|
Alphanumeric Keyboard
The technology of computer keyboards includes many elements. Among the more important of these is 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). Virtual keyboards on touch screens have no physical switches and provide audio and haptic feedback instead. Some newer keyboard models use hybrids of various technologies to achieve greater cost savings or better ergonomics. The modern keyboard also includes a control processor and indicator lights to provide feedback to the user (and to the central processor) about what state the keyboard is in. Plug and play technology means that its 'out of the box' layout can be notified to the system, making the keyboard immediately ready to use without need for further ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Keyboard Construction
{{disambiguati ...
Keyboard may refer to: Text input * Keyboard, part of a typewriter * Computer keyboard ** Keyboard layout, the software control of computer keyboards and their mapping ** Keyboard technology, computer keyboard hardware and firmware Music * Musical keyboard, a set of adjacent keys or levers used to play a musical instrument ** Manual (music), a keyboard played with hands, as opposed to; ** Pedalboard or pedal keyboard, played with feet ** Enharmonic keyboard, one of several layouts that incorporate more than 12 tones per octave * Keyboard instrument, a musical instrument played using a keyboard ** Synthesizer, an electronic keyboard ** Electronic keyboard, a synthesizer See also * Input method * Keypad A keypad is a block or pad of buttons set with an arrangement of digits, symbols, or alphabetical letters. Pads mostly containing numbers and used with computers are numeric keypads. Keypads are found on devices which require mainly numeric inp ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Membrane Keyboard
A membrane keyboard is a computer keyboard whose "keys" are not separate, moving parts, as with the majority of other keyboards, but rather are pressure pads that have only outlines and symbols printed on a flat, flexible surface. Very little, if any, tactile feedback is felt when using such a keyboard. Membrane keyboards work by electrical contact between the keyboard surface and the underlying circuits when keytop areas are pressed. These models were used with some early 1980s home computers, enjoying wide adoption in consumer electronics devices. The keyboards are quite inexpensive to mass-produce, and are more resistant against dirt and liquids than most other keyboards. However, due to a low or non-existent tactile feedback, most people have difficulty typing with them, especially when larger numbers of characters are being typed. Chiclet keyboards were a slight improvement, at least allowing individual keys to be felt to some extent. Aside from early hobbyist/kit/home c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Contact Pad
Contact pads or bond pads are designated surface areas of a printed circuit board (PCB) or die of an integrated circuit. Possibilities to contact to pads include soldering, wirebonding, flip chip Flip chip, also known as controlled collapse chip connection or its abbreviation, C4, is a method for interconnecting dies such as semiconductor devices, IC chips, integrated passive devices and microelectromechanical systems (MEMS), to exter ... mounting, or probe needles. Further reading *Kraig Mitzner, ''Complete PCB Design Using OrCAD Capture and PCB Editor'', Newnes, 2009 . *Jing Li, ''Evaluation and Improvement of the Robustness of a PCB Pad in a Lead-free Environment'', ProQuest, 2007 . *Deborah Lea, Fredirikus Jonck, Christopher Hunt, ''Solderability Measurements of PCB Pad Finishes and Geometries'', National Physical Laboratory, 2001 . Electronic engineering Printed circuit board manufacturing {{Electronics-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Series Circuits
Two-terminal components and electrical networks can be connected in series or parallel. The resulting electrical network will have two terminals, and itself can participate in a series or parallel topology. Whether a two-terminal "object" is an electrical component (e.g. a resistor) or an electrical network (e.g. resistors in series) is a matter of perspective. This article will use "component" to refer to a two-terminal "object" that participate in the series/parallel networks. Components connected in series are connected along a single "electrical path", and each component has the same current through it, equal to the current through the network. The voltage across the network is equal to the sum of the voltages across each component. Components connected in parallel are connected along multiple paths, and each component has the same voltage across it, equal to the voltage across the network. The current through the network is equal to the sum of the currents through each c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tablet (pharmacy)
A tablet (also known as a pill) is a pharmaceutical oral dosage form (''oral solid dosage'', or OSD) or solid unit dosage form. Tablets may be defined as the solid unit dosage form of medicament or medicaments with suitable excipients. It comprises a mixture of active substances and excipients, usually in powder form, pressed or compacted from a powder into a solid dose. Tablets are prepared either by molding or by compression. The excipients can include diluents, binders or granulating agents, glidants (flow aids) and lubricants to ensure efficient tabletting; disintegrants to promote tablet break-up in the digestive tract; sweeteners or flavours to enhance taste; and pigments to make the tablets visually attractive or aid in visual identification of an unknown tablet. A polymer coating is often applied to make the tablet smoother and easier to swallow, to control the release rate of the active ingredient, to make it more resistant to the environment (extending its shel ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dielectric
In electromagnetism, a dielectric (or dielectric medium) is an electrical insulator that can be polarised by an applied electric field. When a dielectric material is placed in an electric field, electric charges do not flow through the material as they do in an electrical conductor, because they have no loosely bound, or free, electrons that may drift through the material, but instead they shift, only slightly, from their average equilibrium positions, causing dielectric polarisation. Because of dielectric polarisation, positive charges are displaced in the direction of the field and negative charges shift in the direction opposite to the field (for example, if the field is moving parallel to the positive ''x'' axis, the negative charges will shift in the negative ''x'' direction). This creates an internal electric field that reduces the overall field within the dielectric itself. If a dielectric is composed of weakly bonded molecules, those molecules not only become pol ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Soldermask
