Electronics

1
Electronics I Study Guide

• Follow the yellow brick road.
• To a passing VOCATS score!

Bill Sorenson, South Stanly High
2
X101 Basic Electrical Theory and Magnetism

• Static electricity static electricity is a
  building of electrical charge (electrons) on an
  object that is not electrically balanced. Think
  about dragging your feet on the carpet and then
  shocking your sibling.
• Electrical work Work happens when in an energy
  system, something causes something else to move
  or change shape. In electrical systems,
  electricity is converted to heat, light, sound
  pressure, etc.
• Electrical Energy Energy is the ability to do
  work. A water tower holds a lot of water with
  gravity pushing down on it. If you open a drain
  at the bottom, the energy causes the water to
  flow, which is work. In electrical systems the
  energy can be either electrical or magnetic or
  others.

3
Energy Levels

• Two types of energy POTENTIAL ENERGY and KINETIC
  ENERGY.
• POTENTIAL ENERGY is defined as energy at rest,
  while KINETIC ENERGY is defined as energy at
  work. Think of it this way a rock on top of a
  hill that is at rest, has Potential to do work.
  Once the rock begins to roll downhill, and is in
  motion, it is doing work. (Kinetic)

A.S. WSHS
4
The Atom

• The atom has three particles
• The proton, inside the nucleus, has a positive
  charge
• The neutron, inside the nucleus, has NO charge
  properties
• The electron, which orbit around the nucleus, are
  negative
• ELECTRONS on the outer shell are called Valence
  electrons
• They are the electrons that move to form
  electrical current.
• The flow of electrons IS electricity!!!

5
What is electricity?

• Current is the flow of electrons from atom to
  atom. Letter symbol is I, measured in amperes
• Voltage is the force or pressure that causes flow
  when a path is available. Letter symbol is E or
  V, measured in volts.
• Resistance is the opposition a material offers to
  that flow. Letter symbol is R, measured in ohms.
• Conductance is the ability for flow that a
  material has. Its the opposite of resistance.
  Letter symbol is G, measured in Siemans

6
Basic Electrical symbols, units

• Visit the following website to Review basic
  electronic units
• http//www.wisc-online.com/Objects/ViewObject.aspx
  ?IDENG902

7
Magnetism

• Magnetism is a natural force that causes certain
  materials to be attracted to others.
• Magnetic attraction/repulsion is VERY similar to
  electromechanical attraction/repulsion
• Magnetic terms
• Permeability ability of a magnet to store
  magnetic force
• Flux the lines of magnetic force
• Pole place in a magnet where lines of flux enter
  or leave the magnet
• Lodestone a naturally occurring magnet
• Reluctance Opposition a material offers to being
  magnetized
• Ferromagnetic materials that aid in developing
  magnetic fields.

8
Magnetism Continued

• Magnets can be made using Electrical current
  looped into coils.
• Placing an iron core in an electromagnet makes it
  much stronger.
• Electronic devices utilize magnetism in a lot of
  different applications.

Lines of force leave the north pole And enter the
south. OPPOSITES LIKE
ATTRACT
REPEL
9
Magneto motive Force

• Magnetic lines of force are created and can be
  used to actually move things. This is how many
  electrical motors work. By using electromagnets
  and fixed magnets, we can produce MECHANICAL
  energy from electrical.
• The way this is done varies greatly.

10
X102 Electrical Safety

• Risks of electrical work
• Lasers Many devices can damage your eyes
• Fire Excess current flow can cause fires
• Class A Combustibles, paper, wood, etc
• Class B Liquids, gas, kerosene, etc
• Class C Electrical/electronic fires
• Class D Burning metals, phosphorus, etc.
• Shock electrons moving through the body.
• Burns, heart stoppage, muscle damage, death
• .1 amp of current across your chest can be fatal
• .01 amps you lose muscle control
• .001 amps you feel a slight tingle

11
NFPA 70 Natl Fire Protection

• National Fire and Protection Association
• Sets NEC code for all wiring which the states
  use for state code
• Set Fire prevention standards for all types of
  construction and electrical electronic codes.
• Local codes may supersede state codes which may
  supersede NFPA codes, but only to be more
  stringent

12
FIRST Aid and Electronics Jobs

• First aid for electrical shock
• Remove Victim from source safely by turning off
  breaker or switch or using non conductive
  material
• Treat for traumatic shock, elevate legs and keep
  warm
• If needed administer CPR IF TRAINED
• Treat burns by keeping them as clean as possible
• GET HELP ASAP!

13
Multimeters how they work

• Multimeters are meters designed to measure the
  big three Current, Voltage, and Resistance
• See picture below

Analog Meter Volt, ohm, milliameter
Digital Meter
14
Analog Meters -VOM

• Use a meter driven by a Darsonval Movement.
  This uses the magnetic field generated by
  voltages to move the needle
• Generally have to be Zerod to measure ohms. Zero
  by touching leads together and adjusting ohms.
• Usually have one or more amperage scales with
  jacks for each.
• Meter scale is more difficult to read but can be
  highly accurate
• Simpson 260 was the standard VOM for decades.

15
Digital Meters

• Digital meters use digital readouts
• Usually have jacks for volts/ohms and different
  amperage levels.
• Range switch selects range of reading.
• Function switch selects what you are measuring.
• Do NOT require zeroing.
• Measure RESISTANCE and VOLTAGE in parallel and
  Current in Series.
• NEVER MEASURE RESISTANCE WITH POWER ON.

16
Light level, SPL, other meters

• Light level meter Measure amount of light
  present in lumens. Used to find optimal levels
  for pictures, videos, etc.
• SPL meter Measure sound pressure or noise in
  Dbs. Decibels are levels of sound relative to a
  specific noise level.
• EMF or Gauss meter Meter designed specifically
  to measure electromagnetic energy in a space.

17
Capacitors BABY BATTERIES

• A capacitor is simply two metal plates separated
  by some kind of insulator.
• A capacitor stores a charge on those plates much
  like a battery.
• A capacitor charges and discharges MUCH faster
  than a battery.
• Capacitors are measured in FARADS, named after
  Faraday.
• Capacitors are always measured in tiny units such
  as microfarads, pico farads.
• Capacitors do NOT work like resistors
  mathematically.
• Capacitors in parallel add up while in series
  they divide (the 1 over method for resistors)

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Capacitors what they look like
Mylar
Electrolytic
Ceramic Disc
19
Capacitors What they do

• Capacitors store a charge.
• Capacitors can be used to BLOCK low frequencies.
• Capacitors are often used to manipulate AC waves
  in radio tuners and such.
• Capacitors do NOT PASS DC current.
• Capacitors are used to filter power supplies,
  they do this by smoothing out voltage.
• Electrolytic capacitors that look like little
  cans can explode if hooked up backwards.

