63 terms

A+ Chapter 11

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Printers
electromechanical output devices that are used to put information from computer onto paper
Impact Printers
use a form of impact and an inked ribbon to make an imprint on the paper
use tractor feed mechanism
special paper, continuous feed paper with holes down both edges
Daisy Wheel Printers
Impact Printer: oldest
wheel with raised letters and symbols on a petal
print head rotates the daisy wheel until character is in place
solenoid (electromechanical hammer) strikes back of petal containing the character, character hits ribbon that strikes paper
speed rated by characters per second (cps), very slow (2 - 4cps), very loud, one font
inexpensive, easily readable (letter quality (LQ))
Dot-Matrix Printers
Impact printer
print head has row of pins, which are triggered in patterns that form letters and numbers as print head moves across paper
printer controller sends signal to print head which energizes which turns print wire into electromagnet which repels print pin forcing it againsttheink ribbon and making a dot on the paper
poor image quality, draft quality
near letter quality (NQL) almost as good as daisy wheel
noisy, faster print speed, 72cps,
Inkjet
spray ink on the page, contain reservoir of ink, pump, nozzle; inexpensive to manufacture
Inkjet Parts
Print Head/Ink Cartridge
Head Carriage, Belt, Stepper Motor
Paper-feed mechanism
Control, interface, power circuitry
Inkjet Printer Head/Ink Cartridge
many small nozzles (100 to 200) that spray ink in small droplets onto page
Ink cartridge contains reservoir of ink and print head may be removable
One print head for each CMYK (cyan, magenta, yellow, black)
Inkjet Ink Cartridge Method
Several small chambers in each ink cartridge at top are a metal plate and tube leading to ink, bottom is a small pinhole, these pinholes spray ink on page to form characters as patterns of dots
two methods of spraying ink: 1) electric signal sent to heating element, energizing it, causes ink to vaporize, ink is pushed out forms a bubble, breaks into droplet; 2) piezoelectric element (small rod or mini drum head) that flexes when energized, outward flex pushed ink out
maintenance station: small suction pump and ink-absorbing pad, pulls ink through nozzles using vacuum suction, pad absorbs expelled ink (place for print head to rest, keeps print head in working order)
Inkjet: Head Carriage, Belt, Stepper Motor
printer head carriage is the part that moves back and forth during printing
physical and electronic connections (keep connections clean)
Stepper motor: precisely made electric motor thatcan move in the same very small increments each time it is activated
Carriage motor or carriage stepper motor makes printer head carriage move
Belt: placed around two small wheels or pulley and attached to print head cartridge, moves print head back ad forth across page
Carriage rests on stabilizer bar
Inkjet: Paper-feed mechanism
picks up paper from paper drawer and feeds into printer
Pickup rollers: rubber, rub against paper as they rotate and feed paper to printer, work against separator pads which help keep rest of paper in place,
pickup rollers are turned by pickup stepper motor
paper feed sensors: tell when printer is out of paper, or a paper jam has occurred
Inkjet: Control, interface, power circuitry
control circuitry: small circuit board contains all circuitry to run stepper motors, monitors health of printer and reporting info back to PC
interface circuitry controls connection to computer, connects to control circuitry, converts signal into datastream for printer to use
power: conductive pathways convert 110V or 220V into 12V or 5V and distributes to other circuitry, uses a transformer
Inkjet Printing Process
calibrate system: process by which device is brought within functional specifications, aligning print heads
Click Print
Software sends data to printer driver
Printer driver converts data being printed into printer format, ensures printer is ready to print
Printer driver sends info to printer
Printer stores received data in print buffer memory
Printer activates cleaning cycle to purge print heads of dried ink
Control circuitry activates paper feed, triggers sensor to stop feed and position paper
Print head stepper motor uses print head belt and carriage to move the printhead across page little by little, step by step print head sprays ink in pattern
Paper feed advances page a small amount, then repeats spraying
Once page is finished feed stepper motor actuates and ejects page from printer to output tray
Once final page is ejected print head is parked (rest position) and print process is done
Duplexing (double sided printing)
Page Printers
