11 Computer Peripherals Part III Chapt 10

11. Computer Peripherals – Part III Chapt. 10 ITEC 1011 Introduction to Information Technologies

Plan • • Printers Scanners Keyboards Pointing Devices ITEC 1011 Introduction to Information Technologies

Printers • Four main types: • • † ITEC 1011 Dot matrix † Laser Ink jet Thermal dye transfer and thermal wax transfer Impact (the others are non-impact) Introduction to Information Technologies

Impact vs. Non-Impact • Impact printers physically transfer a dot or shape to the paper • Of those in the preceding slide, only dotmatrix uses impact printing • Non-impact printers spray or lay down the image with impact • Impact printers remain important because they can print multi-part forms ITEC 1011 Introduction to Information Technologies

Printers • Four main types: • • ITEC 1011 Dot matrix Laser Ink jet Thermal dye transfer and thermal wax transfer Introduction to Information Technologies

How it works A print-head moves back-and-forth in front of forms (paper) on which characters or graphic images are transferred. The print-head contains numerous wires, typically from 9 to 24. Each wire is part of a solenoid-like unit. A pulse applied to the solenoid creates a magnetic field which forces the wire to move briefly forward then backward. As the wire moves forward, it presses against a print ribbon containing ink. The impact transfers an ink dot to the paper. The paper is supported from behind by a platen. ITEC 1011 Introduction to Information Technologies

Demo (well, sort of) ITEC 1011 Introduction to Information Technologies

Dot Matrix Print Head One print wire Print wires (e. g. , 12) Front view ITEC 1011 Side view Introduction to Information Technologies

Dot Matrix Impact Printing Paper Print wire Platen Ribbon Side view ITEC 1011 Side view Introduction to Information Technologies Front view

Specifications • cps • characters per second • Varies by quality of print (e. g. , draft vs. final) • lpm • lines per minute (related to cps) • Forms • Maximum number of layers of paper that can by printed simultaneously • Specified as n-part forms (e. g. , 4 -part forms) • mtbf • Mean time between failure (e. g. , 6000 hours) ITEC 1011 Introduction to Information Technologies

Noise • Dot matrix printers are notoriously noisy! • This is a major disadvantage in many environments ITEC 1011 Introduction to Information Technologies

Uses • Primarily two: • Any situation that requires multi-part forms • Small printers, such as • Calculators • Adding machines • Point-of-sale terminals ITEC 1011 Introduction to Information Technologies

Dot Matrix Printer Example - 1 Specifications • 800 cps • 400 lpm • 6 -part forms (max) Forms. Master 8000 by Printek, Inc. http: //www. printek. com ITEC 1011 Introduction to Information Technologies

Dot Matrix Printer Example - 2 Specifications • Printhead wires: 9 • Printhead life: 200 million characters • Print speed: • near letter quality: 105 cps • utility: 420 cps • high speed draft: 550 cps • Number of copies: 8 • MTBF: 8000 hours @ 25% duty cycle, 35% density Pacemaker 3410 by OKI Data, Inc. http: //www. okidata. com ITEC 1011 Introduction to Information Technologies

Printers • Four main types: • • ITEC 1011 Dot matrix Laser Ink jet Thermal dye transfer and thermal wax transfer Introduction to Information Technologies

How it works • Four steps 1. A laser is fired in correspondence to the dots to be printed. A spinning mirror causes the dots to be fanned out across the drum. The drum rotates to the next line, usually 1000 th or 1600 th of an inch. The drum is photosensitive. As a result of the laser light, the drum becomes electrically charged wherever a dot is to be printed. Photosensitive drum Laser Spinning mirror ITEC 1011 Introduction to Information Technologies

Operation of a Laser Printer • Four steps 1. A laser is fired in correspondence to the dots to be printed. A spinning mirror causes the dots to be fanned out across the drum. The drum rotates to the next line, usually 1000 th or 1600 th of an inch. The drum is photosensitive. As a result of the laser light, the drum becomes electrically charged wherever a dot is to be printed. Photosensitive drum Laser Spinning mirror ITEC 1011 Introduction to Information Technologies

Operation of a Laser Printer • Four steps 1. A laser is fired in correspondence to the dots to be printed. A spinning mirror causes the dots to be fanned out across the drum. The drum rotates to the next line, usually 1000 th or 1600 th of an inch. The drum is photosensitive. As a result of the laser light, the drum becomes electrically charged wherever a dot is to be printed. Photosensitive drum Laser Spinning mirror ITEC 1011 Introduction to Information Technologies

Operation of a Laser Printer 2. As the drum continues to rotate, the charged part of the drum passes through a tank of black powder called toner. Toner sticks to the drum wherever the charge is present. Thus, the pattern of toner on the drum matches the image. Toner ITEC 1011 Introduction to Information Technologies

Operation of a Laser Printer 3. A sheet of paper is fed toward the drum. A charge wire coats the paper with electrical charges. When the paper contacts the drum, it picks up the toner from the drum Charge wire Paper ITEC 1011 Introduction to Information Technologies

