AE-237 (formerly 230 / 231 / 252 ) 
INSTRUCTOR: Eddie Ciletti
updated 6th October 2014

WEEK-1a

WHERE TO BEGIN?  Chemistry and Physics
Like other disciplines (music, math, art) electronics is a language that is 'mastered' when the user is able to think in that language.  It is admittedtly hard to start at the beginning.  The text book addresses this by including  simple chapters on Chemistry and Physics, the most obvious being that conductors - what we know as 'wire' - are the element metals (Copper, Silver Gold, Lead, Tin).  Somewhat less obvious - and less elemental -  are the insulators wood, glass, mica, air, rubber, plastic).  Transistors, Diodes and LEDs are semiconductors  - unlike wire, they pass current in only one direction  and are made from the elements Silicon, Germainium, Gallium, Aresenic and several others. 

Basic Electricity Video

LED CHEMISTRY: how the elements are combined to make a device that gives off a specific color when current is flowing through it

KEY CONCEPTS
In the first two weeks we will explore The Multimeter.  It will let us "see" the relationships of Volts (distance), Amps / Current (tension), Power / Watts (heat) and Resistance (the bungee, the light bulb) rated in Ohms.  When an incandescent lamp is connected to a power source - like a car's headlamp ato the battery - current flows, the filament in the lamp gets so hot it glows.  All connected, these physical relationships produce tangible and measurable results.  The relationships so far are gnerally 'Linear,' and all relate correlate with basic Physics.

LAB EXERCISES

Take a Deep Breath...

Let's start with two simple exercises:

I had this idea to use a string of lites to show the difference between Conventional Current Flow (plus to minus) and Electron Flow (minus to plus). Here goes..

You might be wondering what actually happens when you turn something on.  Everything that matters is MATTER and it's composed of atomic particles - protons, neutrons and electrons.

As the ancient geeks were stumbling upon the basic building blocks - like generating and measuring electricity - they had to "guess" when assigning POLARITY, like POSITIVE and NEGATIVE. They had a fifty-fifty chance of getting it right (they didn't), consequently, we have two ways at looking at how current flows. CONVENTIONAL CURRENT flows from plus to minus - that's what the ancient geeks thought. Later, once everybody had test equipment that could assist in deciphering the laws of physics. It was determined that electrons were doing the moving and shaking during the "current dance."

So, take a look at the sting of lights. Electrons are in BLUE, moving from right-to-left. Holes are in black and move from left to right.

I got this overview of "Holes" from Wikipedia...

In solid state physics, an electron hole (usually referred to simply as a hole) is the absence of an electron from the otherwise full valence band. A full (or nearly full) valence band is present in semiconductors and insulators. The concept of a hole is essentially a simple way to analyze the electronic transitions within the valence band.

Hole conduction can be explained by the following analogy. Imagine a row of people seated in an auditorium, where there are no spare chairs. Someone in the middle of the row wants to leave, so he jumps over the back of the seat into an empty row, and walks out. The empty row is analogous to the conduction band, and the person walking out is analogous to a free electron.

Now imagine someone else comes along and wants to sit down. The empty row has a poor view; so he does not want to sit there. Instead, a person in the crowded row moves into the empty seat the first person left behind. The empty seat moves one spot closer to the edge and the person waiting to sit down. The next person follows, and the next, et cetera. One could say that the empty seat moves towards the edge of the row. Once the empty seat reaches the edge, the new person can sit down.

In the process everyone in the row has moved along. If those people were negatively charged (like electrons), this movement would constitute conduction. If the seats themselves were positively charged, then only the vacant seat would be positive. This is a very simple model of how hole conduction works.

BUILDING A CIRCUIT, ONE COMPONENT AT A TIME

There are a handful of Electronic Components that can be configured into basic  building blocks - useful circuits that must first be "turned-on" to be in a useful state.  The most obvious example, for our purposes, is an audio amplifier.  It is neither fully ON nor OFF, but "biased" to an in-between "static" state state so it is then ready to be dynamically modulated by an AC (alternating current) audio.

There are AC and DC power sources (such as wall power and batteries), Passive Components (resistors, capacitors, switches, lamps and fuses), Active Components (vacuum tubes,  transistors and Integrated Circuits or ICs, the latter being the result of component miniaturization). 

Click For Schematic Symbol Exercise

AC signals can be Audio, Radio Frequency (RF) or Power.  DC signals can be Power (from batteries or power supplies), control or logic signals.   In any electronic circuit, DC is required to turn the active components on via passive components that establish and "center" the operating paramters.  The essence of circuit design is for ALL components to operate within a safe "window," from the obvious - not too hot as to compromise longevity - and the less tangible - not too "cold" as to be unpredictable.

Click For Basic Schematic Exercise

Circuits can be analyzed in both the virtual and the real world, on "paper" and with test equipment, respectively.  There are a handful of formulae, such as Ohm's Law and the Power Formula, that can be used to establish and analyze the operating parameters. 

A digital multimeter can be used to measure "Potential" (in Volts), Current (in Amperes), Resistance (in Ohms) and Capactance (in Micro-farads).  Its pedecessor was an analog VOM (volt-ohm, milliamp meter), still in use today. 

Prior to the VOM, meters were application-specific - capable of measuring one quantity only (volts or amps, for example).  A Wheastone Bridge was used to measure resistance only..

READING and LINKS