Unit 4 - Software Flashcards
What is an input device?
Input devices transfer data form the source in the outside world to the computer
What are some examples of input devices?
- Keyboards
- Mice
- Digital cameras
- Games controllers
- Microphones
How do computer systems work?
- Input devices putting data into the system
- The data is processed
- The processed data may then be saved using primary or secondary storage
- Output devices send data from the computer to the user
How is a keyboard made?
A key is made from plastic and has a small peg underneath which fits exactly into a hole in the keyboard when it is pressed
A small piece of rubber under the key makes it bounce back up so that it is ready to be pressed again
How does a keyboard work?
When a key is pressed, the small bar under the key pushes through a small hole and makes contact with a conducting membrane
What is an optical mouse?
A computer mouse is used for pointing and selecting areas on a display
How does an optical mouse work?
An optical mouse shines light from a red LED onto a surface
A sensor takes repeated images of the surface and compare how these change when the mouse is moved
How does a microphone work?
When sound reaches the microphone, the diaphragm vibrates backwards and forwards
This causes the coil to vibrate which then changes the magnetic field produced by the magnet
Changes in current are detected and a signal is output
How is analogue data converted to digital data?
The output from the microphone is analogue
This analogue signal needs to be converted into a digital signal so the computer can understand the data
An analogue to digital convertor (ADC) carries out
the conversion
What are the 3 different technologies used in touchscreen?
Resistive
Capacitive
Infra-red
What is a resistive touchscreen made off?
Resistive touchscreens are made up of a layer of conductive polyester and a layer of conductive glass
How do resistive touchscreens work?
- 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
- The position where the screen is touched is calculated
by a microprocessor
What are capacitive touchscreens made of?
Capacitive touchscreens are made up of glass layers
How do capacitive touchscreens?
- 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
- The screen behaves like a capacitor, storing electrical energy
- The screen can be touched in more than one place at a time
How does a capacitive screen detect a touch?
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
What are the advantages of using capacitive touchscreens?
- Capacitive screen have a smooth surface
- They are very easy to press
- They are highly accurate
What are the disadvantages of using capacitive touchscreens?
Capacitive screens don’t work if the user is wearing gloves
What are the disadvantages of using capacitive touchscreens?
Capacitive screens don’t work if the user is wearing gloves
How are Infra-red touchscreens made?
LEDs shine infra-red light across the screen from the edges
How do infra-red touchscreens work?
- The infra-red rays form a grid across the screen
- 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
What are two common types of barcode systems?
Universal Product Code version ‘A’
(UPC-A)
- Used in retail and warehousing
Code 128
- Used in transport and
shipment tracking
How does a UPC-A system work?
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. UPC-A uses seven bar elements to form four alternating dark and light bars of varying thicknesses to represent each data item between the guard bars
How does a UPC-A system work?
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. UPC-A uses seven bar elements to form four alternating dark and light bars of varying thicknesses to represent each data item between the guard bars
How do you read UPC-A retail barcodes?
Visually, a grouping of two or more adjacent bars appear as a single wide bar
Right hand codes are the inverse of left hand codes
Left hand codes all have an odd number of black bars. Right hand codes all have an even number
Why are barcodes used?
- It is faster to scan products than enter a price into a till
- Previously, many shops would close to carry out a stock control. This is no longer necessary
- Barcodes reveal a number that identifies each product. This allows a shop to determine how many items are sold which saves the need for shop workers to manually check
stock levels - By having barcodes on products, prices can be changed without needing to update the price on each product
- Customers are able to scan their own items, resulting in a reduced need to till operators
What is a QR code?
QR codes are 2D barcodes and can be read by smartphones or tablets sending you to a hyperlink.
What do QR codes contain?
- link to websites (hyperlinks)
- information
What can QR codes be used for (name 3)?
- Tracking packages
- Restaurant coupons
and menus - Mobile concert tickets
- Estate agency boards
- Business cards
- Tourist information
- Advertising posters
- Self service tills
What are 2D scanners used for?
These are used to convert documents or photographs into a digital format.
How do 2D scanners work?
- A scanner head contains a bright light and lens
- The focused image then falls on to a light-sensitive sheet made up of thousands of pixels which record the light intensity or
colour falling on each pixel - This information is now
stored as an image in
the computer’s memory
What are 2D scanners often embedded in?