20
Capacitor Math

• Capacitors in series act like resistors do in
  parallel.
• 1/C1 1/ C2 1/CT
• Capacitors in parallel add up.
• C1 C2 CT
• IN AC Circuits the opposition Caps give is
  called Capacitive Reactance and its measured in
  Ohms.

XC opposition to changing AC in ohms
21
Capacitor Color Code

• Used for very small caps that utilize a color
  code instead of digits. VALUES below in Pico
  farads

22
Reading Ceramic Disk Caps
Values given in Pico farads. Pico farads are
Trillionths (1/1,000,000,000,000) of a farad
23
SCHEMATICS for Capacitors
24
Resistors They cause voltage drops

• Resistors are devices designed to give resistance
  to manipulate voltages.
• There are several types of resistors.
• Resistors give off power in the form of heat.
• Variable resistors are called potentiometers or
  rheostats.
• Letter Symbol for Resistance is R.
• Resistance is measured in Ohms.

25
Resistors What they look like
26
Series Resistor Math

• In series Resistors simply add up.
• R1 R2 R3 RT Total resistance

27
Resistors Parallel Math

• In parallel, the total opposition actually goes
  down so the formulae is
• 1/R1 1/R2 1/R3 1/RT
• You can also use the product over sum method for
  just two resistors.
• R1 x R2 Divided by R1 R2

28
Resistors The code

• Many resistors are so small they use a color code
  to indicate their value.
• The code is as follows
• First color is first digit
• Second color is second digit
• Third color is multiplier (or number of zeros)
• Fourth color is tolerance (how accurate it is
  designed to be) usually 5 or 10

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Resistor color code example
30
Schematics for Resistors
31
Electrical Insulators

• Insulators have an atomic structure that OPPOSES
  the flow of electricity.
• Common insulators include Rubber, Plastic,
  Glass, Ceramic, Paper
• Insulators generally have 5 or more valence
  electrons in their outermost orbit.
• Insulators are used to CONTAIN/DIRECT current.

32
Electrical Conductors

• Conductors have an atomic structure that make
  them allow for current flow easily.
• Most conductors are metals.
• Good conductors generally have just one electron
  in the outermost shell, called the valence shell.
• Conductors Route Electrical current
• There are literally thousands of different types
  of conductors
• All conductors have some resistance and the
  longer the wire, the more resistance.
• Conductors CAN act as antenna as well so
  sometimes, they have to be grounded.

33
Types of Wire used as conductors

• Conductors can be multi stranded wire or solid
  core.
• Conductors can be made of copper, aluminum, or
  any other metal.
• Wire is measured by feet or meters for length and
  by GAUGE for diameter of conductor.
• The smaller the GAUGE, the BIGGER the wire.
• 22 wire is small while 4 wire is bigger

34
American Wire Gauge
35
Switches

• All a switch is really is just a device that can
  open a circuit by breaking a connection or make a
  circuit by connecting two conductors.
• There are literally thousands of different types.
• OPEN means OFF.
• CLOSED means ON.
• Open and closed are talking about the contacts,
  so open means no path for current and closed
  means a path exists.

36
Some examples of switches
37
Schematics for switches
38
FUSES 1 time safety devices

• Fuses are simply strips of conductive material
  designed to OPEN a circuit upon over current
  conditions.
• FUSES PREVENT FIRES by limiting current to that
  which the circuit can safely handle.
• Fuses are rated for voltage and more importantly
  CURRENT at which it opens.
• Fast acting fuses are designed to open
  immediately.
• Slow Blow fuses are designed to withstand short
  duration over current events.
• Thermal fuses blow on HIGH temperature.

39
Fuses Pix and schematics
40
FUSE SAFETY

• ALWAYS REMOVE POWER BEFORE REMOVING A FUSE!
• NEVER REPLACE A FUSE WITH ONE RATED AT A HIGHER
  CURRENT OR LOWER VOLTAGE!
• LETHAL VOLTAGES ARE PRESENT ACROSS THE
  CONNECTIONS OF A BLOWN FUSE!
• IF A FUSE BLOWS TWICE, LOCATE THE SHORT IN THE
  CIRCUIT

41
If the fuse keeps blowing!

• In a circuit that keeps blowing a fuse, the
  problem is a short circuit somewhere.
• You can troubleshoot by placing a resistor in
  line with the power going to the fuse and then
  looking for component with zero voltage drop.
• Always use extreme care when troubleshooting
  fuses as YOU could make the circuit if you bridge
  the fuses gap.

42
Circuit Breaker Resettable fuse

• A circuit breaker is designed to trip (OPEN) a
  circuit when too much current goes through it.
• Circuit Breakers prevent fires!
• Circuit Breakers are rated for current and trip
  current.
• Some circuit breakers have visual indicators that
  show when they are tripped.
• Find the cause of the breaker tripping before
  resetting.

43
How a circuit breaker works
An over current condition causes the
electromagnet to Pull the catch away from the
other contact.
44
Batteries We got the POWER!

• A battery is physically two different metal
  plates separated by a chemical that causes one
  metal to give off electrons and the other to
  attract them.
• There are hundreds of different types and sizes.
• Batteries are rated in Voltage available and
  mAmps/Amps per hour they can deliver.
• Many batteries pose explosion hazards when
  shorted or disposed of in fire.
• The chemicals in many batteries pose health risks
  so they should NOT be thrown into landfills.

45
Typical Battery voltages
SLA Sealed Lead Acid, NiCD Nickel
Cadmium NiMh Nickel Metal Hybrid, Li-on
Lithium Ion Li-polymer Lithium Polymer
46
Battery Schematics and Pix
Button Cell 3v
Double AA 1.5 V
Sealed Liquid Acid 12/24 V
C battery 1.5V
9 V
3.6 V Cell phone battery
47
Battery Schematics and cells
Cells are single battery units while many
batteries come in manufactured packs. Example a
Car battery has 6 Cells which add up to 12 Volts.
48
Ohms Law The STUFF!

• Ohms law is the relationship between Voltage
  (V), Current (I), and Resistance (R)
• Voltage measured in volts is electrical FORCE or
  pressure. Also called POTENTIAL Difference
• Current measured in Amperes is the actual FLOW
  of Electrons.
• Resistance is the OPPOSITION to the flow of
  electrons.

