A Presentation
On
Printer
Department of Computer Engineering,
M. S. P. V. L. Polytechnic College,
Pavoorchatram.
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Introduction
• Printer is an output device.
• This is used to take hard copies of any computer
based application.
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Types of printer
• Dot matrix printer
• Ink jet printer
• Laser printer
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Dot matrix printer
• In this printer the characters are formed with
the help of dots.
• So this is called dot matrix printer.
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Dot matrix printer
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Dot matrix printer
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Types of Dot matrix printer
• 7-pin printers
• 9-pin printers
• 24-pin printers
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Operation of 7-pin printer
• The print head of the dot matrix printer consists
of a column of 7 small needles.
• Each needle can move freely.
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Cont.,
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Cont.,
• Each needle can be made to print a dot by means
of a hammer action that forced the needle to
come out and press the ribbon against the
paper.
• Standard characters are produced in a 5 x 7 dot
matrix. (7 dots high and 5 dots wide).
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5x7 dot matrix
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Cont.,
• The characters are printed column by column
and not all at once.
• For example to print the character T, initially pin
number 1 is made to contact the ribbon.
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Cont.,
• Thus first column of the characters is got.
• Then the print head is moved towards right and
once again the pin 1 is made to contact the
ribbon.
• Thus second column of the character is got.
Then the print head is moved to get the third
column and so on.
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Cont.,
1 2 3 4 5
1
2
3
4
5
6
7
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Parts of a Dot matrix printer
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Block diagram of Dot matrix printer
Interface
Connector
Power
supply
Front panel
Switches and
LED
Control
electronics
DIP
switches
Driver
circuits
LF
mechanism
Cooling fan
Print
mechanism
Print
head
Print head
control
Carriage
movement
control
Temperature
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Ribbon
motor
sensor
Line feed motor
Paper sensor
Carriage motor
Home sensor
Dot matrix printer head mechanisms in action:
Classical printhead mechanism is showed from the left side. The permanent
magnet printer head mechanism you may see at right.
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Construction of a Dot matrix printer
Power supply
• Normally printers consist of Switch Mode Power
Supply (SMPS).
• This unit is used to convert the AC voltage to
different DC voltage levels.
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Power supply
AC
230 V
SMPS
+5V
-12V
To control electronics, driver circuit
To Buffer
To print head, paper feed motor,
+24V
Carriage motor
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Cont.,
Interface connector
• Printers are connected to the computer through a
36 pin centronics interface cable or a 9-pin RS
232C serial interface cable.
• The serial data from the computer is received and
stored in the printers buffer RAM.
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Centronics Printer connector
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RS232 Connector
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Cont.,
• The Buffer RAM can store one line to one page
depending on the size of the RAM.
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Printer Buffer RAM
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Cont.,
Control electronics
• This unit contains an intelligent processor for
controlling the functions of the printer.
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Cont.,
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Cont.,
Driver circuit
• This unit is used to control the line feed
mechanism, print mechanism and ribbon
movements.
• These mechanisms use stepper motors.
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Driver circuit
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Cont.,
• This circuit provides high current for driving
these stepper motors.
• Also it sends feed back signals to control
electronics for monitoring the
displacement of these mechanisms.
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speed and
Cont.,
Front panel
• This consists of a minimum three status lights
(LED) and three soft touch switches.
• The lights are used to give information about the
status of the printer to the user.
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Front panel
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Cont.,
• Switches are used to give the control commands.
• For example font selection.
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Cont.,
DIP switches
• These switches are present in the interface card
and are used to change the printer settings.
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DIP switches
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Printer setting change
The settings that can be changed are
• Printing
of
graphics
characters
• Page length
• Line spacing
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and
accented
Cont.,
• Print quality
• Auto line speed
• Character set for different countries
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Sensors
• These are used to keep the printer safe from
abnormal conditions.
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Printer sensor
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Different Sensors
Home sensor
• This is used to detect whether the head carriage is
in the extreme left margin.
Paper empty sensor
• This is used to signal when there is no paper in the
printer.
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Cont.,
Temperature sensor
• This is used to detect the abnormal timings used
to fire the pins.
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Cont.,
Print mechanism
• This contains two subsystems
Carriage movement control mechanism
• This moves the carriage bidirectionally by means
of a stepper motor
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Carriage movement control mechanism
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Cont.,
Ribbon feed mechanism
• This feeds the ribbon when the print head is
printing
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Ribbon feed mechanism
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Features of Dot matrix printer
• Both text and graphics can be printed
• Printing cost is very low
• Multiple copies can be taken with the help carbon
papers
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Cont.,
• By increasing the number of pins from 7 to 9 or 24
the quality of printing can be increased.
• It’s operating speed is slow.
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The End
Thank you!
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