- Multi-function printers
- Photocopiers
How do 3D scanners work?
- 3D scanners use a laser to scan across an object
- Two sensors detect the distance from
the laser to the object - This creates a ‘point cloud’ which is then processed
into a 3D representation of
the object
What is an example of 3D scanners in use?
- 3D scanners are used in both industrial and medical fields
- Many 3D scanners rely on a technology called Tomography which involves taking images in very thin slices less than 0.1 mm thick
How does a digital camera work
- Digital cameras focus light onto a CCD sensor (Charge-Coupled Device)
- The CCD breaks up the image into a grid of pixels
- The shutter opens to let light onto a CCD sensor at the back of the lens
- A sensor measures the light intensity of each pixel
- Once processed, the
information is then stored
as an image in the
camera’s memory
What are some physical properties that can be measured?
- Sound intensity
- Acceleration
- Pressure
- Light intensity
- Infra-red (heat) intensity
- Magnetic field
- Moisture
- pH
- Distance
What is the definition of sensor?
A hardware device that can take measurement of physical properties, such as temperature or pressure, from real world surroundings. These measurements are usually a representation of the actual property being measured.
What is an analogue measurement?
Analogue means that data has no discrete value and the data changes smoothly rather than in exact jumps
What applications can temperature sensors be used for?
- a temperature sensor is used to monitor the temperature of the cooling system. If the temperature gets too hot, a fan can be turned on or the driver can be alerted to the problem. Cars may also monitor the temperature inside the car, applying heaters or air conditioning as appropriate - Automatic washing machines - central heating systems - automatic greenhouses - cookers
What is a temperature sensor?
It is a device to measure temperature, can be air temperature, liquid temperature or solid matter.
What applications can pressure sensors be used for?
Pressure sensors are now required inside car tyres on all new cars
- These are located behind the tyre valve used to
inflate the tyre
- They constantly transmit the pressure to the engine control unit (ECU)
- If the ECU detects the pressure is too low, such as with a slow puncture, it will display a warning to the driver
- burglar alarm systems
- washing machines
- robotics
- environmental monitoring
What is a pressure sensor?
Pressure sensors can also be used to indirectly measure other variables such as fluid/gas flow, speed, water level, and altitude.
What applications can proximity sensors be used for?
Car proximity sensors make use of ultrasound
- A sound wave is transmitted from the car
- An echo is produced from a nearby object
- The time it takes for the echo to be received allows the distance to be calculated
- These sensors are helpful
to drivers when reversing
as they warn of objects
that they may reverse into
What is a proximity sensor?
Proximity sensors are able to detect objects without touching them
What are sensors used for?
Used for monitoring and controlling applications.
What does a accelerometer do?
- An accelerometer measures the acceleration of an object and the direction it is moving in
- In smartphones this is used to determine whether the phone is orientated in landscape or portrait
- Some game controllers also use 3-axis accelerometers
to determine the direction
that the controller is moving
What applications is a moisture sensor used for?
- control or monitor the dampness of soil in a greenhouse
- monitor the dampness of clothes as they pass over a sensor in a tumble dryer
- measure water content in a lawn for an automatic watering system
What applications can a humidity sensor be used for?
- monitor the humidity in the air of a greenhouse
- control a dehumidifier in a home
- monitor the humidity in a factory making microchips
What applications can a level sensor be used for?
- monitor the amount of fuel in a car
- monitoring the amount of oil in a car’s engine
- measuring the height of flour in a food processing plant
What applications can light sensors be used for?
- switch street lighting on at dusk and switch street lighting off at dawn
- automatically switch a car’s headlights on when it gets dark
- to close or open the window blinds in a greenhouse to maintain light levels
What applications can infra-red be used for?
- turn on a car’s windscreen wipers automatically when it starts to rain
- detection of intruders in a burglar alarm system
- count the number of people entering or leaving a supermarket
What applications can a flow sensor be used for?
- measure how quickly a chemical is moving through a pipe in a chemical plant
- measure the speed of water in water pipes
- monitor the flow of water in a river
What applications can an acoustic sensor be used for?
- 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
- monitor the sound levels in a car factory
What applications can a gas sensor be used for?
- monitor CO2/O2 levels in a river
- monitor CO2/CO/O2 levels in the air beside a road
- check for the carbon monoxide levels in a car exhaust system
What applications can a pH sensor be used for?
