2D Scanners (how it works) 

1. Document is placed on the glass plate and the cover is closed. 

2. A lamp is used to brighten up the document 

3. Scan head is moved slowly across the document by a belt that is attached to a stepper motor. 

4. Image of the document is reflected by an angled mirror to another mirror. 

5. The last mirror reflects the image onto a lens. The lens focuses the image through a filter on the CCD (Charged Couple Device) array. 

Advantages:- 

● Can produce high-quality digital copies of a document 

● Digital copies of documents can be sent electronically, stored securely, or edited on the computer 

Disadvantages 

● Repeated exposure to x-rays can be harmful 

Applications 

● Computed tomographic (CT) scanners are used to create a 3d image of a solid object. This is based on tomography technology which basically builds up an object using slices.

● X rays – CT scanners

● Radio frequencies MRI magnetic resonance images

● Gamma rays – SPECT signal photon emission computed tomography.

Barcode readers (how it works) 

1. Barcode is read by a red laser (LED) 

2. White bars reflect most of the light while the black bars absorb most of the light, allowing barcode to be read 

3. This reflected light is read by photoelectric cells 

4. A pattern is then generated and is converted to digital data

5. For example, a barcode digit may be represented as BWBBWBWB physically, but as 10110101 digitally.

Advantages 

● Quick and easy to identify products 

● Additional information can be easily retrieved from a database 

● Allows the use of automated stock control and sales reports 

● Related information (e.g. product price) is changed in the database, meaning the barcode always remains the same 

2. A photograph is captured when light passes through the lens onto a light-sensitive cell 

3. A cell is made of pixels. The number of pixels determines the file size used to store the image. By reducing the resolution, the storage requirement is reduced. 

4. The quality of a photograph depends on factors such as lighting and the type of lens used.

Advantages 

● Images can be reviewed immediately via the screen 

● Images can be copied or edited easily on a computer 

● Images can be automatically added to sharing sites 

Disadvantages 

● A good camera is needed to match the quality of the traditional film 

● Large capacity memory cards are needed if shooting lots of photos 

Applications 

● Professional photography, using DSLRs 

● Amateur photography 

● Speed cameras, e.g. using OCR software to read registration plates 

Advantages

● Simple and easy to use 

● Potentially a fast way to enter data 

Disadvantages

● A slow way to enter lots of data if not a trained typist 

● Mistakes can be made if not careful 

Applications

● Used in everyday computing to manually enter data and commands, e.g. writing a report in a word processor 

2. Mice have left-click and right-click buttons for selection and other functions. Some also have a scroll wheel which allows rapid movement up and down a screen.

3. Mice are now optical which means they use a laser to detect and track movement across the surface. 

Advantages 

● Simple and easy to use 

● An efficient way to navigate 

Disadvantages

● Require a flat surface 

● Requires space to operate 

Applications 

● Used in everyday computing to control the pointer in GUIs 

Touchscreen (how it works) 

An interactive device that uses a liquid crystal display and touch-sensitive sensors. The User is able to switch between applications, rotate an image, zooming in on a document, or draw a picture.

It uses 3 systems:  

1. Resistive 

   • has a glass panel covered with a metallic layer. 

   • The layers contact the electric current. The change in the electric field can state where the user touched the screen. 

   • It isn't that expensive and you can use gloves. 

   • However, the visibility is poor in sunlight and it is vulnerable to scratches. 

   • Working

     • Uses two/multiple layers

     • When the top layer touched/pushed two layers make contact

     • The Circuit is completed when layers touch

     • Point of contact is determined/calculated

2. Capacitive 

   • layer that is used to store electrical charge on the glass panel. 

   • It is medium cost and screen visibility is good in strong sunlight. 

   • Also, the screen is durable. However, it only allows the use of bare fingers.

   • Working

     • Conductive layer

     • An electrostatic/electric field is created

     • Sensor(s) (around the screen) monitor the electrostatic field

     • When touched (electrostatic) charge is transferred to finger

     • Location of touch is calculated // Co-ordinates used to calculate the touch 

3. Infrared (heat and optical) 

   • Heat-sensitive uses glass as the screen material and needs a warm object to carry out an operation

   • Optical uses glass as the screen material and uses an array of sensors.

   • It allows multi-touch technology, the optical one can be used with gloves and has good durability.

   • However, it is very expensive and heat-sensitive only allows finger for input.

