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Electronics Merit Badge - PowerPoint PPT Presentation

Electronics Merit Badge. Old Colony Council Merit Badge University March 2012 Joe Mulcahey Len Barrett Sean Mulcahey. jkm@alum.mit.edu http://www.mulcahey.org http://www.crew748.org. Rev. S, 01MAR12.

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Presentation Transcript

Old Colony Council

March 2012

Joe Mulcahey

Len Barrett

Sean Mulcahey

jkm@alum.mit.edu

http://www.mulcahey.org

http://www.crew748.org

Rev. S, 01MAR12

Based on the Electronics Merit Badge classes taught at the 2005 & 2010 National Jamborees

Class 1 Safety (Requirement 1)

March 3 Electricity & Electronics Introduction

Circuit Diagrams & Schematics (2)

SolvingCircuit Problems using Ohm’s Law (5a)

Class 2 Job Opportunities in Electronics (6)

March 10Test Equipment Demos (5b)

Class 3 Proper Soldering Techniques (3)

March 24Kit Assembly (4)

Electricity Safety
• High Voltage ( 120V AC or greater) – Safety mainly about not touching the wrong thing
• Current kills – Only 16 volts can kill when enough electrons flow through the heart or head
• Ventricular fibrillation – Electrons passing through the heart causes muscles to seize, leading to death
• If the shock doesn’t kill you, you can still be badly burned from touching the wrong thing
How to Avoid Shock
• Turn power off before working on equipment
• Don’t touch circuits that could have high voltage on them
• Do not allow electrons to flow through the heart. I don’t think the snake knew about this detail
Electronics Safety
• Electronics generally uses lower voltages (less than 48 volts)
• You are usually working with DC voltage instead of AC voltage
• You are usually more concerned with sparks from connecting the wrong wires together, or burning yourself with a soldering iron, or some similar event
• Even when working with lower voltages, you may still receive an electrical shock from equipment you are using
Personal Safety
• Be aware of what you are doing, and where you are placing equipment and yourself
• Pay attention to hot soldering irons
• Keep a good distance between you and those next to you
• Know when you are working with high current and/or high voltage circuits
• THINK before you do something
• Wear safety glasses when soldering
One Hand Rule
• Prevents current from flowing in one arm, through your heart, and out the other arm
• Keep one hand in your pocket!
Introduction to Electronics

Electrical and Electronics Engineering are both career fields that are involved with Electronics Technology

Electrical engineers specializing in power work with motors and generators, and design transmission lines and power plants

EEs specializing in electronics deal with communications, such as radio, television and telephony, radar and digital & analog circuit technologies

All engineers draw from the fundamentals of science and mathematics

They design and work with electrical, electronic, electro-optical, and electromechanical devices, circuits, and systems

Introduction (Continued)

Electrical Engineers collaborate with other professionals in developing sophisticated software tools that support design, verification, and testing

Electrical engineering is a discipline that integrates many other disciplines, such as physics, chemistry, mathematics, computer software and hardware, solid-state electronics, communications, electromagnetics and optics, signals and signal processing, systems science, reliability, engineering economics, and manufacturing

In order to Learn about Electronics, we must first start by gaining an understanding of what electricity is, both AC (Alternating Current) and DC (Direct Current)

Types of Electricity

Static electricity is usually created when materials are pulled apart or rubbed together, causing positive (+) charges to collect on one material and negative (−) charges on the other surface. Sparks may result!

Static Electricity

• Examples of static electricity:
• Lightning
• Combing hair
• Walking across carpet and getting shocked
• Pulling out scotch tape
Types of Electricity

Alternating Current (AC)

The common form of electricity from power plant to home/office. Its direction is reversed 60 times per second in the U.S.; 50 times in Europe.

• Examples of AC usage:
• Kitchens: Stoves, ovens, mixer, etc.
• Computers (the plug)
• Lights in house
• Home air conditioners
Types of Electricity

Direct Current (DC)

Type of electricity used in most electronics we have today. Current only flows in one direction (not both directions, like AC).

