Download - Computer Peripherals III
-
7/29/2019 Computer Peripherals III
1/25
ITEC 1011 Introduction to Information Technologies
11. Computer PeripheralsPart III
Chapt. 10
-
7/29/2019 Computer Peripherals III
2/25
ITEC 1011 Introduction to Information Technologies
Plan
Printers Scanners
Keyboards
Pointing Devices
-
7/29/2019 Computer Peripherals III
3/25
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)
-
7/29/2019 Computer Peripherals III
4/25
ITEC 1011 Introduction to Information Technologies
Printers
Four main types: Dot matrix
Laser
Ink jet Thermal dye transfer and thermal wax transfer
-
7/29/2019 Computer Peripherals III
5/25
ITEC 1011 Introduction to Information Technologies
How it worksA 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 movesforward, 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.
-
7/29/2019 Computer Peripherals III
6/25
ITEC 1011 Introduction to Information Technologies
Dot Matrix Print Head
Front view Side view
Print wires
(e.g., 12)
One print wire
-
7/29/2019 Computer Peripherals III
7/25
ITEC 1011 Introduction to Information Technologies
Dot Matrix Impact Printing
Print
wire
Ribbon
Paper
Platen
Side view Side view Front view
-
7/29/2019 Computer Peripherals III
8/25
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 printedsimultaneously
Specified as n-part forms (e.g., 4-part forms)
mtbf
Mean time between failure (e.g., 6000 hours)
-
7/29/2019 Computer Peripherals III
9/25
ITEC 1011 Introduction to Information Technologies
Printers
Four main types: Dot matrix
Laser
Ink jet Thermal dye transfer and thermal wax transfer
-
7/29/2019 Computer Peripherals III
10/25
ITEC 1011 Introduction to Information Technologies
How it works
Four steps1. 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
Spinning
mirror
Photosensitive
drum
-
7/29/2019 Computer Peripherals III
11/25
ITEC 1011 Introduction to Information Technologies
Specifications
ppm Pages per minute
Typically 4-10 ppm
dpi Dots per inch
Typically 600-1200 dpi
-
7/29/2019 Computer Peripherals III
12/25
ITEC 1011 Introduction to Information Technologies
Printers
Four main types: Dot matrix
Laser
Ink jet Thermal dye transfer and thermal wax transfer
-
7/29/2019 Computer Peripherals III
13/25
ITEC 1011 Introduction to Information Technologies
Background
Inkjet technology was developed in the1960s
First commercialized by IBM in 1976 with
the 6640 printer Cannon and Hewlett Packard developed
similar technology
Also called bubble jet
-
7/29/2019 Computer Peripherals III
14/25
ITEC 1011 Introduction to Information Technologies
How it worksCharacters and graphics are 'painted line by line to from a pattern of
dots as a print head scans horizontally across the paper. An ink-filledprint 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 forseveral 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.
-
7/29/2019 Computer Peripherals III
15/25
ITEC 1011 Introduction to Information Technologies
Printers
Four main types: Dot matrix
Laser
Ink jet Thermal dye transfer and thermal wax transfer
-
7/29/2019 Computer Peripherals III
16/25
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.
-
7/29/2019 Computer Peripherals III
17/25
ITEC 1011 Introduction to Information Technologies
Plan
Printers Scanners
Keyboards
Pointing Devices
-
7/29/2019 Computer Peripherals III
18/25
ITEC 1011 Introduction to Information Technologies
How it works
A scanner works by digitizing an image. A scanning mechanismconsists 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).
-
7/29/2019 Computer Peripherals III
19/25
ITEC 1011 Introduction to Information Technologies
Scanners
Three main types Flatbed
Sheet-fed
Handheld
-
7/29/2019 Computer Peripherals III
20/25
ITEC 1011 Introduction to Information Technologies
Plan
Printers Scanners
Keyboards
Pointing Devices
-
7/29/2019 Computer Peripherals III
21/25
ITEC 1011 Introduction to Information Technologies
Examples
Natural keyboard by Microsoft Internet keyboard by Microsoft
-
7/29/2019 Computer Peripherals III
22/25
ITEC 1011 Introduction to Information Technologies
Keyboard Connectors
-
7/29/2019 Computer Peripherals III
23/25
ITEC 1011 Introduction to Information Technologies
Plan
Printers Scanners
Keyboards
Pointing Devices
-
7/29/2019 Computer Peripherals III
24/25
ITEC 1011 Introduction to Information Technologies
Examples
-
7/29/2019 Computer Peripherals III
25/25
ITEC 1011 Introduction to Information Technologies
Thank you
Next topic