module 2-input devices

8/11/2019 Module 2-Input Devices

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Module 2 - Input DevicesPC Hardware Advanced Guide

PC Hardware Advanced Guide

Module 2 Input Devices


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Overview

Input devices are used to accept data and commandsfrom the user and send it to the processor for processing.

Keyboard is a character input device.

Mouse is a handheld pointing device. Scanner takes itsinput in graphical form.

Lesson Covered in this Module

Keyboards

Mouse

Other Pointing Devices


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Lesson 1 - Keyboards

Introduction

Keyboard is a character input device which enables theuser to provide input to the computer for processing.

The keys available in the computer keyboard can beclassified as

Alphanumeric Keys

Punctuation Keys

Special Keys

The keyboard also has LEDS for Caps Lock, NumLock andthe Scroll Lock to indicate the status


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Lesson 1 - Keyboards

Topics Covered in this Lesson

Layouts of Keyboard

Keyboard Interfaces

Working of Keyboard

Keyboard Switches

Terms used in Keyboard

Keyboard Troubleshooting

Software Issues related to the Keyboard


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Topic 1 - Layouts of Keyboard

83 Key PC/XT Keyboard

Introduced with the IBM PC

Integrated as a part of thesystem unit

84 Key AT Keyboard

Sys Req is included in thislayout.

The numbers are keptseparately.

LEDsare introduced


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Topic 1 - Layouts of Keyboard

Enhanced AT 101-key

Keyboard The cursor and navigation

keys are present at theright side.

The second ALT and theCTRL keys were

introduced. The position of the

and the hasbeen changed.

Windows 104 keyKeyboard Windows Key are at the

either side of the spacebar key.


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Topic 2 - Keyboard Interfaces

The signals used by the

keyboard

Data The data sent bythe keyboard circuit when

you press a key.

Clock It is sent to

synchronize the data

signals

Power supply uses +5 V

DC power supply

Ground- Provides Signal

ground for the interface

Pin # 5-pin DINConnector

1 Keyboard Clock

2 Keyboard Data

3 (not connected)

4 Ground

5 Power (+5V)

6 --


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Topic 2 - Keyboard Interfaces

6 Pin PS/2 Connector

It has an interface toconnect both mouse andthe keyboard.

Universal Serial Bus (USB)Keyboard

It is connected to the USBport.

It is stackable and

swappable

IrDA Interface It uses the Infra red rays for

transmitting the signals.

Pin No Pin Name

1 Keyboard-Data

2 --

3 GND

4 VCC

5 Mouse-Clock

6 --


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Topic 3 - Working of Keyboard

It requires a lot of hardware circuits.

The large keyboards are using the matrix organization.

The keysoutput is connected to the electronics circuits.

Keys are organized in rows and columns.

PC H d Ad d G id


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Encoding is performed in matrix keyboard, by using

scanning technique.

The method uses row as inputs to the matrix and the

column as the outputs from the matrix.

To scan the matrix, a scan counter is used.

PC H d Ad d G id


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Keyboard Microprocessor

The microprocessor present inside the keyboard is

responsible for identifying the key press

It exchanges the information between the host systems.

Functions performed by the keyboard controller

Scanning the keyswitch matrix

Identifying a key press

Debouncing

PC H d Ad d G id


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Topic 4 - Keyboard Switches

Rubber Dome Switches

It has a small flexible rubber domes and a hard carbon

center beneath them.

They are resistant to corrosion

The rubber layer protects the key matrix

Metal Contact Switches

If a key is pressed the two plates come in contact with

each other.

The circuit is physically closed and the key press is

detected.

M d l 2 I D iPC Ha d a e Ad anced G ide


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Topic 4 - Keyboard Switches

Membrane Switches

A membrane is used as a flat sheet and the printedpattern is present in the membrane.

Foam Contact Switches

A small piece of sponge is made available between thebottom of the plunger and the metal strip.

