1.3.5 (b): describe the principles of operation of HDD's

A Hard Disk Drive (HDD) is a common secondary storage method, which makes use of magnetic disks to store data.

A typical HDD will have a number of disks (or platters) which can spin around 700 times per second. Usually, each platter has two surfaces to store data.

A number of read-write heads have access to the surface of the platters. Typically, they can move from the centre of a platter to the edge and back again 50 times a second

On the platters, data is stored in sectors and tracks. Each sector has a fixed number of bytes.

Note: no need to learn D

-The real disadvantage of HDD's is latency (latency is the time taken for a block of data on a track to to rotate around onto the write/read head)

- Since many applications require the read-write heads to look for the correct sectors to read/write data, a big number of head movements are required.
(A user will experience this latency when you see a message from program saying "Program not responding")

1.3.5 (a): describe the principles of operation of RAM and ROM

There are two types of RAM: static RAM and dynamic RAM.

RAM and ROM are both primary storage (memory)

RAM = random access memory (RAM)is volatile memory used to store data files or part of an operating system which is currently in use. It can be both read from and written to.

-volatile means it's temporary memory. So the contents of the RAM will be lost, when power to the RAM goes.

-RAM never runds out, but it gets slower through time.
-As RAM becomes full, the processor has to access the Hard-Disk Drive (HDD, also secondary storage) to replace old data on the RAM with new data.
-But by increasing the RAM size, the number of times this access operation is done is reduced, making the computer run faster.

DRAM

Dynamic RAM (DRAM) chips are made up on numerous capacitors and transistors.

Capacitor = Holds a bit of information (0 or 1)

Transistor = Like a switch; it allows the control circuitry on the chip to read from or write to a capacitor

-DRAM needs to be refreshed constantly (capacitors need to be recharged). Every 15 microseconds. If they aren't. The capacitors will lose their charges and their values will 0's

SRAM

Static RAM (SRAM) doesn't need to be refreshed.
-Instead of capacitors and transistors, SRAM makes use of "flip flops" to hold bits of memory.
-SRAM also provides faster access speeds 
>DRAM access speed is normally 60 nanoseconds
>SRAM access speed is normally 25 nanoseconds.

ADVANTAGE OF DRAM
-Less expensive to manufacture
-Consumes less energy
-Has a higher storage capacity

ADVANTAGE OF SRAM
-Doesn't need to be refreshed.
-Data access is faster.

ROM

Read-Only Memory (RAM) is non-volatile memory used to store the start-up instructions for a computer system (e.g BIOS). It can only be read from.
-Data isn't lost when power is turned off.

Application of RAM and ROM

Lets say a toy car has a circuitry which contains a RAM chip, a ROM chip and a SSD.

The ROM chip will store the factory settings and the start up routines

The RAM chip stores the instructions sent from the controller

The SSD will be used to store the instructions to operate the car.

And finally, suitable input device. Like a touch screen as there aren't many buttons

1.3.4 (h): describe the principles of operation of projectors and describe how they are applied to real-life scenarios.

Two types of projectors:
-Digital Light Projectors (DLP)
-Liquid Crystal Display (LCD) projector

DLPs

-DLP's use millions of micro mirrors on a chip. The number of micro mirrors and the way they are arranged determines the resolution of the image projected

-When the micro mirrors are tilted towards the light source, they are 'on'. When they are tilted away from the light source, they are 'off'

-So the micro mirrors switch 'on' or 'off' thousands of times a second to create various shades of grey. The typical number of grey shades which can be produces is 1024.

- For example: If the mirror turns on more times than it turns off, a lighter shade of grey will be produced.

-A bright white light source (from a xenon light, for example) passes through a colour filter on it's way to the DLP chip.

-The light is split into the three primary colours (RGB) 

-The on and off states of the mirrors are linked with the 3 colours to produce the coloured image.

-Over 16 million different colours can be produced.

LCD projectors

1.3.4 (g): describe the principles of operation of monitors and describe how they are applied to real life scenarios

Definition: A screen which displays an image generated by a computer

LCD
-Most monitors and TV's nowadays use Liquid Crystal Displays (LCD) technology.

