Output Devices (CIE IGCSE Computer Science)

• An output device shows the results of the processing in a way humans can understand
• In a general purpose computer system, the main output device is the monitor/screen
• Other output devices include projectors, printers, speakers and actuators
  

Actuators

• Actuators are used in conjunction with a motor to translate energy (electrical, air, hydraulic) into real-world movement of a physical object.
• They come in a variety of sizes and have been made specifically for a particular function. 
• Examples of use include turning a wheel, opening or closing a door, controlling a conveyer belt, operating machinery, moving robotic arms, vibrating a machine, starting or stopping a pump, opening or closing a valve
• They are often used with sensors. The input of the sensor is checked against stored values. If the input is within a certain range an actuator is used to provide movement of a physical object

Light projectors

• Used to project computer outputs onto a large screen
• Used to give presentations in both business and education settings
• There are two types - Digital light processing (DLP) projectors and Liquid crystal display (LCD) projectors.
• DLP systems use millions of micro-mirrors arranged in a grid on a microprocessor within the projector. Light is shone through colour filters and the mirrors. The position of the mirrors can be altered to change the intensity of the light
• LCD projectors use three mirror filters to separate an image into red, green and blue wavelengths. The three images are then combined to produce the full colour image which is passed through the lens on to the wall/screen

Laser and Inkjet printers

• Both printers create hard copies of a digital document
• Hard copies are needed when you do not have access to an electronic device

Inkjet printers:

• Have a print head which moves across the page
• Spray liquid ink droplets from ink cartridges through very fine nozzles onto the paper (these are in the print head)
• The droplets can be piezoelectric or thermal bubble technology
• Inkjet printers produce high quality hard copies of digital images or documents

Laser printers:

• Are very fast when making multiple copies of a document
• Are useful for high volume print jobs for example producing leaflets
• Have a low running cost per page. 
• Are often used in business and education setting
• Have large toner (dry ink) cartridges and large paper trays
• Use positive and negative charges to make the toner particles stick to piece of paper, heat is then used to bond the particles to the paper

3D printers

• 3D printers create 3D models of a digital model by depositing layers of material, such as plastic or resin, on top of one another to slowly build up a 3D object
• They allow for precision and can be used in medicine to create prosthetics and blood vessels
• 3D printers can be used to create rapid prototypes
• Models can be transmitted digitally and then models printed out all across the world

Liquid Crystal Display screens

• LCD screens are made up of millions of tiny liquid crystals. 
• The display is made of pixels arranged in a matrix
• The display requires backlighting
• They are used for TVs, monitors, tablets and phones
• They have low power consumption and run at a cool temperature
• They do not suffer image burn or flicker issues
• They provide bright images and colours
• They are cheaper to produce than LED screens

Light emitting diode (LED) screen 

•  An LED screen is made up of tiny LEDs
• They do not need backlighting which makes them thinner and lighter to hang on the wall
• LED screens are replacing LCD displays in TVs, monitors, laptops and mobile devices
• They have better image quality and a longer life span
• They can be used to create very large screens that can be used to show visual content at events such as football matches and music festivals
• They consume very little power making them suitable for being switched on for many hours in the day

Organic light emitting diode (OLED) screen 

• Much thinner and lighter than traditional LCD screens
• Use organic light emitting diodes (OLEDS). 
• They use organic carbon compound to create semiconductors
• No form of back lighting is required
• You can have very thin, flexible screens

Speakers

• Speakers are used to take digital sounds or recordings and output them as sound waves which can be heard by humans
• The digital data is changed into a electric current using a digital to analogue converter (DAC)
• It is then passed through an amplifier to create a current large enough to drive a loudspeaker
• The loudspeaker converts the current into a sound wave
• Typical uses include listening to music, listening to video sound, telephone calls and alarms