Hall-effect Keyboard

The moving of the magnet is detected by the solid stateHall-effect sensor.

M d l 2 I t D iPC Hardware Advanced Guide


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Topic 5 - Terms used in Keyboards

Typematic Delay

It is the time duration for which the key should remainpressed before it is repeated.

Typematic Rate

If the keyboard pressed for more than 0.5 s, it will send

the scancode of a key continually.

This is termed as Typematic.

The typematic rate is 10 times per second.

M d l 2 I t D iPC Hardware Advanced Guide


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Language Setting

Click on Start, Settings,Control panel, Keyboardand Language (or InputLocales)

Make and Break Codes

The keyboardmicroprocessor producesa make scancode related

to the key when it ispressed.

Then it produces a breakscancode related to thesame key.

Module 2 Input DevicesPC Hardware Advanced Guide


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N-Key Rollover

If 4 keys are pressed simultaneously, all the 4 charactersdisplayed correctly.

Key Debouncing

Here, it uses hardware or a software which makes sure

that a signal is generated only once when a key ispressed once.



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Topic 6 - Keyboard Troubleshooting

Problem SolutionArrow Keys typenumbers and vice versa

Check if the NumLock LED isglowing.

A beep sound is heardfrom the keyboard or thePC

Check if any key is pressed for along time.

The system does notrespond when you pressAlt+Ctrl+Del key

simultaneously

The problem may be due to asoftware bug or trapping the keysby the Operating system.

Liquid is spilled in theKeyboard

Switch off the computer and turnthe keyboard upside down and drythe keyboard.



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Topic 7 - Software Issues related to the Keyboard

DOS Keyboard Controls

DOS named keyboard and monitor, combined as "CON:"

When you take input from "CON:" it comes from the

keyboard.

MODE" command is used for changing settings for many

different system devices.



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Topic 7 - Software Issues related to the Keyboard

Typematic Features (Repeat Delay and Repeat Rate)

The ability to have a stream of character codes that are

automatically generated when you hold down a key for a

period of time.

The typematic feature

Repeat Delay:This is the length of time that a key must be held

down before the typematic feature is activated.

Repeat Rate: This sets the frequency with which characters will

be sent once the typematic feature is activated.



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Lesson 2 - Mouse

Introduction

Mouse is a handheld pointing device which is used toprovide input signals to the computer.

Mouse is used to move the cursor to the desired location

And to activate the needed menu to perform the

operation easily.


Classification of Mouse

Different Mouse Interfaces

Configuring the Mouse

Cleaning a Mouse

Error and Troubleshooting



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Topic 1 - Classification of Mouse

Mechanical Mouse

It comprises of a ball onthe underside and isoperated on a flat surface.

Opto-Mechancial Mouse

It uses the optical sensor to

detect the position of thecursor on the screen.



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Optical Mouse

It uses laser to detectthe movement of the

mouse.

Wireless Mouse

It need not be

connected physically

to the computer.

Technique used by this

Mouse is infra red port

and radio frequency

waves.



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Module 2 Input DevicesC a d a e d a ced Gu de

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Ergonomic Mouse

It helps the people withdisabilities.

Wheel Mouse

It is a two button mouse

with a scroll in the middle.

Trackball

The ball is kept inside a

socket

Touch Pad It is used in portable

computers instead of

mouse.



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Topic 2 - Different Mouse Interfaces

Serial Mouse Interface

It is used to connectthe serial devices tothe computer.

It is a 9 pin D typefemale connector onthe mouse side.

Bus Mouse.

It connects to acomputer through anexpansion card.



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Topic 2 - Different Mouse Interfaces

PS/2 Port

It is connecting keyboards and mouse.

It is a 6 pin mini DIN port.

IrDA Interface

Infra red interface is used to transfer the signals wirelessusing infra red rays.



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Topic 3 - Configuring Mouse

The mouse should be first

connected to the systembefore configuring it.

A USB mouse should

connected to the USB port.

A PS/2 mouse should

connected to the PS/2

Port.



