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1.3 Input and Output Devices - Coggle Diagram
1.3 Input and Output Devices
Barcode Readers
Common Types of Barcode System
Universal Product Code version 'A' (UPC-A)
Used in Retail
Used in warehousing
This uses long guard bars to show the start and end of the barcode and also central guard bars to distinguish left uniquely from right.
Code 128
Used in transport
Used in shipment tracking
Can represent letters and numbers whilst UPC-A can only represent numeric digits
QR(Quick Response) codes
QR codes are 2D barcodes and can be read by smartphones or tablets
They contain
Links to websites
Information
Common uses
Restaurant coupons
Mobile concert tickets
Real estate agency boards
Business cards
Tourist information
Advertising posters
Touchscreens
Four common touchscreen technologies are used with tablets, watches and mobile phones
Capacitive
Capacitive touchscreens are made up of glass layers
The screen behaves like capacitor, storing electrical energy
The bottom surface of the upper layer and top surface of the bottom layer are coated in perpendicular lines of transparent conductive material (Indium Tin Oxide) forming a grid
Unlike resistive, capacitive technology allows multiple touches (enabling 'pinching and zooming' on a mobile phone and so on).
When the screen is touched by a finger, there is a change in the electric field at that position
The position where the field changes is calculated by a microprocessor
Strengths and Weaknesses
Strengths
Has good contrast in strong sunlight
Very durable technology
Supports multiple touch facility
Weaknesses
Can only be used with a bare finger or with capacitive pen
Relatively expensive technology
Infra-red touchscreens
Infra-red touchscreens use a grid pattern of LED's and photocells (light sensors)
When the screen is touched by a finger, the infra-red beam is interrupted
A microprocessor calculates the coordinates of where the screen was touched
LED's shine infra-red light in front of the screen
Commonly used in fast food restaurant tills as the screen can then be coated in grease and scratch resistant rubber
Strengths and Weaknesses
Strengths
Good contrast in strong sunlight
Very durable technology
Can be used with bare finger, gloved finger or stylus
Weaknesses
Most expensive touchscreen technology
Ambient light can sometimes cause problems if screen is scratched
Only supports single touch (doesn't support multi-functions)
Resistive
Resistive touchscreens are made up of a layer of conductive polyester and a layer of conductive glass
The two layers are separated by an insulating membrane
When the screen is gently pressed by a finger, the two conducting layers make contact and complete a circuit
Conductive coating of indium tin oxide (ITO)
The position where the screen is touched is calculated by a microprocessor
Strengths and Weaknesses
Strrengths
Relatively inexpensive technology
Can be used with bare finger, gloved hand or stylus
Weaknesses
Not so good in strong sunlight; image sometimes poor
Relatively easy to scratch the polymer screen
Can only support single touch (doesn't support multi-touch functions)
Surface Acoustic Wave (SAW)
Surface Acoustic Wave touchscreens make use of ultrasonic sound waves
two sound wave transducers (which generate the ultrasonic sound) and two receivers are used; the sound waves travel parallel to the edge of the glass vertically and horizontally
The position where the screen is touched is detected by a reduction in the sound wave amplitude
This technology tends to be used at information kiosks, electronic catalogue stations, ticket sale machines and in control rooms found in industry
Strengths and Weaknesses
Strengths
Very good screen clarity
Very durable technology
Pressure sensitive
Weaknesses
Vulnerable to surface contaminants which alter its effectiveness
Won't detect touch from hard objects that reflect rather than absorb sound pulses
Sensors
Input devices transfer data from the source in the outside world to the computer
Sensors often collect data in an analogue form and require conversion to digital data to be processed
Sensors are used in both monitoring and control applications
Some data can be obtained directly through the use of sensors
Definition
A hardware device that can take measurement of physical properties, such as temperature or pressure, from a real world surroundings. These measurements are usually a representation of the actual property being measured
Data taken by sensors is usually in analogue form
Analogue measurements
Analogue means that data has no discrete value and the data changes smoothly rather than in exact jumps
Examples
A speedometer showing speed represented by a needle on a gauge
A seismometer recording the force and duration of ground movement by visualising the motion of a weight on a string using a pen.
A thermometer where temperature is represented by the height of the mercury
Types
There are many types of sensors designed to carry out specific tasks.
