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Unit 4: Input and Output devices (Sensors (Monitor (No change to the…
Unit 4: Input and Output devices
Manual Input devices
- transfer data from the source in the outside world to the computer
Pointing device
Trackerball
Device itself remains stationary, the ball on it moves
Mostly for disabled, or people who has a small table
Humble mouse
Mechanical
Rubber ball underneaths, sensors determine the orientation
Optical
Red LED and sensors to determine the movement
Keyboard and keypads
A small rubber under each pad to make sure that they bounce back
The small bar under the key pushes through a small hole and makes contact with the conducting membrane.
The insulating layers prevent contact of keys accidentally
Microphones
When sounds reaches microphone the diaphragm vibrate, coil vibrate then change magnetic field, change incurrent detected and a signal is output.
ADC then DAC
Touchscreens
Capacitive
Glass layers, behaves like capacitors, storing electrical energy, a grid.
Infra-red
Grid patterns and light sensor, microprocessor calculate the interrupted location.
Resistive
Layers of conductive polyester and glass, separated by an insulating membrane
Surface Acoustic Wave
Sound waves, interruption detected by amplitude
Sensors
Collect data in an analogue form and require conversion to digital data to be processed.
Can be both control or monitor
Infra-red (heat or motion)
Acoustic
Gas (CO2 oxygen)
pH
LIght
Magnetic field
Temperature
Pressure
Moisture/ Humidity
Acoustic
Actuators
motors that are commonly used in conjunction with sensors to control mechanism. E.g. open a valve or door
Monitor
No change to the actual process, simply report
Control
computer can alter how process is operating
Speaker screens and projector
LCD (liquid crystal display) red, green and blue diodes to form each pixel, backlighting using CCFL or LED
CCFL vs LEDs
LED -reach maximum brightness immediately,small, sharper image, reliable screen
Organic LED
Electrons flows from the positive anode
When the 'holes' meet electrons they cancel each other and emit energy in the form of light.
Thinner and lighter than traditional LCD or LED screens
:red_flag: Generates their own light , much less power is consumed, larger field of view.
:red_cross: Increased production cost, wear out faster, easily affected by water containments.
Digital light Projector
mirrors on microchips, 'on' and 'off' of the mirror creates different shades of grey
White light passes through colour filter on a rapidly spinning wheel
Light Crystal Display
depend on bright source of light, dichroic mirror reflects with wavelength then combined suing a prism.
Output devices take data produced by computer and turn it into human-readable form.
Printing technology
Inkjet printers
Thermal bubble
Heated, ink vaporize, bubble created
bubble expands, ink is ejected on the paper
Bubble collapse, new ink is drawn
less durable
Piezoelectric crystal
Crystal receives electric signal, vibrates
vibrate in, ink is ejected
Vibrate out, new ink is drawn
Durable as low heat is produced, more expensive
Interrupts
signals sent to the processor which forces it to stop
E.g. more data to be sent, out of paper
Drivers
Software that concerted data into the specific printing form
Allow applications to carried out printing job without being aware of specific form.
Buffers
Temporary memory that stores data and allows it for later uses
Allows processor to carry put other task during the slow printing process
Laser printer
uses try toner
Use of electrostatic charges
Dot matrix printer
impact printer strike an inked ribbon which imprints dots to form letters
Barcode readers, scanners and cameras
Barcode system
Universal Product Code version 'A"
Used in retail and warehouse
starts with 0 and check digits, Only numbers
Long guard bars to show the start and end of the bar code
Central guard bars to distinguish left and right, right hand is the inverse of left hand
Left -manufacturer number, odd Right: Product number,even
Code 128
Used in transport and shipment tracking
Numbers and letter
Quick response code
can be read by smartphones or tablets
Links to website or information
E.g. restaurant coupons, mobile concert ticket, business card, tourist information, advertising posters
Barcode scanner
Convert hard copy into computer readable format
Bright light, head scanning to produce image and sent a lens, focused image falls on light-sensitive sheet , record light intensity
Application of 2D scanners
Airport security camera, face recognition
3D scanner
medical, industrial uses,E.g. 3D MRI scanning
Tomography which means to image everything in thin slices
Digital camera
Breaks image and see through its lens into grid of pixels
The shutter opens to let light onto a CCD sensor at the back of the lens
The intensity or colour of light is measured by millions of tiny sensors arranged in a grid on the CCD sensor