49
Ohms law, the formulae
Finding Current Example
To find any one of the three, Cover it up and use
the other two.
50
Ohms Law problem
Problem 1 A 110 volt wall outlet supplies
power to a strobe light with a resistance of 2200
ohms. How much current is flowing through the
strobe light?

• Choose your answer below
• 0.5 amps
• 2.0 amps
• 0.05 amps
• 1.0 amps

51
PROBLEM 2

• A CD player with a resistance of 40 ohms has a
  current of 0.1 amps flowing through it. Sketch
  the circuit diagram and calculate how many volts
  supply the CD player?
• Choose your answer below
• 0.0025 volts
• 4.0 volts
• 10.0 volts
• 400.0 volts

52
More Ohms law problems
1. A circuit contains two 1.5 volt batteries
and a bulb with a resistance of 3 ohms.
Calculate the current. ___________ 2. What is
the voltage of a circuit with 15 amps of current
and toaster with 8 ohms of resistance?
_____________ 3. A light bulb has a resistance
of 4 ohms and a current of 2 A. What is the
voltage across the bulb? _________________ 4.
How much voltage would be necessary to generate
10 amps of current in a circuit that has 5 ohms
of resistance? ___________ 5. How many ohms of
resistance must be present in a circuit that has
120 volts and a current of 10 amps?
_______________ 6. An alarm clock draws 0.5 A
of current when connected to a 120 volt circuit.
Calculate its resistance. _____________
53
UNITS OF POWER!

• Power is energy converted
• In electronics we measure power in Watts.
• 1 Watt 1 Volt x 1 Ampere for 1 second.
• We measure energy USED in Kilowatt-hours
• A kilowatt-hour is 1000 watts used over 1 hour.
• A joule is the SI unit for measuring energy.
• One kilowatt hour is 3.6 mega joules, which is
  the amount of energy converted if work is done at
  an average rate of one thousand watts for one
  hour.

54
Watts Laws of Power

• Watts law demonstrates the relationship between
  the big three Current (I), Voltage (V) and
  Resistance (R) to Power in watts.
• Power in Watts Current in Amps x volts
• See the power wheel below for other forms.

P I x E Remember PIE Power!
55
Power problems
A car stereo draws 10 amps at 12 volts. What is
the wattage being Used by the system?_____________
__________
If your 220 volt water heater has a 20 amp fuse
on the power Supply, what is the max power
possible?_________________
56
Scientific Calculator in Oz

• A scientific calculator has many functions useful
  in the study of Electronics
• 1/X or the reciprocal button for solving Parallel
  Resistance problems and Series Capacitive
  problems.
• Squares button. 2 When you take a number and
  multiply it by itself, you get the square of it.
• v or square root for finding resonant frequency
  and in impedance formulae.
• ENG or EE for scientific notation. Given the
  inordinately large and small numbers encountered,
  it is handy to use exponential notation, IE
  Powers of 10 (more on that later)

57
Scientific symbols in electronics

• Symbols used in electronics study include
• O Omega, OHMS, the unit of measure for
  resistance, reactance, and impedance
• ? Lambda, wavelength, the distance a waveform
  travels through space, in meters or fractions of
• ? Beta, ratio of collector current to base
  current in Bipolar Junction Transistor circuits.
• ? Delta, means DIFFERENCE or change in.
• T Theta, represents angular displacement in
  vector diagrams. In phasor graphs for RCL
  circuits, there is an angular displacement
  between vectors for XL and XC. Recall Series
  RCL circuits on the computers.

58
Using the 1/X for electronics

• Given a parallel resistor circuit, you will need
  to find the total resistance. If the 3 resistors
  were 470 ?, 1500 ?, and 3300 ? use the following
  sequence
• 470, 1/X 1500, 1/X 3300, 1/X , 1/X
• The answer is 322 ohms
• NOTE On graphing calculators the process is
• 470, X-1 1500, X-1 3300, X-1 , X-1
• This formula works for Resistors in parallel and
  capacitors in Series for finding TOTALS.

59
Problems using the 1/X
VISIT the following links for practice using the
I/X button in parallel circuits
http//www.wisc-online.com/objects/ViewObject.aspx
?IDDCE8604
60
Square Roots

• The square root of a number is the number that
  multiplied by itself equals that number.
• Example the square root of 16 is 4 because 4
  times 4 equals 16
• The formula for impedance in Series RCL circuits
  is Z vR2 (Xc Xl )2
• Note the Square root is over the entire series.
• If R 47 ohms, XL 980 ohms, XC 1200 ohms,
  find Z using the formula
• Answer is 224 ohms.

61
More math on RCL circuits
We use the formulas for XL And XC first, which
includes Using the 1/X function. Then we use the
impedance Formula which uses square Roots and
squares.
DO NOT GET BLOWN AWAY BY THE MATH, ITS JUST
APPLYING FORMULAE TO SPECIFIC CIRCUITS.
62
Scientific Notation

• In electronics we use numbers that are so small
  that they require prefixes to represent them.
  Micro for example means millionths of or in
  another words, if you cut something up into a
  million pieces, one micro would be one piece.
• We also have to work with numbers so large that
  they have prefixes too. If you counted the
  grains of sand on a beach, you would need a
  prefix to represent trillions of grains.

63
Engineering Notation

• Engineering notation is very similar to
  scientific notation, except that the power of ten
  can only be a multiple of three and the whole
  number can be any number from 1-999.
• Remember Moving the decimal place to the right
  makes the exponent move in a negative direction,
  conversely moving the decimal place to the left
  makes the exponent move in a positive direction.

A.S. WSHS
64
Scientific notation prefixes
exa E 10006 1018 1000000000000000000 Quintillion Quintillion
peta P 10005 1015 1000000000000000 Quadrillion Quadrillion
tera T 10004 1012 1000000000000 Trillion Trillion
giga G 10003 109 1000000000 Billion Billion
mega M 10002 106 1000000 Million Million Million
kilo k 10001 103 1000 Thousand Thousand Thousand
hecto h 10002/3 102 100 Hundred Hundred Hundred
deca da 10001/3 101 10 Ten Ten Ten
10000 100 1 One One One
deci d 1000-1/3 10-1 0.1 Tenth Tenth Tenth
centi c 1000-2/3 10-2 0.01 Hundredth Hundredth Hundredth
milli m 1000-1 10-3 0.001 Thousandth Thousandth Thousandth
micro µ 1000-2 10-6 0.000001 Millionth Millionth Millionth
nano n 1000-3 10-9 0.000000001 Billionth
pico p 1000-4 10-12 0.000000000001 Trillionth
65
Measurements

• Current Measurement Current is the flow of
  electrons through a circuit.
• Letter symbol is I (for Ions or atoms with a
  charge)
• Unit is AMPERES, often referred to amps
• Meter MUST be PART of the circuit for current to
  be measured.
• Just like any flow meter, the meter measures what
  goes through it.

