimes VCD Playing video CDs requires either a video

CD player or a CD-ROM drive that is video CD compatible.

Photo CD

Developed in the early 90s by Kodak and Philips (who seems to have its hand in everything CD-

related),photo CD is an implementation ofCD-ROM extended architecturedesigned to hold

photographic images. They technically use mode 2 form 1 of the CD-ROM XA architecture.Photo CDs are defined in the "orange book" specification.

When you send in film for processing to photo CD, the film is first developed normally. The

developed and printed pictures are then scanned and converted to digital form, encoded into

the photo CD format, and written to the CD. Writing the photos to the CD is done using a

process that is basically the same as howCD-Rworks: a laser burns the information into the

tracks of the CD.

CD CAPACITY:

A standard CD has a capacity of about 74 minutes of standard CD audio music. There are

extended CDs that can actually exceed this limit and pack more than 80 minutes on a disk, but

these are non-standard. Regular CD-ROM media hold about 650 MB of data, but the actual

storage capacity depends on the particular CD format used.

CD DRIVE-BASIC DESIGN:

A schematic of an optical three-beam pick-up of a CD drive is shown in the next figure along

with the laser beam route through the system.

The laser beam from the laser diode passes through the diffraction grating to produce two

secondary beams needed to maintain correct tracking of the disk. Then, the beam passes

polarizing prism (beam splitter) and only the vertical polarized light passes. The light beam is

then converged into a parallel beam (by the collimator) and passes through the 1/4-wave plate

where the beam polarization plane is rotated by 45 degrees. The beam is then focused onto the

disk surface by a lens and a servo-controlled mechanism called 2-axis device. Polarization plane
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of the reflected beam is rotated by another 45 degrees turning its initial vertical polarization

into a horizontal. After a few more reflections, all beams reach six photo detectors: 4 main spot

detectors and 2 side spot detectors enabling read-out of the pit information from the disk

CD DRIVE COMPONENTS:

The CD drive has the job of finding and reading the data stored as bumps on the CD.

Considering how small the bumps are, the CD drive is an exceptionally precise piece of

equipment. The drive consists of three fundamental components:

A drive motor spins the disc. This drive motor is precisely controlled to rotate between 200 and

500 rpm depending on which track is being read.

A laser and a lens system focus in on and read the bumps.


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A tracking mechanism moves the laser assembly so that the laser's beam can follow the spiral

track. The tracking system has to be able to move the laser at micron resolutions.

OPERATIONS OF CD

Writing CDs

In response to this demand, electronics manufacturers introduced an alternative sort of CD that

could be encoded in a few easy steps.CD-recordable discs, or CD-Rs, don't have any bumps or

flat areas at all. Instead, they have a smooth reflective metal layer, which rests on top of a layer

of photosensitive dye.

When the disc is blank, the dye is translucent: Light can shine through and reflect off the metal

surface. But when you heat the dye layer with concentratedlightof a particular frequency and

intensity, the dye turns opaque: It darkens to the point that light can't pass through.

Reading CDs

The conventional CDs store digital data as a pattern of bumps and flat areas, arranged in a long

spiral track. The CD fabrication machine uses a high-poweredlaserto etch the bump pattern

into photoresist material coated onto a glass plate. Through an elaborateimprinting process,this pattern is pressed onto acrylic discs. The discs are then coated with aluminum (or another

metal) to create the readable reflective surface. Finally, the disc is coated with a transparent

plastic layer that protects the reflective metal from nicks, scratches and debris.

INSTALLATION
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REMOVE

1. First of all, you need to shut off your computer.

2. Unplug the power cord and other cords from your computer and find a sturdy flat surface on

which to work on.

3. Unscrew all screws from the back of your computer except the power supply screws.

4. Open your computer up by taking the side panel off, or sliding the cover off.

5. Now before touching anything inside, it is a good idea to hook up to an anti-static wrist strap.

6. Find the CD-Rom drive, it should be about 1.5 inch thick 5 inches wide, and 6 inches long.

Unplug all plugs from the back of the cd-rom drive; there should be an IDE (wide) plug, a CD

plug (small) and a power plug (medium).