- monitor or control the acidity levels in a chemical process
- measurement of pollution levels in a river
- check acidity levels in the soil in an agricultural field
What applications can a magnetic field sensor be used for?
- used in smart phones so they know which direction it is pointing
- used in the motors of CD players
- used in vehicle anti-lock braking systems
What is a moisture sensor?
Measures the water content
What is a humidity sensor?
Humidity sensors are used to measure and monitor the amount of water present in the surrounding air.
What is a level sensor?
A level sensor is a device for determining the level or amount of fluids, liquids or other substances that flow in an open or closed system.
What is an infra-red sensor?
Infrared sensors are also capable of measuring the heat being emitted by an object and detecting motion.
What is a flow sensor?
Flow sensors are devices used for measuring the flow rate or quantity of a moving liquid or gas
What is an acoustic sensor?
Detects sound
What is a gas sensor?
A gas sensor is a device that senses the atmosphere’s presence or concentration of gases.
What is a pH sensor?
A pH sensor helps to measure the acidity or alkalinity of the water with a value between 0-14.
What is a magnetic field sensor?
Magnetic field sensors are used to measure magnetic flux and/or the strength and direction of a magnetic field.
What 3 sensors are used in a security system?
- The pressure sensors monitor an intruder stepping on the floor next to the windows, doors or on the floor next to valuable paintings
- The acoustic sensors pick up the sound of breaking glass or footsteps on the floor
- The infra-red sensors pick up movement in the rooms but also any changes in heat (e.g. heat radiation from an intruder)
How does the sensor give infomation?
The microprocessor will have access to pre-set values for all sensors.
The microprocessor will sample each sensor at a given frequency (e.g. every second)
If any of the sensor readings exceed the pre-set values, then the microprocessor sends a signal to warn the user (this could be a screen output, a siren, a flashing light …. or all three)
Monitoring continues until the user keys in a PIN/passcode to deactivate the system
How is analogue converted into digital data
Data is converted into digital form using an Analogue to Digital Converter (ADC) and is sent to a microprocessor
How would a system work to keep the pH constant would work?
The pH sensor sends analogue data to a microprocessor about the pH currently being output
The system is programmed to be at a certain pH value, e.g. 7
If the pH goes below this value, it is acidic, so a valve will be opened so that a base (alkali) is added
If the pH goes above this value, it is alkali, so a valve will be opened to add an acid
What are some examples of output devices?
- Displays and projectors
- Printers
- Speakers
- Actuators
What are output devices?
Output devices transfer data produced by a computer and turn it into a human-readable form
What are the 2 main types of inkjet printers?
- Thermal bubble
- Piezoelectric crystal
Explain how thermal bubble works?
- Behind hundreds of print nozzles there are tiny resistors that create heat
- The heat causes the ink to vaporise and form tiny bubbles
- 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
Explain how Piezoelectric crystal printing works?
- A small piezoelectric crystal is located at the rear of each ink reservoir of each nozzle
- When the crystal receives a small electric current, it begins to vibrate in and out
- As it vibrates inwards, ink is ejected onto the paper
- As it vibrates outwards again, new ink is drawn in to replace it
What are the benefits and drawbacks of thermal bubble?
BENEFITS:
- Less expensive technology than piezoelectric
- Possible to use more print nozzles
DRAWBACKS
- Produces larger droplet sizes
- Only certain inks can be used because of the high heat
- More maintenance is needed because of the high
- temperatures involved
What are the benefits and drawbacks of piezoelectric crystal?
BENEFITS:
- 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
DRAWBACKS:
- More expensive technology than thermal bubble
- Can use fewer print heads
How do laser printers work?
Laser printers use dry toner rather than liquid ink
as in inkjet printers
- The laser will scan across the print drum to apply an electrostatic charge to it
- The drum will pick up a charged powder known as toner
- The toner will stick to the paper
- A heated fuser then makes sure the toner can’t be rubbed off the page
- Pages are printed faster than inkjet printers
What is a 3D printer?
3D printers can print using plastic filament, powdered resin, ceramic or metal powder, or paper
Intricate objects can be printed, including hollow areas.
What are the uses of 3D printers?
3D printers produce physical objects
These may be custom made parts or aesthetic objects
Recently, 3D printers have also begin to be used for:
- Food printing
- House building
- Replacement parts
- Medical devices
