4 Flashcards
Input devices
transfer data from the source in the outside world to the computer
Examples include:
Keyboards
Mice
Digital cameras
Microphones
Types of Touchscreens
Resistive
Capacitive
Infra-red
Resistive touchscreens
Resistive touchscreens are made up of a layer of conductive polyester and a layer of conductive glass
- your fingers make those 2 layers touch
Capacitive touchscreens
Capacitive touchscreens are made up of glass layers
-When the screen is touched by a finger, there is a change in the electric field at that position. That position is then calculated by a microprocessor
-can be touched in more than one place at a time
Infra-red touchscreens
LEDs shine infra-red light across the screen from the edges and the infra-red rays form a grid across the screen
-When the screen is touched by a finger, the infra-red beam is interrupted
advantages and disadvantages of
-Capacitive screen have a smooth surface
-They are very easy to press
-They are highly accurate
-Capacitive screens don’t work if the
user is wearing gloves
Barcode readers
UPC-A systems:
This uses long guard bars to show the start and end of the barcode
Left hand codes- odd number of black bars.
Right hand codes- even number
Digital cameras
Digital cameras focus light onto a CCD sensor
3D scanners
3D scanners use a laser to
scan across an object
2D Scanners
These are used to convert documents or photographs into a digital format.
Examples:
Multi-function printers
Photocopiers
They can contain:
Describe how barcodes are used within supermarkets today.
Each product has a barcode located on it.
The barcode is scanned by a handheld scanner / at the checkout.
The computer processes the barcode to find its barcode/ID number.
The item is looked up to find the product name and price.
The stock in the shop is automatically updated.
Give two other applications of barcodes.
Uses may include:
Library books and library cards.
Tracking luggage at airports.
Tracking packages.
Why use barcodes?
- It is faster to scan products than enter a price in to a till
- no stock control necessary
- Barcodes reveal a number that identifies each product. This allows a shop to determine how many items are sold
-Saves the need for shop workers to manually check stock levels - Prices can be changed without needing to update the price on each product
QR codes
QR codes are 2D barcodes and can be read by smartphones or tablets
They contain:
Links to websites or
Information
Uses of QR codes in society
Tracking packages
Restaurant menus
Mobile concert tickets
Tourist info
uses for 3D sanners
Checking parts for faults.
Tomography
MRI scans.
Medicine
Gas sensor
Detecting CO2 levels
Detecting O2 levels
Detecting CO (carbon monoxide) levels in a home alarm
pH sensor
Detecting the acidity of soil
Detecting the acidity of liquids
Light sensor
Automatic turning on of car lights
Turning on street lights
Level sensor
Finding how much fuel is left in a car
Finding the amount of grain stored
Pressure sensor
Detecting if someone is standing on a special mat at an entrance
Detecting how much air is in a car tyre
Infra-red sensor
Security lights
Detecting movement in alarm systems
Moisture sensor
control or monitor the dampness of soil in a greenhouse
measure water content in a lawn for an automatic watering system
Humidity sensor
monitor the humidity in the air of a greenhouse
control a dehumidifier in a home
Flow
measure how quickly a chemical is moving through a pipe in a chemical plant
measure the speed of water in water pipes
Magnetic field
used in smart phones so they know which direction it is pointing
used in the motors of CD players
Acoustic
pick up noise levels (e.g. footsteps) in a burglar alarm system
detect the noise of liquids dripping from a pipe in an oil refinery
Output devices
transfer data produced by a computer and turn it into a human-readable form
Examples include:
Displays and projectors
Printers
Speakers
Actuators
Speakers and headphones
Digital data is sent from the computer to a Digital to Analogue Converter (DAC) where it is converted into an analogue signal
Actuators
Actuators are output devices used to move mechanisms or systems
examples include:
Central locking on cars
Opening and closing valves on pipes
LCD screens
- Liquid Crystal Display (LCD) screens are made from millions of pixels.
- The pixels are switched on or off very rapidly to make the moving colour picture
-LCD screens are backlit with a fluorescent backlight
LED screens
LED screens use LEDs (light emitting diodes) to light them
advantages of LCD
- cheaper to produce
- better contrast / sharper image
- more energy efficient.
advantages of LED
-very bright
-suitable for outdoors
-good for shows with big screens
There are two types of technology that are used in projectors.State what each technology is and describe how it works.
DLP uses millions of micro mirrors on a small microchip within a single projector. When these micro mirrors are tilted towards the light source, they are on, if they are tilted away from the light source, they are off. The micro-mirrors can switch between ‘on’ and ‘off’ thousands of times a second creating different and changing shades of grey light.
DLP projectors have a mirror for each pixel and a rotating wheel with the colours red, green and blue
As well as LCD works in a way where screens are made from millions of pixels, each pixel separates red, green and blue lights that can be switched on and off electronically using liquid crystals. They are switched on and off very fast to make moving colour pictures.
LCD projectors use three LCD screens, one for red, green and blue. The three images are then combined into colour
Laser printers
A laser scans across a print drum and apply electro change
The drum will pick up the dry powder know as toner, and the toner sticked to paper
The heated fuser makes sure that toner does not come of the page
A page is printed quickly and the quality is high for text.
3D printers
A plastic is squeezed from the head (the nozzle) .
A 3D model is built up in layers from top to bottom going side to side and up and down.
Inkjet printers
Thermal bubble:
Droplets of ink are produced using a thermal bubble
- behind the print nozzles there are resistors that create heat
- The heat causes tiny bubbles to form inside
- As each bubble
expands, ink is ejected onto the paper
- As it cools, the bubble collapses and draws in fresh ink and the process continues until the page is printed
Piezoelectric crystal:
small piezoelectric crystal is located at the top of each ink reservoir of each nozzle
- When the crystal receives a small electric current
- As it vibrates, ink is ejected onto the paper
- new ink comes to replace
-this is repated until page is printed
Benefits and drawbacks of thermal bubble
- Less expensive technology than piezoelectric
- Possible to use more print nozzles
- Produces larger droplet sizes
- Only certain inks can be used because of the high heat
- More maintenance needed because of the high temperatures involved
Benefits and drawbacks of Piezoelectric crystal
- Very precise ink drop sizes can be produced
- Wide range of ink types can be used
- Can produce very small ink droplets
- Can run for longer since less heat is generated
- More expensive technology than thermal bubble
- Can use fewer print heads
State two other uses for 3D printers.
Spare parts (such as for cars)
models for houses
prosthetics
medicine
