COMPUTER SCIENCE

1. COMPUTER SCIENCE
Chapter 5
INPUT AND OUTPUT
DEVICES

2. PRINTERS
• IMPACT PRINTERS
• NON IMPACT PRINTERS

3. PRINTERS
A device used for printing is known as
printer
It receives information from computer and
print it on paper
All printing devices have a paper transport
that automatically moves the continues
forms or single sheets as printing progresses

4. IMPACT PRINTERS.
• Impact printers are printers which works by
creating a direct contact between ink ribbon and
paper. These printers are noisy yet popular.
• Impact printers have mechanical moving parts to
conduct printing.
• Examples: line printers. Dot-matrix printers
Daisy-wheel printers
•

5. NON IMPACT PRINTERS
• A non-impact printer prints characters and
graphics on a piece of paper without striking the
paper. Some of these printers use spray ink while
others use heat and pressure to create images.
These printers are faster than impact printers.
The three main types of non impact printers are
• Thermal printers
• Laser and Ink Jet Printers.

6. INKJET PRINTERS
• An inkjet printer is a computer peripheral that
produces hard copy by spraying ink onto paper. A
typical inkjet printer can produce copy with
a resolution of at least 300 dots per inch ( dpi ).
• Some inkjet printers can make full color hard
copies at 600 dpi or more. Many models include
other devices such as a scanner , photocopier ,
and dedicated fax machine along with the printer
in a single box.

7. INKJET PRINTERS
INKJET PRINTERS are essentially made up of:
• a print head which consists of nozzles which spray
droplets of ink on to the paper to form characters
• an ink cartridge or cartridges; either a group of
cartridges for each colour (blue, yellow and
magenta) and a black cartridge or one single
cartridge containing all three colours + black
• a stepper motor and belt which moves the print
head assembly across the page from side to side
• a paper feed which automatically feeds the
printer with pages as they are required.

8. NOZZLE
When referring to a non-impact printer, like an
inkjet printer, a nozzle is a small hole found on
a printer cartridge's print head. Nozzles can be
smaller than a human hair. Each nozzle produces
millions of ink droplets used in creating the
images and text generated by the printer.

9. STEPPER MOTOR
• Stepper motors are used in printers, disk
drives, and other devices where precise
position control is required. Stepper
motors do not turn continuously like
DC motors. They move in steps such as 1.8
degrees. There are several types of stepper
motors such as unipolar and bipolar.

10. Ink Droplets Technologies
• Thermal Bubble
https://www.youtube.com/watch?v=QNIeVR8luO
A
• Piezoelectric
https://www.xaar.com/en/about/technology-
overview/

11. THERMAL TECHNOLOGY
• Thermal technology is the technology of
producing, storing, controlling,
transmitting, and getting work from heat
energy. Whenever the amount of energy
in one place or form diminishes, the
amount in other places or forms
increases by the same amount.

12. The process of droplet ejection in a thermal bubble
inkjet system: (a) initial state (b) DC voltage applied
across the piezo electric material and a droplet is
ejected (push) (c) DC voltage is removed (pull).

13. PIEZOELECTRIC
TECHNOLOGY
• Piezoelectric Effect is the ability of certain
materials to generate an electric charge in
response to applied mechanical stress. The
word Piezoelectric is derived from the Greek
pieze in, which means to squeeze or press,
and piezo, which is Greek for “push”.
• Piezoelectric inkjet printing, generation of high
voltages, electronic frequency generation,
microbalances, to drive an ultrasonic nozzle, and
ultrafine focusing of optical assemblies.

15. LASER
PRINTERS

16. LASER PRINTERS
• What is a laser printer?
• A laser printer is a popular type of personal
computer printer that uses a non-impact
(keys don't strike the paper), photocopier
technology.
• When a document is sent to the printer,
a laser beam "draws" the document on a
selenium-coated drum using electrical
charges.

17. How a laser printer works. ...
• It makes a laser beam scan back and forth
across a drum inside the printer, building up a
pattern of static electricity. The static
electricity attracts onto the page a kind of
powdered ink called toner. Finally, as in a
photocopier, a fuser unit bonds the toner to
the paper.

19. What printers are laser
printers?
Laser printers are machines that melt toner
powder onto paper to create a print. Laser
printers are more expensive than inkjet
printers upfront and uses pricier toner
cartridges but is still a more economical option
in the long run with its overall lower cost per
page, faster print speeds.

