Hardware - Input + Output devices Flashcards
what is an input device
any device that allows you to pass information from the outside world into a computer system
how does a barcode scanner work
- red laser light shone at a barcode to illuminate it
- white lines reflect back
- black lines absorb some light and reflect less
- sensors in scanner detect the pattern of strong and weak reflections
- reflection strength from each lie is interpreted by a microprocessor and converted into a binary value
what 3 uses for barcode scanners used for
- scanning goods at supermarket checkout
- checking library books in and out
- tracking packages out for delivery
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why are barcodes required
- faster checkout queues
- reduces errors caused by manual input
- more detailed tracking information
- automatic stock control
what does a QR code scanner do
- QR code is read by using a camera, commonly on a mobile device
- 3 large squares in the corners are used for alignment
- smaller black and white quares reflect or absorb light
- software on device converts each pixel into a binary value to process the image
what does a QR code commonly contain
a hyperlink to an online file
what are QR codes typically used for
- advertising products
- quick links to websites
- sharing contact details instantly - no need to type
why are QR codes required
- hold far more information than a traditional barcode
- much quicker access
how do 2D scanners work
- 2D (flatbed) scanner shines a strip of light onto a document/ photo
- strip moves over whole document , reflected light is captured using mirrors + lenses and the light intensity is measured per pixel
- information is converted into a **digital file(( to produce a digital image of the original document
how do 3D scanners work
- shine a laser over the surface of an object
- records the geometry and dimensions of the object to produce a digital file
- from this file a digital model is created
- parts can then be printed using a 3D printer
what are 2 things 2D canners are used for
- creating digital versions of documents and photographs
- reading passports at airports
what are 4 things 3D scanners used for
- creating 3D models for use with computer-aided design (CAD)
- Dentistry
- product development
- quality inspection and research
why are scanners required
simple, cheap and effective way of generating a digital representation of 2D or 3D objects for further manipulation
how does a digital camera work
- as light enters lens, it falls onto the sensor which is divided up into millions of individual squares or pixels
- each pixel measures the light intensity
- this value is converted into digital data as a pixel with a single binary colour value
- image can be stored as a file on flash memory
- or a microprocessor within camera reassembles image on a screen using each pixel’s information
what are digital cameras typically used for
- integrated into smartphones
- security and surveillance cameras
why are digital cameras required
- camera on phone is smaller, lighter - largely replaces traditional, film-base cameras - chunky
- instant photographs - very accessible + quick
- easily transmitted via Wi-Fi, Bluetooth, etc.
- embedded editing software
how do keyboards work
- when key is pressed , a peg under the key is pressed into a springy layer to make contact with a conducting membrane
how do optical mice work
- use red LED and a Sensor to determine movement
- analysed by digital signal processor to cream same movement
how do microphones work
- uses diaphragm to vibrate in response to sound
- vibrations cause a coil to move around a magnet –> creates changes in electromagnetic field
- changes detected + recorded by processor** using an analogue to digital converter (ADC)
what device are touch screens
both input and output
what are the 3 types of touchscreen
- resistive
- Infra-red
- Capacitive
what are resistive screen made of
- layer of conductive polyester + layer of conductive glass
- 2 layers separated by insulating layer
- when pressed - 2 conducting layers make contact –> complete circuit
- position where touched is calculated by microprocessor
where are resistive touch screens used
- ATM screens
- medical equipment - users often wear gloves
how to Infra-red screens work
- LEDs chine infra-red light across the screen from top and sides
- infra-red rays form a grid
- when touched, infra-red beam interrupted
- microprocessor calculates coordinates
where are infra-red screens most commonly used
staff tills in fast food outlets
how does capacitive screens work
- made up of glass layers
- bottom surface of upper layer and top surface of lower layer coated in perpendicular lines of transparent conductive material forming a grid
- screen behaves like a capacitor - stores electrical energy
- when touched - change in electrical field in that position
- microprocessor calculated position where field changes
what are the advantages of capacitive screens
can be touched in multiple places simultaneously
where are capacitive screens used
- smartphones
explain why you cannot control the capacitive screen when wearing gloves
- gloves are an insulative layer
- prevents electric field being changed and sensed by the screen
what device are screens with no touch function
output device
what are the 2 types of output screens
- Liquid crystal display (LCD)
- Light emitting diode (LED)
how to LCD’s work
- made from millions of pixels
- each pixel is a separate red, blue, green light that can be switched on or off electronically using liquid crystals to rotate polarised light
- pixels are switched on or off rapidly to make a moving colour picture
- a special fluorescent lamp required to provide necessary backlight
how to LEDs work and what are the adv compared to LCD
- screen uses light from LEDs to produce a brighter backlight almost instantly –> replacing need for additional fluorescent lamp in LCD
where are LEDs often used and how are they made
- big sport stadiums / concerts
- made of many smaller screens in a cluster
what are the 2 types of projectors
- Digital light processing (DLP) projectors
- Liquid crystal display (LCD) projectors
how to DLP projectors work
- millions of micro-mirors arrand in a **grid on a small microchip(( within the projector
- shining white light through **colour filters* alters colour
- angle of mirror alters colour intensity
how to LCD projectors work
- 3 mirror filters to separate image into red , green, blue wavelengths
- 3 images combined using a prism
- produces full colour image which then passes through lens and projected on screen
what are the adv of DLP
- higher contrast + definition
- smoother video
- smaller
what are the adv of LCD
- cheaper
- quieter
- less power and heat output
what are the 2 types of printers
inkjet printers
laser printers
how to inkjet printers work
- use liquid ink reservoirs, forcing droplets through fine nozzle
what are inkjet printers best used for
- small print runs
- high resolution colour photos, esp when specialist coated photo paper used
how do laser printers work
- dry ink in powder form caller toner that is electrostically charged
- printer creates mirror image of the printed
