Keyboard technology | Wikipedia audio article
Computer. Keyboards, can be classified, by the switch technology that, they use. Computer. Alphanumeric. Keyboards, typically, have 80 to 110. Durable, switches, generally, one for each key, the. Choice of switch technology affects. Key response, the positive, feedback that a key has been pressed and, pre-travel, the distance needed to push the key to enter a character reliably. Newer. Keyboard, models, use hybrids, of various, technologies, to achieve greater, cost savings. Topic. Types. Topic. Membrane. Keyboard. There. Are two types of membrane based keyboards, flat-panel, membrane, keyboards. And full travel membrane, keyboards. Flat. Panel membrane, keyboards, are most often found on appliances, like microwave, ovens or photocopiers, a, common. Design consists, of three layers the. Top layer has the labels, printed, on its front and conductive, stripes printed, on the back, under. This it has a spacer, layer which, holds the front and back layer apart, so that they do not normally, make electrical, contact, the. Back layer has conductive, stripes printed, perpendicularly. To those of the front layer, when. Placed together the, stripes form a grid when, the user pushes, down at a particular position, their, finger, pushes the front layer down through the spacer layer to, close a circuit, at one of the intersections, of the grid this. Indicates, to the computer, or keyboard, control, processor. That a particular button, has been pressed. Generally. Flat panel membrane, keyboards. Do not produce, a noticeable, physical, feedback. Therefore. Devices. Using these issue a beep or flash a light when the key is pressed, they. Are often used in harsh environments. Where water or leak proofing, is desirable. Although. Used in the early days of the personal, computer on, the sinclair, zx80. Zx81. And Atari, 400 they, have been supplanted, by the more tactile, dome and mechanical, switch keyboards. Full. Travel, membrane based keyboards. Are the most common, computer, keyboards, today, they. Have one-piece plastic, key top switch plunges which press down on a membrane, to actuate, a contact, in an electrical, switch matrix. Topic. Dome, switch keyboard. Dome switch keyboards are, a hybrid of flat-panel membrane, and mechanical, switch keyboards. They. Bring two circuit, board traces, together under, a rubber or silicone keypad. Using, either metal dome. Switches. Or polyurethane form. Domes the metal, dome switches, are form pieces, of stainless, steel that when compressed give the user a crisp positive, tactile, feedback. These. Metal, types of dome switches, are very common, are usually, reliable to over five million cycles, and can be plated, in either nickel, silver, or gold, the. Rubber dome switches, most commonly, referred to as poly domes are formed, polyurethane. Domes where the inside bubble, is coated, in graphite. While. Poly domes are typically, cheaper than metal domes they lack the crisp snap of the metal domes and usually, have a lower life specification. Poly. Domes are considered, very quiet but purists, tend to find them mushy. Because. The collapsing, dome does not provide as much positive response, as metal domes for, either. Metal or poly downes when a key is pressed it collapses, the dome which connects, the two circuit, traces, and completes, the connection, to enter the character, the. Pattern on the pc board is often gold-plated. Both. Are common switched, technologies. Used in mass-market. Keyboards, today this. Type of switch technology happens. To be most commonly, used in handheld controllers. Mobile, phones automotive. Consumer, electronics. And medical devices. Dome. Switch keyboards are also called, direct, switch keyboards. Topic. Cesar switch, keyboard. A special. Case of the computer, keyboard dome, switch is the scissor switch, the. Keys are attached to the keyboard, via two plastic pieces that interlock inner scissor. Like. Fashion, and snap, to the keyboard, and the key it, still uses rubber domes but a special, plastic scissors, mechanism. Links the key cap to a plunger, that depresses, the rubber dome with a much shorter travel, than the typical rubber, dome keyboard. Typically. Scissor switch keyboards also. Employ three layer membranes, as the electrical, component, of the switch, they. Also usually, have a shorter, total, key travel distance, two millimeters, instead, of 3.5. To 4 millimeters, for, standard, dome switch key switches. This. Type of key switch is often found on the builts and keyboards, on laptops, and keyboards, marketed, as low-profile.
