Computer Service and Repair Chapter 7 Input Device Computer Service and Repair Chapter 7 Ch. 7

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. Ch. 7

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 Ch. 7

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) Ch. 7

Keyboards Mechanical Switch Capacitor Switch Ch. 7

Keyboards Rubber Dome Ch. 7

Keyboards Membrane Ch. 7

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 Ch. 7

Keyboard Virtual Keyboards: consists of light sensor, infrared light source, pattern projector Ergonomic Keyboards: designed to prevent carpal tunnel syndrome Ch. 7

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! Ch. 7

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 Ch. 7

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) Ch. 7

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 Ch. 7

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 Ch. 7

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 Ch. 7

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 Ch. 7

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 Ch. 7

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 Ch. 7

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 Ch. 7

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 Ch. 7

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 Ch. 7

Wireless Devices Wireless Technology Standards (cont’d) Bluetooth Standard: 2.4 GHz short-range devices Class 1 - 100 meters Class 2 - 10 meters Class 2 - 1 meter 1200 page standard Specifies protocol used to Identify device Maximum data transmitted Speed devices operate If encrypted how to be encrypted Ch. 7

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 Ch. 7

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 Ch. 7

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 Ch. 7

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 Ch. 7

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. Ch. 7

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 Ch. 7

End Of Chapter 7 Any Questions Ch. 7