Output Devices

Device Usage
Monitor
A monitor is the most common output device that displays text and graphics on screen. Monitors are used to show temporary output i.e. softcopy.
CRT Monitor
CRT stands for cathode ray tube. CRT monitors are considerably heavier than other types and use lots more power than Plasma or LCD displays. However they do have special advantages.
  • First they are much brighter than LCD monitors.
  • Second they work with alternate resolutions quite well. Example a CRT with a max of 1600x1200 will display with no error at other resolutions, say like 1280x1024 or 640x480.
Inside a CRT monitor is a picture tube that narrows at the rear into a bottleneck. In the bottleneck is a negative charged filament or cathode enclosed in a vacuum. When electricity is supplied, the filament heats up and a stream or "ray" of electrons pour off the element into the vacuum. The negatively charged electrons are attracted to positively charged anodes which focus the particles into three narrow beams, accelerating them to strike the phosphor-coated screen. Phosphor will glow when exposed to any kind of radiation, absorbing ultraviolet light and emitting visible light of fluorescent color. Phosphors that emit red, green and blue light are used in a color monitor, arranged as "stripes" made up of dots of color. The three beams are used to excite the three colors in combinations needed to create the various hues that form the picture.

Negatives of the CRT include radiation emission,high power consumption, weight and bulk.
TFT Monitor
A TFT monitor uses thin-film transistor technology for the ultimate LCD display. LCD monitors, also called flat panel displays, are replacing the old style cathode ray tubes (CRTs) as the displays of choice. Nearly all LCD monitors today use TFT technology. The benefit of a TFT monitor is a separate, tiny transistor for each pixel on the display. Because each transistor is so small, the amount of charge needed to control it is also small. This allows for very fast re-drawing of the display, as the image is re-painted or refreshed several times per second.
A TFT monitor delivers crisp text, vibrant color and an improved response time for multimedia applications.
Multimedia Projector
Multimedia projector is used to project images, video etc. onto a surafce, normally a projection screen.
Printer
It is an output device to produce paper copy (hard copy) for a document, pictures etc. The job of a printer is to put on paper what is seen on the monitor. Printers vary mainly in cost, quality, speed and noise levels. Eg: Dot Matrix Printer, Inkjet /Deskjet / Bubblejet Printer, Laser Printer. The printers are classified as under:
  • Impact Printers - These printers have a mechanism that touches the paper in order to create an image. The Dot Matrix Printer is an example of this type.
  • Non-impact Printers - These printers do not touch the paper when creating an image. The inkjet and laser printers are examples of this type.
Laser printer
These printers use a technique, which is a combination of laser and Xerox technology. The technology involves dry powder based ink, which is adhered to a drum through magnetic force, and when a paper is passed through the drum it releases ink on that paper. These are the fastest available printers in the category and are most suitable for uses involving high-speed quality prints.
Inkjet/Deskjet/Bubblejet Printer
Printers in this category are most popular. These printers are very low priced with high running/maintenance cost. These printers work on liquid ink technology and print the image using circuit-controlled jet of ink. An inkjet sprays the ink onto the paper in tiny droplets to form text and graphics. Printing speed of these printers is not very high compared to Laser Printers. These printers are suitable for people having less printing jobs with a desirable print quality. These printers are available in 'Coloured' and 'Black & White' options.
Dot matrix printer
Printers in this category print the characters / images using dots through inked ribbon. These printers are very economic and require very less maintenance cost. The print quality of the dot matrix printer is decided by the quantity of pins it has. The number of the pins can vary from nine to twenty four, depending on the kind of dot matrix printer. When compared to the other kind of printers, like the laser printers or the ink jet printer, the dot matrix printer is much more expensive. The dot matrix printer has a tendency to make a lot of noise when compared to the other kinds of printers. This is why the dot matrix printer is not very popular among customers. Quality of print in this category is not very high but is highly suitable for printing situations requiring multiple copies.
Graph plotter
Plotters are expensive output devices specially designed to produce outputs of diagrams, illustrations and other graphics.
  • Flat-bed plotters - The paper lies on flat surface and pens are moved across the surface to draw diagrams
  • Drum-plotters - The paper is on a roll and as it unrolls pens draw on it.
Speakers
Speaker is the computer peripherals that emit music, voices, and other sounds.
Computer controlled devices in Control applications
Technology has touched almost all aspects of our Life. Whether it is banking, telecom, communication, Health, engineering or automated processes Computer controlled devices not only make our lives Convenient but also enable us to take important Decisions.
A computer controlled device accepts physical inputs from external source and pairs this information with computer controlled instructions to perform specific function.
Actuators
Actuators are used to convert energy e.g. Computer signals into motion-linear, motion, or oscillatory.
Motors
The most common form of motor used with computer is the stepper motor. Motors are used in many computer control applications:
  • In computers themselves they are used to cause moving parts to work in diskdrives, both optical and magnetic, as well as in scanners, printers and plotters.
  • In industry they are used to move robot arms.
  • In the home they are used in automatic washing machines to make the drum go around.
  • Motors are used in automaticcookers to switch on the heating fans.
  • Motors are also used in computer controlled greenhouses to open the windows and switch on fans.
A stepper motor is a brushless, synchronous electric motor that converts digital pulses into mechanical shaft rotation. As its name implies, it moves in steps that can be very tiny, enabling precise control because of these small steps.
Buzzers
A buzzer is an audio signaling device. An actuator is connected from the computer to the buzzer. The actuator is set to switch the buzzer on or off. Buzzers are used in many computer control applications:
  • Buzzers are used in automatic cookers and microwaves to tell you when the cooking process has been completed.
  • Buzzers are also used in automatic washing machines
Heaters
A heater is device that emits heat. An actuator is connected from the computer to the heaterand set to switch the heater either on or off. Heaters are used in many computer control applications:
  • Heaters are required in computer-controlledgreenhouses to increase the temperature of the greenhouse
  • They are an integral part of the central heating systems as they are needed to heat the water before it is pumped to the radiators.
  • Heating elements are needed in automatic washing machines to heat the water to the required temperature.
Lights/lamps
Light make things visible. An actuator is connected from the computer to the light bulb and set to switch the light either on or off. Lights are used in computer controlled greenhouses to increse the amount of light for the plants.
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