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3.Hardware - Coggle Diagram
3.Hardware
Input and output devices
Laser printers
Prints a whole page at a time
Use dry powdered ink called toner
A rotating drum inside the printer is coated in a chemical which holds an electrical charge
The laser beam is reflected onto the drum and where the light hits the drum the charge is discharged, effectively creating the image on the drum
As the drum rotates it picks up toner which is attracted to the charged part of the drum
Paper is passed over the drum and, by charging the paper with the opposite charge to the toner, the toner is attached to the paper and away from the drum
The paper is heat treated to fuse the toner onto the paper
Inkjet printers
Thermal bubble
Droplets of ink are produced using a thermal bubble
Behind hundreds of print nozzles there are tiny resistors that create heat (the temperature momentarily exceeds 1000 degrees celsius)
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
Piezoelectric crystal
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
Made up of a print head which consists of nozzles which spray droplets of ink, an ink cartridge, a stepper motor and belt which moves the print head assembly across the page from side to side, and a paper feed which automatically feeds the printer with pages as required
3D printers
Primarily based on inkjet and laser printing technology
Subtractive manufacturing is where an object is made by removing material
Additive manufacturing builds up an object layer by layer
Objects are made from powered resin, powdered metal, paper, or ceramic
Direct 3D printing
- based on inkjet printer technology. The print head doesn't just move left and right, but it also moves up and down to create the 3D model
Binder 3D printer
- involves 2 passes to produce each layer of the object. One pass sprays dry powder and another sprays a binder (a type of glue) which makes the powder stick together to build a solid object
Speakers
Speakers take sounds from the computer (digital) and converts to analogue
The digital data is first passed through a DAC where it is converted into an electric current
The current is then passed through an amplifier to create a current large enough to drive a loudspeaker
The electric current is then fed to a loudspeaker where it is converted to sound
When an electric current flows through a coil of wire that is wrapped around an iron core, the core becomes a temporary electromagnet - a permanent magnet is positioned very close to this electromagnet
As the electric current through the coil of wires varies, the induced magnetic field in the iron core also varies. This causes the iron core to be attracted towards the permanent magnet and as the current varies this will cause the iron core to vibrate
Since the iron core is attached to a cone (made from paper or a thin synthetic material), this causes the cone to vibrate, producing sound
Microphones
A microphone converts sound waves into an electric current
When sound is created, it causes the air to vibrate
When a diaphragm in the microphone picks up the air vibrations, the diaphragm also begins to vibrate
A copper coil is wrapped around a permanent magnet and the coil is connected to the diaphragm using a cone. As the diaphragm vibrates, the cone moves in and out causing the copper coil to move backwards and fowards
This forwards and backwards motion causes the magnetic field around the permanent magnet to be disturbed, inducing an electric current
The electric current is then either amplified or sent to a recording device. The electric current is analogue in nature
Screens
OLEDs
Use organic materials (made up of carbon compounds) to create flexible semiconductors. Organic films are sandwiched between two charged electrodes (one metallic cathode, one glass anode)
When an electric field is applied to the electrodes, they give off light. This means that no form of backlighting is required, allowing for very thin screens
Capacitive touchscreens
Made up of many layers of glass that act as a capacitor creating electric fields between the glass plates in layers
When the top glass layer is touched, the electric current changes at that position and the coordinates where the screen was touched are determined by an onboard microprocessor
Most touchscreen phones manufactured in the last few years uses a capacitive touchscreen
Benefits
Medium costs technology
Screen visibility is good even in strong sunlight
Permits multi-touch capability
Screen is very durable
Drawbacks
Only allows the use of bare fingers as the form of input
You can buy special conductive gloves to tackle this problem
Resistive touchscreens
Made up of 2 layers (layer of conductive polyester and a layer of conductive glass)
The 2 layers are separated by an insulating membrane
When the screen is pressed, the two conducting layers make contact and complete a circuit, allowing electricity to pass through
The position where the screen is touched is calculated by a microprocessor
Benefits
Relatively cheap
Possible to use bare fingers, gloved fingers or stylus to carry out an input operation
Drawbacks
Screen visibility is poor in strong light
Doesn't permit multi-touch capability
Screen durability is only fair (vulnerable to scratches)
VR headsets
Has stereo sound, embedded head movement sensors, and separate image projection received by each eye
The Graphics Processing Unit (GPU) is responsible for responding to changes in various inputs by producing a rendered display
Rendering issues are reduced if the headset is fitted with eye-tracking hardware and software
Video is sent from a computer to a headset
