CH3

• Resistive touchscreen

  • Has an upper layer of polyester and a bottom layer of glass
  • When top polyester layer is touched, the top layer and bottom layer complete a circuit
  • Signals are then sent out, which are interpreted by a microprocessor and the calculations determine the coordinates of where the screen was touched
• Capacitive touchscreen

  • Made up of many layers of glass that acts like a capacitor creating electric fields between the glass plates in layers
  • When top glass is touched, the electric current changes and the coordinate where the screen is touched are determined by an on board microprocessor
  • Coordinates sent to touch screen driver
• Resistive touchscreen advantages

  • Cheap
  • Can use bare fingers, gloved or stylus for input
• Resistive touchscreen disadvantages

  • Screen visibility is poor in strong sunlight
  • Does not permit multi-touch capacity
  • Screen durability is weak
  • Vulnerable to scratches and wears out though time
  • Only bare fingers and cannot use gloves to styluses for input
• Capacitive touchscreen advantagesExpensive

  • Screen visibility is good under strong sunlight
  • Permits multi-touch capability
  • Screen is very durable
• Capacitive touchscreen disadvantages


  • Only bare fingers can be used for input
• Microphone


  • When sound is created, air vibrates
  • Diaphragms pick up the air vibrations, hence the diaphragm also vibrates
  • Copper coils is wrapped around the permanent magnet and coil is connected to the diaphragm using a cone
  • As diaphragm vibrates, the cones moves in and out, causing the copper coil to move backwards and forwards
  • This movement causes the magnetic field around the permanent magnet to be distributed, inducing an electric current
  • Electric current is then either amplified or sent to a recording device
  • The electric current is analogue in nature
• Virtual headset

  • Video is sent from a computer to the headset either using HDMI cable or smartphone is fitted into the headset
  • Two feeds are sent to an LCD/OLED displays
  • Lenses placed between the eyes and the secret allow for focusing and reshaping of the image/video for each eye, thus giving a 3D effect and adding to the realism
  • As the user moves their head, a series for sensor and LED measure this movement, which allows the image/video on the screen to react to the user's head movement
  • Headset also use binaural sound so speaker output appears to come from behind, side, from a distance
  • Infrared sensors to monitor eye movement which allows the depth of field on the screen to be more realistic
• Laser printer

  • The revolving drum is initially given an electrical charge
  • A laser beam bounces off moving mirrors and scans back and forth across the drum
  • Discharge certain points
  • The drum is coated with oppositely charged toner
  • Pattern on the drum is transferred to paper & Paper is passed through the fuses to seal the image
  • Electrical charge is removed from the drum
• Inkjet printer

  • Data from the document is sent to a printer driver
  • Printer driver ensures that the data is in a format that the s hose printer can understand
  • Cheerleader is made by the printer drive to ensure that the chosen printer is available to print
  • Data is sent to the printer and stored in a temporary
• Speaker

  • An electric current is sent to the speaker
  • The electric current passes through the coil the current in the coil creates an electromagnetic field
  • Changes in the audio signal cause the direction of the electrical current to change
  • This determine the polarity of the electromagnet
  • The electromagnet is repelled by or attracted to a permanent magnet
  • The movement of the coil causes the diaphragm to vibrate
  • The vibration creates sound waves
• Virtual headset output

  • Most important component are the two eyepieces
  • Fed paired images from the controlling system which, when looked at together, give the eyes a sensation of being in a 3D environment
  • Images can be collected using a specialized photographic techniques
  • The wearer can control which part of the 3D environment is in view
  • They do this by moving their head or by a controlling device
• ROM

  • Non-volatile
  • Read only
  • Stores the operating system
  • Stores the boot-up instructions
  • Can't be changed
• RAM

  • Volatile
  • Read/write
  • Stores currently running parts
  • Stores data on the current progress and about the device
  • Can be changed
• PROM

  • Made of matrix fuses
  • Requires the use of a PROM writer which uses an electric current to alter specific cells by 'burning' fuses in the matrix
  • Can only be written once
• EPROM

  • Use floating gate transistors and capacitors
  • Ultraviolet light is used to program an EPROM
• SRAM

  • Use flip flops to hold each bit of memory
  • Does not need to be constantly refreshed
  • Faster data access time than DRAM
  • Used as Processor memory cache
• DRAM

