Download Electricity: The flow of electrons through a conductor Electronics

Electricity and
Electronics.
Yes? Yes!
Electricity: The flow of electrons through a
conductor
Electronics: using changing electrical properties to
convey information. Converting one form of energy
into another, and interpreting that information.
—Transduction and Transducers
What is a circuit?
“load”
“battery”
“switch”
“A closed loop containing a source of electrical energy (battery), and a
load (light)”
Every component in a circuit has electrical
characteristics
Battery can provide a certain amount of
electrical energy
Bulb resists a certain amount
Too little energy = dim bulb
Too much energy= kaboom
Let’s start with a battery.
too many electrons
not enough electrons
B a s i c
Vo c a b u l a ry
when working
with Electricity
Current (I)
»The flow of electrons through a conductor
»Measured in Amps. The symbol is I.
»Some materials conduct better than others. They
are knows as conductors, semi-conductors and
insulators.
»Conventionally, we think of current as flowing
from positive to negative (look at the battery
picture)
»Current flow requires an imbalance of charge
between two points.
»Think about water: The amt of water flowing past
a certain point at a given point in time.
Voltage (V)
»The difference in charge, or potential between
two points
»Measured in Volts (V)
»Think of it like water pressure. A geyser vs. a
low-flow shower head.
Resistance
» Whatever “resists” the flow of current
» Measured in Ohms (R)
» All materials have some degree of
resistance, depending on the strength of the
electron bonds.
Now put em together...
“Ohm’s Law”
V = I*R
Voltage = Current * Resistance
V = IR
I =V / R
R =V / I
Ground
» A zero-voltage point.
» Current want to flow to ground.
» “True” Ground is literally, the ground.
» Floating ground is relative to the circuit it’s a
part of...
» A reference point from which to measure
Voltage
» The earth is idealized as an infinite heat-sink
for current. It can aborb an unlimited amount
without changing its potential...
“Electron” vs. “Conventional” flow
High Potential
Low Potential
The “Water Analogy” helps
+
–
Voltage is like water pressure
Current is the amount of water flowing past a given point.
Conventional Circuit Diagrams:
» How they flow & What they look like.
Electronic
Components
Conductors
» A low resistance path for current
to flow
» Insulated by plastic
» Diameter expressed by a “gauge”
Larger gauge = smaller wire
» Solid or Stranded
Switches
» Interrupt the flow of current, mechanically
» Characterized by the number of “poles” and
“throws”
Single Pole - Single Throw
Single Pole - Double Throw
» “momentary” or “toggle”
Resisters
» Conductive material that impedes current flow.
» Converts electrical energy into heat energy
» Typical Power rating: 1/4 to 2 Watts
» Color Bands on the resister tell you the value
Resister Symbol
Resister Color Bands
Diodes
» Allows current to flow in only one direction
(from anode to cathode only)
» Cathode usually marked by a band
» Check it:
LED’s are fun.
» “Light Emitting Diode”
» Converts electrical energy into light
» Directional (anode and cathode)
Remember: “short things are closer to the
ground”
» Requires a nominal 0.6V to work.
Prefers 1.6–2V for optimal awesomeness.
Connecting Components to make a Circuit
» We’ll use a BREADBOARD
Power Supplies
-Converts AC to DC
-Check V and I ratings
-Up to 1A is good,
but 300-500mA is
usually sufficient
+
-
Back to Circuits!
+9V
R1
R1 = 470Ω
+9V
Does this make more sense now?
We’re about to build it in real life...
Lighting an LED
+9V
R1 = 470 ohms
GND
BUILD IT!
Add a switch
R1 = 470 ohms
+9V
gnd
YES!
Capacitors
-Caps can store and release voltage
-When connected to DC voltage, the capacitor “pulls”
and stores voltage.
-They hold charge when disconnected from power
supply.
-When given the opportunity, they release the stored
voltage.
Ceramic Caps
Electrolytic Caps
» Amount of charge a capacitor can hold is measured
in Farads.
» 1 Farad is equal to 1 amp of current at 1 volt for 1
second.
» 1 Farad is a lot of charge. Capacitors we work with
are typically measured in Micro Farads (µF ) and Pico
Farads (pF).
Capacitor Circuit
+9V
Circuits in SERIES
- Components connect end-to-end
- Single path for electrons to flow
All components share the same current
- Total Resistance of the circuit is equal to
sum of individual resisters.
- Total Voltage of the circuit equal to all the
individual “voltage drops”
Circuits in PARALLEL
- Components connect parallel to one another
- Multiple paths for electrons to flow
All components share the same voltage
- Total Current of the circuit is equal to sum of
individual branch currents.
Batteries in SERIES
+
-
+
Double the Voltage
Same Current
Batteries in PARALLEL
Double the Current
Same Voltage
+
+
-
-
-
How to succeed at
Electronics:
» Document your process. Keep track of work.
» Expect things to go wrong the first time...
Budget your time accordingly.
» Help one another out!! Think “lab” more
than “studio” (when working with tech).
» THE INTERNET KNOWS EVERYTHING.
Soldering Demo
-Contact Mic
-2 potentiometers
Integrated Circuits (IC’s)
1) Multiple components (resisters, transistors, diodes,
etc) built into a small single package.
2) Analog ICs deal with varying levels of voltage.
3) Digital ICs deal with only high (1) or low (0) states.
4) ICs are labeled with part number and manufacturing
info.
Identifying ICs
1) All ICs have useful datasheets which can be found by entering the part # into
google or searching through online retailers such as digikey.com, or mouser.com
2) Datasheets contain package information, electrical information, pin diagram, and
hopefully application notes. Datasheets are your friend.
3) ICs come in a variety of packages. (ex. Voltage Reg. vs. 555 timer)
4) Surface mount components are extra small and are not meant for prototyping. You
will be sad if you buy these by mistake.
5) DIP (Dual in line package) have pins spaced .1 inches apart, just like your
breadboard. DIPs are your friend.
5) The top of an IC is typically marked with a notch or dot, or both.
6) Pins are numbered counterclockwise, starting in the upper left.
DIP
Surface Mount
555 Timer
1) 555 is a precision timer that can operate as either
a single shot timer (monostable mode) or an oscillator
(astable mode).
2) 555 is "programed" by wiring it with resistors and
capacitors. These create RC circuits that control the
timing.
3) Easy to use, cheap and has many applications such
as led/light flashers, tone generators, one-shot timer
circuits, etc
555 Astable mode
1) No stable state. Output jumps between Vcc and
Ground.
2) Output is a square wave with a mark period and a
space period.
3) Frequency is set by R1, R2 and C
4) Uses - flashing light, tone, pulse width modulation
An alternate version
1) Pin order is different -- Be careful! Not always in order.
2) There’s an extra LED coming out of pin 3.
3) De-coupling capacitor between the power rails.