7. Once you find the CD-Rom drive, find the screws holding it onto the chassis. Unscrew those

screws on both sides of the cd-rom drive. Be careful not to unscrew any screws holding the CDD

8. Now, you just have to remove the cd-rom drive, carefully by sliding it either forward or

backward. Check the jumpers on your new cd-rom before moving to the next step. A typical cd-

rom drive should be set on slave if it is using the same IDE cable on the same cable.

9. Now that you've removed the cd-rom drive the next step is to install your new CD-ROM

drive. To do this, simply slide the cd-rom drive in from the front of the computer, controlsfacing forward. Plug all the plugs back into the cd-rom and screw everything back into place.

TROUBLESHOOTING

There are several factors that can cause problems with CD-ROM drives.

a) The cabling is not properly connected

1) The power connector has to be plugged in.

2) The IDE data cable has to be properly connected. This cable is normally connected to the IDE

primary or secondary motherboard connector and can have either one or two plugs on the end.

The cable has to be inserted on the drive connector so that the colored edge is on the same

side as pin 1 on the drive connector.

b) BIOS settings might be incorrect


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On some newer computers, the BIOS have to be changed to tell the computer that a new

device has been added. There are two distinct places that might need to be changed.

1) If the drive is installed on a secondary IDE controller, then you will need to go into the BIOS

and find the entry that enables the secondary IDE controller.

2) On some systems the drive type (which is normally the place where the drive parameters are

entered) has to be set to the "Auto" selection.

On both of the above entries, after the change you will need to exit the BIOS and Save the

changes, then allow the computer to reboot.

c) Software

The quickest way to check for hardware conflicts is to look in the open the device manager and

look for yellow exclamation points in front of the device names.

When connected to a computer running Windows 95, IDE CD-ROM drives are detected

automatically. After the computer is turned on and a window is loaded, you should see briefly a

message that a new device was installed.

The drive will be given the next available drive letter.

If the drive does not seem to be detected then should check the device settings to see if there is

a problem.

Double Click the "My computer" on the desktop, the My Computer window will be displayed

Double Click the "Control Panel" icon, the Control panel window will be displayed

Double click the "System" icon; the System window will be displayed.

Click on the "Device Manager" tab on the top of the screen, the System Properties window will

be displayed

If there are any problems with the drive a Yellow Exclamation point will be shown in front of

the "+CD ROM" entry on the device manager window.

Click on the + sign in front of the "+CD ROM". This will open the CD-ROM section and show you

the drive name that window has detected. Click on the name so it is highlighted (blue) and

press the properties button on the bottom of the screen. The CD ROM properties window will

be displayed. There are at a minimum 2 tabs on the top of the screen. The General and the

Settings.


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When the General tab is pressed the "Device status" will be shown in the middle of the screen.

This should normally say "This device is working properly".

When the Settings tab is pressed, you will see specific information for that drive. The assigned

drive number is located here. If for some reason the computer chose a drive name that is

already in use by another device or if you want the drive to have a different drive letter you

change it on this screen by setting the "reserve drive letters" of "Start drive " and "End drive" to

the new drive letter you want

Most of the problems are caused by improper Master/Slave settings or not having the IDE

controller in the BIOS enabled.


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Experiment No. 6

AIM: To study keyboard and its functions.

THEORY: In computing, a keyboard is a typewriter-style keyboard, which uses an arrangement

of buttons or keys, to act as mechanical levers or electronic switches. Despite the developmentof alternative input devices, such as the mouse, touch screen, pen devices, character

recognition and voice recognition, the keyboard remains the most commonly used and most

versatile device used for direct (human) input into computers.

A keyboard typically has characters engraved or printed on the keys and each press of a key

typically corresponds to a single written symbol. While most keyboard keys produce letters,

numbers or signs (characters), other keys or simultaneous key presses can produce actions or

computer commands. A computer keyboard distinguishes each physical key from every other

and reports all key presses to the controlling software

KEY TYPES:

A computer keyboard comprises character keys for typing, modifier keys for altering the

functions of other keys, navigation keys for moving the text cursor on the screen, function keys

and system command keys such as and for special actions, and often a numeric keypad to

facilitate calculations.


