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11.ComputerPeripherals-III

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					      11. Computer Peripherals – Part III




                                                        Chapt. 10
ITEC 1011    Introduction to Information Technologies
                               Plan
     •   Printers
     •   Scanners
     •   Keyboards
     •   Pointing Devices




ITEC 1011        Introduction to Information Technologies
                                    Printers
     • Four main types:
            •   Dot matrix †
            •   Laser
            •   Ink jet
            •   Thermal dye transfer and thermal wax transfer



            †
                Impact (the others are non-impact)

ITEC 1011                Introduction to Information Technologies
            Impact vs. Non-Impact
     • Impact printers physically transfer a dot or
       shape to the paper
     • Of those in the preceding slide, only dot-
       matrix uses impact printing
     • Non-impact printers spray or lay down the
       image with impact
     • Impact printers remain important because
       they can print multi-part forms


ITEC 1011       Introduction to Information Technologies
                                  Printers
     • Four main types:
            •   Dot matrix
            •   Laser
            •   Ink jet
            •   Thermal dye transfer and thermal wax transfer




ITEC 1011              Introduction to Information Technologies
                       How it works
         A print-head moves back-and-forth in front of forms
     (paper) on which characters or graphic images are transferred.
     The print-head contains numerous wires, typically from 9 to
     24. Each wire is part of a solenoid-like unit. A pulse applied
     to the solenoid creates a magnetic field which forces the wire
     to move briefly forward then backward. As the wire moves
     forward, it presses against a print ribbon containing ink. The
     impact transfers an ink dot to the paper. The paper is
     supported from behind by a platen.




ITEC 1011          Introduction to Information Technologies
            Demo (well, sort of)




ITEC 1011    Introduction to Information Technologies
                 Dot Matrix Print Head



                                                          One print wire

   Print wires
   (e.g., 12)


                 Front view         Side view



ITEC 1011           Introduction to Information Technologies
            Dot Matrix Impact Printing

                   Paper
 Print
 wire



                     Platen
 Ribbon




             Side view                        Side view      Front view
ITEC 1011         Introduction to Information Technologies
                           Specifications
     • cps
            • characters per second
            • Varies by quality of print (e.g., draft vs. final)
     • lpm
            • lines per minute (related to cps)
     • Forms
            • Maximum number of layers of paper that can by printed
              simultaneously
            • Specified as n-part forms (e.g., 4-part forms)
     • mtbf
            • Mean time between failure (e.g., 6000 hours)

ITEC 1011               Introduction to Information Technologies
                             Noise
     • Dot matrix printers are notoriously noisy!
     • This is a major disadvantage in many
       environments




ITEC 1011       Introduction to Information Technologies
                                    Uses
     • Primarily two:
            • Any situation that requires multi-part forms
            • Small printers, such as
               • Calculators
               • Adding machines
               • Point-of-sale terminals




ITEC 1011             Introduction to Information Technologies
       Dot Matrix Printer Example - 1
                                                  Specifications
                                                  • 800 cps
                                                  • 400 lpm
                                                  • 6-part forms (max)




            FormsMaster 8000 by Printek, Inc.
                  http://www.printek.com

ITEC 1011     Introduction to Information Technologies
       Dot Matrix Printer Example - 2
                                 Specifications
                                 • Printhead wires: 9
                                 • Printhead life: 200 million characters
                                 • Print speed:
                                      • near letter quality: 105 cps
                                      • utility: 420 cps
                                      • high speed draft: 550 cps
                                 • Number of copies: 8
                                 • MTBF: 8000 hours @ 25% duty cycle,
                                   35% density



            Pacemaker 3410 by OKI Data, Inc.
                 http://www.okidata.com
ITEC 1011     Introduction to Information Technologies
                                  Printers
     • Four main types:
            •   Dot matrix
            •   Laser
            •   Ink jet
            •   Thermal dye transfer and thermal wax transfer




ITEC 1011              Introduction to Information Technologies
                                   How it works
     •      Four steps
             1.     A laser is fired in correspondence to the dots to be printed. A spinning
                    mirror causes the dots to be fanned out across the drum. The drum
                    rotates to the next line, usually 1000th or 1600th of an inch.

