1. Computer Service and Repair Chapter 7
Input Device
Computer Service and Repair
Chapter 7
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2. Input Devices
Input Devices is any piece of equipment used to communicate with the PC system.
Keyboards
Mouse
Bar code readers
scanners
Most attach to PC via USB or a card inserted into a motherboard expansion slot.
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3. USB Implementers Forum
USB Implementers Forum (USB-IF): consists of industry people with an interest in creating a standard guideline for the development of USB drivers, input and output devices
USB standard: most input and many output devices are based on this standard. Standard supports bidirectional communications
Previsions for wired and wireless
Human Interface Device (HID) standard: a standard for software drivers (except for features unique to device) for input devices so that all devices are compatible with computers
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4. Keyboards
Common keyboards are serial devices that convert keystrokes into digital data via a microprocessor installed on the keyboard controller
Four types of switches used in keyboards are:
Mechanical -uses actual mechanical switches
Membrane - uses a membrane w foil over circuit board
Rubber dome -uses a rubber dome and carbon contacts (keeps switch cleaner longer)
Capacitor - uses two plates that never touch (not affect by dirt and dust)
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5. Keyboards
Mechanical Switch
Capacitor Switch
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6. Keyboards
Rubber Dome
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7. Keyboards
Membrane
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8. Keyboards
The Keyboard is a matrix of electrical connections. When a key is pressed a binary signal is sent to the controller who then generates an ASCII Character
Keyboard connections
PS/2 becoming obsolete
USB
System clock signal is transmitted through keyboard. Keyboard data is synchronous with system data
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9. Keyboard
Virtual Keyboards: consists of light sensor, infrared light source, pattern projector
Ergonomic Keyboards: designed to prevent carpal tunnel syndrome
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10. Troubleshooting keyboards
Keyboards are not worth repairing!
Preventive maintenance
Vacuum or use can of dry air to remove dirt and corrosion (remember to unplug computer if using vacuum plugged into same branch circuit)
If liquid is spilled into keyboard flush with distilled water
Keys are easily removed with a chip puller warning typical spacebar is difficult to replace!
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11. Adjusting Keyboard Properties
Keyboard properties can be adjusted by using control panel / hardware / keyboard
Can adjust
Curser blink rate
Length of time key is pressed and keystroke is repeated
How fast keystroke is repeated
Language the keyboard types
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12. Optical Mouse
An Optical Mouse traces movement by transmitting a light beam onto a surface. The reflected light strikes a digital camera that takes thousands of images a second then compares images to determine direction and speed of travel.
Light source is Laser or LED
Quality is measured in Frames Per Second (FPS) and Dots Per Inch (DPI)
Laser Mice 1600 DPI and 6000FPS
Ball Mice 100 DPI and 100 FPS (equivalent)
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13. Optical Mouse Mouse interface Troubleshooting optical mice
PS/2
USB
Wireless – Uses USB connection
Troubleshooting optical mice
Not cost effective to fix a mouse
No mechanical parts
Just clean dust from light source and receptor lint free cloth no special chemicals are required
If optical Mouse stops working usually sign that batteries need replacing
Adjust Mouse Properties: Control/hardware/mouse
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14. Other Input Devices
Trackball is a mouse with the ball embedded in the top
Don’t need to move just roll ball
Need periodic cleaning
Game pad applies to any device used as input for a game application (CHECK DRIVERS!!!)