66
Current measurement diagram
The current in the circuit will go thru THE METER
to be measured
67
Steps to measure Current

• Turn off the circuit
• Set meter to highest range first
• Insure common lead in the black jack.
• Insure red lead is in the correct amperage jack.
  There are often two jacks, hi and low.
• Connect to circuit
• Restore power
• Read meter and adjust range scale.
• DANGER DO NOT CONNECT OR DISCONNECT WITH POWER ON

68
Voltage Measurement

• Voltage is electrical pressure that pushes
  electrons.
• Letter symbol is V (voltage) or E (electromotive
  force)
• Unit is VOLTS
• Voltage is either AC (alternating) or DC (direct)
• AC is constantly changing direction and size
• DC is consistently in one direction and polarity.
• VOLTAGE Is MEASURED ACROSS the device.

69
Measure DC and AC Voltage
Remember! You can only test voltage when the
circuit is powered If there is no voltage coming
in (power supply) then there will be no voltage
in the circuit to test! It must be plugged in
(even if it doesn't seem to be working) Voltage
is always measured between two points There is no
way to measure voltage with only one probe, it is
like trying to check continuity with only one
probe. You must have two probes in the circuit.
If you are told to test at a point or read the
voltage at this or that location what it really
means is that you should put the negative
(reference, ground, black) probe at ground (which
you must determine by a schematic or somewhere
else in the instructions) and the positive (red)
probe at the point you would like to measure. If
you're getting odd readings, use a reference
voltage (even a 9V battery is a reasonable one)
to check your voltage readings. Old meter
batteries and wonky meters are the bane of your
existence but they will eventually strike! Good
places to take reference voltages are regulated
wall plugs such as those for cell phones. Two
meters might also be good ) Voltage is
directional If you measure a battery with the
red/positive probe on the black/negative contact
and the black probe on the positive contact you
will read a negative voltage. If you are reading
a negative voltage in your circuit and you're
nearly positive (ha!) that this cannot be, then
make sure you are putting the black probe on the
reference voltage (usually ground) DC voltage
and AC voltage are very different Make sure you
are testing the right kind of voltage. This may
require pressing a mode button or changing the
dial. Unless otherwise indicated, assume DC
voltages Multimeters have different input
impedances that affect readings of high impedance
circuits For example, measuring a sensor that has
1Mohm impedance with a 1Mohm impedance meter will
give you only half the correct reading
70
Correct Jacks for Voltage
Black Lead usually in The Common Jack. Red
Lead usually in the Volts/Ohm Jack.
SAFETY ONLY HOLD PROBES BY INSULATED PART!
71
DMM Voltage Function switches
Volts AC Function Wavy line
Volts DC Function V with two lines
72
DMM Voltage Range selection
20 V range selected For expected values UP TO 20V
Find the RANGE that will be LARGER than the
voltage you expect. If unknown voltage is
expected, use HIGHEST RANGE!
73
Voltage measurement Examples
Measuring a 1.5V Battery
Measuring a plug in power adapter. Note the
polarity is indicated on the label Of the
adapter. If you get a negative voltage You may
have the leads backwards.
74
Measuring adapters AC
AC output, use the Volts AC function
75
Measuring adapters DC
9 Volts DC output Use 20 Volt DC function Note
an unloaded power Adaptor usually reads Higher
than rated. You Might see 11 or 12
volts Here. OBSERVE POLARITY
76
Measuring RESISTANCE
RESISTANCE is electrical opposition to the flow
of current. Letter symbol is R (voltage) Unit is
OHMS DC Resistance is NOT the same as AC
reactance even Though they behave
similarly Resistance Is MEASURED ACROSS the
device. NEVER MEASURE RESISTANCE WITH POWER
APPLIED. YOU WILL DAMAGE THE METER!!!!!!
77
Measuring Resistance
Remember! You can only test resistance when the
device you're testing is not powered. Resistance
testing works by poking a little voltage into the
circuit and seeing how much current flows, its
perfectly safe for any component but if its
powered there is already voltage in the circuit,
and you will get incorrect readings You can only
test a resistor before it has been
soldered/inserted into a circuit. If you measure
it in the circuit you will also be measuring
everything connected to it. In some instances
this is OK but I would say that in the vast
majority it is not. If you try, you will get
incorrect readings and that's worse than no
reading at all. You can make sure your meter is
working well by having a 'reference resistor' to
test against. A 1 1KO or 10KO resistor is
perfect! Low batteries can make your multimeter
inaccurate. Resistance is non-directional, you
can switch probes and the reading will be the
same. If you have a ranging meter (as most
inexpensive ones are), you'll need to keep track
of what range you are in. Otherwise, you will get
strange readings, like OL or 1., or similar, or
you may think you're in KO when really you're in
MO. This is a big problem for beginners so be
careful!
78
Jack it up for Resistance
Black Lead is in Common Red Lead is in
Volts/Ohm (Most meters)
79
Range and Function for Resistance.
For most meters, there is a range Of resistance
functions. Select the Range Above the expected
resistance. Ex, to Measure a 470,000 ohm
resistor, You Would move the selector to 2 M
for 2 million ohms. For unknown values start at
LOWEST Range first as you can damage
some Components with the high ranges.
This meter is set to measure UP TO 20k (20,000)
Ohms
80
Example checking a resistor
Note that the range/function switch is set to 20k
ohms indicating this is a reading of 9,820.
Probably a 10 K ohm resistor
81
Checking a photo sensor (ohms)
This is an example of testing a photodiode with
an ohmeter. The photodiode changes resistance
based on light. As you change the amount of
light available to the component, the resistance
value will change.
to see a video of this go to http//www.ladyada.
net/learn/multimeter/resistance.html
82
Continuity IS a resistance check
The continuity test is a check to see if there is
a low resistance path for current to flow. Its
useful in checking fuses, lamps, and conductors.
Most meters indicate continuity with an audio
BEEP so it is sometimes referred to as a BEEP
Check. YOU HEAR A BEEP, YOU HAVE A PATH OF LOW
RESISTANCE, IE, CONTINUITY. On many meters the
continuity function is the same as the Diode
Check. Since diodes and bipolar transistors have
very small resistance values, the meter Will, by
default send a very small current through to
check. NEVER USE A HIGH RESISTANCE RANGE ON A
SEMICONDUCTOR Diode Or transistor. You can
destroy the device.
Meter set to continuity and diode check. This
particular meter also checks capacitance.
83
Measuring Power

• Since power is energy converted it is much more
  complicated to measure than voltage, current,
  resistance.
• Mathematically electrical power is voltage times
  current so it is often calculated versus
  measured.
• A wattmeter is a tool designed to measure power.
  Most techs do NOT carry wattmeters.
• Kilowatt meters are used to measure power
  consumed. The unit for power used is often Kwh
  or Kilowatt hours, discussed earlier.
• A line monitor/analyzer is a power meter that
  records voltage and current levels.