Operation of a Laser Printer 4. As the paper rolls from the drum, it passes over a heat and pressure area known as the fusing system. The fusing system melts the toner to the paper. The printed page then exits the printer. As the same time, the surface of the drum passes over another wire, called a corona wire. This wire resets the charge on the drum, to ready it for the next page. Corona wire ITEC 1011 Introduction to Information Technologies Fusing system

Specifications • ppm • Pages per minute • Typically 4 -10 ppm • dpi • Dots per inch • Typically 600 -1200 dpi ITEC 1011 Introduction to Information Technologies

Laser Printer Example Laserjet 5000 Series from Hewlett Packard Co. (http: //www. hp. com) ITEC 1011 Introduction to Information Technologies

Printers • Four main types: • • ITEC 1011 Dot matrix Laser Ink jet Thermal dye transfer and thermal wax transfer Introduction to Information Technologies

Background • Inkjet technology was developed in the 1960 s • First commercialized by IBM in 1976 with the 6640 printer • Cannon and Hewlett Packard developed similar technology • Also called bubble jet ITEC 1011 Introduction to Information Technologies

How it works Characters and graphics are 'painted‘ line by line to from a pattern of dots as a print head scans horizontally across the paper. An ink-filled print cartridge is attached to the inkjet's print head. The print head contains 50 or more ink-filled chambers, each attached to a nozzle. An electrical pulse flows through thin resistors at the bottom of each chamber. When current flows through a resistor, the resistor heats a thin layer of ink at the bottom of the chamber to more than 900 degrees Fahrenheit for several millionths of a second. The ink boils and forms a bubble of vapour. As the vapour bubble expands, it pushes ink through the nozzle to form a droplet at the tip of the nozzle. The droplet sprays onto the paper. The volume of the ejected ink is about one millionth that of a drop of water from an eye-dropper. A typical character is formed by an array of these drops 20 across and 20 high. As the resistor cools, the bubble collapses. The resulting suction pulls fresh ink from the attached reservoir into the firing chamber. ITEC 1011 Introduction to Information Technologies

Inkjet Printer Example ITEC 1011 Introduction to Information Technologies

Printers • Four main types: • • ITEC 1011 Dot matrix Laser Ink jet Thermal dye transfer and thermal wax transfer Introduction to Information Technologies

How it works Thermal dye transfer printers, also called dye sublimation printers, heat ribbons containing dye and then diffuse the dyes onto specially coated paper or transparencies. These printers are the most expensive and slowest, but they produce continuous-tone images that mimic actual photographs. Note that you need special paper, which is quite expensive. A new breed of thermal dye transfer printers, called snapshot printers, produce small photographic snapshots and are much less expensive than their full-size cousins. Thermal wax transfer printers use wax-based inks that are melted and then laid down on regular paper or transparencies. Unlike thermal dye transfer printers, these printers print images as dots, which means that images must be dithered first. As a result images are not quite photorealistic, although they are very good. The big advantages of these printers over thermal dye transfer printers are that they don't require special paper and they are faster. ITEC 1011 Introduction to Information Technologies

Dithering is creating the illusion of new colours and shades by varying the pattern of dots. Newspaper photographs, for example, are dithered. If you look closely, you can see that different shades of grey are produced by varying the patterns of black and white dots. There are no grey dots at all. The more dither patterns that a device or program supports, the more shades of grey it can represent. In printing, dithering is usually called halftoning, and shades of grey are called halftones. Note that dithering differs from grey scaling. In grey scaling, each individual dot can have a different shade of grey. black ITEC 1011 grey light grey Introduction to Information Technologies white

Plan • • Printers Scanners Keyboards Pointing Devices ITEC 1011 Introduction to Information Technologies

How it works A scanner works by digitizing an image. A scanning mechanism consists of a light source and a row of light sensors. As light is reflected from individual points on the page, it is received by the light sensors and translated to digital signals that correspond to the brightness of each point. Colour filters can be used to produce colour images, either by providing multiple sensors or by scanning the image three times with a separate colour filter for each pass. The resolution of scanners is similar to that of printers, approximately 300 -600 dpi (dots per inch). ITEC 1011 Introduction to Information Technologies

Scanners • Three main types • Flatbed • Sheet-fed • Handheld ITEC 1011 Introduction to Information Technologies

Flatbed Scanner Example ITEC 1011 Introduction to Information Technologies

Sheet-fed Scanner Example Office. Jet Series 700 from Hewlett Packard Co (http: //www. hp. com) ITEC 1011 Introduction to Information Technologies

Handheld Scanner Example Quick. Scan GP Bar Code Scanner from PSC, Inc. (http: //www. pscnet. com) ITEC 1011 Introduction to Information Technologies

Plan • • Printers Scanners Keyboards Pointing Devices ITEC 1011 Introduction to Information Technologies

Examples Natural keyboard by Microsoft ITEC 1011 Internet keyboard by Microsoft Introduction to Information Technologies

Keyboard Connectors ITEC 1011 Introduction to Information Technologies

Plan • • Printers Scanners Keyboards Pointing Devices ITEC 1011 Introduction to Information Technologies

Examples ITEC 1011 Introduction to Information Technologies

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