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Mouse - Input Device

Input Device

Tracy Pettigrue
Tracy Pettigrue
Oct 3, 2009
0 Comments | 2210 Views | 21 Hits


Mouse

Definition: Mouse, is a common pointing device, popularized by its inclusion as standard equipment with the Apple Macintosh.

The mouse is a small hand-operated device which is moved over a surface. It is a relative pointing device because there are no defined limits to the mouse's movement and because its placement on a surface does not map directly to a specific screen location.

The main goal of any mouse is to translate the motion of our hand into signals that the computer can use.

Mouse Types:

1 Mechanical

2. Optical.

Mechanical Mouse, in computer science, a type of mouse in which the motion of a ball on the bottom of the mouse is translated into directional signals. As the user moves the mouse, the ball typically spins a pair of wheels inside the mouse. These conductive wheels might, in turn, rotate additional wheels via axles or gears. At least one pair of wheels has conductive markings on their surface. Because the markings permit an electric current to flow, a set of conductive brushes that ride on the surface of the conductive wheels can detect the conductive markings. The electronics in the mouse translate these electrical-movement signals into mouse-movement information that can be used by the computer.

Optical mouse have no rolling parts, and therefore they do not normally require maintenance other than removing debris that might collect under the light-emitter. However, they generally cannot track on glossy and transparent surfaces, including some mouse-pads, sometimes causing the cursor to drift at random during operation.

Optical Mouse, in computer science, a type of mouse that uses a pair of light-emitting diodes (LEDs) and a special reflective grid pad to detect motion. The two lights are of different colors, and the special mouse pad has a grid of lines in the same colors, one color for vertical lines and another for horizontal lines. Light detectors paired with the LEDs sense when a colored light passes over a line of the same color, indicating the direction of the movement.
 

Sources:

A) Software: Microsoft Encarta 2004

B) Internet Websites: 1) http://www.wikipedia.com & 2) http://www.inventors.about.com

C) Book: ‘Computer Peripherals’ by Barry M. Cook and Neil H. White

 

Scanner

Definition:

Scanner is device that can read text or illustrations printed on paper and translate the information into a form the computer can use. It can take image and automatically transform it into a digital bitmap.

Scanner Types:

1. Flatbed scanners

2. Sheet-fed scanners

3. Handheld scanners

4. Drum scanners

Scanners differ from one another in the following respects:

* Scanning technology:

Most scanners use charge-coupled device (CCD) arrays, which consist of tightly packed rows of light receptors that can detect variations in light intensity and frequency. The quality of the CCD array is probably the single most important factor affecting the quality of the scanner.

* Resolution:

The denser the bit map, the higher the resolution. Typically, scanners support resolutions of from 72 to 600 dpi.

Bit depth:

The number of bits used to represent each pixel. The greater the bit depth, the more colors or grayscales can be represented.

Size and shape:

Some scanners are small hand-held devices that you move across the paper. These hand-held scanners are often called half-page scanners because they can only scan 2 to 5 inches at a time.


Sources:

A) Software: Microsoft Encarta 2004

B) Internet Websites: 1) http://www.wikipedia.com & 2) http://www.inventors.about.com

C) Book: ‘Computer Peripherals’ by Barry M. Cook and Neil H. White

 

Joystick

Definition:

Joystick, in computer science, a popular pointing device, used mostly for playing computer games but used for other tasks as well. It can be used to control the position of an onscreen cursor.

Types:

1. Analog
2. Digital

Basic idea:

A joystick usually has a square or rectangular plastic base to which is attached a vertical stem. Control buttons are located on the base and sometimes on top of the stem. The stem can be moved Omni directionally to control the movement of an object on the screen. The buttons activate various software features, generally producing on-screen events. The movement of the stick is used to give a direction and the size of the movement is used to control the speed that the cursor moves. In this manner accurate positioning is possible.

