|
Detent
A detent is a mechanical or magnetic means to resist or arrest the movement of a mechanical device. Such a device can be anything ranging from a simple metal pin to a machine. The term is also used for the method involved. Magnetic detents are most often used to divide a shaft rotation into discrete increments. Magnetic detents are inherent in some types of electric motors, most often stepper motors. Mechanics Arresting movement Ratchet and pawl The ratchet-and-pawl design arrests movements by employing a small gravity- or spring-actuated lever paired with a notched wheel. The lever is mounted on a pivot point in proximity to the wheel. The vertical angle of the sides of the notches that face the direction that rotation is desired is generally very acute (45 degrees or less), so that as the wheel rotates in that direction, the end of the lever is easily lifted or pushed out and over the top of a notch. Following this, the lever drops into the next notch and the next et cet ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ball Detent
A ball detent is a simple mechanical arrangement used to hold a moving part in a temporarily fixed position relative to another part. Usually the moving parts slide with respect to each other, or one part rotates within the other. The ball is a single, usually metal sphere, sliding within a bored cylinder, against the pressure of a spring, which pushes the ball against the other part of the mechanism, which carries the detent - which can be as simple as a hole of smaller diameter than the ball. When the hole is in line with the cylinder, the ball is partially pushed into the hole under spring pressure, holding the parts at that position. Additional force applied to the moving parts will compressing the spring, causing the ball to be depressed back into its cylinder, and allowing the parts to move to another position. Applications Ball detents are commonly found in the selector mechanism of a gearbox, holding the selector rods in the correct position to engage the desired gear. O ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ball Detent
A ball detent is a simple mechanical arrangement used to hold a moving part in a temporarily fixed position relative to another part. Usually the moving parts slide with respect to each other, or one part rotates within the other. The ball is a single, usually metal sphere, sliding within a bored cylinder, against the pressure of a spring, which pushes the ball against the other part of the mechanism, which carries the detent - which can be as simple as a hole of smaller diameter than the ball. When the hole is in line with the cylinder, the ball is partially pushed into the hole under spring pressure, holding the parts at that position. Additional force applied to the moving parts will compressing the spring, causing the ball to be depressed back into its cylinder, and allowing the parts to move to another position. Applications Ball detents are commonly found in the selector mechanism of a gearbox, holding the selector rods in the correct position to engage the desired gear. O ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Stepper Motor
A stepper motor, also known as step motor or stepping motor, is a brushless DC electric motor that divides a full rotation into a number of equal steps. The motor's position can be commanded to move and hold at one of these steps without any position sensor for feedback (an open-loop controller), as long as the motor is correctly sized to the application in respect to torque and speed. Switched reluctance motors are very large stepping motors with a reduced pole count, and generally are closed-loop commutated. Mechanism Brushed DC motors rotate continuously when DC voltage is applied to their terminals. The stepper motor is known for its property of converting a train of input pulses (typically square waves) into a precisely defined increment in the shaft’s rotational position. Each pulse rotates the shaft through a fixed angle. Stepper motors effectively have multiple "toothed" electromagnets arranged as a stator around a central rotor, a gear-shaped piece of iron. The e ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Stepper Motor
A stepper motor, also known as step motor or stepping motor, is a brushless DC electric motor that divides a full rotation into a number of equal steps. The motor's position can be commanded to move and hold at one of these steps without any position sensor for feedback (an open-loop controller), as long as the motor is correctly sized to the application in respect to torque and speed. Switched reluctance motors are very large stepping motors with a reduced pole count, and generally are closed-loop commutated. Mechanism Brushed DC motors rotate continuously when DC voltage is applied to their terminals. The stepper motor is known for its property of converting a train of input pulses (typically square waves) into a precisely defined increment in the shaft’s rotational position. Each pulse rotates the shaft through a fixed angle. Stepper motors effectively have multiple "toothed" electromagnets arranged as a stator around a central rotor, a gear-shaped piece of iron. The e ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Scroll Wheel
A scroll wheel is a wheel used for scrolling. The term usually refers to such wheels found on computer mice (where they can also be called a mouse wheel). It is often made of hard plastic with a rubbery surface, centred around an internal rotary encoder. It is usually located between the left and right mouse buttons and is positioned perpendicular to the mouse surface. Sometimes the wheel can be pressed left and right, which is actually just two additional macros buttons. Functionality The scroll wheel is placed horizontally between the mouse buttons and commonly uses vertical scrolling, wherein rolling the wheel from the bottom side to the top is known as scrolling "upward" or "forward", while the reverse, i.e. rolling the wheel from the top side to the bottom, is known as scrolling "downward" or "backward". In a graphical user interface, the "upward" motion moves contents of the window downward (and the scrollbar thumb, if present, upward), and vice versa. In other confi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rotary Switch
