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					Output Devices
How many output devices can you
           name?

– Screen (VDU)
– Printers (dot-matrix, laser, ink-jet)
– Plotter
– Speakers
– Motors
                     The VDU
• Differ by size and
                                  1024x768
  resolution                        Pixels
                                                                   17
                                                                  Inch
• How is size
  measured?
• How is resolution
  measured?
• What are the main
  types?
            This is an old fashioned cathode ray tube (CRT) monitor
             Modern PCs and Laptops have flat screens with liquid
                              crystal displays (LCD)
            Dot Matrix Printers
• How do these work?

• The printer contains a
  ribbon covered in ink which
  is located in front of the
  paper
• The print head has a series
  of pins that are banged
  against the ribbon which
  transfers the ink to the      Cheap but slow, noisy and
                                poor quality
  paper
               Ink Jet Printers
• How do these work?

• The print head sprays ink
  onto the paper through a
  series of nozzles

• Ink jet printers have good
  quality images, are cheap
  but can be slow and
  expensive to run
                                 Laser printers are fast,
  Laser Printers                 high quality and quiet
                                 BUT complex and
                                 expensive
• How do they work?

      (1) Drum in printer is
      negatively charged               (2) Laser etches a
                                       positively charged
      (3) Ink powder from
                                       image onto the drum
      the toner cartridge
      sticks to the positively        (4) Paper passes
      charged part of the             over the drum and
      drum                            the ink powder
      (5) A fuser unit heats          transfers to the paper
      the paper and fuses
      on the ink
               Plotters
• Some images need to be done on a large
  scale such as architects plans
• Plotters have an arm with a pen that
  passes over the paper
                Sound
• Sound can be output with speakers
        Motors or actuators
• Motors are powered by electrical signals
  from the computer

 Stepper Motors – the motor is moved in a
 series of tiny steps

 Servo Motors – The motor moves
 continuously at high speed
                     Tasks
Use the Internet to find a picture of each of these
output devices:
– Screen (VDU)
– Printers (dot-matrix, laser, ink-jet)
– Plotter
– Speakers
– Motors
Write about each device, using what you have learnt
from the presentation

Extension Exercise: Your friend wishes to buy a printer.
Explain which type of printer he should buy and why.

				
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