• Examples of DC usage:
• MP3 players
• Electricity in cars
• Anywhere you use a battery for power
Basics of Electronics
• Current: Defined as “flow of electrons”
• Current: Units of current is the AMP
• Current: Electrical symbol for current is I
Current Flow – Water Analogy
• Water flows in the hose, entering at the top and exiting the bottom
• The water is the “current”; the flow of electrons
• The more water flowing in the pipe, the more electrons are flowing in the wire
• Different pipe diameters illustrates different resistance to water flow, which correlates to different resistor values
Current
• Current: Defined as “flow of electrons”
• Current: Units of current is the AMP
• Current: Electrical symbol for current is I
• Common units for current are:
• amps
• milliamps (mA): 1 mA = 0.001 amp
• microamps (mA) : 1 mA = 0.000001 amp, or 0.001 mA
• nanoamps (nA) : 1 nA = 0.000000001 amp, 0.000001 mA, or 0.001 mA
Voltage – Water Analogy

Small height = low voltage

Big height = high voltage

height

height

• Gravity provides the force for water (current) to flow
• This illustrates a small voltage, so electron flow is small
• Gravity provides the force for water (current) to flow
• This illustrates a larger voltage, so electron flow is larger
Voltage
• Volts is the electrical force that causes

electrons (current) to flow

• Units of volts is the VOLT
• The symbol of volts is E or V. We will use V
• Common units for voltage are:
• volts
• Millivolt (mv) : 0.001 volt
• Microvolt (mv) : 0.000001 volt, or 0.001 mV
• Nanovolt (nv) : 0.000000001 volt, 0.000001 mV, or 0.001 mV
Resistance – Water Analogy

10000Ω

• Different pipe diameters represents different resistor values
• The smaller the diameter of the pipe, the larger the resistance

1000Ω

100Ω

10Ω

Resistance
• Resistance is an electrical property of a material that “resists” the flow of electrons
• The schematic symbol for a resistor is:
• Common units for resistance are:
• ohms
• kiloohm: 1KΩ = 1000 ohms, 10KΩ = 10,000 ohms
• megaohm: 1MΩ = 1,000,000 ohms
• The units symbol for ohms is: Ω (ohms)
Power – Water Analogy
• In electronics, power is equal to current X voltage
• The units for power is the WATT
• The symbol for power is W or P
• In our water analogy, power is
• equal to water flow X pressure
• You can see from the picture that more water flow will mean more force, and more pressure will mean more force
Ohm’s Law
• One of the most important laws in electronics/electricity
• V = I x R : Voltage = Current x Resistance
• Voltage is measure in volts, current is measured in amps, and resistance is measured in ohms
• 1 amp, going through 1 ohm of resistance, results in a voltage drop of 1 volt
• 1 V = 1 A x 1 Ω
More Ohm’s Law

Different forms of Ohm’s Law:

V = I x R : Voltage = Current X Resistance

I = V / R : Current = Voltage / Resistance

R = V / I : Resistance = Voltage / Current

Volts = 10

Resistance = 1000Ω

Compute current:

I = V / R

I = 10 / 1000 = .01A

.01A = 10mA

Question: what would the current be if the voltage was 1 V? How about 1000 V?

+

10V

1000 Ω

Ohm’s Law Pie Chart

If you know any two values, you can get the other two with these formulas

Bonus Ohm’s Law Question: Resistor Cube

R

R

Resistances in parallel divide: RTotal=R/2

What is the resistance between points A and B?

Where Did the Names of the Electrical Parameters Come From?

Volts: Count Alessandro Volta (1745-1827), Italian Scientist

Ohms: Georg Simon Ohm (1787-1854), German Physicist

Amps: André-Marie Ampère (1775-1836), French Physicist

Watts: James Watt (1736-1819), British Engineer

Henrys: Joseph Henry (1797-1878), American Physicist

Other Units:

Coulomb, Gauss, Joule, Tesla and of course Smoot

Smoot? What’s A Smoot?

Smoot: A humorous unit of distance invented in 1958 by a fraternity at the Massachusetts Institute of Technology. The fraternity pledges of Lambda Chi Alpha measured the length of Harvard Bridge using pledge Oliver R. Smoot ('62). According to Smoot himself, the bridge turned out to be 364.4 smoots long "plus epsilon," but this has been recorded as 364.4 smoots "plus an ear." The bridge is still marked in smoots. Proposals to change the definition of the unit by remeasuring it with Smoot's son Steve (MIT '89) or daughter Sherry ('99) were rebuffed. One smoot equals 67 inches (170.18 centimeters). Oliver Smoot became an attorney but continued his interest in standards and measurement. He is a past Chairman of the Board of Directors of the American National Standards Institute (ANSI) and past President of the International Organization for Standardization (ISO).