Additionally joysticks often have one or more fire buttons, used to trigger some kind of action. These are simple on/off switches.

Some joysticks have force feedback capability. These are thus active devices, not just simple input devices. The computer can return a signal to the joystick that causes it to resist the movement with a returning force or make the joystick vibrate.

Working principle:

In order to communicate a full range of motion to the computer, a joystick needs to measure the stick's position on two axes -- the X-axis (left to right) and the Y-axis (up and down).

In the standard joystick design, the handle moves a narrow rod that sits in two rotatable, slotted shafts. Tilting the stick forward and backward pivots the Y-axis shaft from side to side. Tilting it left to right pivots the X-axis shaft. When the stick is moved diagonally, it pivots both shafts. Several springs center the stick when it is let go of it. To determine the location of the stick, the joystick control system simply monitors the position of each shaft. The conventional analog joystick design does this with two potentiometers, or variable resistors.
 

Sources:

A) Software: Microsoft Encarta 2004

B) Internet Websites: 1) http://www.wikipedia.com & 2) http://www.inventors.about.com

C) Book: ‘Computer Peripherals’ by Barry M. Cook and Neil H. White 

 

Barcode reader

Definition:

A barcode reader (or barcode scanner) is a computer peripheral for reading barcodes printed on various surfaces.

Types of Barcode readers:

1. Pen type readers,
2. Laser scanners,
3. CCD readers and
4. Camera-based readers.

Working Principle:

Pen type readers:

They consist of a light source and a photo diode that are placed next to each other in the tip of a pen or wand. To read a bar code, you drag the tip of the pen across all the bars in a steady even motion. The photo diode measures the intensity of the light reflected back from the light source and generates a waveform that is used to measure the widths of the bars and spaces in the bar code. Dark bars in the bar code absorb light and white spaces reflect light so that the voltage waveform generated by the photo diode is an exact duplicate of the bar and space pattern in the bar code.

Laser scanners:

They work the same way as pen type readers except that they use a laser beam as the light source and typically employ either a reciprocating mirror or a rotating prism to scan the laser beam back and forth across the bar code.

CCD Readers

CCD (Charge Coupled Device) readers use an array of hundreds of tiny light sensors lined up in a row in the head of the reader. Each sensor can be thought of as a single photo diode that measures the intensity of the light immediately in front of it. Each individual light sensor in the CCD reader is extremely small and because there are hundreds of sensors lined up in a row, a voltage pattern identical to the pattern in a bar code is generated in the reader by sequentially measuring the voltages across each sensor in the row.

Camera-Based Readers

It uses a small video camera to capture an image of a bar code. The reader then uses sophisticated digital image processing techniques to decode the bar code. Video cameras use the same CCD technology as in a CCD bar code reader except that instead of having a single row of sensors, a video camera has hundreds of rows of sensors arranged in a two dimensional array so that they can generate an image.
 

Sources:

A) Software: Microsoft Encarta 2004

B) Internet Websites: 1) http://www.wikipedia.com & 2) http://www.inventors.about.com

C) Book: ‘Computer Peripherals’ by Barry M. Cook and Neil H. White

 

Webcam

Definition:

A web camera (or webcam) is a real-time camera whose images can be accessed using the World Wide Web, instant messaging, or a PC video calling application.

A simple Webcam setup consists of a digital camera attached to the computer, typically through the USB port. The camera part of the Webcam setup is just a digital camera. The "Webcam" nature of the camera comes with the software. Webcam software captures a frame from the digital camera at a preset interval and transfers it to another location for viewing.

Use:

1. Videoconferencing
2. Video security
3. Games
4. Other applications

Construction:

Webcams typically include a lens, an image sensor, and some support electronics. Various lenses are available, the most common being a plastic lens that can be screwed in and out to set the camera's focus. Image sensors can be CMOS or CCD, the former being dominant for low-cost cameras, but CCD cameras do not necessarily outperform CMOS-based cameras in the low cost price range. Consumer webcams usually offer a resolution in the VGA region, at a rate of around 25 frames per second. The higher resolution of 1.3 Megapixel is also available from the brands Microsoft, Kinamax, Sabrent, Logitech, Vije, and HP.

