Short Notes (I/O)

2D SCANNERS

·         Document is placed

·         Light illuminates

·         Scan head moves

·         Image is produced

·         Sent to lens

·         Charge couple device (CCD) is used to convert the scanned image to digital form

·         Applications: Airports to read passports (key parts of facial images matched)

3D SCANNERS

·         Scan solid objects at several points of x, y, z coordinates

·         Digital image//Produces a three dimensional image

·         Can be used in Computer aided design/3D printers

·         Technologies used: Laser, Magnetic, Resonance, White light

·         Applications: Computed tomographic scanners – CT Scans/MRI//X-rays

BARCODE READER/SCANNERS

·         Shines light / (red) laser at barcode

·         Light is called an illuminator

·         Light is reflected back // White lines reflect light // Black lines reflect less light/absorbs light

·         Sensors / photoelectric cells detect the light

·         Different reflections / bars will give different binary values / digital values // pattern converted to digital values

·         A microprocessor interprets the data

·         Computer reads

·         Barcode is looked up in the database

·         If found—the price and stocks sent to checkout (or point of sale terminal)

·         Number of stocks reduced by one //Automatic stock control

DIGITAL CAMERAS

·         Capture images and videos

·         Uses image sensor chip to capture images/videos

·         Image is converted from analogue to digital (using ADC)

·         Image is turned into pixels

·         Each pixel is given a binary value

·         Pixels form a grid (to create the image)

·         Each pixel has a colour

·         Pixels are stored in sequence (in a file)

·         Meta data is stored (to describe the dimensions/resolution of the image) // It stores the dimensions/colour/depth/etc.

·         An example of a suitable photo file format e.g. JPEG

·         uses memory cards for storage

KEYBOARD

·         Membrane / matrix / circuit board present at base of keys

·         A key is pressed that presses a switch

·         When a key is pressed it completes a circuit // changes the current in a circuit

·         The location of the keypress is calculated

·         An index of characters is searched to find the corresponding keypress

·         Each character has an ASCII / Unicode value

·         The ASCII / Unicode value has a binary value

·         Keypress generates an interrupt

·         Each character / keypress is added to a buffer to wait to be processed

·         The binary can then be processed by the CPU to action the key press

POINTING DEVICES

·         Selection of applications by clicking

·         coordinates and movement of the onscreen cursor/pointer

·         E.g Mouse, Trackball

·         Wired (Connected with USB) or Wireless

·         Used in GUIs

·         Mouse – Mechanical or optical mouse.

MICROPHONES

·         Analogue sound waves and converts them into electrical signals

·         Used in  speech/voice recognition//Voice over

·         Internally/Externally connected

·         Sound—Diaphragm vibrates—produces electric signal—sound card coverts it to digital signal

INKJET PRINTERS

·         Used in a home or small office

·         Low volume printing.

·         Ideal for High quality photos

·         Affordable

·         They have 4 cartridges for CMYK colours

·         Technologies used:

o   Thermal Bubble

o   Piezoelectric

·         Ink sprayed through nozzles onto paper

·         Print Buffer is maintained

·         Prints the page line by line

LASER PRINTERS

·         Uses Dry powdered ink//toner.

·         Print Buffer is maintained

·         Prints the page in one go

·         For high volume printing jobs

·         Working:

o   Uses a heated wire to positively charge a drum

o   Which is then passed over by a laser

o   This reverses the charge in the areas that it hits

o   A toner roller is passed over the drum

o   toner particles stick to the negatively charged areas

o   creating a printer copy of a digital document or image.

·         Found in businesses and offices.

·         Expensive

·         Heavy

·         Toner needs to be refilled.

3D PRINTERS

·         Uses Computer-aided design (CAD)

·         Produces solid object

·         Use Powdered resin, metal, paper, ceramic powder, etc.

·         Uses Additive manufacturing (Built object layer by layer)

·         Used in prosthetics, medical aids, prototyping parts, commercial use, etc.

·         Expensive

ACTUATORS

·         Creates real world movement.

·         Computerized control system

·         Acts upon a signal sent by the microprocessor

·         Include electric motors, pistons, and pumps

·         E.g opening automatic shop doors, lowering the landing gears on a plane, Robotics, control system, etc.

·          

LOUDSPEAKERS/HEADPHONES

·         Uses Digital to Analogue converter (DAC)

·         Sampling rate: rate at which DAC translates digital to analogue voltages

·         Passes through an Amplifier

·         Produces sound

LED MONITORS

·         Light emitting diodes (technology)

·         The display is made up of pixels

o   that are arranged together as a matrix

o   each is formed of three LEDs/filters

·         Shades of colour are achieved by mixing red, blue and green

·         The screen can be back-lit/edge-lit

·         NOTE: Use of liquid crystals with LED technology can also be awarded

·         Advantages:

o   Energy efficient // low power consumption

o   Long lasting // longevity

o   Focussed beam // less light strays from beam

o   Brighter/vivid colours

o   High resolution

o   No flicker

o   Display is thinner

o   Mercury free technology // environmentally friendly

o   Fewer pixel failure

o   Increased viewing in sunlight

LCD MONITORS

·         Liquid crystal display

·         The display is made of pixels

o   arranged in a matrix

·         Uses a flat panel display

·         Backlit display

o   with CCFLs/LEDs

·         Uses light-modulating properties of liquid crystals

·         Crystals can be turned between opaque and transparent (to allow light to pass)

·         Colours created using RGB

Any three from:

− Low power consumption

− Runs at cool temperature

− Do not suffer image burn

− Do not suffer flicker issues

− Bright image/colours

− High resolution image

− Cheaper to purchase than e.g. LED screen

DIGITAL LIGHT PROJECTORS (DLP)

·         Uses a large number of tiny mirrors

·         Mirrors are laid out in a grid/matrix

·         Each mirror creates a pixel in the image

·         Mirrors can tilt toward or away from light source

·         The mirrors reflect light toward a (projection) lens

·         Colour is produced using a colour wheel // Light passes through colour wheel // filters light into red/green/blue

·         Can be used to display an image on a wall/screen

LCD PROJECTORS

·         Older technology than DLP

·         Beam of white light is generated via Bulb/LED

·         Passed through chromatic-coated mirrors

·         Lights reflects at different wavelengths in RGB format

·         Projected as pixels

·         Prism produces it in full colour onto screens