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Topic 3 - Configuring Mouse

Installing device driver from a Compact Disk

Click StartSettings Control PanelAdd/ Remove Hardware

option

Follow the instructions as given by the Add new Hardware

Wizard

Open My Computer and open the CD containing the driver

Select the setup.exe file and follow the instructions.

The installation will be successfully completed

check the Device Manager. It should display as the device is

functioning properly



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Topic 4 - Cleaning the Mouse

Rotate and remove

the ring that is presentin the center of themouse.

Remove the mouseball from inside themouse.

Clean the mouse ball

Use cotton swabwhich is dipped in a

chemical by nameIsopropyl Alcohol



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Topic 5 - Troubleshooting Mouse

Problem Solution

Mouse is not movingproperly.

Clean the Mouse

Mouse not beingdetected

The drivers may not installedproperly or there is someconflict with the hardwaresettings.

Mouse pointer moves onthe screen randomlywithout any interventionof the user.

If the mouse is placed in a verybright area there are chancesof stray light entering in to thecase or the gaps in betweenthe buttons.



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Lesson 3 - Other Input Devices

Introduction

Pointing devices are available in many forms such as foot

mouse, standard computer mouse, mouse keypad, light

pen, joystick, touchpad, touch screen, and trackball.


Bar code reader

Touch screen

Light pen

Biometric devices



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Topic 1 Bar code reader

Bar code reader

The device which decodes this printed symbol of barsand spaces is called a bar code reader.

Bar code can be used as a very inexpensive method of

encoding the information.

It has a high degree of accuracy and speed.

The four types of Bar code readers are Pen type readers

Laser type reader

CCD reader

Camera based reader



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Topic 2 - Touch screen

The major components are touch sensor, a controller,

and a software driver.

Touch Sensor

Controller

Software Driver



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Topic 2 - Touch screen

Touch pens as input device

All the touch screens are working like a mouse.

The touch screen imitates the mouse functions

if the software driver for the touch screen is installed. Thescreen can be tapped twice to perform the double-click.

At the same time you can also drag your finger across

the touch screen to perform drag and drop function.



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Topic 3 - Light pen

It is shaped like a pen.

It uses a light sensitive pen instead of finger.

The tip of the Lightpen has a light sensitive aspect.

It will work with any CRT based monitor.



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Topic 3 - Light pen

Advantages of Light pen Vs Touch Screen

Advantages Light pen Touch screen

Economy It is less expensive. It is expensive.

Flexibility In any screen size light

pen can be used.

It is not possible in Touch

screen.

HigherResolution

It gives moreaccuratecommunicationbetween the user and

the system.

If the touch screen is old,it will move the activearea away from thedisplay image.

Portability It is portable It requires more difficultand complex set-upprocedures to move.



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Topic 4 Biometric devices

Biometric devices

Biometric devices canbe used as input to acomputer.

It is like a fingerprintscanner can be used foradditional level ofsecurity.

It can also beprogrammed to verify apersonsidentity



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Multimedia input devices

Multimedia is the combination of sound and images withtext and graphics.

To capture sound and image data we need to use somespecial input devices.

The other multimedia input device is Web/digitalcameras.

Digital cameras record photographs in the form of digitaldata, which can be stored on a computer.



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Multi media input devices



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Conclusion

The keyboards can be classified according to their layout as

83 key PC/XT keyboard 84 Key AT keyboard

Enhanced AT 101 key Keyboard

Windows 104 key Keyboard

Mouse can be classified in to four types namely Mechanical Mouse

Optomechanical Mouse

Optical Mouse

Wireless Mouse

Flatbed scanners are the most flexible and popular format.

Light pen cannot work with LCD screens and projectors.



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Conclusion

The device which decodes this printed symbol of bars

and spaces is called a bar code reader

Biometric devices can be used as input to a computer.

A biometric device like a fingerprint scanner can be

used for additional level of security.

module 2-input devices

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