Sources:

A) Software: Microsoft Encarta 2004

B) Internet Websites: 1) http://www.wikipedia.com & 2) http://www.inventors.about.com

C) Book: ‘Computer Peripherals’ by Barry M. Cook and Neil H. White

 

Touch Screen:

Definition:

A touch screen is a computer display screen that is sensitive to human touch, allowing a user to interact with the computer by touching pictures or words on the screen. Touch screens are used with information kiosks, computer-based training devices, and systems designed to help individuals who have difficulty manipulating a mouse or keyboard.

Typical construction:

A touch screen kit includes a touch screen panel, a controller, and a software driver. The touch screen panel is a clear panel attached externally to the monitor that plugs into a serial or Universal Serial Bus (USB) port or a bus card installed inside the computer. The touch screen panel registers touch events and passes these signals to the controller. The controller then processes the signals and sends the data to the processor. The software driver translates touch events into mouse events.

Technologies Available:

Resistive: A resistive touch screen panel is coated with a thin metallic electrically conductive and resistive layer that causes a change in the electrical current which is registered as a touch event and sent to the controller for processing.

Surface wave: Surface wave technology uses ultrasonic waves that pass over the touch screen panel. When the panel is touched, a portion of the wave is absorbed. This change in the ultrasonic waves registers the position of the touch event and sends this information to the controller for processing.

Capacitive: A capacitive touch screen panel is coated with a material that stores electrical charges. When the panel is touched, a small amount of charge is drawn to the point of contact. Circuits located at each corner of the panel measure the charge and send the information to the controller for processing. Capacitive touch screen panels must be touched with a finger unlike resistive and surface wave panels that can use fingers and stylus.
 

Sources:

A) Software: Microsoft Encarta 2004

B) Internet Websites: 1) http://www.wikipedia.com & 2) http://www.inventors.about.com

C) Book: ‘Computer Peripherals’ by Barry M. Cook and Neil H. White

 

Microphone:

Definition:

A microphone takes varying pressure waves in the air and converts them into varying electrical signals. It is a device made to capture waves in air, water or hard material and translate them to an electrical signal. Most microphones in use today for audio use electromagnetic generation (dynamic microphones), capacitance change (condenser microphones) or piezoelectric generation to produce the signal from mechanical vibration.

Types of microphone technology:

CONDENSER MICROPHONE: In a condenser microphone, also known as a capacitor microphone, the diaphragm acts as one plate of a capacitor, and the vibrations produce changes in the distance between the plates.

DYNAMIC MICROPHONES work via electromagnetic induction. They are robust, relatively inexpensive, and resistant to moisture, and for this reason they are widely used on-stage by singers. Dynamic microphones are velocity receivers.

A CARBON MICROPHONE, formerly used in telephone handsets, is a capsule containing carbon granules pressed between two metal plates. A voltage is applied across the metal plates, causing a small current to flow through the carbon. One of the plates, the diaphragm, vibrates in sympathy with incident sound waves, applying a varying pressure to the carbon.

A PIEZO MICROPHONE uses the phenomenon of piezoelectricity—the ability of some materials to produce a voltage when subjected to pressure—to convert vibrations into an electrical signal. An example of this is Rochelle salt (potassium sodium tartrate), which is a piezoelectric crystal that works as a transducer, both as a microphone and as a slimline loudspeaker component.

A LASER MICROPHONE is an exotic application of laser technology. It consists of a laser beam that must be reflected off a glass window or another rigid surface that vibrates in sympathy with nearby sounds. This device essentially turns any vibrating surface near the source of sound into a microphone.

