3.2 Input Output Devices Flashcards
What is an input device
A device that allows data to be entered into a computer system
Describe the operation of a 2D scanner
- Shines light onto the surface of a document
- Refelected light is captured…
- … using mirrors and lenses
- captured image is converted into a digital file
- produces a 2d digital file
Describe the operation of a 3D scanner
- Scanner shine a laser/light over te surface of a 3d object
- records the measurements of the dimensions of the object
- measurements are converted into a digital file
- produces a 3d digital model
Describe the operation of a bar code reader
- Reader shines a light/red laser at barcode
- photoelectric cells detect light reflected back
- white lines reflect more light
- different reflections convert to different binary values
Describe the operation of a QR code reader
Quick Response Code
- QR code is captured by a cmaera
- processed by an app
- data is decoded
- modules are used for alignment
How does a barcode help a supermarket manage stock
- barcode identifies a (unique) product
- barcode can be used to look up product (in a database)
- data about stock levels can be stored on a system
- stock can be automatically deducted from the system
- can check stock is below a certain level // check stock level
- automatic re-order // alerts when stock is low
- automatically update new stock level
- to locate if an item of stock is available in another location
Bar Code vs QR code
Barcode:
- 1d
- uses vertical lines
- some need to be lined up
QR:
- 2d
- uses squares
- more data can be stored
- can be read from any angle
- faster to scan
Both are faster than typing, no human input so less errors
Describe the operation of a digital camera
- Shutter opens and lets light onto the CCD sensor at the back of the lens
- intensity and colour of light is measured by millions of tiny sensors arranged in a grid
- converted to binary values
- stored as an image in the cameras memory
Pros & Cons of a conventional keyboard
Pros: simple and easy to use, potentially faster
Cons: slow if not trained, greater potential for mistakes
Pros & Cons of a concept keyboard
Pros: fewer errors, faster, less training, less vulnerable to dirt/food damage
Cons: not suitable for large amounts of choices, not suitable for all tasks
Describe the operation of mechanical mice
a rubber ball under the mouse moves around on a hard surface and sensors work out the orientation of the mouse
Describe the operation of an optical mouse
Uses a red LED and a sensor to determine the movement of the mouse as it passes of patterns on the surface
Pros & Cons trackball
Pros: little desk space, fine control , can be integrated into a keyboard
Cons: time getting used, expensive
Pros & Cons of touchscreen
Pros: output and input occupy same space, simple and easy to use, works well with icons
Cons: low precision, difficult to use if damaged
Describe how a capacitive touchscreen work
- Made up of many layers of glass that act as a capacitor
- As your finger comes close to a capacitor it changes the local electrostatic field
- Sensors are located around the screen // sensors are used to read the electric field
- The system monitors each capacitor to discover where the finger touched the screen
- Coordinates of touch determined/calculated/measured
Pros & Cons of Capacitive touch screen
Pros: works in sunlight, durable, multi-touch
Cons: glass screen, doesn’t work with gloves
Explain why a capacitive touch screen will not register the touch of a glove
Gloves are not conductive (insulator)
Blocks the charge from a finger
Stops the electrostatic field being changed/disturbed
Describe how a resistive touch screen works
- 2 layers
- flexible plastic surface seperated from a layer of glass coated in conductive material
- separated by tiny spacers
- -when touched the plastic deforms and the 2 conductve films meet
- -Calculation is carried out on where layers are connected
Pros & Cons of a resistive touch screen
Pros: cheap, works with styluses
Cons: scratching, low durability, no multi-touch
Describe how an infrared touch screen works
- The screen has grid of infrared LED beams
- Photocells detect where a beam is broken
- The position of the touch is calculated
Pros & Cons of infrared touch screen
Pros: durable, multi touch, works with gloves
Cons: expensive, objects can trigger a ‘touch’, sensitive to dust/dirt
Pros & Cons of an interactive whiteboard
Pros:
- large display allows multple people to work,
- interactive - helps with presentation,
- text/drawings can be captured for later
Cons:
- requires a board, projector & computer to work
- low precision
- bad in bright light
How do microphones work
- When sound reaches the microphone a diaphragm vibrates back and forth
- the causes the coil to vibrate which changes the magnetic field produced by the magnet
- this produces an electric signal
- this signal goes to a ADC and converted to digial volume
List 8 sensors
- Temperature
- moisture/humidty
- light
- infrared/motion
- acoustic
- gas
- pH
- magnetic field