In LCD's, the front layer of the screen is made up of liquid crystal diodes. These diodes are grouped in threes or fours, (known as pixels!)

The groups if three are: Red, Green and Blue
The groups of four are: Red, Green, Blue and Yellow. (This makes the colours more vivid)

Modern LCD monitors are back-lit using Light-Emitting Diode (LED) technology, which is designed to give the image better contrast and brightness.

Back then, LCD's used Cold-Cathode Fluorescent Lamp (CCDL) technology as the back lighting method.

Whats the difference between the way LCD's light up the screen and CCDL's light up the screen?

CCDL's use two fluorescent tubes behind the LCD screen, while LED's (LED technology) use a matrix of tiny LEDs behind the LCD screen.

Advantages of LEDs over CCFL's:

-LED's reach their max brightness faster than CCFL's do.
-LED's produce a white light, sharpening the image and make the colours look more vivid.
-LED's produce a brighter light, improving colour definition.
-LED's last much longer, making their use more reliable.
LED's are more efficient and use less energy, this mean they produce less heat.
-Monitors that use LED technology are much thinner than those which use CCFL technology.

OLED

We also see advancements in LED technology: we have Organic Light Emitting Diode (OLED) technology.

-These make use of organic materials, made up of carbon compounds, to create flexible semi-conductors.

-Organic films are placed in between two charged electrodes (a metallic cathode and a glass anode)

-When an electric field is applied to the electrodes. They emit light! This means no backlighting is required, allowing for very thin screens.

-OLED is a self contained system, which means that there is no need for LCD technology.

-OLED allows screens to be curved, since they are flexible. This ensures a good picture from any angle.

-Due to its flexibility and thinness, OLED screens can be bent into any shape. If this is applied to mobile phones, you can fold your phone and put it in your pocket or wrap it around your wrist!

Advantages of OLED's over LCD/LED's:

- OLED screens are thinner, lighter and more flexible.
-OLED layers can be made of plastic rather than glass, which means they can be made into large, thin sheets.
-OLED's give a brighter light.
-OLED's have a large field of view (around 170°), making them ideal for TV's and advertising.

1.3.4 (f): describe the principles of operation of speakers and describe how they are applied to real-life scenarios

Definition: A device that converts electrical impulses into sound.

Sound is produced from a computer by transmitting digital values through a DAC and then through an amplifier and finally to the speaker where it is output

-The rate that the DAC can convert the digitial data into analogue voltages is known as the sampling rate. 

-If the DAC is 16-biit, it can accept 2^19 numbers. 
Then the speed that these values can be converted is the sampling rate.

-The typical sample rate is 44,100 Hz (samples per second). This means the DAC can convert 44,100 values every second.

Example:
A CD holds music files
Each music file is sampled at 44,100 times per second, each sample being 16 bits.
We must also take into consideration the music being stereophonic.
Taking the above into account, we can calculate how many bits per second can be sampled to the CD.

44,100 = sample rate
16 = sample amount of bits
2 = stereophonic so theres two sides

44,100 x 16 x 2 = 1,411,200 bits per second

8 bits = 1 byte

1,411,200 / 8 = 176,400 bytes per second

1.3.4 (e): describe the principles of operation of actuators and describe how they are applied to real-life scenarios.

What is an actuator?

An actuator is an electromechanical device used to operate or control something.

(e.g a motor or a valve)

-An actuator is used in controlling applications

-When energised, an actuator can operate or control a system (for example, a solenoid could be used to operate a plunger or control a fuel injection system)

- A digital to analogue (DAC) converter is some time required to control an actuator. A computer (or microprocessor) is connected with the actuator and data sent to it will go through the DAC when being transmitted to the actuator.

1.3.4 (d): describe the principles of operation of 2D and 3D laser cutters and describe how they are applied to real-life scenarios

-A laser cutter can cut materials such as glass, polymer, metal, crystal and wood.

-A 2D laser cutter cuts in the x,y direction, while a 3D laser cutter cuts in the x,y,z direction.
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-Laser cutters are controlled by computers which allows for complex ideas.