These. Keyboards. Are generally, quiet and the keys require, little force to press. Scissor. Switch keyboards, are typically, slightly, more expensive they. Are harder to clean due to the limited, movement, of the keys and their multiple, attachment, points but also less likely to get debris, in them as the gaps between the keys are often smaller as there is no need for extra room to allow for that wiggle in the key as typically, found on a membrane, keyboard. Topic. Capacitive. Keyboard. In, this type of keyboard pressing. A key changes. The capacitance, of a pattern of capacitor, pads, the. Pattern consists, of two D shaped capacitor. Pads for each switch printed, on a printed, circuit board PCB and. Covered, by a thin insulating. Film of solder, mask which acts as a dielectric. Despite. The sophistication. Of the concept, the mechanism, of capacitive, switching, is physically, simple, the. Movable, part ends with a flat foam element, about the size of an aspirin, tablet finished. With aluminum, foil. Opposite. The switch is a PCB. With the capacitor, pads, when. The key is pressed the, foil tightly, clings to the surface, of the PCB, forming. A daisy chain of two capacitors, between, contact, pads in itself separated. With thin solder, mask and thus, shorting. The. Contact, pads with an easily detectable, drop of capacitive, reactance, between them, usually. This permits a pulse or pulse train to be sensed, because. The switch doesn't have an actual electrical, contact, there is no de balancing, necessary. The. Keys do not need to be fully pressed to be actuated, which enables, some people to type faster. The. IBM, model F keyboard, is mechanical. Key design consisted. Of a buckling, spring over a capacitive. PCB. Similarly. To the later model, M keyboard that. Used a membrane, in place of the PCB, the. Most, known company, for their capacitive. Electrostatic. Switching, technology. Is top rack or a pan. Unfortunately. Though their products, are not available in, large parts, of the world. Topic. Mechanical. Switch keyboard. Each, key on a mechanical, switch keyboard. Contains, a complete switch underneath. Each. Switch, is composed, of a housing a spring, and a stem. Switches. Come in three variants, linear, with consistent, resistance tactile. With a non audible bump, and clicky a tactile, with an audible click. Depending. On the resistance of the spring the key requires, different amounts, of pressure to actuate, the. Shape of the stem varies, the actuation, distance. And travel distance, of the switch the amount of sound produced, by actuation. Can also be changed. Mechanical. Keyboards, allow for the removal and replacement of, keycaps. Mechanical. Keyboards, also, have a longer, lifespan than, membrane, or dome switch keyboards with, an expected, life span of 50 million clicks per switch for Cherry MX switches, while, switches, from razer have a rated, lifetime, of sixty million clicks per switch, the. Major current, mechanical, switch producer, is cherry Alps. Electric, a former, major producer. Ended, production in, the early 2000s. But helped style switches continued to be made by others companies, as may chess sheyang, men XM, Thai Hal APC, and who a G a K, others. Switch manufacturer. A gaturro n-- kai huey Cael Guyot, our Teemu, gree tech TTC. And Omron. Topic. Buckling. Spring, keyboard. Many. Typists, prefer buckling, spring keyboards, the, buckling, spring mechanism expired. U.s. patent, four million one hundred and eighteen thousand, six hundred and eleven atop, the switch is responsible. For the tactile, and aural response, of the keyboard. This. Mechanism controls. A small hammer that strikes a capacity, of or membrane, switch in, 1993. Two years after spawning Lexmark. IBM. Transferred, its keyboard operations. To the daughter company. New. Model M keyboards, continued, to be manufactured, for IBM, by Lexmark, until 1999.
When, Unicom purchased, the keyboard, technology. Today. New, buckling, spring keyboards, are manufactured. By uni Comp uni. Comp also repairs. Old IBM and, Lexmark, keyboards. Topic. Whole, effect, keyboard. Whole. Effect, keyboards. Use magnets, and Hall effect sensors. Instead of switches, with mechanical. Contacts. When. A key is depressed it moves a magnet, that is detected, by a solid-state, sensor. Because. They require, no physical. Contact, for actuation. Hall effect keyboards. Are extremely, reliable and, can accept millions, of key strokes before failing. They. Are used for ultra high reliability. Applications. Such as nuclear, power plants, aircraft, cockpits, and critical, industrial, environments. They. Can easily be made totally, waterproof and, can resist large amounts, of dust and contaminants. Because. A magnet, and sensor are required, for each key as well as custom, control electronics. They are expensive, to manufacture. Topic. Laser, projection, keyboard. A laser. Projection, device approximately. The size of a computer, mouse projects, the outline, of keyboard, keys onto a flat surface such as a table or desk, this. Type of keyboard is portable, enough to be easily used with PDAs, and cell phones and many models, have retractable. Cords and wireless, capabilities. However. Sudden, or accidental. Disruption, of the laser will register, unwanted, keystrokes. Also. If the laser malfunctions. The whole unit, becomes useless, unlike, conventional keyboards. Which can be used even if a variety, of parts, such as the key caps are removed. This. Type of Klee board can be frustrating. To use since it is susceptible to errors, even in the course of normal typing. And its complete, lack of tactile, feedback makes, it even less user-friendly, than, the lowest quality membrane. Keyboards. Topic. Roll, up keyboard. Keyboards. Made of flexible silicone, or polyurethane, materials. Can roll up in a moderately, tight bundle. Tightly. Folding, the keyboard, may damage the internal membrane, circuits, when, they are completely, sealed in rubber they are water resistant, like. Membrane, clay boards they are reported, to be very hard to get used to as there is little tactile, feedback and, silicone, will tend to attract, dirt dust and hair. Topic. Optical. Keyboard, technology. Also. Known as photo, optical, keyboard, light responsive. Keyboard, photoelectric. Keyboard, and optical, key actuation. Detection, technology. Optical. Keyboard, technology. Was introduced, in, 1962. By Harley, he Keltner for use in a typewriter, machine, with the purpose of reducing the noise generating. By actuating the typewriter, keys an. Optical. Keyboard, technology. Utilizes. Light emitting, devices and photo sensors, to optically, detect, actuated, keys. Most. Commonly, the emitters and sensors, are located at the perimeter, mounted, on a small, PCB, the, light. Is directed, from side to side of the keyboard interior. And it can only be blocked by the actuated. Keys. Most. Optical, keyboards. Require, at least two beams most commonly, a vertical, beam and a horizontal, beam to determine, the actuated, key, some. Optical keyboards. Use a special, key structure, that blocks the light in a certain pattern allowing. Only one beam per row of keys most commonly, a horizontal. Beam. The. Mechanism, of the optical, keyboard, is very simple, a light beam is sent from the emitter to the receiving, sensor, and the actuated, key blocks reflects, refract, Saur otherwise interacts.