Solder mask, solder stop mask or solder resist is a thin lacquer-like layer of polymer that is usually applied to the copper traces of a printed circuit board (PCB) for protection against oxidation and to prevent solder bridges from forming between closely spaced solder pads. A solder bridge is an unintended electrical connection between two conductors by means of a small blob of solder. PCBs use solder masks to prevent this from happening. Solder mask is not always used for hand soldered assemblies, but is essential for mass-produced boards that are soldered automatically using reflow or wave soldering techniques. Once applied, openings must be made in the solder mask wherever components are soldered, which is accomplished using photolithography. Solder mask is traditionally green, but is also available in many other colors. Solder mask comes in different media depending upon the demands of the application. The lowest-cost solder mask is epoxy liquid that is silkscre ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Printed Circuit Board
A printed circuit board (PCB; also printed wiring board or PWB) is a medium used in electrical and electronic engineering to connect electronic components to one another in a controlled manner. It takes the form of a laminated sandwich structure of conductive and insulating layers: each of the conductive layers is designed with an artwork pattern of traces, planes and other features (similar to wires on a flat surface) etched from one or more sheet layers of copper laminated onto and/or between sheet layers of a non-conductive substrate. Electrical components may be fixed to conductive pads on the outer layers in the shape designed to accept the component's terminals, generally by means of soldering, to both electrically connect and mechanically fasten them to it. Another manufacturing process adds vias: plated-through holes that allow interconnections between layers. Printed circuit boards are used in nearly all electronic products. Alternatives to PCBs include wire ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Canada
Canada is a country in North America. Its ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, covering over , making it the world's second-largest country by total area. Its southern and western border with the United States, stretching , is the world's longest binational land border. Canada's capital is Ottawa, and its three largest metropolitan areas are Toronto, Montreal, and Vancouver. Indigenous peoples have continuously inhabited what is now Canada for thousands of years. Beginning in the 16th century, British and French expeditions explored and later settled along the Atlantic coast. As a consequence of various armed conflicts, France ceded nearly all of its colonies in North America in 1763. In 1867, with the union of three British North American colonies through Confederation, Canada was formed as a federal dominion of four provinces. This began an accretion of provinces ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Keycap
A keycap is a small cover of plastic, metal, or other material placed over the keyswitch of a computer keyboard. Keycaps are often illustrated to indicate the key function or alphanumeric character they correspond to. Early keyboards were manufactured with the keyswitch and keycap integrated in ''one'' unit; keycaps ''separate'' from the switch were introduced to facilitate the production of different keyboard ''layout''s. History Typical keycaps in the 1970s and 1980s were produced using two-shot molding, with the markings molded into each keycap in a different color of plastic. This eventually fell out of favor, as it was more expensive (particularly in tooling costs), and tended to produce keycaps more durable than the equipment on which they were mounted. Modern keycaps are usually labelled by stamping or laser engraving. However, two-shot molding ("doubleshot") keycaps are still available today, known for their feel and general durability. Modern keycaps Keycaps can ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Scissors Mechanism
A scissors mechanism uses linked, folding supports in a criss-cross 'X' pattern. Workings Extension is achieved by applying pressure to the outside of a set of supports located at one end of the mechanism, elongating the crossing pattern. This can be achieved through hydraulic, pneumatic, mechanical or simply muscular means. It may require no power to return to its original position, but simply a release of the original pressure. Also used in kinematics of mechanisms Uses This mechanism is used in devices such as lift tables and scissor lifts. Modern low-profile computer keyboards make an extensive use of it as well, installing each key on a scissor support to ensure their smooth vertical movement, allowing the use of a cheap and reliable rubber dome contact set, instead of expensive and complex array of mechanical switches. See also * Pantograph * Telescopic cylinder * Linear actuator A linear actuator is an actuator that creates motion in a straight line, in contras ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Scissor Switch Mechanism
Scissors are hand-operated shearing tools. A pair of scissors consists of a pair of metal blades pivoted so that the sharpened edges slide against each other when the handles (bows) opposite to the pivot are closed. Scissors are used for cutting various thin materials, such as paper, cardboard, metal foil, cloth, rope, and wire. A large variety of scissors and shears all exist for specialized purposes. Hair-cutting shears and kitchen shears are functionally equivalent to scissors, but the larger implements tend to be called shears. Hair-cutting shears have specific blade angles ideal for cutting hair. Using the incorrect type of scissors to cut hair will result in increased damage or split ends, or both, by breaking the hair. Kitchen shears, also known as kitchen scissors, are intended for cutting and trimming foods such as meats. Inexpensive, mass-produced modern scissors are often designed ergonomically with composite thermoplastic and rubber handles. Terminology The ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