A rotary switch is a switch operated by rotation. These are often chosen when more than 2 positions are needed, such as a three-speed fan or a CB radio with multiple frequencies of reception or "channels". A rotary switch consists of a spindle or "rotor" that has a contact arm or "spoke" which projects from its surface like a cam. It has an array of terminals, arranged in a circle around the rotor, each of which serves as a contact for the "spoke" through which any one of a number of different electrical circuits can be connected to the rotor. The switch is layered to allow the use of multiple poles; each layer is equivalent to one pole. Alternatively the rotation can be limited to a fraction (half; third etc.) of a circle and then each layer can have multiple (two; three etc.) poles. Usually, such a switch has a detent mechanism so it "clicks" from one active position to another rather than stalls in an intermediate position. Thus a rotary switch provides greater pole and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ratchet (device)
A ratchet (occasionally spelled rachet) is a mechanical device that allows continuous linear or rotary motion in only one direction while preventing motion in the opposite direction. Ratchets are widely used in machinery and tools. The word ''ratchet'' is also used informally to refer to a ratcheting socket wrench. __TOC__ Theory of operation A ratchet consists of a round gear or a linear rack with teeth, and a pivoting, spring-loaded finger called a '' pawl'' (or ''click'', in clocks and watches) that engages the teeth. The teeth are uniform but are usually asymmetrical, with each tooth having a moderate slope on one edge and a much steeper slope on the other edge. When the teeth are moving in the unrestricted (i.e. forward) direction, the pawl easily slides up and over the gently sloped edges of the teeth, with a spring forcing it (often with an audible 'click') into the depression between the teeth as it passes the tip of each tooth. When the teeth move in the opposite ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Game Show
A game show is a genre of broadcast viewing entertainment (radio, television, internet, stage or other) where contestants compete for a reward. These programs can either be participatory or demonstrative and are typically directed by a host, sharing the rules of the program as well as commentating and narrating where necessary. The history of game shows dates back to the invention of television as a medium. On most game shows, contestants either have to answer questions or solve puzzles, typically to win either money or prizes. Game shows often reward players with prizes such as cash, trips and goods and services provided by the show's sponsor. History 1930s–1950s Game shows began to appear on radio and television in the late 1930s. The first television game show, '' Spelling Bee'', as well as the first radio game show, '' Information Please'', were both broadcast in 1938; the first major success in the game show genre was ''Dr. I.Q.'', a radio quiz show that began in 193 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Camera
A camera is an optical instrument that can capture an image. Most cameras can capture 2D images, with some more advanced models being able to capture 3D images. At a basic level, most cameras consist of sealed boxes (the camera body), with a small hole (the aperture) that allows light to pass through in order to capture an image on a light-sensitive surface (usually a digital sensor or photographic film). Cameras have various mechanisms to control how the light falls onto the light-sensitive surface. Lenses focus the light entering the camera, and the aperture can be narrowed or widened. A shutter mechanism determines the amount of time the photosensitive surface is exposed to the light. The still image camera is the main instrument in the art of photography. Captured images may be reproduced later as part of the process of photography, digital imaging, or photographic printing. Similar artistic fields in the moving-image camera domain are film, videography, and cinematog ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Shutter (photography)
In photography, a shutter is a device that allows light to pass for a determined period, exposing photographic film or a photosensitive digital sensor to light in order to capture a permanent image of a scene. A shutter can also be used to allow pulses of light to pass outwards, as seen in a movie projector or a signal lamp. A shutter of variable speed is used to control exposure time of the film. The shutter is constructed so that it automatically closes after a certain required time interval. The speed of the shutter is controlled by a ring outside the camera, on which various timings are marked. Camera shutter Camera shutters can be fitted in several positions: * Leaf shutters are usually fitted within a lens assembly (''central shutter''), or more rarely immediately behind (''behind-the-lens shutter'') or, even more rarely, in front of a lens, and shut off the beam of light where it is narrow. * Focal-plane shutters are mounted near the focal plane and move to uncover the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Computer Mouse
A computer mouse (plural mice, sometimes mouses) is a hand-held pointing device that detects two-dimensional motion relative to a surface. This motion is typically translated into the motion of a pointer on a display, which allows a smooth control of the graphical user interface of a computer. The first public demonstration of a mouse controlling a computer system was in 1968. Mice originally used two separate wheels to track movement across a surface: one in the X-dimension and one in the Y. Later, the standard design shifted to utilize a ball rolling on a surface to detect motion. Most modern mice use optical sensors that have no moving parts. Though originally all mice were connected to a computer by a cable, many modern mice are cordless, relying on short-range radio communication with the connected system. In addition to moving a cursor, computer mice have one or more buttons to allow operations such as the selection of a menu item on a display. Mice often also featur ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Screw
A screw and a bolt (see '' Differentiation between bolt and screw'' below) are similar types of fastener typically made of metal and characterized by a helical ridge, called a ''male thread'' (external thread). Screws and bolts are used to fasten materials by the engagement of the screw thread with a similar ''female thread'' (internal thread) in a matching part. Screws are often self-threading (also known as self-tapping) where the thread cuts into the material when the screw is turned, creating an internal thread that helps pull fastened materials together and prevents pull-out. There are many screws for a variety of materials; materials commonly fastened by screws include wood, sheet metal, and plastic. Explanation A screw is a combination of simple machines: it is, in essence, an inclined plane wrapped around a central shaft, but the inclined plane (thread) also comes to a sharp edge around the outside, which acts as a wedge as it pushes into the fastened material, and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