Two feeds are sent to an LCD/OLED display (sometimes 2 screens are used - one for the left side and one for the right side of the image)
As the user moves their head, a series of sensors measure this movement, which allows the image on the screen to react to the user's head movements (sensors are usually accelerometers)
Headsets also use binaural sound (surround sound) creating a very realistic 3D sound
Some headsets use infrared sensors to monitor eye movement which allows the depth of field on the screen appear fuzzy when the user's eye indicate they are looking into the distance (and vice versa)
Sensors
Data taken by sensors are in analogue form
Data needs to be converted into a digital form using an ADC so that computers can understand it
Sensor types: gas, infra-red, pH, light, temperature, magnetic field, pressure, humidity, acoustic/sound
Monitoring system: the computer or microprocessor will make no changes to the actual process - it will simply report the values to and inform the user of the status of the process being monitored
Control system: the output from the computer or microprocessor can alter how the process is operating
Secondary storage
Non-volatile storage
Magnetic storage
e.g. HDD (Hard Disk Drive)
Concentric tracks are created on a magnetic disk
Disk spins at high speed (about 7000 times per second)
Spinning platters are each read by drive heads (read/write heads). Data is read and written as the sector moves under the head
The platter is coated with an emulsion of iron or cobalt oxide particles that act as tiny magnets. Binary data is recorded by aligning these tiny magnets in one direction to represent binary 0 and in the opposite direction to represent binary 1
Binary data is recorded in concentric rings, or tracks, subdivided into sectors that hold a fixed number of bytes
Positive or negative polarisation of magnetic particles creates a binary pattern on the disk
Changes from negative to positive, or vice versa, creates an electromagnetic pulse
Each pulse is read as a 1. Anything else is a 0
Surface address - which platter the data is on
A whole sector of a track is read/written each time
A whole sector of a track is often called a disk block. Because of this, a magnetic HDD is known as
a block-oriented storage device
When a file or data is stored, the required number of sectors needed to store the data will be allocated, although the allocated sectors many not be adjacent to each other
Disk buffer
Executing programs don't write directly to magnetic hard disks. Instead they write to an area of main memory (RAM) called a disk buffer
When a file is opened, a disk buffer is created in RAM
The program writes to this buffer until the buffer becomes full, then the operating system writes the buffer to the HDD.
When a file is read from storage, a disk buffer is created. The buffer receives a block at a time belonging to the file and, when the buffer becomes empty, the operating system transfers the next disk block belonging to the file into this buffer
Disk latency
The time it takes for a specific block of data on a data track to rotate around to the read/write head
Includes seek delay, rotational delay, and transfer time
Seek delay - The time the head takes to move across the disk
Rotational delay - The time the disk takes to move to the correct sector underneath the read/write head
Transfer time - Time to move the actual data
Optical storage
e.g. CDs and DVDs
An optical disk is a flat, usually circular disc which encodes binary data in a special reflective layer (binary is encoded in the form of pits and lands)
Both CDs and DVDs use a singular spiral track which runs from the centre of the disk to the edge. When a disk spins, the optical head moves to the point where the laser beam contacts the disk surface and follows the spiral track from the centre outwards
A CD/DVD is divided into sectors allowing direct access of data
CDs
A red laser is used to read and write the data
CDs can be designated R (write once only) or RW (can be written to or read from many times)
DVDs
DVDs use dual layering which considerably increases the storage capacity (uses two 0.6mm thick disks)
Two individual recording layers are joined together with a transparent (polycarbonate) spacer, and a very thin reflector sandwiched between the two layers
Reading and writing of the second layer is done by a red laser focusing at a fraction of a millimetre difference compared to the first layer
Used as backup systems (e.g. photos, music, and multimedia)
CDs and DVDs can be used to transfer files between computers
DVDs and Blu-ray is commonly used in supplying movies and games, as CD capacity isn't large enough to store most movies
Blu-Ray
Use a blue laser to carry out read/write operations
Using a blue laser means that the pits and bumps can be much smaller, so a blu-ray disk can store up to 5 times more much data than a DVD
Uses a single 1.1mm thick polycarbonate disk
Because blu-ray only uses one layer the disks don't suffer from birefringence (light is refracted into two separate beams causing reading errors)
Automatically come with a secure encryption system which helps to prevent piracy and copyright infringement
Solid state storage
e.g. USB sticks, SSDs
SSD (Solid State Disk)
Have no moving parts and all data is retrieved at the same time
The most common type of SSD store data by controlling the movement of electrons within NAND chips
Comprises millions of NAND or NOR flash memory cells
Data is stored as 1s and 0s in the millions of tiny transistors (at each junction) - one transistor is called a floating gate and the other is called a control gate within the chip, creating a non-volatile re-writable memory
