comp eng notes

3 biggest saftey hazards

electrical

falling

fire

Avoid falling

disconnect cables

dont climb

keep clean

avoid electrical

* 0.1-0.2 amps = lethal
* don’t mix with water
* report cabling problems
* treat as live cables
* switch off before connecting/disconnecting cables


* Don't place electrical equipment near combustible materials
* Never use w/ wet hands
* Use type C(electrical) or ABC fire extinguishers
* Wear gloves with high voltage
* If comp. smoking/sparking - unplug and dont touch case/pwr. button

Explosive hazards

* Lithium ion batteries explode violently if over charged/over loaded
* Wiring dead battery = in closed circuit w/ fully charged battery cause fire/explosion

poison/toxic hazards

* Lead solder = toxic
* Rubbing alcohol - flammable and toxic

Environmental hazards

* Comp parts create toxic/harmful envion
* Old electronics - e waste bins
* Old batteries - not thrown in garbage

Compressed/corrosive hazards

* Clearing solvent = acidic and chemical burn
* Always wear Personal Protective Equipment

Laser hazards

* In optical drives - sufficient pwr. To cause eye injury w/out direct exposure
* Blue ray - hot enough to start fire
* Unshielded cathode tube rays emit high level ultraviolet radiation
* Smoke detectors have radioactive materials emitting ionizing radiation
* Electrons generate magnetic fields dangerous to digital devices

Binary

* base 2 system
* each new digit hv value greater than symbol to the rightpositio

positional notation

related to the next by a constant multiplier

alphanumeric

using alphabet to replace numbers

* base 32 - capitals and numbers

URL shorteners

using base 62

* capital letters, lowercase and numbers

\

Microtransistors

on/off - count using switches

1 bit

1 transistor

byte

8 transistors

ASCII

American Standard Code Information Interchange

* convert numbers to letters
* 225 symbols/letters (1 byte)

Arduino

open source hardware and software company

\
programmable with any PC - using USB cable

coded with C++

reset button

resets ATmega microcontroller

USB port

* powering arduino
* uploading sketches
* communing with sketches

TX and RX LEDS

show that Arduino and computer are communicating

Power Pins

distribute power to input and output

Analog In

receive analog value

ATmega microcontroller

heart and brain of Arduino Uno

Power LEDS

indicates that its receiving power

Digital Pins

send and receive digital signals

Pin 13 LEDS

built in LED

LAN - Local Area Network

w/out external connect

* no internet

WAN - Wide Area Network

connects with computers not in the same building - internet access

WLAN - Wireless Local Area Network

radio to transmit data across local network

MAC address - Media Access Control Address

* physicals address on hardware


* never changed
* included on sticker attached to network devices

IP - Internet Protocol Address

* mailing address on internet
* Subnet number - IP issued to LAN devices
* geographically traced

Data Packet

* thing being transmitted


* broken down into smaller structure of data before transmission
* then reassembled to original chunk once reaching destination
* sent receipt for each - allowing to determine if any dropped

Hub

* simple connection
* repeat data to any devices connected
* slower
* no security

Switch

* connected to LAN
* remembers MAC address
* read destination of all devices connected and send packet to specific intended computer
* faster
* security

Router

* connected between LAN and WAN (local to outside)
* built in switches - smaller LANS
* send data packet to other routers attaches to outside networks

Modem

* convert digital signals for transmission across long distances
* modulates and de modulates
* built into most routers

soldering

joining process of metals by melting together (alloy melted with hot iron/gun)

heated to 200 degrees Celsius

Soldering gun

heavy work, heavy weight and heats quickly

soldering iron

used for fine work, light weight and takes long to heat up

sponges

clean soldering iron/gun tips

flux

prevents oxidation/rust and creates cleaner soldering connection

Lead solder

high quality and easier to work with

soldering lead precautions

* ventilated areas
* fume extraction system'
* filtered breathing protection
* safety glasses
* neoprene/latex gloves

ENIAC (Electronic Numerical Integrator and Computer)

* first programmable general purpose electronic digital computer
* building hydrogen bombs
* vacuum instead of transistors
* programmed with combination of wired plug board and switches

evolution of a cpu

1800% increase of processing power, less expensive and less power consumption

How a cpu works

bit transmitted and voltage levels


1. fetch
2. decode
3. execute

Fetch

* gets instructions from memory
* software instruction/data stored in ram
* each instruction provided in blocks of data
* program counter, instruction register, bus, address

Instruction register

instructions being executed and held

program counter

keeps track of instructions that hv been completed and where in RAM is stored

Bus

multilane between CPU and RAM

* data bus and address bus

decode

* bitfields - opcode and operand code
* takes instructions and convert unto useable form for CPU
* into compatible languages - RISC, ARM, x86

Execute

completes instructions

* result sent to register for placement in system memory

ALU - carry over, over flow, 0, less than flags

CPU (computer processing unit

* electronic circuitry that executes the instruction that make up a computer program
* basic math, logic, controlling and input/output

Boolean logic and logic gates

true/false

\

NOT gate

AND Gate

XNOR

XOR

NOR

OR

NAND

Amps

current - amount of electricity flowing through wire

volts

pressure electricity is under

resistance

how hard a martial is to pass electricity through

watts

measure of power

ground fault circuit interrupter

120V outlet

240 V outlet

orange outlet

isolated ground

red outlet

emergency generator supply

blue outlet

surge supply

series circuit

double volts

parallel circuit

double amps

battery safety

connecting batteries - connection cables to be equal length and resistance

wires

* Typical cylinders or braided strands of metal (or other highly conductive material) used to conduct electricity.
* Typically encased in non-conductive material called insulation.  This insulation may also contain shielding (typically strands of metal such as copper) to protect from signal leakage or interference.

breadboard

* Also known as a Solderless Circuit Board or a Protoboard.