print job instructions one a time rather than one line at a time
EP
electrophotographic print process: either scan image onto photosensitive drum or use an array of LEDs to create image on drum
Laser printers
printers that use EP process
Basic components of a laser printer
toner, laser scanner, high voltage power supply, DC power supply, paper transport assembly, transfer corona, fusing assembly, printer controller circuitry, ozone filter
Toner Cartridge
holds toner (black carbon substance mixed with polyester resins to make it flow better and iron oxide particles to make it sensitive to electrical charges)
able to be attracted to toner drum and of melting into paper
contains developer which carries toner until it is used by EP
contains print drum coated with photosensitive material that can hold a static charge when not exposed to light but cannot hold a charge when it is exposed to light
contains cleaning blade to scrape used toner off photosensitive drum
Laser Scanning Assembly
when exposed to light the drum discharges but only where it is exposed
as drum rotates the laser scanning assembly scans laser across photosensitive drum writing image to it
High Voltage Power Supply (HVPS)
EP needs high voltage electricity, converts AC 120V or 60V into higher V, energizes the charging corona and the transfer corona
DC Power Supply
DCPS: powers logic circuitry and motors, +5VDC and +24VDC, converts house current into +5, -5, for logic and +24VDC for paper transport motors
Paper Transport Assembly
responsible for moving paper through printer
motor and rubberized rollers
feed roller or paper pickup: D-shaped, rotates against paper and pushed one sheet into printer, works with separator pad to prevent more than one from going in
registration roller: synchronize paper movement with the image formation process in EP cartridge, use electronic stepper motor, powers paper transport and fuser rollers
Transfer Corona Assembly
given a high voltage charge which is transferred to the paper which in turn pulls toner from photosensitive drum
static charge eliminator strip drains away charge on paper (don't drain the paper sticks to EP cartirdge)
corona wire: small diameter, charged by HVPS, under EP print cartridge
corona roller: directly in contact with paper, high speeds
Fusing Assembly
two rollers apply pressure and heat to fuse plastic toner particles to the paper
halogen heat lamp, teflon coated aluminum-fusing roller and rubberized pressure roller
halogen heats fusing roller between 329degrees and 392degrees, pressuer roller pushed paper to fusing roller which melts toner to paper
Printer controller circuitry
circuit board converts signals from comp to various assemblies in the laser printer using rasterizing
formats info into a page's worth of line by line commands for laser scanner
Ozone Filter
ozone is a chemically reactive gas that is created by high voltage coronas, must be replaced
Duplexing Assembly
print on both sides
Electrophotographic Print Process (EP)
process by which EP laser printer forms images on paper
1) Processing
2) Charging
3) Exposing (writing)
4) Developing
5) Transferring
6) Fusing
7) Cleaning
1) Processing
receiving image and creating the image
computer sends print job, printer creates print job, render one horizontal strip at a time to create image, each strip is a scan line or raster line
Raster Image Processor (RIP) manages raster creation, creates image of the final page in memory
2) Charging
charging corona with EP toner gets high voltage from HVPS, applys strong -600VDC uniform negative charge to the photosensitive drum
3) Exposing
exposing drum to image
laser turned on and scans drum from side to side, flashing on and off according ot bits of info that printer controller sends
wherever laser beam touches drum's charge is reduced to -100VDC
pattern of exposed area is formed representing image ot be printed
controller sends signal to pickup roller to feed paper
4) Developing
discrete electrical charges need to be converted into something that can be transferred to a piece of paper
toner is transferred to the areas that were exposed in the writing step
developing roller inside EP cartridge acquires a -600VDC charge
toner sticks to roller because of electrostatic charges between toner and developing roller
creates fog of toner between EP drum and developing roller
toner stuck to drum were laser has written
5) Transferring
controller notifies registration rollers that paper should be fed
controller sends signal to charging corona to turn on, and it acquires a strong positive charge +600VDC and applies charge to paper
paper pulls the toner from the photosensitive drum at the line of contact between the roller and the paper