84
Wattmeters
Residential Kilowatt hour meter
Hand Held Wattmeter
This guy measures the power that goes into your
home or business. It does this by measuring
current at line voltage.
This guy plugs in between your wall and a device
and measures the power used.
85
How to read a watt meter

• Most newer residential meters use digital
  displays showing kwhs used. This is based on
  current measured through the meter and the
  voltage of the service.
• On older spinning dial meters Use a stopwatch
  (many smart phones have this function built-in)
  to determine how long it takes the spinning disk
  in an analog meter to make a single revolution.
  Now use your Kilowatt factor number in this
  simple equation 3600 times your Kilowatt factor
  divided by the number of seconds for the disk to
  make one revolution. The number you get is your
  usage rate in watts. Kwatt factor is listed on
  the label.
• Read more How to Read a Wattmeter eHow.com
  http//www.ehow.com/how_6158336_read-wattmeter.htm
  lixzz1M3XlqZUs
• NOTE Some watt meters actually send a reading
  via radio signal.

86
Wattmeter test equipment
Specialized hand held wattmeter used to measure
power. Uses special breakout connectors to
measure current AND voltage simultaneously. These
are NOT commonly used and are expensive tools.
87
SERIES DC Circuits 1Path!

• A series DC circuit has only one path for current
  to flow.
• The current flow is the SAME throughout the
  circuit IT IR1 IR2 IR3
• The resistances will add up to a total
• RT R1 R2 R3
• The loss of electrical pressure at each load will
  add up to total voltage
• ET ER1 ER2 ER3

88
Series Example

• The electrical current leaves the negative
  terminal of the battery and flows through R3 and
  then through R2 and finally R1 before returning
  to the battery.
• ITS THE SAME CURRENT EVERYWHERE!
• The total resistance is 1.2k 3.3 k 680 5180
  ohms (RT)
• (IT) or total current is found using Ohms law
  10 volts divided by 5180 ohms .00193 or 1.93
  mAmps
• Anywhere you measure current, it will be the SAME

89
Series Circuit Formulae
Kirchoffs V Law
90
Kirchoffs laws for Series

• Kirchoffs voltage law states The algebraic sum
  of the drops around a closed loop equals the
  applied voltage.
• This is a fancy way of saying that the voltage
  applied to the circuit (battery) will equal the
  voltage drops of the loads added up.
• ET E1 E2 E3

91
Series circuit Pictorial
Instead of resistors, this circuit uses lamps but
the math is the same. The SAME current that
lights one bulb, lights them all.
Challenge Question If you removed one of the
three lamps, would the other two be brighter or
dimmer?????
ANSWER BRIGHTER
92
Short circuit in Series
A short circuit is an UNWANTED path for current
to flow with little or no resistance. In the
circuit above, what will happen to the first lamp
if the second lamp is shorted out? IT WILL GET
Brighter because there is less resistance and
voltage is no longer being dropped across the
second lamp. SHORTS CAN CAUSE FIRES!!!!!!
93
Open Circuit Fault in Series
Another thing that go wrong is a break in a
circuit (Called an Open). If there is a piece of
wire that broke, what would happen to the lights?
They would go out because there would be NO path
for current to flow. An interesting thing that
happens is that you could measure your battery
voltage across the break in the circuit.
OPEN
94
Series Circuit Resources
For a good interactive activity on Series
circuits, visit this link
http//www.wisc-online.com/Objects/ViewObject.aspx
?IDDCE8304
95
Parallel DC Circuits

• A parallel DC circuit has 2 or more paths for
  current to flow.
• The current flow through each branch adds up to
  equal the total in the circuit
• IT IR1 IR2 IR3
• The resistances will NOT add up to a total
• 1/RT 1/R1 1/R2 1/R3 (this is called the
  reciprocal method)
• Each Branch is connected to both sides of the
  battery so VOLTAGE IS THE SAME for each load
• ET ER1 ER2 ER3

96
Parallel Example
Every resistor or lamp is connected directly to
the battery. This means that THE BATTERY VOLTAGE
IS AVAILABLE TO ALL LOADS and THEY ARE THE SAME
VALUE Adding more branches actually causes
resistance to GO DOWN, because there are more
paths for electrons to flow!
97
Parallel Pictorial
Electrons leave the negative terminal of the
battery travel down the line and some of it goes
to the first bulb, some goes to the second bulb
and whatever is left goes to and through the
third bulb. The current returns to the batterys
positive terminal.
NODE
Each light bulb is hooked up to both sides of the
battery. This is how your home is wired. You
can turn off a light in your living room without
turning off the TV.
NODE
Nodes are places where current can divide into
different paths.
98
Parallel Circuit Analysis (math)

The potential drops of each branch equals the
potential rise of the source
The total current is equal to the sum of the
currents in the branches.
The inverse of the total resistance of the
circuit (also called effective resistance) is
equal to the sum of the inverses of the
individual resistances.
One important thing to notice from this last
equation is that the more branches you add to a
parallel circuit (the more things you plug in)
the lower the total resistance becomes. Remember
that as the total resistance decreases, the total
current increases. So, the more things you plug
in, the more current has to flow through the
wiring in the wall. That's why plugging too many
things in to one electrical outlet can create a
real fire hazard.
99
Go online and Check it out!
For a great interactive lessons about parallel dc
circuits visit the following links
http//www.wisc-online.com/Objects/ViewObject.aspx
?IDHVC403 http//www.wisc-online.com/Objects/View
Object.aspx?IDDCE14705 http//www.wisc-online.com
/Objects/ViewObject.aspx?IDDCE14805
100
Series/Parallel Circuits
Many times a circuit will contain some components
in series and some in parallel, these are
referred to as series parallel or combination
circuits.
R2, R3, and R4 are in series with each other!
R1 is in Parallel with the other three combined.
101
Solving the SP circuit step 1

