[standard 101-key keyboard]
A computer keyboard contains an array of switches, which each sends the PC a signal when pressed. This is the most basic input device. A necessity for every PC.
[daryl shows how to operate an optical mouse]
The most common mouse used today is opto-electronic. Its ball is steel for
weight and rubber-coated for grip, and as it rotates it drives two rollers,
one each for x and y displacement. A third roller holds the ball in place.
Optical mouse was introduced in 1999, a infrared optical sensor emits a red glow beneath the mouse to capture movement and reflect it on e monitor. Due to the absence of moving parts, it is highly popular among consumers.
a touch-screen is an intuitive computer input device that works by simply touching the display screen. Users can navigate a computer system by touching icons/links on the screen. This interface is highly popular and used in public information systems and customer self-services.
[an A4 sized dektop scanner]
A device used to get images into a PC, it converts light into 0s and 1s (a computer-readable format), reproducing images on a hardcopy into the computer.
A photosensitive device used to read numerical data at a rate of up to 480 characters per second. OCR systems include an optical scanner for reading text, and software for analysing images. In the past, OCR systems used a combination of hardware (specialized circuit boards) and software to recognize characters. Now, however, a separate device is no longer necessary. Any scanner purchased nowadays comes with quite advanced OCR software, and the user merely has to place a document in his scanner and press the "OCR" button. Advanced OCR systems can read text in large variety of fonts, but they still have difficulty with handwritten text. However, noone has yet created a perfect OCR software.
Barcode readers are widely used in retail shops, supermarkets etc as it is cheap to use and maintain. Also, it is easy to store information (item prices) in the barcode labels, which are all unique, allowing a myriad of items to be represented.
A cheap and easy-to-use electronic instrument that records temperature, relative humidity, voltage, pressure etc. over time. Most data loggers utilize software on a personal computer to initiate the logger and view the collected data. It is ideal for those involved with field studies, transportation and monitoring. All science students nowadays have been taught how to use dataloggers in their experiments.
A device that can read text printed with magnetized ink. It is used almost exclusively by the banking industry for processing checks, as MICR is difficult to forge. The characters represent the check number, the bank number, and the account number of customers. Documents can still be read when folded or written on. However, MICR readers and encoders are very expensive and can only accept a few character sets.
[17 inch CRT monitor]
These devices are devices which act as a visual aid for the user, keeping the user informed about the going ons in the computer visually. CRT monitors consist of CRTs in which rays of electrons are beamed onto a phosphorescent screen to produce images (the same technology used in television). It is the most widely used type of monitors in the computer world. Another type of monitors used widely is the LCD: a display technology that relies on polarising filters and liquid crystal cells rather than phosphors illuminated by electron beams to produce an on-screen image. This means that the liquid crystals change colours when different voltages are passed through the polarising filters which are sets of incredibly fine parallel lines. It is easier on the eyes and more ergonomically conducive. LCDs are much smaller and flatter than CRTs.
[inkjet printer with its cartridges ontop]
There ar two types of printers that are widely used now. Laser and inkjet. An inkjet printer technology where fine droplets of ink are sprayed onto paper to form an image or character whereas a laser printer utilises a laser beam to produce an image on a drum. The light of the laser alters the electrical charge on the drum wherever it hits. The drum is then rolled through a reservoir of toner, which is picked up by the charged portions of the drum. Finally, the toner is transferred to the paper through a combination of heat and pressure. This is also the way copy machines work. Inkjets printers are cheaper than laser printers but they have high printing costs (as ink cartridges are expensive relative to toner cartridges). Laser printers are popular because of their high quality print and rand speed.
[a speaker on top of a subwoofer]
As computers are used more and more at home for entertainment, consumers have been demanding better performance in terms of audio output. The first PCs were only capable of producing beeps of different pitch (akin to ringtones on older handphones). But now PCs are equppied with soundcards that can output high quality music, in stereo and some even in surround sound.
Analogue Devices For Speech Generation
Analogue devices for speech generation are devices like microphones and
speakers.It converts the sound waveform into digital information and then
copies this in real time onto the hard disk. Essentially, it is using the
disk as a digital tapeless recorder. To hear what's been recorded, the sound
card takes the digital information off the hard disk, converts it back into
analogue, and then feeds it to loudspeakers, headphones or a conventional
Numerically-Controlled Devices For Control Of Machine Tools And Robots
This is also known as “mechatronics”. The elements of mechatronics systems include sensors, actuators, microcontrollers (or microprocessors) and real-time control software. One of the features which distinguishes mechatronic systems or products from earlier electromechanical systems or products is the replacement of some mechanical functions with electronic and software ones. This results in much greater flexibility of both design and operation. Another is increased speed and precision of performance. A third is the ability to conduct automated data collection and reporting. In addition, advanced mechatronics systems now have the ability to implement distributed control in complex systems. Mechatronics systems are used in a large and growing range of applications. Examples include robots, industrial production machinery, cameras and computer disk drives. Mechatronic components include high-performance motors and CCD image sensors. Other mechatronical applications include industrial uses i.e. In the production of cars, engineers program robotic arms to precisely cut and wield car parts together.
Comparison of Serial and Parallel Interfaces
[see how messy cables in a PC can be!]
Serial cables and parallel cables are typically used as a medium of transfer between the motherboard and the devices. Serial ports were introduced in the 1960s and its speed was 20Kbps, parallel ports were introduced in 1981 and its speed was 1.1Mbps. Serial has a lower voltages and pin count than parallel ports. It also has a thinner, smaller and easier routing wire cables. It also has improved data robustness compared to the parallel port.
Comparison of Analogue and Digital Devices
In an analogue signal numerical values are represented by physical variables such as voltage, current, etc. Analogue video represents an infinite number of smooth gradations between given video levels. Analogue devices are characterised by dials and sliding mechanisms. A method of signal representation by turning a voltage on or off. Each on or off state represents a binary 1 or 0, respectively. Unlike analogue signals, digital signals can be repeatedly regenerated without introducing noise or distortion. E.g. errors in sound recording might occur in analogue when other sounds and distortions are picked up by the analogue instrument (e.g. Microphone) and messes up the resulting sound file. Errors in digital data might occur when the file is corrupted due to alterations in the registry, file, or a virus attack. ADC: a device that converts continuously varying analogue signals from instruments that monitor such conditions as movement, temperature, sound, etc., into binary code for the computer. It may be contained on a single chip or can be one circuit within a chip. A situation where ADC would be used is in science experiments where data loggers are used
Why different output devices are used
Why, you may ask, is there a need for all the many types of printers? Well, all these different types have evolved over the times due to different needs and changing state of technology. And these devices are used depending on the situation, as each type has an advantage over the other in one way or another, but which advantage is more important in depenmdant on the type of usage it will going through.
For example, inkjet printers are mostly used by home users because of their low cost. The more expensive laser printers are used in the office because of their speed and low noise pollution, and of course they are a more economic choice becuase of the high volume of printing that goes on in an office (the toners are much less expensive than inkjet cartridges).
CRT monitors are mostly used by gamers because of superior image quality and LCD monitors are mostly used by office workers as desktop space is a premium.
Analogue devices are used when physical information is to be converted into digital information. If the user wants to record his voice he will use a microphone which will convert it into digital sound files. If the user wants to store and calculate empirical results, a data logger can be used to do so. It will convert physical conditions i.e. pH levels, light intensity etc. into digital data which is stored and can be extrapolated at a future date.
Mechatronics is used in industries where utmost precision is required to
produce engineered products like cars and airplanes. The precision required
is not humanly possible, and thus naturally we make computer-controlled robots
do it for us.