Download Lesson 13 - Input Output Devices

Hardware Devices
Input methods and devices
• Mouse
• Keyboard
• Bar code reader
• Scanners
• Flatbed Scanner
• Fingerprint scanner
• Retina Scanner
• Iris Scanner
• Optical Mark Reader (OMR)
• Optical Character Reader (OCR)
• Magnetic Stripe reader
• Smart Card Reader
• RFID Reader
• Touch Sensitive Screen
• Graphics Tablet
•Voice recognition
• Digital Still Camera
Hardware Devices
Mouse
Designed in 1964 by Douglas Engelbart
Use as a tool to aid use of Graphical user interfaces.
Uses a X-Y positioning system
Latest mouse uses wireless technology and more buttons for different
functions.
Hardware Devices
Keyboard
Enter text and numbers into a computer
Electronic circuits continually scan the keys to detect key presses
Converted to ASCII code or UNICODE for the computer to understand
Each key press sent as an interrupt to the CPU
 Braille Keyboards are used for disabled people.
Hardware Devices
Bar code reader
Electronic Device for reading barcodes on various items
A sequence of black and white bars with coded information identifying the
product.
 Uses the change in light source to read the information.
 Converted to ASCII by the scanner for a computer to understand.
Hardware Devices
Scanner - Flatbed
Glass plane illuminated from beneath by a bright light
An array of light detecting sensors spanning the width of the glass pane is
moved slowly up to pick up any light reflected from the course above.
 Converted into an equivalent electric signal.
 Colours scanner have three arrays – Red, Green, Blue
 A digitised imaged is stored by the computer.
Hardware Devices
Scanner - Fingerprint
A security device that takes a picture of your finger.
 Sensor and decoder circuitry analyses the captured image and converts it
into electric form for processing by a computer against stored fingerprint
data.
Some are optical devices using light sensors – others use electrical currents
to scan the finger.
Used on PCS to authenticate users.
Hardware Devices
Scanner - Retina
Low energy infrared light source that is directed onto the retina
 Photoelectric detectors convert the reflected light into an electrical signal
to be processed by the computer.
 Like the fingerprint the retina is unique for each person.
Hardware Devices
Optical Mark Reader
Detects marks placed in predefined positions on a form
 Passed under a light source
 Intensity of reflected light from each row in the form is measured and
converted by photoelectric sensors into an electrical equivalent.
Hardware Devices
Optical Character reader
Uses an optical scanner
 Scans in the text then analysis the digital images.
 Used to automate postal sorting by recognising the postcode on the
letters.
 Some bills are created in a machine readable font.
Hardware Devices
Magnetic Stripe Reader
Reads information encoded magnetically in a stripe on the back of a plastic
card.
 The particles on the magnetic strip is orientated in a way to encode binary
data
 Can store up to 2k of information
Hardware Devices
Smart Card Reader
Reads from plastic cards that holds an integrated circuit chip
 The Chip contains a microprocessor, a small amount of ROM, a small
amount of EEPROM, a small amount of RAM and a computer bus system.
 The chip is provided power when it is inserted into the reader.
 Like a computer the mini applications are loaded into the RAM from the
ROM and EEPROM and the microprocessor executed the applications.
Hardware Devices
RFID Reader
Radio Frequency Identification
 Uses radio frequencies to transmit data.
 Receives data from a carrier without any physical contact.
 Data capacity of RFID transponders is normally a few bytes to several Kb
Hardware Devices
Touch Sensitive Screen
A VDU that allows user interaction with an application on the display.
 Screen has been specially adapted so that the region just in front of the
screen is criss-crossed by horizontal and vertical beams of infrared light. The
breaking of these beams determines where on the application has been
selected.
 The coordinates of the broken beams is determined and sent back to the
application.
 The application maps these coordinates into an action.
 Also uses a accelerometer to determine at what angle the device is held.
Hardware Devices
Graphics Tablet
Allows graphics to be drawn into the computer by hand like using a pencil.
 Consists of a flat board and a stylus.
 Pressing the board with the stylus operates a microswitch which is
detected by the computer.
 The boards contains electronics to detect the position of the stylus tip.