1. Find the equivalent resistance for three
   resistors in series. (R2R3R4) (680 4,700
   1,500) 6880
2. Use the 1 over formula to solve total. 1/1,000
   1/6880 .0011453
3. Find 1/.0011453 to get RT
4. Total Resistance is 873 ohms

102
Solving the SP circuit step 2
If total resistance is 873 ohms and total voltage
is 12volts, just use ohms law to find IT, Total
Current. 12v/873.013745 amps. Converts to 13.745
mA. Are there ANY resistors in series with the
batter? In this case no, which means there is no
resistor with total current. Note the resistor
R1 IS in parallel with the battery. This means
R1 has THE SAME Voltage 12v across it.
103
Solving the SP step 3
If R1 has 12 volts available and 1000 ohms of
resistance, then we can use Ohms law to find the
current through it (IR1) 12V/1,000 .012 Amps
or 12mA IR1 12mA
What we know so far RT 873 IT .0137 A or
13.7 mA VR1 12V cause its in parallel with the
battery.
104
Solving the SP step 4
Since we KNOW that 13.745 mA entered the node
AND that 10 mA went THRU the 1K resistor,
whatever is left MUST have gone thru the other
path. 13.745 12 1.745mA This means that
1.745 mA went through R2, R3, and R4 (as they are
all in the same path).
What we know so far RT 873 IT .013745 A or
13.745 mA VR1 12V cause its in parallel with
the battery. IR1 .012 amps or 12 mA
105
Solving the SP step 5
Since we KNOW that 3.7 mA flows through the
resistors R2, R3, and R4, all we have to do is
use Ohms law to find the voltage for each. V
I x R VR2 .003745 x 680 VR3 .003745 x
4,700 VR4 .003745 x 1,500 VR1 1.1866 VR2
8.2015 VR3 2.6175 CHECK THIS OUT! The three
HAVE to add up to 12Volts cause strung together,
they are in parallel with R1
What we know so far RT 873 IT .013745 A or
13.745 mA VR1 12V cause its in parallel with
the battery. IR1 .012 amps or 12 mA IR2,
IR3,IR4 are ALL .001745 or 1.745 mA
106
Solving the SP step 6
Finding POWER is the same for every circuit and
is actually quite simple. For each component,
take Voltage x Current to find the power for that
component. For TOTAL power, simply use Total
Voltage and Total Current.
What we know so far RT 873 IT .013745 A or
13.745 mA VR1 12V cause its in parallel with
the battery. IR1 .012 amps or 12 mA IR2,
IR3,IR4 are ALL .001745 A VR1 1.1866 VR2
8.2015 VR3 2.6175
Examples PR2 .001745 Amp x 8.2015 Volts
.0143 watts or 14.3 mWatts PT 12v x .013745 A
.1649 Watts or 163.9 mWatts
107
Series Parallel conclusion

• Series parallel circuits contain elements in
  series and in parallel.
• The mathematical formula for series circuits will
  work for all components in series
• The mathematical formula for parallel circuits
  will work for all components in parallel.
• The trick is to simplify the circuit

108
Get out there and practice!

• Great interactive labs on Series Parallel can be
  found at
• http//www.wisc-online.com/Objects/ViewObject.aspx
  ?IDDCE12904
• Note that there are several good labs that allow
  you to practice Series Parallel at the same web
  site. Remember You may have to redraw them to
  solve them.
• The next slide covers redrawing to simplify
  circuits.

109
Circuit simplification example
Step 1 Solve for equivalent resistance of R2
and R3 using 1/x Req (resistance equivalent) 12
ohms. Step 2 Add Req and R1 Step 3 This gives
you RT of 20 ohms. NOTE Start furthest away from
battery and work back.
110
The Wheatstone Bridge
It is used to measure an unknown electrical
resistance by balancing two legs of a bridge
circuit, one leg of which includes the unknown
component. Its operation is similar to the
original potentiometer
111
The Wheatstone continued
To see a simulation of how the Wheatstone
MEASURES resistance Visit the following
hyperlink. Vary the R3 variable resistor and see
what happens. http//www.magnet.fsu.edu/education
/tutorials/java/wheatstonebridge/index.html
112
Thevenins theorem

• In circuit theory, Thévenin's theorem for linear
  electrical networks states that any combination
  of voltage sources, current sources, and
  resistors with two terminals is electrically
  equivalent to a single voltage source V and a
  single series resistor R.
• This is used to solve circuits with multiple
  voltage sources or current sources.
• Follow the pattern on the next slide to see how
  Thevenins theorem works in a simple circuit.

• To calculate the equivalent circuit, the
  resistance and voltage are needed, so two
  equations are required. These two equations are
  usually obtained by using the following steps,
  but any conditions placed on the terminals of the
  circuit should also work
• Calculate the output voltage, VAB, when in open
  circuit condition (no load resistormeaning
  infinite resistance). This is VTh.
• Calculate the output current, IAB, when the
  output terminals are short circuited (load
  resistance is 0). RTh equals VTh divided by this
  IAB.
• The equivalent circuit is a voltage source with
  voltage VTh in series with a resistance RTh.
• Step 2 could also be thought of as
• 2a. Replace voltage sources with short circuits,
  and current sources with open circuits.
• 2b. Calculate the resistance between terminals A
  and B. This is RTh.

113
Example of Thevenins Theorem
Original circuit
Calculate the equivalent output voltage
114
Continued
The equivalent circuit, simplified
115
Seems confusing?

• For an EXCELLENT resource to practice with, visit
  the following link. You will see animations and
  practice problems.
• http//www.wisc-online.com/objects/ViewObject.aspx
  ?IDDCE5903

116
The Voltage Divider Circuit

• Many times we need several voltages from a single
  source.
• By placing resistive or reactive loads in series
  we can take a voltage and break it down into
  fractions of the original voltage.
• For simplicity, we will look primarily at a DC
  voltage divider using resistors.

117
The Voltage Divider
If we apply 12 VDC to this circuit and have two
resistors of equal value, we can get 6 volts
across either R1 or R2 or 12 Volts across the two
combined. 12 volts gives us essentially three
different outputs.
This works because of Kirchoffs voltage law
which says the drops of each series connected
load add up to the total.
118
Another Voltage Divider
This BASIC Series circuit can also be used as a
voltage divider. Using ohms law and Kirchhoff's
laws we can pull several different voltages off
of one 45 Volt source. Find VR1, VR2, and VR3 to
get those voltages.
VR1 IR1 x 5000 (10V) VR2 IR2 x 10000
(20V) VR3 IR3 x 7500 (15V) HINT
Remember in Series ALL currents ARE the same, so
just Use IT.
How did you find IT to solve the divider? Ohms
law 45V / 22.5 K
119
DIGITAL Numbers for a digital age!

