Printers

Chapter 19

Impact Printers

Leave an image on paper by physically striking an ink ribbon against the surface of the paperDaisy wheel and dot matrix printers are 2 examplesDaisy wheel – single font and only one size

Dot-matrix printers

Use an array of pins to strike an inked printer ribbonDownside – need for ongoing maintenance

Must keep the platen and print head clean with denatured alcoholPicture (p.481)

Dot-matrix problems

White bars on textDirty or damaged print head

Chopped textPrint head needs to be adjusted

Peppered lookPlaten is dirty

Faded imageMove print head closer to the platen

Light to darkPlaten is out of adjustment

Inkjet Printers

Eject ink through tiny tubes. The ink is ejected through tubes by heating the ink with tiny resistors or plates that are at one end of the tube. The resistors literally boil the ink, creating a tiny air bubble that ejects a droplet of ink onto the paper, thus creating portions of the image.(page 483)

Laser printers

Parts – most parts are put into the toner cartridge so that small little parts don’t need to be replaced at a regular basis.Photosensitive drum

An aluminum cylinder coated with particles of photosensitive compoundsUsually contained in the toner cartridge, can be wiped clean if dirty, but if it is scratched every page show the scratch

Laser printers

Erase lamp – exposes the entire surface of the photosensitive drum to light, making the photosensitive coating conductivePrimary corona wire – located close to the drum, charges the drumLaser – acts as the writing mechanism of the printer, any part of the drum that is struck by the laser is conductive

Laser printers

Toner – fine powder made up of plastic particles bonded to iron particles, have charges of between –200 to –500 voltsTransfer corona – applies a positive charge to the paper, which draws the negatively charged toner particles to the paperFuser – 2 rollers that attach the toner to the paper to make the image permanent

The printing process

Cleaning (cloning)Conditioning (Connie)Writing (will)Developing (double)Transferring (the)Fusing (fun)

The printing process

CleaningThe printing process begins with both physically and electronically cleaning the drum

Conditioning (charging)To make the drum more receptive to new images, the primary corona applies a uniform negative charge between –600 to –1000 volts

The printing process

WritingThe laser writes a positive image on the surface of the drum. For each point contacted on the drum the voltage is reduced. The difference between voltage on the drum represents the image to be printed

The printing process

DevelopingEvery particle on the drum hit by the laser release most of its negative charge into the drum. Those particles with a lesser negative charge are relatively positive to the toner particles and will attract them. The toner is attracted to these spots.

The printing process

Transferring The transfer corona positively charges the paper, and then the negatively charged toner particles leap from the drum to the paper.

FusingThe toner is melted to the paper by the rollers

Printers

Laser printers have two power suppliesSystem board – printers have RAM which can be replaced and updated, but make sure you contact your manufacturer to make sure you have the right typeOzone filters – the coronas generate ozone, so the printer has a filter that should be replaced periodically

Printers

Read section on Electronics pp. 1118-1119Printer languages

ASCII (standard printing language)POSTSCRIPTPCL (Hewlett Packard)

Troubleshooting / Disposal

It is important to know how to fix certain problems with laser printersRead pp. 1123-1126 (know this) on common problems with laser printersDon’t throw away toner cartridges - certain companies will pay for themConsult local laws as far as disposal is concerned

Parallel communication

Printers work with parallel communication

much faster than serial (8 bits at a time rather than 1)

Speed of normal parallel ports is 150 KBpsStandard for parallel - IEEE 1284

Parallel modes

Centronics mode - standard mode

Nibble mode - bi-directional (4 bits each way), limited to 50 KBps

Byte mode - bi-directional (8 bits each way), limited to 150 KBps

Parallel modes

Enhanced Parallel Port (EPP) - high speed communications (500 KBps)

software on both sides needs to be compatible and agree to mode

Extended Capability Mode (ECP) - good for multi-purpose devices

when using fax/printer/scanner devices

Connections and cabling

Although there is no true standard, “the standard parallel cable” usually refers to a printer cable with male DB25 on one end and a 36-pin Centronics connector on the otherKeep under 6 feetNow printers use USB