Joysticks
Steering wheels
Logitech gameboard
Digitizer Pad – virtual drawing surface that allows user to create or modify drawings or photos with a stylus
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15. Other Input Devices
Bar Code Readers convert bar code images to digital data
Scanners and Digital Cameras: take optical images and digitizes it, can convert printed word into word-processing software files via optical character recognition (OCR)
CCD Charged coupled device is a series of light activated capacitors on a single chip that create analog signals based on intensity of light that strikes them
Analog to digital converter converts CCD signal to digital
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16. Other Input Devices Scanners (cont’d)
Cameras use a matrix of ‘windows’ that capture entire image at once
Scanners use a wire and row of windows that capture image one line a time
CMOS is an alternative to CCD that transistors instead of capacitors
CMOS devices can be smaller that CCD devices
Neither is a dominate technology
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17. Touch Screens
Touch Screen Display is a modified computer display that accommodates input information
Requires a touch screen panel assembly
Controller
Port connector and software driver (USB)
Types of Touch Screen Technology
Resistance
Capacitance
Near Field effect
Acoustical Wave
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18. Touch Screens Resistance: most common and inexpensive design
Two layers of conductors seperated by very tiny spacers places over display screen
When screen is touched a connection is made at that point of the matrix
Capacitance: touch screen is coated with a metal oxide
Creates equally distributed electronic field
When screen is touched a drop in field is detected at that point in the matrix
Don’t work well in humid environment
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19. Touch Screens
Near Field: also operates on capacitance but screen is constructed of two laminates of glass each with a pattern of metal oxide coating.
Users do not have to touch the screen just point close enough to disturb electrical field
Works well where uses might be wearing gloves
Infrared uses a matrix of infrared transmitters and receivers along edge of screen
Breaking beams identifies location in matrix that is being touched
Acoustical Wave works same as Infrared but uses sound
Infrared and acoustical don’t work well is dusty environment
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20. Wireless Input Device
Wireless input devices use radio signal (RF) or infrared (IR)
Infrared (IR) work like TV remote
Requires direct line of sight
Typically limited to two devices
Not susceptible to radio interference
Data transfer rate 512Mbps – 1 Gbps
Radio Signal (RF) operates from 27 MHz – 2.4 GHz
Can transmit through wall
Can transmit to more than two devices
IS Susceptible to radio interference
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21. Wireless Devices Wireless Technology Standards
IEEE Organization developed and released wireless standards
ZigBee wireless standard for home entertainment systems
Ultra-Wideband (UWB) is an international Standards Organization
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22. Wireless Devices Wireless Technology Standards (cont’d)
Bluetooth Standard: 2.4 GHz short-range devices
Class meters
Class meters
Class meter
1200 page standard
Specifies protocol used to
Identify device
Maximum data transmitted
Speed devices operate
If encrypted how to be encrypted
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23. Wireless Devices
Wireless Technology Standards (cont’d)
Wi-Fi Specifications for interfacing networking devices
Closely follows Bluetooth and IEEE 802 standards
Similar range limitations (FCC)
Wireless USB
Uses 3.1 GHz to 10.6 GHz radio frequency
Transfers more data than Bluetooth and Wi-Fi
Ultra Wideband
3.1 GHz to 10.6 GHz Frequency Standard for FireWire and USB technology
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24. Wireless Devices Synchronizing the Wireless Device:
If wireless device fails may need resynchronizing
Push sync button (or sequence) on device and receiving unit
If no button or sequence auto sync when powered up
Wireless Device Failure
Battery failure most common reason for failure
Radio interference (baby monitors, garage door openers, wireless phones, microwaves, and more
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25. Wireless Devices Troubleshooting Wireless devices:
Turn device off then back on
Plug USB receiver into another USB port
Restart Computer
Replace Batteries
Download and reinstall device driver
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26. Managing Input Devices
Device manager: identifies problem devices with red x and yellow !
Devices and Printers: provides and centralized location to add and remove devices
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27. Managing Input Devices
Ease of Access: designed for people with disabilities
Turn on Mouse keys (uses arrow keys as mouse)
Turn on sticky keys ([ctrl][alt][delete] w/o holding all keys at same time)
Turn on toggle Keys (toggle keys plays alert each time presses [caps lock])
Turn on filter keys (ignores key strokes that happen too fast
Underline Keyboard shortcuts and access
Prevent windows from being automatically arranged when moved to edge of screen.
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28. KVM Switch
Keyboard-video-mouse (KVM) Switch is used to share a mouse, keyboard, and monitor with two or more computers or servers
Black USB mouse and keyboard
Green USB audio
Switching is either by physical switch / or keystrokes
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29. End Of Chapter 7
Any Questions
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