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1) CHARACTER KEYS:

The core section of a keyboard comprises character keys, which can be used to type letters and

other characters.

Typically, there are three rows of keys for typing letters and punctuation, an upper row for

typing digits and special symbols, and the on the bottom row.

The positioning of the character keys is similar to the keyboard of a typewriter.

2) MODIFIER KEYS:

Besides the character keys, a keyboard incorporates special keys that do nothing by themselvesbut modify the functions of other keys.

For example, the key can be used to alter the output of character keys, whereas the (control)

and (alternate) keys trigger special operations when used in concert with other keys.

To facilitate this, modifier keys usually come in pairs, one functionally identical key for each

hand, so holding a modifier key with one hand leaves the other hand free to strike another key.

3) DEAD KEY:

A dead key is a special kind of a modifier key that, In some systems, there is no indication to theuser that a dead key has been struck, so the key appears dead, but in some text-entry systems

the diacritical mark is displayed along with an indication that the system is waiting for another

keystroke: either the base character to be marked, an additional diacritical mark, or to produce

the diacritical mark in isolation.

4) COMPOSE KEY:

A Compose key can be characterized as a generic dead key that may in some systems be

available instead of or in addition to the more specific dead keys.

It allows access to a wide range of predefined extra characters by interpreting a whole

sequence of keystrokes following it.

KEYBOARD LAYOUT:


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A keyboard layout is any specific mechanical, visual, or functional arrangement of the keys,

legends, or key-meaning associations (respectively) of a computer, typewriter, or other

typographic keyboard.

Mechanical layout : The placements and keys of a keyboard.

Mechanical layouts only address tangible differences among keyboards. When a key is pressed,

the keyboard does not send a message such as the A-key is depressed but rather the left-most

main key of the home row is depressed. (Technically, each key has an internal reference

number, "raw keycodes", and these numbers are what is sent to the computer when a key is

pressed or released.) The keyboard and the computer each have no information about what is

marked on that key, and it could equally well be the letter A or the digit 9.

Visual layout : The arrangement of the legends (labels, markings, engravings) that appear on

the keys of a keyboard.

The user of the computer is requested to identify the visual layout of the keyboard when

installing the operating system. Visual layouts vary by language, country, and user preference,

and the same mechanical layout can be produced with a number of different visual layouts. For

example, the "ISO" keyboard layout is used throughout Europe, but typical French, German,

and UK variants of mechanically identical keyboards appear different because they bear

different legends on their keys.

Functional layout : The arrangement of the key-meaning associations, determined in software,

of all the keys of a keyboard.

The functional layout of the keyboard refers to the mapping between the physical keys, such as

the key, and software events, such as the letter "A" appearing on the screen.

Usually the functional layout is set to match the visual layout of the keyboard being used, so

that pressing a key will produce the expected result, corresponding to the legends on the

keyboard.

KEYBOAD TECHNOLOGY:

There are many different types of computer keyboards, usually differentiated by the switchtechnology employed in their operation.

The choice of switch technology affects key response (the positive feedback that a key has been

pressed) and travel (the distance needed to push the key to enter a character reliably can be

different on other keyboards).

1) MEMBRANE KEYBOARD:


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There are two types of membrane-based keyboards, flat-panel membrane keyboards and full-

travel membrane keyboards:

Flat-panel membrane keyboards are most often found on appliances like microwave ovens or

photocopiers.

Full-travel membrane-based keyboards are the most common computer keyboards today.

2) DOME SWITCH KEYBOARD:

Dome-switch keyboards are a hybrid of flat-panel membrane and mechanical keyboards.

The rubber dome switches, most commonly referred to as polydomes, are formed polyester

domes where the inside bubble is coated in graphite.

While polydomes are typically cheaper than metal domes, they lack the crisp snap of the metal

domes, and usually have a lower life specification.

Polydomes are considered very quiet, but purists tend to find them "mushy" because the

collapsing dome does not provide as much positive response as metal domes.

