A Presentation On

Printer

Department of Computer Engineering,M. S. P. V. L. Polytechnic College,

Pavoorchatram.www.ustudy.in

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.www.ustudy.in

Cont.,

1 2 3 4 5

1234567

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Parts of a Dot matrix printer

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Block diagram of Dot matrix printer Interface

Connector

Controlelectronics

Driver circuits

Power supplyPower supply

Front panelSwitches and

LED

Front panelSwitches and

LED

LFmechanis

m

LFmechanis

mPrintmechanis

m

Printmechanis

m

Print head

control

Print head

control

Carriage movementcontrol

Carriage movementcontrol

DIP switches

Cooling fan

Print head

Temperaturesensor

Ribbon motor

Home sensor

Carriage motor

Paper sensor

Line feed motor

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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. www.ustudy.in

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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To control electronics, driver circuitTo BufferSMPSAC

230 V

+5V-

12V

+24V

To print head, paper feed motor,

Carriage motor

Power supply

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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.www.ustudy.in

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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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 speed and

displacement of these mechanisms.

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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 and accented

characters

• Page length

• Line spacing

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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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