                    The drum is photosensitive. As a result of the laser light, the drum
                    becomes electrically charged wherever a dot is to be printed.



                                                                           Laser
                  Photosensitive
                  drum
                                                                          Spinning
                                                                          mirror




ITEC 1011                  Introduction to Information Technologies
              Operation of a Laser Printer
     •      Four steps
             1.     A laser is fired in correspondence to the dots to be printed. A spinning
                    mirror causes the dots to be fanned out across the drum. The drum
                    rotates to the next line, usually 1000th or 1600th of an inch.

                    The drum is photosensitive. As a result of the laser light, the drum
                    becomes electrically charged wherever a dot is to be printed.



                                                                           Laser
                  Photosensitive
                  drum
                                                                          Spinning
                                                                          mirror




ITEC 1011                  Introduction to Information Technologies
              Operation of a Laser Printer
     •      Four steps
             1.     A laser is fired in correspondence to the dots to be printed. A spinning
                    mirror causes the dots to be fanned out across the drum. The drum
                    rotates to the next line, usually 1000th or 1600th of an inch.

                    The drum is photosensitive. As a result of the laser light, the drum
                    becomes electrically charged wherever a dot is to be printed.



                                                                           Laser
                  Photosensitive
                  drum
                                                                          Spinning
                                                                          mirror




ITEC 1011                  Introduction to Information Technologies
             Operation of a Laser Printer
            2.   As the drum continues to rotate, the charged part of the drum passes
                 through a tank of black powder called toner. Toner sticks to the drum
                 wherever the charge is present. Thus, the pattern of toner on the drum
                 matches the image.




                                                               Toner


ITEC 1011               Introduction to Information Technologies
             Operation of a Laser Printer
            3.   A sheet of paper is fed toward the drum. A charge wire coats the
                 paper with electrical charges. When the paper contacts the drum, it
                 picks up the toner from the drum



                  Charge
                  wire




                 Paper




ITEC 1011                Introduction to Information Technologies
             Operation of a Laser Printer
            4.   As the paper rolls from the drum, it passes over a heat and pressure
                 area known as the fusing system. The fusing system melts the toner to
                 the paper. The printed page then exits the printer.

                 As the same time, the surface of the drum passes over another wire,
                 called a corona wire. This wire resets the charge on the drum, to
                 ready it for the next page.




                                                                             Fusing
                                                          Corona             system
                                                          wire


ITEC 1011               Introduction to Information Technologies
                       Specifications
     • ppm
            • Pages per minute
            • Typically 4-10 ppm
     • dpi
            • Dots per inch
            • Typically 600-1200 dpi




ITEC 1011           Introduction to Information Technologies
               Laser Printer Example




            Laserjet 5000 Series from Hewlett Packard Co.
                        (http://www.hp.com)

ITEC 1011          Introduction to Information Technologies
                                  Printers
     • Four main types:
            •   Dot matrix
            •   Laser
            •   Ink jet
            •   Thermal dye transfer and thermal wax transfer




ITEC 1011              Introduction to Information Technologies
                     Background
     • Inkjet technology was developed in the
       1960s
     • First commercialized by IBM in 1976 with
       the 6640 printer
     • Cannon and Hewlett Packard developed
       similar technology
     • Also called bubble jet


ITEC 1011      Introduction to Information Technologies
                            How it works
          Characters and graphics are 'painted‘ line by line to from a pattern of
     dots as a print head scans horizontally across the paper. An ink-filled
     print cartridge is attached to the inkjet's print head. The print head
     contains 50 or more ink-filled chambers, each attached to a nozzle. An
     electrical pulse flows through thin resistors at the bottom of each chamber.
     When current flows through a resistor, the resistor heats a thin layer of ink
     at the bottom of the chamber to more than 900 degrees Fahrenheit for
     several millionths of a second . The ink boils and forms a bubble of
     vapour. As the vapour bubble expands, it pushes ink through the nozzle to
     form a droplet at the tip of the nozzle. The droplet sprays onto the paper.
          The volume of the ejected ink is about one millionth that of a drop of
     water from an eye-dropper. A typical character is formed by an array of
     these drops 20 across and 20 high. As the resistor cools, the bubble
     collapses. The resulting suction pulls fresh ink from the attached reservoir
     into the firing chamber.
ITEC 1011              Introduction to Information Technologies
            Inkjet Printer Example




