Input devices Flashcards
Input device
A device that allows data to be entered into a computer system
2D scanner
Shines light onto the surface of a document
scan head moves across document
Reflected light is captured using mirrors and lenses to focus image onto a CCD
The captured image is converted into a digital file
It produces a 2d digital file
3D scanner
Scanner shines a laser/light over the surface of the 3d object
Camera records the measurements of the dimensions of the object by detecting reflection of light
The measurements are converted into a digital file
It produces a 3d digital model
Bar code reader
Reader shines a light/red laser at barcode
Sensors(photoelectric) cells detect light reflected back (white lines reflect more)
different reflections convert to different binary values
microprocessor interprets the data
unique code is searched in product database and identified
QR code reader
Quick response code
QR code is captured by a camera
processed by an app
data is decoded into binary values
position and alignment markers are used for alignment
7 ways a barcode help manage a supermarket stock
- barcode identifies unique product
- barcode can be used to look up product in a database
- stock can be automatically deducted from the system
- can check stock level
- automatically re-orders when stock is low
- automatically updates new stock level
- locates 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 contains squares more data can be stored(7000 vs 30) can be read from any angle faster to scan
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
Advantage of conventional keyboard
simple and easy to use
Disadvantages of conventional keyboard
slow if not trained
greater potential for mistakes
4 advantages of Concept keyboard
fewer errors
faster
less training
less vulnerable to dirt/food damage
Disadvantages of Concept keyboard
not suitable for large amounts of choices
not suitable for all tasks
mechanical mice
rubber ball under the mouse moves around on a hard surface
sensors work out the orientation
optical mouse
red LED and a sensor determines the movement of the mouse as it passes of patterns on the surface
3 advantages of mechanical mice
takes up little desk space
fine control
can be integrated into keyboard
Disadvantges of mechanical mice
expensive
have to spend time getting used to it
Conventional Keyboard
When a key is pressed, the small bar under the key pushes through a small hole and makes contact with a conducting membrane
signal is sent to computer
3 advantages of Touchscreen
output and input occupy same space
simple and easy to use
works well with icons
2 disadvantages of Touchscreen
low precision
difficult to use if damaged
Capacitive touchscreen
Made up of many layers of glass coated with conductive material that act as a capacitor(current flows from all 4 corners of the screen)
As your finger comes close to a capacitor it changes the local electrostatic field
The system constantly monitors each capacitor to discover where the finger touched the screen
Sensors are located around the screen
Coordinates of touch are then calculated
3 Advantages of capacitive touchscreen
good visibility in sunlight
durable surface
allows multi-touch
2 disadvantages of capacitive screen
screen will shatter on impact
doesn’t work with gloves
Resistive touch screen
2 layers
One flexible plastic surface with thin film of conductive material on underside
separated from a layer of glass coated in conductive material
separated by tiny spacers
when touched, the plastic deforms and the 2 conductive films meet so electric current changes
Calculation(resistance of both layers at contact) is carried out on where layers are connected
2 advantages of resistive touch screen
cheap to manufacture
can use stylus/gloves