20. What is the advantage of
laser printer over inkjet?
• The main advantages of laser printers
are speed, precision and economy. A laser
can move very quickly, so it can "write" with
much greater speed than an ink jet. And
because the laser beam has an unvarying
diameter, it can draw more precisely, without
spilling any excess ink.

21. PRINTING PROCESS
STAGES
1.Ink Jet Printer 2.Laser Printer

22. PRINTING PROCESS
STAGES
Ink Jet Printer
• The data from the document is sent to a
printer driver.
• The printer driver ensures that the data is in
a format that the chosen printer can
understand
• A check is made by printer driver to ensure
that the chosen printer is available to print

23. PRINTING PROCESS
STAGES
Ink Jet Printer
• The data is sent to the printer and it is stored
in a temporary memory known as a printer
buffer A sheet of paper is then fed into main
body of the printer
• Sensor detects whether paper is available in
the paper feed tray –if it is out of the paper
then the error message is send back to the
computer

24. PRINTING PROCESS
STAGES
Ink Jet Printer
• As the sheet of paper is fed through the
printer, the print head moves from side to side
across the paper printing the text or image;
the four ink colours are sprayed in their exact
amounts to produce the desired final colour.
• At the end of each full pass of the print head,
the paper is advanced very slightly to allow
the next line to be printed; this continues until
the whole page has been printed

25. PRINTING PROCESS
STAGES
Ink Jet Printer
• If there is more data in the printer buffer, then
the whole process from stage 5 is repeated
until the buffer is finally empty
• Once the printer buffer is empty, the printer
sends an interrupt to the processor in the
computer; this is a request for more data to
be sent to the printer; the whole process
• continues until the whole of the document
has been printed

26. PRINTING PROCESS
STAGES
Laser Printer
• If there is more data in the printer buffer, then
the whole process from stage 5 is repeated
until the buffer is finally empty
• Once the printer buffer is empty, the printer
sends an interrupt to the processor in the
computer; this is a request for more data to
be sent to the printer; the whole process
• continues until the whole of the document
has been printed

27. PRINTING PROCESS
STAGES
Laser Printer
The data from the document is sent to a printer
driver.
The printer driver ensures that the data is in a
format that the chosen printer can understand
A check is made by the printer driver to ensure
that the chosen printer is available to print (e.g.
is it busy, is it off line, is it out of ink, and so on)

28. PRINTING PROCESS
STAGES
Laser Printer
The data is then sent to the printer and it is stored
in a temporary memory known as a printer buffer
The start of the printing process involves a printing
drum being given a positive charge; as this drum
rotates, a laser beam is scanned across it removing
the positive charge in certain areas; this leaves
negatively charged areas which exactly match the
text/images of the page to be printed

29. PRINTING PROCESS
STAGES
Laser Printer
• The drum is then coated with positively
charged TONER
• (powdered ink); since the toner is positively
charged, it only sticks
• to the negatively charged parts of the drum
• A negatively charged sheet of paper is then
rolled over the drum

30. RINTING PROCESS
STAGES
Laser Printer
The toner on the drum now sticks to the paper
to produce an exact copy of the page sent to
the printer
To prevent the paper sticking to the drum, the
electric charge on
The paper is removed after one rotation of
the drum

31. PRINTING PROCESS
STAGES
Laser Printer
• The paper finally goes through a fuser which is
a set of heated rollers; the heat melts the ink
so that it fixes permanently to the paper
• At the very end, a discharge lamp removes all
the electric charge from the drum making it
ready to print the next page

32. Applications of inkjet
printers
• Inkjet printers are closely related to the
advertising industry and are widely used, such as
posters, car stickers, personalized decorative
painting
• Inkjet printers have great advantages in realizing
the printing output of high-precision advertising
images both inside and outside the homes, etc
• http://www.subli-star.com/application-inkjet-
printers-various-fields/

33. Applications of Laser Printers
Businesses use laser printers almost exclusively
because they have the reputation of being reliable
while making a quality print product.
Some common uses for laser printers
include printing company stationery, making
labels, and creating company fliers and brochures.
http://hyperphysics.phy-
astr.gsu.edu/hbase/optmod/lasapp2.html

34. ASSIGNMENT
Activity 5.8
• Find out how the operation of color laser
printers differs from the operation of
monochrome laser printers.
• Find out how stepper motors work in disk
drive .