• Digital electronics utilizes only 2 distinct
  states.
• 1s and 0s represent On or Off AND High or
  Low
• Analog electrical signals have varying levels and
  can be either constant or constantly changing.
• Digital electronics IS the world you live in so
  we need to understand the numbering systems used.

120
Numbers we are familiar with

• The numbering system we are most familiar with is
  decimal.
• Decimal is based on 10 digits, starting with 0
  and going up to 9
• As you exceed the decimal number 9, the next
  number moves to the left and has a place value of
  tens.
• As you add digits the numbers value increase by
  powers of ten

121
Decimal Examples

• The number 7 equals 7 unique items
• The number 17 equals 7 unique items PLUS 10 times
  1 more
• The number 177 equals 7 unique items, 7 times ten
  more, plus 1 times 100 more.
• This seems awful silly to go over but it is
  important to recognize how decimal numbers work.
• Decimal numbers can be indicated by a small 10 in
  subscript after the number
• Example 177 in decimal is actually 17710

122
Place Values in Decimal
123
Decimal Math examples

• It is easy math but do the following to help you
  relate place value in decimal numbers
• 23 11 ______ how many tens? Ones?
• 120 45 ______ how many hundreds?
• 56 45 ______ What did you do with the carry
  from the ones place?
• Decimal math is easy isnt it?

124
Binary Math, 1s and 0s ONLY

• In binary there are only two digits, 1 and 0
• Just like 10 is the base or radix of decimal, in
  binary it is 2 because there are only two digits.
• Everything digital at its most basic level is
  using nothing more than a series of 1s and 0s
  to work.
• These 1s or 0s are called Bits for binary
  digits.
• A series of 8 bits is called a Byte. Notice the
  lower case b means bit and upper case B means
  Byte.

125
Binary place values

2 6 64, 2 5 32 ,2 4 16 ,2 4 16 ,2 3 8
,2 2 4 ,2 1 2 ,2 0 1
An easy way to remember is to start at the RIGHT
side and write a 1, then as you go LEFT, just
keep doubling the number. It doubles because the
base is 2.
Example 1012 1 one, zero 2s and one 4
Since we are using Decimals to represent binary
place values, just add where the ones are. In
this case one 410 one 110 510 WE JUST
Converted a binary number to a decimal number!
126
Practice converting Binary

• Convert the following binary numbers to decimal.
• 102 _____ 10
• 1112 _____10
• 10002 _____10
• 1111002 _____10
• 111111112 ______10

127
Decimal to Binary conversionGotta go both ways.
Draw the binary equivalent chart to the left and
find the first number LESS than the number you
are converting. Then, moving left to right,
subtract the first number smaller than that. If
the next digit will fit in, subtract it. If not,
place a zero in that place. For every number
used put a one and for every number skipped, put
a zero.
128
Binary numbers in review

• Binary numbers are all 1s and 0s.
• The Radix or base number is 2
• A binary digit is often called a bit
• 8 bits equals one byte
• In the binary numbering system each place value
  goes up in increments of 2.
• 3 binary digits can represent decimal 0 -710
• 4 binary digits can represent decimal 1-1510

129
Binary conversions practice

• For some practice converting go the following
  website
• http//www.mathebook.net/middleschool/eworkbook/bi
  narytodecimalconversion.pdf

130
Octal Numbers8

• Octal means 8 so octal is a base 8 system
• Octal uses the same digits we use in decimal
  numbers
• Octal includes 0,1,2,3,4,5,6, and 7 for a total
  of 8 digits per place value.
• Three binary digits can represent any Octal
  value.
• Original Computers were 8 bit devices and that is
  why there is an octal system.

131
Octal continued, base 8

• 238 equals three 1s and two 8s
• 2 x 8 16 3 1910
• Converting binary to octal is easy, just recall
  there can only be 3 bits and the biggest single
  digit number is 7
• 1012 510 58
• 11012 1310 13 / 8 equals 1 with 5 remainder so
  11012 1310 158

132
Octal conversions worksheets
For practice visit the following
link http//www.mathebook.net/middleschool/eworkb
ook/octaltodecimalconversion.pdf
133
Gonna put a HEX on you, Hexadecimal, that is

• Because of the inordinately large numbers
  encountered in electronics and specifically in
  computer systems, sometimes we need a numbering
  system with more digits.
• Imagine a class with 8 students all needing a
  unique 1 digit number. Binary would not work,
  there are only 2 digits. OCTAL would work because
  there are precisely 8. Decimal would also work
  with 10 digits.
• Now think about how many cell phones are in the
  world (over 5 Billion). Each cell phone MUST
  have a unique electronic identifier. If we used
  decimal numbers there would have to be 9 digits
  used to give each a unique number.

134
Hexadecimal continued

• Now imagine how many memory addresses are in a
  terabyte hard drive. Terabyte means
  1,000,000,000,000 bytes. 13 digits in decimal
• We need a numbering system that has MORE digits
  so that fewer digits can be used to make unique
  identifiers. These numbers are used in Cell
  phones and computers and are call Hexadecimal.
• Hex means 6 and decimal means 10 so it is a base
  16 numbering system.

135
The wonder of Hexadecimal

• Since just one hexadecimal digit can represent up
  to 16 unique things, you need fewer digits to
  represent larger numbers.
• Remember the class room example of 8 students?
  What if the class had 12? Now octal and decimal
  both do not work, but Hexadecimal would. (up to
  16 unique s)
• Students 0 thru 9 and three students with letter
  ids, A, B, and C

136
The hex code compared to decimal

• Hex uses decimal numbers and the letters A thru F
• 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, A, B, C, D, E, F
• The letter symbols are equivalent to our decimal
  numbers
• A16 10 10
• B16 11 10
• C16 12 10
• D16 13 10
• E16 14 10
• F16 1510

137
Converting hex, the math

• Hexadecimal place values
• EXAMPLE 12F16
• THE F means number of 1s
• The 2 is number of 16s (the base)
• The 1 is number of 162 or 256s
• Therefore (1 x 256) (2 x 16) (15 x 1)
  30310
• REMEMBER the letter F16 is the same as 15 in
  decimal.
• 12F16 30310