Both are common switch technologies used in mass market keyboards today.

Dome-switch keyboards are also called direct-switch keyboards.

It still uses rubber domes, but a special plastic 'scissors' mechanism links the keycap to a

plunger that depresses the rubber dome with a much shorter travel than the typical rubber

dome keyboard.

3) MECHNICAL SWITCH KEYBOARD:


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Mechanical-switch keyboards use real switches underneath every key. Depending on the

construction of the switch, such keyboards have varying response and travel times. Notable

keyboards utilizing this technology are the Apple Extended Keyboard (the original or the "II"), as

well as its modern imitator, the Matias Tactile Pro. These two keyboards use ALPS switches. On

PCs, the OmniKey series from Northgate Computers was popular, and the line is now carried byCreative Vision Technologies under the Avant brand.

4) ROLL-UP KEYBOARD:

Some keyboards are designed out of flexible materials that can roll up in a moderately tight

bundle. Normally the external materials are either silicone or polyurethane. It is important to

note that although many manufacturers claim that the keyboards are foldable, they cannot be

folded without damaging the membrane that holds the circuitry. Typically they are completely

sealed in rubber, making them watertight like membrane keyboards.

Like membrane keyboards, they are reported to be very hard to get used to, as there is little

tactile feedback, and silicone will tend to attract dirt, dust, and hair.

5) OPTICAL KEYBOARD:


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An optical keyboard technology utilizes light-emitting devices and photo sensors to optically

detect actuated keys. Most commonly the emitters and sensors are located at the perimeter,

mounted on a small PCB. The light is directed from side to side of the keyboard interior, and it

can only be blocked by the actuated keys. Most optical keyboards require at least 2 beams

(most commonly a vertical beam and a horizontal beam) to determine the actuated key. Someoptical keyboards use a special key structure that blocks the light in a certain pattern, allowing

only one beam per row of keys (most commonly a horizontal beam).

The mechanism of the optical keyboard is very simple a light beam is sent from the emitter to

the receiving sensor, and the actuated key blocks, reflects, refracts or otherwise interacts with

the beam, resulting in an identified key.


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Experiment No. 7

Aim:To Study mouse and its operation.

Apparatus Required:mouse-scroll and optical.

MOUSE: Mouse is a computers peripheral device used along with the keyboard, which allows

a user to indicate what function he wants that his computer to carry out by selecting from a list

of commands presented as a menu. The first mouse system was introduced for IBM PCs in

1982. With the help of mouse, the user points at a menu selection by physically moving the

input device, which causes a core on screen movement of the cursor. One more button at the

top of the mouse enables the user to indicate that he can select a menu item.

The mouse is small enough to fit under the pole of hand with the button

under the fingertip. There is a cord connecting the device to its computer host trailing like a tail.

The whole process of moving the mouse on the screen is termed as dragging the mouse.

On the basis of the technique of use, a mouse can be classified as:

1. MECHANICAL MOUSE: The design is based on a small boll that is fixed at the bottom and

rotated as the mouse is pushed along the surface. Switches inside the mouse detect the

movement in four directions (i.e. cores to two axes of 2- D system) and relay the direction of

balls rotation to the host computer. This mouse requires that the user move it across a surface.

The parts of mechanical mouse can break, so care must be taken.

2. OPTICAL MOUSE: In this type of mouse, instead of rotating the ball, a light beam is used todetect movement across a specially designed mouse pad. The mouse uses two pairs of LEDs

and photodiodes at its bottom. One pair is oriented at the right angles with the other. The

matching mouse pad is coated with an overlapped pattern of blue and yellow grids. Each pair of

LED and photodiode detects the motion in either direction across one axis of the grid.

On the basis of interface, the mouse can be classified as:

1.Serial Mouse: This mouse is interfaced via a serial port. it has a standard 9 or 25 pin plug at

the end of its cable. This type of mouse draws its power from RTS line of the RS-232-C port. It

processes the electrical signal received from the mouse and converts those signals to the serial

port.