* Used to quickly construct and test electrical circuits

resistors

passive two-terminal electrical component that implements electrical resistance as a circuit element. In electronic circuits, resistors are used to reduce current flow, adjust signal levels, to divide voltages, bias active elements, and terminate transmission lines, among other uses.

transistors

semiconductor device used to amplify or switch electrical signals and power

at least 3 terminals for connection to electronic circuit

NPN transistor

current flows between collector to emitter when the positive supply is given to the base

PNP transistor

charge carrier flows from the emitter to collector when negative supply is given to the base

Silicon-Controlled Rectifier

 react to the amount of voltage being applied.  There has to be sufficient voltage to open/close the “gate”.

maintain their “gate” state until power is is cycles off and on again

MOSFETs (Metal-Oxide-Semiconductor-Field-Effect-Transistor) function in largely the same was as SCRs but have very different construction and are better suited to voltage control than current switching

diodes

semiconductor device that essentially acts as a **one-way switch** for current. It allows current to flow easily in one direction, but severely restricts current from flowing in the opposite direction.

\n aka. rectifiers because they change alternating current (ac) into pulsating direct current (dc).

LED

semiconductor device that emits light when an electric current is passed through it.  Light is produced when particles that carry current (electrons) combine together within the semiconductor material.

Capacitors

**energy-storing devices** available in many sizes and shapes. They consist of two plates of conducting material (usually a thin metal) sandwiched between an insulator made of ceramic, film, glass or other materials, even air.

As compared to batteries, capacitors have much lower storage capacity but much higher discharge/recharge speeds

Photocell

**resistor that changes resistance depending on the amount of light incident on it**. A photocell operates on semiconductor photoconductivity: the energy of photons hitting the semiconductor frees electrons to flow, decreasing the resistance.

More light = less resistance.

potentiometer

form of **variable resistor**.  It is a three-terminal resistor with a sliding or rotating contact that forms an adjustable voltage divider.

speaker

electrical energy into mechanical (kinetic) energy.  The mechanical motion produces sound waves in air by vibrating a thin diaphragm.  

This is done by varying an electrical current through copper windings (Coil) to create an electromagnet.  The electromagnet is then attracted or repelled by the permanent magnet in rapid vibrations that create sound waves.

push button

type of electric switch which closes a circuit when pressed and opens it when released

555 - Integrated circuits

timer/pulse generator

steady

4011 - Integrated circuits

4 NAND gates - each has 2 inputs

4029 - Integrated circuits

counts in 10s - switches between binary and decimals

contains multiple flip flops to convert

cpu types

* Mobile (ultralight)
* Laptop
* Desktop
* Workstation
* Server

cpu architecture

basic design rules of a CPU, the way it is organized internally and how it communicates externally.  Architecture also refers to the way in which binary data is processed, in what order it is executed and where it is stored in memory.

x86 (16/32 bit)

* backwards compatibility
* high clock speeds
* custumizable - BIOS allows fine tuning/expandability
* more vulnerable and potentially less reliable
* open pathways for malicious software and opportunities for inept users to damage their own systems.
* more powerful but power hungry
* needs active cooling and larger power supply. (280+ Watts of power
* good for gaming

x64 (64 bit)

* same basic architecture as x86, however the processor Fetches, Decodes and Executes 64-bit blocks (words) of data rather than 16 (8086) or 32 (i386)
* improved processor performance only if the software has been optimized
* switch for the memory

x86 vs x64

* more than 4GB of memory.
* The CPU industry is still years away from being able to take full advantage of the maximum memory potential of 64-bit systems.
* x64 processors are backwards compatible, meaning can run software that was written for an x86 system.
* The opposite is not true;  x86 processors cannot run software written for a x64 systems.

clock speed

* aka. frequency
* how many cycles(instruction) completed per second per CPU core
* multicore - capable of more instructions than single core
* does not always equate to more performance.  Software needs to be optimized to take advantage of multiple cores.
* Ghz (gigahertz) = 1 billion cycles per second
* change based on usage and temperature.

core counts

* **ALUs.**


* **Multi Core = faster, more reliable, far superior at multitasking and generally results in reduced power consumption.**


* **Individual applications may not benefit from multi Core CPUs if not optimized for them**
* **Some old or poorly written software may slow down all processes on a multi-core system.**


* **Multi core - need more memory and BUS resources.**

ARM (Advanced RISC Machines)

* company that designs CPUs and SOCs (system on a chip) and sells their designs to other companies for manufacture. 
* ARM processors use RISC architecture (Reduced Instruction Set Computer) which provides greatly increased efficiency and simplicity at the cost of reduced performance and compatibility.


* not good at multitasking.  Most ARM operating systems can only run one program (or have 1 open window) at a time
* closed hardware - Meaning there is no BIOS in which to customize systems. 
* Simplistic linear coding makes programming easier and more energy efficient.
* Rarely suffer catastrophic errors

SOC

system on a chip

* single chip that contains all components find in a computer (even storage)
* interior volume of most modern smartphones and tablets is dominated by the battery