Electronic Symbols

NC

Single Pole, Double Throw Switch (SPDT)

W

NO

Capacitor

Battery

or

Resistor

Light Emitting Diode (LED)

Ground

Buzzer

Fuse

Lamp

CIRCUIT DIAGRAM (SCHEMATIC)

FLASHLIGHT

SWITCH

LAMP

+

BATTERY

GROUND

GROUND

TWO GROUND SYMBOLS IS THE SAME AS CONNECTING WITH A WIRE

GROUND = 0 VOLTS

DC Circuit Wiring

Design three different DC circuits

Switch

Power

Supply

Buzzer

Wired to turn Buzzer On/Off

Light

Switch

Wired to turn Light On/Off

Power

Supply

Buzzer

Light

Switch

Wired to turn Light On in one

direction and Buzzer On in other direction

Power

Supply

Buzzer

Light

Direct Current

Circuit to Switch Buzzer On / Off - Draw the rest of the wires

Switch

Power

+ 12

Fuse

Buzzer On

Light

Buzzer

Direct Current

Circuit to Switch Buzzer On / Off

Switch

Power

+ 12

Fuse

Buzzer On

Light

Buzzer

Direct Current

Draw Circuit to Switch Light On / Off

Switch

Power

+ 12

Fuse

Light On

Light

Buzzer

Direct Current

Draw Circuit to Switch Light On / Off

Switch

Power

+ 12

Fuse

Light On

Light

Buzzer

Direct Current

Draw Circuit to Turn Buzzer on in one Direction and Light in other Direction

Switch

Power

+ 12

Fuse

Light On

Buzzer On

Light

Buzzer

Direct Current

Draw Circuit to Turn Buzzer on in one Direction and Light in other Direction

Switch

Power

+ 12

Fuse

Light On

Buzzer On

Light

Buzzer

Electronic Components

Microphone

Sound → Current

Batteries

In volts

Inductor or Coil

In henries

Resistor

In Ohms

+

Power Supply

Outputs Volts

Transformer

Input voltage

Speaker

Current → Sound

Potentiometer

Variable

Resistor

120V

AC In

DC

volts

Out

Isolated

Capacitors

Step

Down

+

Step

Up

Electronic Components

Diode

PN junction. Current flows in direction of arrow only

Transistor

Electronic Switch. Emitter, Base & Collector terminals. Small current (B-E) controls a larger one (C-E). Made of N (negative) and P (positive) sections

Switch

Normally Open (n.o.)

Normally Closed (n.c.)

Anode (P)

Cathode (N)

n.c.

n.o.

LED

Light

Emitting

Diode

Slide Switch

Can connect the center Pole to one of two Throws (SPDT)

NPN

(“Never Points iN”)

PNP

(“Points iN Proudly”)

Meters

Current Meter

Voltage Meter

Resistance Meter

Bonus Question: Which type is the Transistor on the Electronics Merit Badge?

Resistor Color Rings

A Resistor’s value is indicated

by its color bands and is measured in ohms

First Ring is First number / Closest to edge of resistor

Second Ring is second number

Third Ring is number of zeros

Fourth Ring is tolerance 1% or 5% or 10% etc.