2. Bus mouse: These mouse are attached to the dedicated mouse adapter that plug into

computer expansion slots. The mouse works identically as that of the serial mouse except that


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it uses its own dedicated supply. Also, this type of mouse is not directly accessible by dos

because OS does not know what I/O addresses the ports are assigned


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Experiment No. 8

Aim: TO STUDY PRINTER ASSEMBLY AND ELEMENTARY FAULT DETECTION IN DMP AND LASER

PRINTER

Apparatus Required: Various printers

THEORY :

Laser Printer:

The laser printer was invented at Xerox in 1969 by researcher Gary Stark weather, who had an

improved printer working by 1971and incorporated into a fully functional networked printer

system by about a year later. The prototype was built by modifying an existing xerographic

copier. Stark weather disabled the imaging system and created a spinning drum with 8 mirrored

sides, with a laser focused on the drum. Light from the laser would bounce off the spinningdrum, sweeping across the page as it traveled through the copier. The hardware was completed

in just a week or two, but the computer interface and software took almost 3 months to

complete.

The first commercial implementation of a laser printer was the IBM model 3800 in 1975, used

for high-volume printing of documents such as invoices and mailing labels.

How it works:

Raster image processing:- Each horizontal strip of dots across the page is known as a raster line

or scan line. Creating the image to be printed is done by a Raster Image Processor (RIP),

typically built into the laser printer. The source material may be encoded in any number of

special page description languages such as Adobe PostScript (PS, BR-Script), HP Printer

Command Language (PCL), or Microsoft XML Page Specification (XPS), as well as unformatted

text-only data. The RIP uses the page description language to generate a bitmap of the final

page in the raster memory. A raster image processor (RIP) is a component used in a printing

system which produces a raster image also known as a bitmap. The bitmap is then sent to a

printing device for output. The input may be a page description in a high-level page description

language such as PostScript, Portable Document Format, XPS or another bitmap of higher or

lower resolution than the output device. In the latter case, the RIP applies either smoothing orinterpolation algorithms to the input bitmap to generate the output bitmap. Raster image

processing is the process and the means of turning vector digital information such as a

PostScript file into a high-resolution raster image.

Stages of RIP:-


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1. Interpretation: This is the stage where the supported PDLs (Page description languages) are

translated into a private internal representation of each page. Most RIPs process pages serially

so the current machine state is only for the current page; i.e. one page at once. Once a page has

been output the page state is discarded to ready it for the next page.

2. Rendering: A process through which the private internal representation is turned into a

continuous tone bitmap. Note that in practical RIPs, interpretation and rendering are frequently

done together. Simple languages were designed to work on minimal hardware so tend to

"directly drive" the renderer.

3. Screening: In order to print, a continuous-tone bitmap is converted into a halftone (pattern

of dots). Two screening methods or types are Amplitude Modulation (AM) screening and

stochastic or Frequency Modulation (FM) screening. In AM screening, dot size varies depending

on object densitytonal values; dots are placed in a fixed grid. In FM screening,

dot size remains constant and dots are placed in random order to create darker or lighter areas

of the image; dot placement is precisely controlled by sophisticated mathematical algorithms.

Charging:-

Applying a negative charge to the photosensitive drum older printers, a corona wire positioned

parallel to the drum, or in more recent printers, a primary charge roller, projects anelectrostatic charge onto the photoreceptor (otherwise named the photo conductor unit), a

revolving photosensitive drum or belt, which is capable of holding an electrostatic charge on its

surface while it is in the dark.

An AC bias is applied to the primary charge roller to remove any residual charges left by

previous images. The roller will also apply a DC bias on the drum surface to ensure a uniform

negative potential.