LIQUID MICROPHONE: The liquid transmitter consisted of a metal cup filled with dilute sulfuric acid. A sound wave caused the diaphragm to move, forcing a brass tube to move up and down in the liquid. The electrical resistance between the wire and the cup was then inversely proportional to the length of wire submerged. Elisha Gray filed a patent for a version using a needle instead of the brass tube.

The MEMS MICROPHONE is also called a digital microphone, microphone chip or silicon microphone, since the output is already in digital form and originates from an IC. The pressure-sensitive diaphragm is etched directly on a silicon chip by MEMS techniques, and is usually accompanied with integrated preamplifier and ADC on the same CMOS chip.
 

Sources:

A) Software: Microsoft Encarta 2004

B) Internet Websites: 1) http://www.wikipedia.com & 2) http://www.inventors.about.com

C) Book: ‘Computer Peripherals’ by Barry M. Cook and Neil H. White


Light pen:

Definition:

A small, photosensitive device connected to a computer and moved by hand over an output display in order to manipulate information in the computer.

A light-sensitive stylus wired to a video terminal used to draw pictures or select menu options. The user brings the pen to the desired point on screen and presses the pen button to make contact. Contrary to what it looks like, the pen does not shine light onto the screen; rather, the screen beams into the pen. Screen pixels are constantly being refreshed. When the user presses the button, the pen senses light, and the pixel being illuminated at that instant identifies the screen location.

Light pens have the advantage of 'drawing' directly onto the screen, but this can become uncomfortable, and they are not as accurate as digitising tablets.

Working Principle:

The light pen works by sensing the sudden small change in brightness of a point on the screen when the electron gun refreshes that spot. By noting exactly where the scanning has reached at that moment, the X,Y position of the pen can be resolved. This is usually achieved by the light pen causing an interrupt, at which point the scan position can be read from a special register, or computed, from a counter or timer. The pen position is updated on every refresh of the screen.
 

Sources:

A) Software: Microsoft Encarta 2004

B) Internet Websites: 1) http://www.wikipedia.com & 2) http://www.inventors.about.com

C) Book: ‘Computer Peripherals’ by Barry M. Cook and Neil H. White 

 

Digitizer:

Definition:

A digitizer is a device for manual digitizing. Documents can be attached to the flat surface that it consists of, and a cursor or puck that is used to locate and input map features into the computer. It is a device for entering the spatial coordinates of mapped features from a map or document to the computer.

Types:

1. Digitizing Table
2. Digitizing Tablet

Description:

Digitizing Table:

A device consisting of a table and a cursor (often with crosshairs and keys) that is used for capturing and recording the locations of map features as x,y Cartesian coordinates. It is a table with an electronic grid and equipped with a cursor. It could trace (digitize) a paper maps and convert it into a GIS data.

We can use existing maps as inputs by tracing contour lines on a digitizing tablet or table. The data are organized into cell arrays whose X-Y positions in the rectangular grid are related to map coordinates.

Digitizing Tablet:

It is graphics drawing tablet used for sketching new images or tracing old ones. Also called a "graphics tablet," the user contacts the surface of the device with a wired or wireless pen or puck. Most tablets allow parts of the tablet surface to be customized into buttons that can be tapped to select menus and functions in the application. When drawing or tracing on the tablet, a series of x-y coordinates (vector graphics) are created, either as a continuous stream of coordinates, or as end points. Drawings created or traced on tablets are stored as mathematical line segments. Objects are drawn with a pen or puck, but are traced with the puck.

Sources:

A) Software: Microsoft Encarta 2004

B) Internet Websites: 1) http://www.wikipedia.com & 2) http://www.inventors.about.com

C) Book: ‘Computer Peripherals’ by Barry M. Cook and Neil H. White

Author's note: Hope it will be useul for students who are studying Computer Science And Engineering at their early stages
Keywords: Hope it will be useul for students who are studying Computer Science And Engineering at their early stages



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