Light
Temperature
pH (i.e. acid or alkalinity)
Magnetic Field
Infra-red (e.g. motion or heat source)
Pressure
Moisture / Humidity
Acoustic (i.e. sound)
Gas (e.g. oxygen, carbon dioxide)
Printers
Inkjet printers
There are two main types of inkjet printers with similar internal workings
Thermal bubble
Droplets of ink are produced using a thermal bubble
The heat causes the ink to vaporise and form tiny bubbles
As each bubble expands, ink is ejected onto the paper
Behind hundreds of print nozzles there are tiny resistors that create heat (the temperature momentarily exceeds 1000 degrees C
As it cools, the bubble collapses and draws in fresh ink and the process continues until the page is printed
Benefits and Drawbacks
Drawbacks
Only certain inks can be used because of the high heat
More maintenance needed because of the high temperatures involved
Produces larger droplet sizes
Benefits
Less expensive technology than piezoelectric
Possible to use more paint nozzles
Piezoelectric crystal
A small piezoelectric crystal is located at the rear of each ink reservoir of each nozzle
As it vibrates inwards, ink is ejected onto the paper
As it vibrates outwards again, new ink is drawn in to replace it
When the crystal receives a small electric current, it begins to vibrate in and out
Benefits and Drawbacks
Benefits
Wide range of ink types can be used
Can produce very small ink droplets
Very precise ink drop sizes can be produced
Can run for longer since less heat generated
Drawbacks
More expensive technology than thermal bubble
Can use fewer print heads
3D printers
3D printers can print using plastic filament, powdered resin, ceramic or metal powder, or paper
Additive manufacturing builds up an object layer by layer
This is very different to subtractive manufacturing where an object is made by removing material
Direct and binder printing
Direct 3D printing is based on inkjet printer technology
With 3D printers, the print head doesn't just move left to right, but it also moves up and down to create the 3D model
Binder 3D printing involves two passes to produce each layer of the object
One pass sprays dry powder and another pass sprays a binder (a type of glue) which makes the powder stick together to build a solid object
Applications
Medicine
Manufacturing of prosthetic limbs or orthotics
Huge reduction in cost and greater accuracy in matching limb to individual patient
Reconstructive surgery or general surgery
Surgeon can 'try out' a procedure first to ensure actual surgery is more accurate; can produce very accurate parts for surgical procedures
Manufacturing and Art
Manufacturing parts for cars
Very old cars are very likely to need parts no longer manufactured; by using an existing part as a blueprint it is possible to print new components at a fraction of the cost
Prototyping for design, fashion and art can save huge costs
Speakers
Digital data is sent from the computer to a Digital to Analogue Converter (DAC) where it is converted into an analogue signal
LCD Monitors
Liquid Crystal Display (LCD) screens contain groups of red, green and blue diodes to form each pixel
Monitor screens require backlighting using Cold Cathode Fluorescent Lamps (CCFL) or LED's since the crystals act as a light valve and do not emit light themselves
LED's
Using LED's to back-light LCD screens has a number of advantaged over the older CCFL technology
They produce a brighter light which leads to better picture definition
Since LED's are very small, this allows the screens to be much thinner in construction
They last almost indefinitely which makes the screens much more reliable
The image is sharper with more realistic and vivid colours
They reach their maximum brightness almost immediately
They consume very little power and therefore produce very little heat as well and reduce running costs
Organic LED technology
Organic LED (OLED) technology uses 6 layers
'Holes' represent a space for a missing electron
When the 'holes' meet electrons they cancel each other out and emit energy in the form of light
Electrons flow from the cathode towards the positive anode
A set of red, green and blue OLED's works like an LCD pixel
Uses of OLED screens
OLED screens are much thinner and lighter than traditional LCD or LED screens
Plastic, rather than glass also makes them flexible
The light emitted from an OLED system is much brighter than the LCD or LED screens
Benefits
Much less power is consumed; this has a clear advantage when producing screens for battery operated devices (e.g. mobile phones, tablets and smart watches); it also means little heat is produced (reducing fire risks) and running costs are also reduced
They have a larger field of view than LCD screens - and this is further enhanced when the screen is curved
OLED's generate their own light so there is no need for the complexity of back lighting