A Fifth Ring, if present, could indicate reliability or temperature sensitivity

Resistor Color Code Values

Fourth Ring

Brown = +/- 1%

Red = +/- 2%

Gold = +/- 5%

Silver = +/- 10%

None = +/- 20%

First Ring

Black = 0

Brown = 1

Red = 2

Orange = 3

Yellow = 4

Green = 5

Blue = 6

Violet = 7

Gray = 8

White = 9

Second Ring

Black = 0

Brown = 1

Red = 2

Orange = 3

Yellow = 4

Green = 5

Blue = 6

Violet = 7

Gray = 8

White = 9

Third Ring Multiplier

Silver = X .01

Gold = X .1

Black = X 1

Brown = X 10

Red = 2 = X 100

Orange = 3 = X 1,000

Yellow = 4 = X 10,000

Green = 5 = X 100,000

Blue = 6 = X 1,000,000

Violet = 7 = X 10,000,000

G-Rated Resistor Color Code Mnemonics
• Black Brown Red Orange Yellow Green Blue Violet Gray White (Gold Silver None)
• 0 1 2 3 4 5 6 7 8 9
• Big Brown Rabbits Often Yield Great Big Vocal Groans When Gingerly Slapped
• Black Bears Run Over Yellow Grass, But Vultures Glide over Water
• Better Be Right Or Your Great Big Venture Goes West
• Bye Bye Rosie Off You Go to Birmingham Via Great Western
• Black Bart's Rambler Over Yonder Gave Bad Vibes Going West
• Bright Boys Rave Over Young Girls But Veto Getting Wed
• Big Boys Race Our Young Girls Behind Victory Garden Walls
• Big Boys Race Our Young Girls But Violet Generally Wins
• Black Birds Ruin Our Yellow Grain, Butchering Very Good Wheat
• Billy Brown Ran Over a Yodeling Goat Because Violet's Granny Was Grumpy
• Billy Brown Revives On Your Gin, But Values Good Whisky
• Black Beetles Running On Your Garden Bring Very Good Weather
• Bowling Balls Roll Over Your Grandpa But Victim Gets Well
• Batman Bests Robin On Yonder Gotham Bridge; Very Good, Will Get Superman Next!
• Big Bart Rides Over Your Grave Blasting Violent Guns Wildly
• Bad Borg Raid Our Young Galaxy Before Vaporizing Good Walter
Resistor Value Examples

Ring

Black = 0

Brown = 1

Red = 2

Orange = 3

Yellow = 4

Green = 5

Blue = 6

Violet = 7

Gray = 8

White = 9

First Ring is first digit

Second Ring is second digit

Third Ring is number of zeros

Example of Color Rings

First Ring

Red = 2

Black = 0

Second Ring

Red = 2

Red = 2

Third Ring

Red = X 100 = 2200 ohms

Brown = X 10 = 020 ohms

Test of Color Rings

Second Ring

Green = ____

Red = ____

First Ring

Brown = ____

Green = ____

Third Ring

Brown = ____ = ___ ohms

Yellow = _____ = ____ ohms

Resistor Value Examples

Ring

Black = 0

Brown = 1

Red = 2

Orange = 3

Yellow = 4

Green = 5

Blue = 6

Violet = 7

Gray = 8

White = 9

First Ring is first digit

Second Ring is second digit

Third Ring is number of zeros

Example of Color Rings

First Ring

Red = 2

Black = 0

Second Ring

Red = 2

Red = 2

Third Ring

Red = X 100 = 2200 ohms

Brown = X 10 = 020 ohms

Test of Color Rings

Second Ring

Green = 5

Red = 2

First Ring

Brown = 1

Green = 5

Third Ring

Brown = x10 = 150 ohms

Yellow = x10,000 = 520k ohms

Transistors

A Transistor is an Electronic Switch

Transistor come in

different sizes depending

on the amount of current

and voltage required

Transistor

NPN

Switch

Transistor Switch Circuit

Mechanical Switch Circuit

Light

12 Volt

Battery

Switch open

Light off = 0

Switch close

Light on = 1

12 Volt

Battery

NPN Transistor

Computer can

send a signal to turn

on the transistor which

then turns on the light

Integrated Circuits

An integrated circuit (IC) consists of multiple transistors. The number of transistors can vary from just a few (circuits shown below), to over two billion that are in the latest Intel microprocessor.

This IC has 6 inverters

An inverter contains

6 Transistors = 36 total

Functions

Inverters

Gates

Flip flops

Counters

Memory

MPU

Watch ICs

Calculators ICs

Microwave Timer ICs

Dialer ICs

Car Controller ICs

6 Transistors in one IC

Education & Certification Required for Engineering Careers
• Engineering Assistant
• 6 months to 2 years of Technical School during or after High School
• Entry-Level Design Engineer
• 4-year Bachelor of Science in Engineering Degree
• Senior-Level Design Engineer, Engineering Manager
• 4-year BS Degree, 2-year MS Degree
• 2-20 years experience
• Some Engineering Positions Require State Registration (P.E.)
• Professor, University or Industry R&D Laboratory Researcher
• Ph. D. or Sc. D. Degree in Physics or Engineering
US Numbers by Type

From the American Society for

Engineering Education, 2009

(http://www.asee.org)

US News & World Report 2011US Undergraduate Engineering School Rankings(with Ph. D. Program)
Starting Salaries

Top Jobs for 2010 Bachelor’s Graduates (www.jobweb.com)

Before College

Built lots of Heathkits, installed an intercom and an alarm system in my tree house, performed various dangerous high-voltage experiments

Studied, passed FCC tests and became an amateur radio operator

Studied some more and passed more FCC tests, got a commercial radio operator’s license enabling me to work as a studio and transmitter engineer at a 50,000 Watt radio station in Hartford

College

Co-op student at Raytheon in the Antenna and Microwave Department

Earned the BSEE and MSEE degrees from MIT in 1984

Raytheon (since 1981)

