U3 Hardware Flashcards
What is an embedded system?
Small computer system such as microprocessor that are often part of a larger system
Performs a specific function
What are benefits of embedded systems?
- Low cost to make
- Dedicated to one task so simple interface
- Consume little power
What are the drawbacks of embedded systems?
- Difficult to upgrade to new technology
- Expert help needed for repairs
How does a laser printer work?
1) Laser beam and rotating mirrors used to draw image on drum
2) Image converted to electric charge attracts negatively charged toner
3) Electrostatic charged paper rolled against drum
4) Charge pulls toner away from drum to paper
5) Heat applied in fuser fuses toner to paper
6) Electrical charge removed from drum and excess toner collected
How does a 3D printer work?
1) Computer sends digital file that holds blueprint of object to be printed
2) Object built by adding layers of a material
3) Object then cured
How does a microphone work?
1) Incoming sound waves enter microphone, causing diaphragm to vibrate
2) Vibrations cause coil to move over magnetic core
3) Electrical current generated and sent down wire
How does a speaker work?
1) Electric current in coil generates EM field
2) Changes in digital audio signal cause change in direction changing polarity of magnetic field
3) Speaker cone vibrates, generating sound waves
- Degree of vibrations determines amplitude and frequency of sound waves
How does a magnetic hard disk work?
- Has platters with surfaces covered in magnetisable material
- Platters mounted on central spindle and rotated at high speed
- Surface of platters divided into tracks and sectors
- Surface accessed by read/write heads
- When writing: Current variation in head causes magnetic field variation on disk
- When reading: Magnetic field variation from disk produces current variation in read head
How does solid state memory work?
- Uses NAND-based flash memory
- Have a grid of columns and rows that has 2 transistors at each intersection
Two transistors include: - Floating gate: Stores electrons and presence of charge = 1 and absence = 0
- Control gate: Controls charge flow for read/write
How does an optical disk reader/writer work?
- Disc surface has reflective metal layer and is spun
- Tracking mechanism moves laser
- Lens focuses laser onto disc, laser beam shone onto disc to read/write
- Tracks have pits and lands on metallic layer
- When reading: Reflected light from pits and lands encoded as bit patterns
- When writing: Laser changes surface to pits or lands along track, corresponding to 1s and 0s
What is a resistive touchscreen?
- Consists of two charged plates
- Pressure causes plates to touch, completing circuit
- Position where screen touched calculated by microprocessor
What is a capacitive touchscreen?
- Bottom surface of upper layer and top surface of lower layer coated in grids of conducting material
- Screen behaves as a capacitor, storing electrical energy
What is a VR headset?
- Consists of 2 lenses, LCD display and circuit board with sensors
- Display provides simulation of 3D environment
- User can move in virtual environment by moving their head or using controllers
What are buffers?
Short-term memory storage that stores data right before it is used e.g. RAM
RAM:
Random access memory
Volatile
Can be read and altered
Used to store program currently being executed