  • Consist of a number of transistors and capacitors
  • Needs to be constantly refreshed
  • Less expensive than SRAM
  • Higher memory
• Internal secondary storage

  • Magnetic media
  • Solid state drive
  • Optical disc
• Magnetic media

  • Large capacity to store large files
  • Reasonably fast access speed
  • Users won't have to wait for videos to load
  • Cheap per unit storage
  • If a large number is needed, cost would be quite low
  • Slower degradation of data
  • Last longer and more reliable under heavy use
• Solid state drive

  • Large capacity to store large files
  • Fast access speed
  • Users won't have to wait for videos to load
  • Reliable
  • Can be damaged and would still work
  • No moving parts
  • Not possible to overwrite the existing data
  • Need to erase the old data to write
  • To read/write uses movement of electrons
• Optical disc

  • Can hold a lot more data than a standard DVD, meaning it can store movies with better picture and sound quality
  • Portable
  • More expensive than DVDs
  • Requires a Blu-ray player
  • Can lose data when scratched
• Internal operations of magnetic hard disk

  1. Hard disk drive has one or mole platters made of aluminum or glass

  2. Each surface of the plater is capable of being magnetized

  3. The platters are mounted on a central spindle and rotated at a high speed

  4. Each surface of the platter had a read/write head mounted on arm positioned just above the surface

  5. Electrical circuits control the movement of the arm and heads

  6. The surface of the platter is divided into concentric tracks and sectors

  7. One track in one sector is the basic unit called a block

  8. The data is encoded as a magnetic pattern for each block

  9. When writing to disk, a variation in the current in the head produces a variation in magnetic field on the disk

  10. When reading the disk, a variation in magnetic field produces a variation in current through the head
• Internal operations of solid state memory

  1. Uses semiconductor chips to store data

  2. Have individual memory cells which trap different level of electrons on a charge trap

  3. Memory cell is copied horizontally and vertically to make storage capacity

  4. Making a 3D spreadsheet

  5. There's a stack in layers of many spreadsheet

  6. To isolate and determine which row and layer to read/write from, use control agent selectors (layers) and bitline selectors (rows)
• Internal operations of optical disc

  1. Drive motors is used to spin the disc

  2. Tracking mechanism moves the laser assembly

  3. A lens focuses the laser onto the disc

  4. Laser beam is shone onto disc to read/write

  5. Surface of disc has a reflective metal layer

  6. Tracks on the disc have sequence of pits and lands

  7. Reflected light in the encoded as a bit pattern
• Embedded system

  • Installing microprocessors into devices to enable operations to be controlled in a more efficient way
  • At the core is an integrated circuit designed to carry out computation for real-time operations
  • Embedded systems are managed by microcontrollers or digital signal processors (DSP), application-specific integrated circuits (ASIC), field-programmable gate arrays (FPGA), GPU technology, and gate arrays
  • These processing systems are integrated with components dedicated to handling electric and/or mechanical interfacing
• Embedded system advantages

  • Small in size to fit into devices
  • Low cost
  • Consume little power
• Embedded system disadvantages

  • Difficult to upgrade devices
  • Troubleshoot faults in the device need a specialist
  • Can be access over the internet (hackers, viruses)
• Buffer

  • To act as a holding are, enabling CPU to manipulate data before transferring it to a device
  • Keep track of data in buffer and then copy the buffer to a disk due to slow read/write
• Sensor

  • Measures and converts the physical quantity to an electrical signal, which can then be read by an embedded systems engineer or any electronic instrument
  • Stores the measured quantity to the memory
• 1. D Converter

  Converts the analog signal sent by the sensor into a digital signal
• Processor & ASICs

  Assess the data to measure the output and store it to the memory
• 1. A Converter

  Changes the digital data fed by the processor to analog data
• Actuator

  Compares the output given by the D-A Converter to the actual output stored and stores the approved output
• AND gate

  Output is 1 only if both inputs are 1
• NOT gate

  Output is the opposite of the input
• OR gate

  Output is 1 if either or both inputs are 1
• NAND gate

  Output is 1 unless both inputs are 1
• NOR gate

  Output is 1 only if both inputs are 0
• XOR gate

  Output is 1 if either but not both inputs are 1