With The beam resulting. In an identified. Key. Some. Earlier optical, keyboards, were limited, in their structure, and required special, casing, to block external, light no multi, key functionality, was supported, and the design was very limited to a thick rectangular. Case. The. Advantages. Of optical, keyboard, technology. Are that it offers a real waterproof, keyboard, resilient, to dust and liquids and it uses about 20%. PCB, volume, compared, with membrane, or dome switch keyboards, significantly. Reducing, electronic, waste. Additional. Advantages. Of optical, keyboard, technology. Over other keyboard, technologies. Such as Hall effect laser. Roll-up, and transparent. Keyboards, line cost Hall effect keyboard. And feel optical, keyboard, technology. Does not require, different key mechanisms, and tactile, feel of typing, has remained the same for over 60, years. The. Specialist, data hand keyboard, uses, optical technology. To sense key presses with a single, light beam and sensor, per key, the. Keys are held in their rest position by, magnets, when the magnetic, force is overcome, to press a key the optical, path is unblocked, and the key press is registered. Topic. Debouncing. When, striking a keyboard, key the key oscillates, or bounces, against, its contact, several, times before settling. When. Released, it oscillates, again until it reverts to its rest state. Although. It happens on such a small scale as to be invisible to, the naked eye, it's sufficient, for the computer, to register, multiple keystrokes. Inadvertently. To. Resolve this problem the processor, in a keyboard D. Bounces, the. Keystrokes, by aggregating, them across time to produce one confirmed. Keystroke. That usually, corresponds. To what is typically, a solid, contact. Early. Membrane. Keyboards, had limited, typing, speed because they had to do significant. - bouncing, this. Was a noticeable, problem, on the zx81. Topic. Keycaps. Key. Caps are used on full travel keyboards. While, modern key caps are typically surface, printed, they can also be double, shot molded laser printed, sublimation. Printed, engraved, or they can be made of transparent material with, printed, paper inserts. There. Are also clear, caps which are thin shells that are placed over key bases, these. Were used on IBM, PC, keyboards. Topic. Other parts. Of the PC, keyboard. The. Modern PC, keyboard, also includes, a control processor, and indicator, lights to provide feedback to the user about what state the keyboard, is in. Depending. On the sophistication of. The controller's programming, the keyboard, may also offer other special, features, the. Processor, is usually, a single, chip, 8048. Microcontroller. Variant. The. Keyboard, switch matrix is wired to its input and it processes the incoming, keystrokes, and sends the results, down a serial, cable, the keyboard, cord to a receiver, in the main computer, box, it. Also controls. The illumination. Of the caps, lock num. Lock and. Scroll. Lock lights. A. Common. Test for whether the computer has crashed is pressing, the caps. Lock key. The, keyboard, sends, the key code to the keyboard, driver running, in the main computer, if the main computer, is operating, it commands, the light to turn on, all. The other indicator, lights work in a similar way the. Keyboard, driver also, tracks the shift alt and control, state of the keyboard. Topic. Keyboards. Switch matrix. The. Keyboard, switch matrix is often drawn with horizontal, wires and vertical, wires in a grid which is called a matrix circuit. It. Has a switch at some or all intersections.
Much Like a multiplex. Display. Almost. All keyboards, have only the switch at each intersection which, causes, ghost. Keys and. Key. Jamming, when. Multiple, keys are pressed roll over certain. Often, more expensive keyboards. Have a diode between each intersection, allowing. The keyboard, microcontroller. To accurately, sense any number of simultaneous keys. Being pressed without generating, erroneous. Ghost keys. Topic. C also. List, of mechanical. Keyboards.