Numerous patents describe the photosensitive drum coating as a silicon sandwich with a photo

charging layer, a charge leakage barrier layer, as well as a surface layer. One version[specify]uses amorphous silicon containing hydrogen as the light receiving layer, Boron nitride as a

charge leakage barrier layer, as well as a surface layer of doped silicon, notably silicon with

oxygen or nitrogen which at sufficient concentration resembles machining silicon nitride

Exposing:-


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Laser neutralizing the negative charge on the photoreceptive drum to form an electrostatic

image. The laser is aimed at a rotating polygonal mirror, which directs the laser beam through a

system of lenses and mirrors onto the photoreceptor. The cylinder continues to rotate during

the sweep and the angle of sweep compensates for this motion. The stream of rasterized data

held in memory turns the laser on and off to form the dots on the cylinder. Lasers are usedbecause they generate a narrow beam over great distances. The laser beam neutralizes (or

reverses) the charge on the black parts of the image, leaving a static electric negative image on

the photoreceptor surface to lift the toner particles.

Fusing:-

Melting toner onto paper using heat and pressure. The paper passes through rollers in the fuser

assembly where heat (up to 200 Celsius) and pressure bond the plastic powder to the paper.

One roller is usually a hollow tube (heat roller) and the other is a rubber backing roller

(pressure roller). A radiant heat lamp is suspended in the center of the hollow tube, and its

infrared energy uniformly heats the roller from the inside. For proper bonding of the toner, the

fuser roller must be uniformly hot.

Some printers use a very thin flexible metal fuser roller, so there is less mass to be heated and

the fuser can more quickly reach operating temperature. If paper moves through the fuser

more slowly, there is more roller contact time for the toner to melt, and the fuser can operate

at a lower temperature. Smaller, inexpensive laser printers typically print slowly, due to this

energy-saving design, compared to large high speed printers where paper moves more rapidly

through a high-temperature fuser with a very short contact time.

Cleaning:-

Magnification of color laser printer output, showing individual toner particles comprising 4 dots

of an image with a bluish back ground. When the print is complete, an electrically neutral soft

plastic blade cleans any excess toner from the photoreceptor and deposits it into a waste

reservoir, and a discharge lamp removes the remaining charge from the photoreceptor.

Toner may occasionally be left on the photoreceptor when unexpected events such as a paper

jam occur. The toner is on the photoconductor ready to apply, but the operation failed before it

could be applied. The toner must be wiped off and the process restarted.

DMP are the most popular types for use with PCs. They have a printer head that is pulled

horizontally across the paper from left to right and back again using a rubber belt and electric

motor. Each character is generated from an array on matrix of dots. The printer head consists

of tiny pins that are operated electro magnetically. As head moves across the paper, the pins


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move rapidly in and out under the control of the printer electrons. Characters are formed when

the pins strike the ribbon, leaving dots on paper.

The resolution and quality of DMP is determined by the number of pins in the printer head.

Usually the head is of ninepins. Most of the printers have a lever that adjusts the distance of

the printer head from the roller to accommodate different thickness of stationary. Anotherlevel controls the pinch rollers that allow the use of single sheet, non-sprocket fed paper. Price

is obviously a major factor of contributing to the popularity of DMPs .

PRINTERS ARE CLASSIFIED INTO VARIOUS TYPES:

1. IMPACT AND NON-IMPACT PRINTERS::

In an impact printer the character is formed by physical contact of print head against the ink

ribbon onto the paper. In the non-impact printers, the character can be pulled at a time they

are known as serial.

2.CHARACTER AND LINE PRINTERS:

Printers, which print one character at a time, are called character printers and the printers,

which print one line at a time, are called line printers.

Printers have three major assemblies:

Power supply

Control mechanism

Printing mechanism

POWER SUPPLY:

It consists of DC regulator for safety logic and a filter. The safety logic sheets of the power

supply in abnormal condition prevent any damage to device.

CONTROL MECHANISM:

This subassembly consists of one or more PCBs. the CE provides following circuits:

Up address latch RAM and ROM Address decoder

RESET logic Head driver CR and CF monitor drive Interface drive/receiver

The reset signal is generated either during power on or when init is recognized, received

from PC. It is sent to various logic in the printer to perform the init sequence.


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Moving the printer head to the home PCs Cleaning buffer Resetting the microprocessor Providing online/ready status

PRINTER MECHANISM:

Function pattern causage assembly Printer head Paper fed mechanism Home rents 8 pocket on it Paper end session

LASER PRINTER: -

The main parts of the laser printer are:

1. Charging electrode

2. Cleaning rode

3. Photoreceptor drum

4. Toner

5. Rotating hexagonal mirror

6. Laser scanning unit

Laser beam produced by the laser-scanning unit passed through the character generator box.

