3.4 Output Devices Flashcards
Actuator
Any motor that moves objects about
Servomechanism
A machine that uses feedback to regulate motion, eg. IRL used to keep an aircraft at a constant altitude, by measuring changes in air pressure to detect change in altitude
Control system
A control system uses feedback to control a physical process
Feedback
When the computer measures the effect of a process that it controls; input sensors “feed back” the results of the computer’s actions to the processor
Liquid Crystal Display (LCD)
Some computer monitors contain a layer of liquid crystal held between transparent sheets. In an electric field, the structure of the crystal alters to line up its molecules. This affects light passing through. Sending different electrical signals to the display makes a pattern of opaque and transparent spots. A microscopic colour filter over each position changes the colour of each spot. The LCD itself doesn’t emit light. A backlight shines through the display.
Light-emitting Diode (LED)
An LED is an electronic device that makes coloured light when an electric current flows through it; it is like a small bulb. It uses less power and emits less heat than an ordinary light bulb but it is more expensive. Millions of tiny organic LEDs (OLEDs) arranged in a grid are used to make bright, clear high-resolution displays for smartphones and tablets. (more expensive too)
LCD projector
Where a beam of light passes through the LCD and onto a wall screen, and you look at the screen
Digital Light Projector (DLP)
It works by shining light onto a grid of tiny mirrors that can move. As the mirrors tilt, some shine light towards the wall screen, and some deflect the light away. This makes the shapes and colours of the image. DLP is used in cinemas and it is called digital cinema.
Inkjet printers & application
- ROLLERS are used to move the paper through the printer
- NOZZLES spray ink onto the paper
- Nozzles are moved across the paper to distribute the ink
- Different colour inks are mixed to create required colours
The spray from each jet is turned on and off by an electrical signal. Inkjet printers can produce a wide range of high quality colour printing. The highest quality realistic colour images are produced by photographic quality inkjet printers. However, they are not very fast and refilling the ink is very expensive.
Application:
- small quantities of documents
- photographs
Laser printers & application
A laser printer uses toner to print. A rotating drum inside the printer is coated with static charge. The pattern of static electricity is altered by a laser beam shining on it. The static electricity picks up the toner in the shape of a page of printing and makes it stick on the outside of the drum. A piece of paper rolls past the drum and the toner drops off the drum onto the page. This transfers the image onto the paper. Laser printers are usually larger and more expensive, though they are much faster and can print a lot at once.
Application:
- producing flyers/leaflets/magazines
Speakers
Most speakers contain a plastic or metal cone. The bottom of the cone is attached to a coil of wire surrounding a magnet. Electrical signals make the magnet attract and repel the coil. The coil moves backwards and forwards, pulling and pushing the speaker cone. The moving cone pumps sounds out into the air.
3D printers & application
A print head moves over a table, melting and sticking tiny dots of the material where it is needed. The joined-together dots solidify into a flat layer of material. The first layer is laid directly on the table; then the print head moves up slightly and lays the next layer on the first. It continues until enough layers have been built to make the entire shape.
Application:
- physical prototype from CAD
- physical model from a blueprint
5 advantages of using LED technology compared to the older cold cathode fluorescent lamp (CCFL) method
- Brighter image
- Much thinner monitors possible / lighter weight
- Uses much less power / more efficient
- Higher resolution
- Longer lasting