138
Man, theres gotta be an easier way!

• Method 1 Divide by 16 and list remainders. See
  the following for demonstration
• http//www.wisc-online.com/ListObjects.aspx
• Method 2 Each Hex digit represents 4 binary
  bits. Convert each into the binary equivalent,
  combine the binary numbers and convert to
  decimal.
• Example F416
• F16 11112 and 416 01002
• Combined they give you 111101002
• 111101002 24410
• Remember to convert binary to decimal start at
  the farthest right digit, write a 1 above it and
  going left, just double it each time. Where ever
  there is a 1, simply add the decimal equivalent

139
The numbering systems together
Decimal Binary Octal Hexadecimal
Base-10 Base-2 Base-8 Base-16
0 0 0 0
1 1 1 1
2 10 2 2
3 11 3 3
4 100 4 4
5 101 5 5
6 110 6 6
7 111 7 7
8 1000 10 8
9 1001 11 9
10 1010 12 A
11 1011 13 B
12 1100 14 C
13 1101 15 D
14 1110 16 E
15 1111 17 F
16 10000 20 10
17 10001 21 11
18 10010 22 12
19 10011 23 13
20 10100 24 14
21 10101 25 15
22 10110 26 16
23 10111 27 17
24 11000 30 18
25 11001 31 19
26 11010 32 1A
27 11011 33 1B
28 11100 34 1C
29 11101 35 1D
30 11110 36 1E
31 11111 37 1F
32 100000 40 20
140
Binary Coded Decimal

• In computing and electronic systems, binary-coded
  decimal (BCD) is a digital encoding method for
  decimal numbers in which each digit is
  represented by its own binary sequence. In BCD, a
  numeral is usually represented by four bits
  which, in general, represent the decimal range 0
  through 9.

141
BCD to Decimal and back

• Example of a decimal number displayed in BCD
  9110
• Decimal 9110 UNCOMPRESSED BCD
• Binary 0000 1001/ 0000 0001

9
1
9110

• Now in Compressed BCD 9110
• 9 1
• 1001 0001

142
MORE BCD
As you can see, the highest number that BCD can
represent is 910
Since many devices use BCD, knowing how to handle
this system is important. You must realize that
BCD and binary are not the same. For example,
4910 in binary is 1100012, but 4910 in BCD is
01001001BCD. Each decimal digit is converted to
its binary equivalent. 4 BITS per BCD
number NOTE the SUBSCRIPT BCD to represent the
number system
143
There is a house in New Booleans?

• Boolean algebra is the algebra of two values.
  These are usually taken to be 0 and 1, although
  false and true, etc. are also in common use
• In digital circuits, there are 1s and 0s that
  represent statements of true or false.
• Example It is time to go eat but to make the
  statement true, there would be two decisions
• It has been several hours since you ate
• You are hungry

144
Decisions, decisions, decisions

• It is time to go eat but to make the statement
  true, there would be two requirements
• It has been several hours since you ate
• You are hungry
• We can express that statement by saying it is
  time to eat BECAUSE A It has been several hours
  since you last ate AND B You are hungry

145
Logic (decision Gates)

• We can express that with this AND gate. An AND
  gate needs all the inputs to be true (high) for
  the output to be true

A 1 here means A is true
Y means output or YES Its time to EAT!
A 1 or high here, means B is true
146
Logic (And Gates)

• It is time to go eat but to make the statement
  true, there would be two decisions
• A It has been several hours since you ate
• B You are hungry

A 1 here means A is true
Y means output or YES Its time to EAT!
A 1 or high here, means B is true
We can express that as a math formula as AB
which means A AND B have to be true for the
output to be true. Its a little confusing
because in the math we are used to AB would mean
A times B but in Boolean, it means A AND B.
147
The AND gate Looks like a bullet

• It is time to go eat but to make the statement
  true, there would be two decisions
• A It has been several hours since you ate
• B You are hungry

Y means output or YES Its time to EAT!
We can express that as a math formula as AB. We
can also use a chart to show the relationship,
called a TRUTH TABLE
INPUT INPUT OUTPUT
A B A AND B
0 0 0
0 1 0
1 0 0
1 1 1
Only high output
148
The Logic gate Or

• Another decision or logic gate is the OR gate.
• The OR gate only has a high output when one or
  more inputs are true, but NOT necessarily all.
• Example I need to go to sleep is the gate
• I havent slept in two days
• The doctor just gave me a sleeping pill

149
The Or gate (looks like an arrow)
I havent slept in two days
I need to go to sleep!
The doc just gave me a sleeping pill
In this instance, I need to go to sleep if EITHER
input statement is true. If I have not slept in
two days OR the doctor just gave me a sleeping
pill IT IS TRUE. This is called an OR gate and
the Boolean representation would be A B.
Again, this is a little confusing because in our
math that would mean A plus B, but in Boolean
logic it means OR.
INPUT INPUT OUTPUT
A B A OR B
0 0 0
0 1 1
1 0 1
1 1 1
High output for ANY high input or both
150
Exclusive Or Gate?

• For some decisions we have either/or but not BOTH
  situations.
• The gate that makes this logical decision is
  called an Exclusive OR Gate.
• The output is high when one or the other but NOT
  both inputs are high.
• The following page is an example of an exclusive
  OR decision, the Boolean math expression and the
  truth table

151
XOR or exclusive or

• The output statement is May has a date Friday
  night.
• The input statements would be
• She has a date with John at 9 PM
• She has a date with Jerry at 9 PM
• Obviously, May can have a date with one but not
  both or May could not have a date at all.
• On the next slide you will see the XOR symbol,
  Boolean expression, and truth table

152
XOR, one or the other, not both
Going with John
May has a date!
Going with Jerry
Lets hope may either has a date with John or
Jerry and not both, ).
The circle around the OR sign () means
exclusive. One or the other, but NOT both
Boolean expression
INPUT INPUT OUTPUT
A B A XOR B
0 0 0
0 1 1
1 0 1
1 1 0
A or B, but NOT Both
153
Inverters aka NOT GATE

• Because digital systems have a high and a low
  representing 1 or 0, sometimes you need to flip a
  signal.
• A gate that specifically inverts an input is
  called an inverter or Not Gate.
• The truth table is too simple High in, Low out.
  Low in, High out.

The Bar above the A means Invert it. You would
say this as A NOT
154
The Not gate as part of another

• The inverter gate is sometimes actually part of
  an AND Gate or an OR Gate.
• We say that an AND gate with a built in inverter
  is a NOT AND or NAND GATE.
• We say that an OR gate with a built in inverter
  is a NOT OR or NOR Gate.

NAND NOT AND
NOR NOT OR
155
The NOT AND, NAND GATE
Boolean expression
This means NOT (A and B)
One way to solve the NAND is to just go with the
and gate logic and flip over the output.
INPUT INPUT O