The responsibility of the character generator box is allow or not to allow the laser beam to passthrough according to the character. This beam is strike to the rotating hexagonal mirror, which

deflect the beam towards the drum. Drum is already positively charged and the surface at

which the beam strikes becomes negatively charged. Toner is also positively charged. The

character that we want to print on the paper is obtained on the drum due to beam. The

negatively charged portion of the drum attracts the positively charged toner particles, and the

image is produced on the paper. Then this paper is passed through the heating section so that

the image becomes permanent.

Color laser printers

Fuji Xerox color laser printer C1110BColor laser printers use colored toner (dry ink), typically

cyan, magenta, yellow, and black (CMYK).

While monochrome printers only use one laser scanner assembly, color printers often have two

or more scanner assemblies.


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Color printing adds complexity to the printing process because very slight misalignments known

as registration errors can occur between printing each color, causing unintended color fringing,

blurring, or light/dark streaking along the edges of colored regions. To permit a high

registration accuracy, some color laser printers use a large rotating belt called a "transfer belt".

The transfer belt passes in front of all the toner cartridges and each of the toner layers areprecisely applied to the belt. The combined layers are then applied to the paper in a uniform

single step.

Color printers usually have a higher cost per page production cost than monochrome printers.

Drum printer

It is awide-format inkjet printer. The paper is taped onto a drum for precise alignment to the

nozzles.An old line printer technology that used formed character images around a cylindrical drum as

its printing mechanism. When the desired character for the selected position rotated around to

the hammer line, the hammer hit the paper from behind and pushed it into the ribbon and

onto the character.

Drum Printer Mechanism


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The hammer pushes the paper into the type slug when it

rotated around to the proper position. Such printer

technologies seem ridiculous compared to the quiet, high-

speed workings of today's laser printers.

An impact printer in which a complete set of characters for each print position on a line is on a

continuously rotating drum behind an inked ribbon, with paper in front of the ribbon; identical

characters are printed simultaneously at all required positions on a line, on the fly, by signal-

controlled hammers.

In a typical drum printer design, a fixed font character set is engraved onto the periphery of a

number of print wheels, the number matching the number of columns (letters in a line) the

printer could print. The wheels, joined to form a large drum (cylinder), spin at high speed andpaper and an inked ribbon is stepped (moved) past the print position. As the desired character

for each column passes the print position, a hammer strikes the paper from the rear and

presses the paper against the ribbon and the drum, causing the desired character to be

recorded on the continuous paper. Because the drum carrying the letterforms (characters)

remains in constant motion, the strike-and-retreat action of the hammers had to be very fast.

Typically, they were driven by voice coils mounted on the moving part of the hammer.

Often the character sequences are staggered around the drum, shifting with each column. This

obviates the situation whereby all of the hammers fire simultaneously when printing a line that

consists of the same character in all columns, such as a complete line of dashes ("----").Lower-cost printers did not use a hammer for each column. Instead, a hammer was provided for every

other column and the entire hammer bank was arranged to shift left and right, driven by

another voice coil. For this style of printer, two complete revolutions of the character drum

were required with one revolution being used to print all the "odd" columns and another

revolution being used to print all of the "even" columns. But in this way, only half (plus one) the

number of hammers, magnets, and the associated channels of drive electronics were required.

Band printer Band

printers are a variation of chain printers, where a thin steel band is used instead of a chain, with

the characters embossed on the band. Again, a selection of different bands was generally

available with a different mix of characters so a character set best matched to the characters

commonly printed could be chosen. Data products was a well known manufacturer of band

printers, with their B300, B600, and B1000 range, the model number representing the lines per

minute rate of the printer. (The B300 was effectively a B600 with only half the number of
http://en.wikipedia.org/wiki/Dataproductshttp://en.wikipedia.org/wiki/Dataproducts


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hammersone per two character positions. The hammer bank moved back and forth one

character position, requiring two goes to print all characters on each line.)

