External hardware devices Flashcards
Describe the three components of a barcode reader
Light emitter: Shines a red light at a pattern of black and white vertical lines
Light sensor: Reads the pattern of reflected light
Decoder: Converts the pattern to digital data
How does a digital camera work?
Light enters through the shutter
The light is focused by the lens
It is focused by RGB colour filters which seperate the amount of red, green and blue light captured
The light lands on the sensor array
Each sensor represents a pixel in the image
The sensors react to the light and generate an electrical signal
The signal is processed by an ADC and turned into binary data
Each pixel is generated based on the combination of RGB light
How does an RFID read data?
Using radio waves
What are some advantages of RFID?
doesn’t need line of sight
tags are difficult to damage
data can be read quickly
tags don’t need to be on a flat surface
How does a laser printer work?
The document is converted to a bitmap image
The drum is coated in static electrical charge
A laser is aimed at the drum using a mirror and draws the image
Wherever the laser touches the drum the charge is removed, which is where the toner is intended to stick
The powdered ink (toner) has the same electrostatic charge as the drum so is repelled by it
The toner sticks to the drum where the charge has been removed
The paper is rolled over the drum to transfer the the toner to the paper
The toner is fused to the paper using heated rollers that apply heat and pressure
What are the two main components of a Hard disc drive?
Read/Write head
Magnetic discs
How is the platter used in a Hard disc drive?
It is split up into tracks and sectors where each sector has a magnetic charge (+/-)
What are the components of a solid state drive?
NAND flash gates
controller
How is data stored on an optical disc?
Pits and lands in a track. Light is shone onto the track as it spins at a constant linear velocity. Where there is no transition it is a 0, and where there is it is a 1