My specialty is designing and testing really big and expensive phased array radar antennas for missile defense

Raytheon is an industry leader in defense and government electronics, space, information technology, technical services, business aviation and special mission aircraft, with more than 71,000 employees world-wide, including over 30,000 engineers

Eagle Scout with Gold Palm, 2009

Crew Guide, Venturing Crew 748

NEU Sophomore in Electrical Engineering

Currently on co-op at Bose, in the Product Safety Laboratory

Test returned and not-yet-released products for safety

Take expensive and fragile audio equipment and set it on fire, apply massive overvoltages, shake and drop

Test Equipment
• Power Supply
• Power Equipment or Components for Test
• Volt-Ohm Meter (VOM) or Digital Volt Meter (DVM)
• Check AC & DC Voltages, Resistance, Opens/Shorts
• May also Measure Capacitance, Inductance, Gain, etc.
• Oscilloscope
• Graphs one Voltage vs. Time or vs. another Voltage
• Signal Generator
• Power Meter
• Spectrum Analyzer
• Graphs Voltage versus Frequency
• Network Analyzer
• Field Strength Meter

Now go get some hands-on experience!

End of Class 2

Soldering

Safety Note: A Soldering Iron gets hotter than 300 F. Do not touch

the soldering iron’s metal parts or you will receive a third degree burn

A good solder joint depends on the following:

1) Solder iron must have a clean, well-tinned tip

2) Parts to be soldered must be clean

3) There must be a sound mechanical joint

4) Parts to be soldered must be well heated before applying solder

5) Wait approx. 5 seconds after soldering to allow strong mechanical

joint to form

Soldering – Heating Junction

Iron

Iron

Wire

Wire

PC Board

PC Board

Wrong

way

Right

way

Iron

Solder melts at 310° F. The wire and PC (Printed Circuit) board must be the same temperature for the solder to melt on both items.

Wire

Place soldering iron so that it touches both the PC board and wire. The heat from the soldering iron will transfer to the PC board and wire at the same time.

PC Board

Soldering – Applying Solder

When the board and wire are hot enough the solder will flow and create a cone shape. If

the board is not hot enough the solder will be rounded on the board creating somewhat

of a ball. The finishing solder should also be shiny. Clip extra wire at board level.

Wrong

way

Wire

Iron

After 3 seconds place the solder on the tip of theiron, the wire and the PC board all together.

The solder should flow to everything making a good connection.

Solder

PC Board

Wire

Iron

Wire

Right

way

PC Board

Solder

PC Board

Un-Soldering
• Use pliers to hold the component next to the lead to be unsoldered (If the lead is held with the pliers it will draw heat from the lead)
• Apply soldering iron tip to PC board and wire
• Either use solder wick or solder sucker to draw solder off the board, or simply pull wire from PC board when hot
• The soldering iron will damage electronic components if left on device for greater than 15 seconds, so work quickly
• Sometimes it helps to put more solder on the solder joint to improve the thermal conductivity
• Clean the soldering iron tip and keep it shiny
Un-Soldering

Iron

Wire

With pliers, hold device close to lead that is to be unsoldered. As heat is applied from soldering iron, pull with pliers. With one side out, do the same on other side.

PC Board

Iron

Pliers

PC Board

Kit Assembly

1) Place components into PC board in the order recommended on instruction

sheet

2) When components are placed into PC board, bend leads out slightly to

keep parts from falling out, when the PC board is turned over for soldering.

3) Follow instructions as to proper orientation of components.

PC Board

Wrong

Clip wire at board

Correct

Red

+

LED

Note Flat Edge

Black

Anode of LED1

Q1 and Q2 are connected in a criss-cross fashion making a square wave oscillator running at about 1.5 Hz. The frequency is determined by C1 and R6. (Also C2 and R4.)

The Oscilloscope is displaying plots of voltage vs. time

C2 Negative, Q2 Base

When Q1 conducts, Q2 gets turned off until the voltage at Q2 base rises above about 0.7V. C2 has to discharge through R4 for this to happen. This determines the time the multi-vibrator will stay in one state.

IC1 pin 2 & 6

IC1 is also an oscillator that drives the speaker at a frequency that we can hear. It oscillates at either the low tone of about 720 Hz or the high tone of about 980 Hz. C4 charges through R5 but discharges through R9.

IC1 pin 3

This shows pin 3 of IC1 that drives the speaker. This oscilloscope shot captured the 985 Hz tone. The output at pin 3 is a square wave (almost).

End of Class 3