Advantages 

● Allows disabled users to give instructions to a computer 

● Enables the use of speech recognition software 

● Allows voice calls and the audio in video calls (VoIP)

Disadvantages

● Speech recognition accuracy can sometimes be hit and miss 

Applications

● Mobile phones, e.g. for traditional phone calls or VoIP 

● Tablets and laptops, e.g. for video conferencing or VoIP 

● Voice recognition systems, e.g. to input data and commands using spoken words 

• acoustic (measures sound levels. Used in security systems)

• accelerometer (measures acceleration forces. Used in Phones, earthquake monitoring)

• flow (amount of liquid/gas/steam flowing/moving through an environment. Used in factories, nuclear power plants)

• gas (measures the concentration of the gas in the atmosphere)

• humidity (measures level of moisture. Used in farming, agriculture, greenhouses)

• infra-red(measures infra-red radiation. Used in security systems)

• level (measures amount of substance. Used in cars-oil/fuel)

• light (measures the presence of light/lasers. Used in automated lighting system)

• magnetic field (measures the presence of magnetic fields. Used in counting cars passing an area)

• moisture(measures amount of water in a substance/soil. Used in farming, agriculture)

• pH(measures pH level of a substance. Used to monitor pollution level in rivers/lakes)

• pressure(measures amount of pressure applied. Used in security systems)

• proximity(measures objects distance. Used in robots, self driving cars)

• temperature(measures temperatures. Used in air conditioning levels)

Inkjet Printers (how it works) 

• Rollers are used to move the paper through the printer

• Nozzles spray/drop/jet ink onto the paper

• Ink jets/print head/nozzles are moved across the paper (to distribute the ink)

• Different colour inks are mixed to create required colours

• Technology could be piezoelectric

• Technology could be thermal bubble

  • Ink is heated

• and expands/evaporates into a bubble

• Bubble is pushed through the nozzle on to the paper

  • then the bubble collapses

• Electrical current is applied to a crystal

  • which makes it vibrate

  • which forces a droplet of ink through the nozzle

Disadvantages 

● Generally slower at printing than compared to laser printers 

● Ink cartridges can be expensive 

● Printed text is nice and clear but laser printed text is still superior 

Applications 

● Low volume printing where speed isn’t critical 

● High quality photographic documents 

● Home and small office 

● Printing on heat sensitive stationary, such as labels

Laser printer (how it works) 

● A printer that makes use of powdered ink (powdered toner) and static electricity to print. 

● Laser printers are ideal for high volume printing because they produce very high quality documents at fast speeds. 

1. The rotating printing drum is given a positive charge. 

2. A laser removes the positive charge from certain areas of the drum as it scans across it, creating a negatively charged copy of the text/image to be printed. 

3. On an ink roller, the toner is given a positive charge which attracts it to only the negatively charged areas on the printing drum. 

4. The toner then transfers from the negatively charged areas of the drum to some positively charged paper. 

5. A fuser is used to heat the document and permanently melt the toner onto the page. 

Disadvantages

● Good quality images, but inkjet images are superior 

● The initial cost for the printer can be expensive 

● Heavy and bulky 

● Toner is expensive but is replaced infrequently

Applications 

● High volume printing where speed is critical 

● Shared printer for several users 

● Predominantly text based documents 

● Found in businesses and offices 

Advantages 

● Prototype objects can be created at a fraction of the cost of a factory 

● A variety of intricate and “impossible” objects can be printed in a variety of materials 

● Computer designs can be shared and printed by others

Disadvantages 

● Expensive to buy although entry models are becoming more affordable 

Applications 

● Home and commercial use 

● Prototyping parts and solutions 

● Human prosthetics 

● Medical aids 

Speakers and Headphones (how they work) 

● Speakers and headphones are the output devices responsible for producing sounds. 

● Speakers and headphones convert digital signals into analogue sound waves that are audible to our human eardrums. 

● Speakers come as standard as most portable computing devices. Desktop computers usually require the purchase of separate speakers. 

● Speakers and headphones aren’t just for music, they also allow us to hear computer warning signals and other people when communicating via voice or video calls. 

Applications

● Headphones keep sound personal so as not to disturb others 

● Speakers allow for sound that can fill the room 

● Music 

● Communications (phones, tablets, laptops) 

Actuators (how it works) 

● Actuators are the output devices responsible for creating real world movement. This could range from physically opening automatic shop doors to lowering the landing gears on a plane. 

● They are often used in a computerized control system, acting upon a signal sent by the microprocessor. Actuators include electric motors, pistons, and pumps. 

Advantages 

● Low power consumption means that displays can be placed on battery powered devices 

● Screens are now lighter and thinner – meaning they can be used in a variety of places 

● Sharp high resolution images 

● Vivid colours with good contrasts 

● Reach maximum brightness quickly 

● Reliable and long-lasting 

Disadvantages  

● Keeping up with the absolute latest screen technology can be expensive 

Applications

● Phone and tablets 

● Laptops and computer screens 

● Televisions 

● Gaming devices 

● Cameras 

● Household appliances 

LCD & DLP Data Projectors 

● Data projectors are output devices used to project the digital output from a computer device on to a large screen or wall. 

● The user can usually choose whether the projector mirrors their computer screen, extends it, or replaces it. 

● Projectors are ideal when training or presenting information to a large audience. 

● Prices are very reasonable for basic projectors, however, a data projector capable of showing cinema films or sports footage in a bar is far more expensive. 

● Data projectors come in two mains types, LCD and DLP. 

Advantages 

● Projected content can be seen easily be a large audience 

● Allow a wide range of media and ideas to be shared with others 

● Entry level projectors are affordable 

Disadvantages 

● Top quality projectors are very expensive 

● Some projectors do not work very well in natural light 

Applications 

● Presenting to a large audience 

● Education and training environments 

● Boardrooms 

● Cinemas and bars