static eliminator strip removes charge from paper
6) Fusing
fuser rollers at 350degrees melt polyester resin of toner and the pressure rollers press it permanently to paper
once paper is out, sensor tells printer to clean
7) Cleaning
rubber blade inside EP cartridge scrapes any leftover toner off drum fluorescent lamp discharges any remaining charge on photosensitive drum
Thermal Printers
POS systems, fax machines, waxy paper
use print head that is width of paper, turns black when heat passes over it
few moving parts, long life
Virtual Printers
sends desired output to a file instead of paper
print to XPS (Open XML Paper Specification) is Microsoft's PDF
Printer Interface Components
collection of hardware (port) and software that allows the printer to communicate with a computer
Serial Printers
one bit at a time
Parallel Printers
receives 8 bits at a time over 8 wires, DB 25 connector to computer and 36pin Centronics connector to printer IEEE 1284 compliant
Universal Serial Bus (USB)
most popular interface, higher transfer rate
Ethernet
have internal NIC and ROM to allow communication on a network
Wireless
802.11 and bluetooth (10m) uses radio waves
ad hoc: non permanent
infrastructure mode: permanently on network
Interface Software
page description language (PDL): determines how efficient the printer is at converting info to be printed into signals printer can understand
Driver software: understands and controls printer
PDL
page description language: describes a whole page being printed by sending commands that describe the text as well as margins and other settings
controller interprets signals into laser pulses
printer languages: PostScript, Printer Command Language (PCL), Graphics Device Interface (GDI)
PostScript: developed by Adobe, printer driver describes page in terms of draw and position commands, page is divided into grid, gives start and end points to draw from and to
move some processing power from comp to printer
Driver Software
controls how printer processes the print job
must be for OS and printer
configured to use a specific PDL
Installing and Sharing Printers
connect to device, install and update driver, calibrate device, configure options and settings, print test page, verify compatibility with OS and device, educate users about functionality
Installing and Sharing Networked Printers
making print server part of printer itself, or making it a separate network device
Print Server
device that hosts the printer and processes the necessary printer commands
Local Network Printing
accessible to others on the network
printer needs to be attached to network
need to tell computer printer is networked, not local
Integrated print server
printer itself has print server
TCP Printing
printers that are networked need IP addresses
adding a printer via TCP
RAW: Standard TCP/IP Port Monitor and is default, port 9100, uses SNMP for bidirectional communication between comp and printer
LPR: older, ports 721 - 731, destination is 515
allows clients with different OSs print, sends job directly to printer
Bonjour
Apple introduced in 2002, zero configuration networking
designed to enable automatic discovery of devices and services using TCP/IP and to provide hostname resolution
AirPrint
print from iPhone, iPod, iPad
no drivers on client side
Cloud Printing
printing to a remote device
setup printer in cloud
Data Privacy Concerns with Networked Printing
secure printing: indicate its a private print job, must enter a PIN, then print, must enter PIN on printer before it prints
deselect keep print job
Printer Maintenance
use authorized parts, replace consumables
Paper: composition, basis weight (weight of a ream (500 pieces)), caliper (thickness of sheet)
Ink and Toner: always buy exact model printer calls for, use authorized ink
Printer Scheduled Maintenance
look for quoted monthly volume of print capacity
printers keep track of the number of pages they print
use maintenance kit from manufacturer, reset page count in menu
run cleaning sequence every time you replace ink
Ensure a suitable environment for printer
ensure laser printers are in well-ventilated areas
reduce humidity
don't open toner cartridges
reduce ozone by replacing ozone filter every so often
don't use ammonia
Installing Printer Upgrades
memory, network cards, firmware
Printer Memory
buy only compatible memory
make sure it can be upgraded
Printer NIC
proprietary, NIC has small processor
faster, more efficient printing
Upgrading Printer Firmware
download from manufacturer's website
offers new features
Other Upgrades
printer-resident fonts, need hard drive to store them
trays and feeders expansions
finisher: stapling, hole punching, folding, sorting, collating
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