ITEC 1011     Introduction to Information Technologies
                                  Printers
     • Four main types:
            •   Dot matrix
            •   Laser
            •   Ink jet
            •   Thermal dye transfer and thermal wax transfer




ITEC 1011              Introduction to Information Technologies
                          How it works
           Thermal dye transfer printers, also called dye sublimation printers,
      heat ribbons containing dye and then diffuse the dyes onto specially
      coated paper or transparencies. These printers are the most expensive and
      slowest, but they produce continuous-tone images that mimic actual
      photographs. Note that you need special paper, which is quite expensive.
      A new breed of thermal dye transfer printers, called snapshot printers,
      produce small photographic snapshots and are much less expensive than
      their full-size cousins.
           Thermal wax transfer printers use wax-based inks that are melted and
      then laid down on regular paper or transparencies. Unlike thermal dye
      transfer printers, these printers print images as dots, which means that
      images must be dithered first. As a result images are not quite photo-
      realistic, although they are very good. The big advantages of these
      printers over thermal dye transfer printers are that they don't require
      special paper and they are faster.
ITEC 1011             Introduction to Information Technologies
                                 Dithering
         Dithering is creating the illusion of new colours and shades by varying
    the pattern of dots. Newspaper photographs, for example, are dithered. If
    you look closely, you can see that different shades of grey are produced by
    varying the patterns of black and white dots. There are no grey dots at all.
    The more dither patterns that a device or program supports, the more shades
    of grey it can represent. In printing, dithering is usually called halftoning, and
    shades of grey are called halftones.
         Note that dithering differs from grey scaling. In grey scaling, each
    individual dot can have a different shade of grey.




               black             grey              light grey         white
ITEC 1011              Introduction to Information Technologies
                               Plan
     •   Printers
     •   Scanners
     •   Keyboards
     •   Pointing Devices




ITEC 1011        Introduction to Information Technologies
                            How it works
          A scanner works by digitizing an image. A scanning mechanism
     consists of a light source and a row of light sensors. As light is reflected
     from individual points on the page, it is received by the light sensors and
     translated to digital signals that correspond to the brightness of each point.
     Colour filters can be used to produce colour images, either by providing
     multiple sensors or by scanning the image three times with a separate
     colour filter for each pass. The resolution of scanners is similar to that of
     printers, approximately 300-600 dpi (dots per inch).




ITEC 1011              Introduction to Information Technologies
                             Scanners
     • Three main types
            • Flatbed
            • Sheet-fed
            • Handheld




ITEC 1011           Introduction to Information Technologies
            Flatbed Scanner Example




ITEC 1011      Introduction to Information Technologies
            Sheet-fed Scanner Example




             OfficeJet Series 700 from Hewlett Packard Co
                         (http://www.hp.com)

ITEC 1011          Introduction to Information Technologies
            Handheld Scanner Example




            QuickScan GP Bar Code Scanner from PSC, Inc.
                       (http://www.pscnet.com)

ITEC 1011           Introduction to Information Technologies
                               Plan
     •   Printers
     •   Scanners
     •   Keyboards
     •   Pointing Devices




ITEC 1011        Introduction to Information Technologies
                               Examples




      Natural keyboard by Microsoft                Internet keyboard by Microsoft




ITEC 1011             Introduction to Information Technologies
            Keyboard Connectors




ITEC 1011    Introduction to Information Technologies
                               Plan
     •   Printers
     •   Scanners
     •   Keyboards
     •   Pointing Devices




ITEC 1011        Introduction to Information Technologies
                    Examples




ITEC 1011   Introduction to Information Technologies
                   Thank you


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ITEC 1011   Introduction to Information Technologies

				
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