The drum printer offers offset printing for the pharmaceutical and confectionary industries; in

addition, it precisely centers the print on tablets, caplets, and capsules. A simplified operatorinterface has digital display for printer operating conditions. Electronic push-button controls are

featured for setup, logo registration and operation. Servo motors with optical encoder feedback

for speed and position provide accurate control of printing registration. The drum printer is

designed for film- or sugar-coated tablets and caplets and for hard-shell gelatin capsules.

Printing can be one- or two-sided, linear or radial, and no rectified or rectified. It can be in one

or two colors. Change parts are designed to be easily removed for a quick change to a different

product. Printing capabilities are as follows: 250,000 one- or two-sided tablets per hour;

150,000 one- or two-sided caplets per hour; and 150,000 linear or rotary capsules per hour

Inkjet

An inkjet printer is any printer that places extremely small droplets of ink onto paper to create

an image. If you ever look at a piece of paper that has come out of an inkjet printer, you know

that:

The dots are extremely small (usually between 50 and 60 microns in diameter), sosmall that they are tinier than the diameter of a human hair (70 microns)!

The dots are positioned very precisely, with resolutions of up to 1440x720 dots perinch (dpi).

The dots can have different colors combined together to create photo-quality images.In this article, you will learn about the various parts of an inkjet printer and how these parts

work together to create an image. You will also learn about the ink cartridges and the special

paper some inkjet printers use.

Inside

Parts of a typical inkjet printer include: Print head assembly:

Print head - The core of an inkjet printer, the print head contains a series of nozzlesthat are used to spray drops of ink.

Ink cartridges - Depending on the manufacturer and model of the printer, inkcartridges come in various combinations, such as separate black and color cartridges,


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color and black in a single cartridge or even a cartridge for each ink color. The

cartridges of some inkjet printers include the print head itself.

Print head stepper motor - A stepper motor moves the print head assembly (printhead and ink cartridges) back and forth across the paper. Some printers have another

stepper motor to park the print head assembly when the printer is not in use. Parking

means that the print head assembly is restricted from accidentally moving, like

a parking brake on a car.

Belt - A belt is used to attach the print head assembly to the stepper motor. Stabilizer bar - The print head assembly uses a stabilizer bar to ensure that

movement is precise and controlled.

Paper feed assembly:

Paper tray/feeder - Most inkjet printers have a tray that you load the paper into.Some printers dispense with the standard tray for a feeder instead. The feedertypically snaps open at an angle on the back of the printer, allowing you to place

paper in it. Feeders generally do not hold as much paper as a traditional paper tray.

Rollers - A set of rollers pull the paper in from the tray or feeder and advance thepaper when the print head assembly is ready for another pass.

Paper feed stepper motor - these stepper motor powers the rollers to move thepaper in the exact increment needed to ensure a continuous image is printed.

Power supply - While earlier printers often had an external transformer, mostprinters sold today use a standard power supply that is incorporated into the printer

itself.

Control circuitry - A small but sophisticated amount of circuitry is built into theprinter to control all the mechanical aspects of operation, as well as decode the

information sent to the printer from the computer.

Interface port(s) - The parallel port is still used by many printers, but most newprinters use the USB. A few printers connect using a porter small computer system

interface (SCSI) port.

Thermal bubble - Used by manufacturers such as Canon and Hewlett, this method iscommonly referred to as bubble jet. In a thermal inkjet printer, tiny resistors create

heat, and this heat vaporizes ink to create a bubble. As the bubble expands, some of

the ink is pushed out of a nozzle onto the paper. When the bubble "pops" (collapses),a vacuum is created. This pulls more ink into the print head from the cartridge. A

typical bubble jet print head has 300 or 600 tiny nozzles, and all of them can fire a

droplet simultaneously. Click the button to see how a thermal bubble inkjet printer

works.

Piezoelectric - Patented by Epson, this technology uses piezo crystals. A crystal islocated at the back of the ink reservoir of each nozzle. The crystal receives a tiny

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