Hardware Devices
Voice recognition
The computer can be trained to recognise a human voice and transforms
speech into text using a microphone, sound card and appropriate software
 This system can be used to issue commands to the computer and to dictate
sentences directly into applications.
Hardware Devices
Digital Still Camera
An electronic device used to capture and store photographs digitally on a
memory cards before uploading to a computer via an USB Connection.
 Can also record sound and video.
Hardware Devices
Output Methods and devices
• Visual Display unit
• Cathode – ray tube
• Flat Screen
• Plasma Screen
• Speech Output
• Electronic Paper
• Printer
• Impact Printer
• Inkjet Printer
• Laser Printer
• Plotter
Hardware Devices
Visual Display Unit - CRT
A vacuum tube with a narrow neck and a flat rectangular base
 Screen inside coated with a phospher that emits light when struck with an
electron beam
 The electron beam starts at the top and does line by line to the bottom.
 Whole process is done many times per second.
 If the process is completed in less that 0.05 seconds the human brain does
not register any flicker.
 Colour CRTs use three electron beams – The screen consists of triplets of
phosphers – Red, Green and Blue.
 The intensity of the light from the beams produce the colour.
Hardware Devices
Visual Display Unit – Flat screen
Liquid crystal Display is a matrix of liquid crystals cells
 The liquid crystal changes the polarisation of light when an electric field is
applied to the screen
 Each cell consists of 1 pixel at full resolution. Each pixel is subdivided into
RGB.
 TFT (Thin Film Transistors). Each pixel is made up of a TFT, a capacitor and
the liquid crystal. Transistor acts as a switch, and the capacitor as a reservoir
for the electrical charge needed to create the electric field that changes the
polarisation of the light passing through the liquid crystal.
Hardware Devices
Visual Display Unit – Plasma Screen
Each pixel is controlled by a miniature fluorescent light
 When the control voltage is applied, the gas becomes plasma and releases
ultraviolet light, which strikes phospers on the front of the screen to emit
visible light.
 Generates a lot of heat.
Hardware Devices
Speech output
Words in electronic documents can be output as spoken words using
specialist speech synthesis software, a sound card and speakers.
Electronic Paper
 Flexible paper thin displays which create images using tiny coloured beads
that move or rotate in response to an electric field.
 An electrically charged pencil can be used to write on the display.
 Fed through a device that erases the image and writes a new page.
Hardware Devices
Impact Printer.
Used in applications that require multi-part stationary or printing through
carbonised envelopes
 Use an inked ribbon to mark paper with an impression of a character
 Dot matrix printer uses 24 metal pins that form the outline of a character
 Very noisy
 Pin Number printing – the ribbon is removed so that the impact is shown
but not the ink.
Hardware Devices
Inkjet Printer.
Printers that transfer ink to paper using electrostatics or non-impact
technique
 Colour printers print a line of colour at a time until the entire line is
complete.
 Colour printers use four ink cartridges – Cyan, Magenta, Yellow and Black.
These colours are mixed at the right quantities to produce the desired colour
– subtractive mixing.
 Special paper is required for higher quality prints to absorb the ink.
Hardware Devices
Laser Printer.
Prints a whole page at a time,
 Processor in the printer generates a bitmap of the page to be printed.
 A negative charged is applied to the photosensitive drum at the heart of
the laser printer.
 One or more lasers are directed at the drum surface effectively drawing
the image onto the drum neutralising the negative charge.
 The charged surface of the drum is exposed to toner. The particles are
negatively charged so they attach to the neutralised part of the drum.
 A piece of paper is passed under the drum and pressed causing the toner
to make the image on the paper.
 Heated rollers fuse the toner to the paper which is why the paper comes
out warm.
 Colour laser printers have several drums.
Hardware Devices
Plotter
A output device that moves a pen across paper in a continuous movement
so that a two dimensional drawing can be made.
 The pen is lifted and placed when required.
 Pens of different colours are placed to the side and are picked up by the
drawing arm when required.
 Perforated paper is placed over a drum in some instances and moved back
and fore in the plotter to produce certain shapes – e.g. Circles.
Hardware Devices
Your Task
Using online mind mapping software (https://bubbl.us/) or shapes in power point
create a mind map of the devices you have learned about that follows this format.