Arranged within an array of chips on a circuit board
Use EEPROM, which mainly uses NOR chips instead of NAND
EEPROM allows data to be read or erased in single bytes at a time, whereas NAND only allows blocks of data to be read or erased
Advantages of SSD over HDD
Faster access speed (no moving read/write head)
Lower power consumption (extended battery life and devices stay cooler)
Less susceptible to damage (no moving parts to go wrong)
Silent in operation
Lighter in weight
Thinner due to no moving parts
Drawback - longevity, so SSDs aren't used in servers
NAND Flash memory cells
Contain no moving parts
Floating gate transistors trap and store a charge
The charge is retained without power
The cells are arranged in a row and have a bit line structure that connects into a memory address called a word line. The address provides a means of identifying a location for data storage, and the word line forms an electrical path allowing all the memory cells on that row to be activated at the same time for storage or retrieval
Cells are combined in blocks. An electron trapped inside the middle layer reads as a 0, outside the middle is read as a 1. Data must be read, deleted, or written in blocks. Data can't be overwritten without being erased first
Storage devices that aren't directly accessible by the CPU
Data access time is slower than primary storage
All applications, the operating system, device drivers and general files are stored in secondary storage
Logic gates
NOT gate
Boolean algebra: P = NOT A
Boolean notation: P = ¬A
AND gate
Boolean algebra: P = A AND B
Boolean notation: P = A•B
OR gate
Boolean algebra: P = A OR B
Boolean notation: P = A + B
XOR gate
Boolean algebra: P = A XOR B
Boolean notation: P = A ⨁ B
If only one input is 1 then the output is 1
NAND gate
Boolean algebra: P = NOT (A AND B)
Boolean notation: P = ¬(A•B)
Known as a universal gate as different combinations of NAND gates can act like NOT, OR, and AND gates
Advantages
Minimise cost of production (using only NAND gates)
Can speed up processing (by using fewer gates)
NOR gate
Boolean algebra: P = NOT (A OR B)
Boolean notation: P = ¬(A+B)
The output is 1 only if both inputs are 0
Embedded systems
Any manufactured item that has a mechanical or electrical parts will likely have one or more embedded systems
An embedded system must contain a processor, memory and an input/output capability
For some applications, the system will have an input and output solely associated with the internal workings of the host system
Pros
Small in size and therefore easy to fit into devices
Relatively cheap to make
Usually dedicated to one task, making for simple interfaces and often no requirement of an operating system
Consume very little power
Very fast reaction to to changing input - in real time
Cons
Difficult to upgrade devices to take advantage of new technology
Troubleshooting faults in the device becomes a specialist task
Although the interface can appear to be simple, in reality it can be more confusing
Any device that can be accessed over the internet can be hacked
Due to difficulty in upgrading and fault finding, devices are often just thrown away rather than being repaired
Memory vs storage
Memory - the internal devices which the computer can access directly, which can be the user's workspace, temporary data, or vital data key to running a computer
Storage devices allow users to store applications, data and files, which is stored permanently and they can change it or read from it
Storage is larger than internal memory
Internal memory includes registers and memory cache, used to store data which the processor will probably need to use again
Primary storage
Accessed directly from the CPU
RAM
Volatile memory - requires a continuous supply of electrical energy in order to work
Can be written to and read from
Used to store data, files, programs, part of the operating system currently in use
DRAM (dynamic RAM)
Consists of a number of transistors and capacitors
Needs to be constantly refreshed
Less expensive to manufacture than SRAM
Higher memory capacity than SRAM
Main memory is constructed with DRAM
Consumes more power than SRAM under reasonable levels of access, as it needs to be constantly refreshed
SRAM (static RAM)
Uses flip-flops to hold each bit of memory
Doesn't need to be constantly refreshed
Has a faster data access time than DRAM
Processor memory cache (a high speed portion of memory) makes use of SRAM
If accessed at higher frequency, power usage can exceed that of DRAM
Temporary memory device
ROM
Non-volatile memory device
Read only memory
Stores startup information for the computer
PROM (Programmable read-only memory)
A type of ROM chip that can be altered once
Made up of a matrix of fuses
Programming a PROM requires a PROM writer which uses an electric current to alter specific cells by "burning" fuses in the matrix
Can only be written to once
Often used in mobile phones and RFID tags
EPROM (Erasable programmable read-only memory)
Use floating gate transistors and capacitors
Data can be erased using ultraviolet light and new data can be written
This reprogramming usually requires the chip to be removed from the circuit
Often found in video game cartridges
EEPROM (Electrically erasable PROM)
Works similar to EPROM except an electrical signal can be used to remove existing data
The chip can remain in the circuit while the contents are changed
Often used in smart cards and remote keyless systems
Made up of floating gate transistors and capacitors
Buffer - a temporary storage created for data transmitted from one part of the system to another which functions as a queue
