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Electrical and Electronics - The Basics
Bridgwater College
tmc
ELECTRONICS - Today and Yesterday
The Electronic Age
Electronics is about using things such as transistors and silicon
chips to make electricity work for us.
The Transistor was invented in the late 1940’s followed by silicon
chips in the 1960’s. A silicon chip (or integrated circuit), may
contain up to several thousand transistors and other devices, all
formed on a sliver of silicon so small you could lose it on your
fingernail. Miniaturising electronic circuits in this way is called
Microelectronics and it has far reaching effects on nearly all aspects
of life.
ELECTRONICS - Today and Yesterday
Today we take for granted the way in which electronics makes our
life easier and more enjoyable - lets look at some of it’s benefits.
• Consumer goods - washing machines, T.V. and video, stereo system
alarms, cameras, video/digital cameras, P.C.’s,
vehicle systems, the list is endless.
• Communications - man made satellites have been put into orbit
around our planet, to provide world wide
communication.
• Medical Electronics - use of ECG, X-rays and bio-electronics.
• Control Electronics - used in motor vehicle systems.
• Computer Electronics - fully integrated into out society.
ELECTRONICS - Today and Yesterday
The Compact Disc
Lets use this one piece of technology as an example. The compact
disc has revolutionised the way in which we store and record any
information, whether it is sound, video, DVD or both.
This is a plastic disc about 120 mm in diameter and 1.2 mm thick,
which stores sound/picture in the form of microscopically small pits
along a track that spirals out from the centre of the disc. Each pit
is about 1000th of a mm long and about a 10th as deep. The track is
so narrow that thirty tracks are about as wide as a human hair.
Sixty minutes of sound requires about ten million such pits.
ELECTRONICS - Today and Yesterday
The Compact Disc
The compact disc is then coated in a thin layer of Aluminium over
which is paced a thin layer of transparent plastic.
The disc is then rotated at high speed, where a laser beam reads the
information on the disc. The stream of on/off pulses of laser light is
converted to electrical signals which are processed into sound.
ELECTRONICS - Today and Yesterday
Looking Back - what was it like before?
Less than 100 years ago, electronics
was unknown. There were no radios,
no televisions, computers, robots or
artificial satellites and none of the
products and services we take for
granted today. In such a short space of
time there has been a revolution in the
way we communicate, control, measure, take care of people and
enjoy ourselves.
ELECTRONICS - Today and Yesterday
Looking Back - what was it like before?
This revolution came naturally out of the
study of electricity, an old science not
unknown to the Greeks over 2000
years ago. Electricity was a
subject of great interest to Victorian
scientists and to Sir William Crookes in
particular.
ELECTRONICS - Today and Yesterday
A Snap Shot of History
1897 - Sir J. J. Thomson stated that Cathode Rays were rapidly
moving electrical charges. This marked the discovery of the
electron (named after the Greek word for Amber).
1904 - Sir John A. Fleming invents the thermionic valve. This was an
early diode, where electrons would only flow in one direction.
1907 - Lee de Forest invents the triode. This was used on the first
communication devices, such as the system fitted to the
Titanic.
ELECTRONICS - Today and Yesterday
A Snap Shot of History
1922 -The use of Thermionic valves for the BBC transmitter. Firms
such as Marconi, HMV made radio sets with parts and valves
supplied from Mazda and Ozram.
1936 - The start of regular television broadcasts.
1939-45 - Invention of Radar.
1948 - Invention of the Transistor by, Shockley at the Bell telephone
laboratories.
ELECTRONICS - Today and Yesterday
A Snap Shot of History
1960’s - First integrated circuits are used on a silicon chip. This takes
man to the Moon.
1970 - NOW - The electronics industry is one of the fastest evolving
and changing in the world. Technology is ever making
advances which can be seen in the world around us
both at work and in the home.
ELECTRONICS - Today and Yesterday
The Apollo Space Programs
The space race in which JFK took the
U.S.A. was responsible for one of the
biggest steps forward in the development
of electronics. The computers which
were developed using the new I.C. chips
were known as 3rd generation computers.
They were responsible for navigation and the
guidance control of all Apollo spacecraft.
Today the computers on motor vehicles have
far superior power and accuracy.
ELECTRONICS - Today and Yesterday
How much has the Motor Vehicle been affected?
A LOT!!!
ELECTRONICS - The Basics
Electrons in Atoms
Atoms are extremely small bits of material - millions lie side by side
on the dot at the end of this sentence. All atoms have a nucleus in
which particles called protons and neutrons live. Electrons however
make up an electron cloud outside the nucleus. The nucleus is very
small compared with the overall size of the atom - say the size of an
orange compared with the size of a cathedral. Using this model you
can imagine electrons to be flies in the cathedral.
From the point of electronics the 2 most important properties of an
electron are its electrical charge and its small mass.
ELECTRONICS - The Basics
Electrons in Atoms
An electron carries a negative charge and the proton an equal
positive charge. Since these charges are opposite, protons and the
electrons attract each other. The neutron carries no electrical charge
that is to say it is neutral.
ELECTRONICS - The Basics
Atomic Structure
electrons
protons
nucleus
neutrons
ELECTRONICS - The Basics
Atomic Structure
Hydrogen and oxygen are 2 very common substances since their
atoms go to make up that very useful substance called water.
A Hydrogen Atom
electron
shell
proton
As you can see it has just 1 proton and 1 electron. It is this single
proton that tells us it is Hydrogen since it is the number of protons
in the nucleus of an atom that determines its properties.
ELECTRONICS - The Basics
Atomic Structure
The electrical charge of on a proton is equal and opposite to the
charge of an electron, making the hydrogen atom electrically neutral.
An Oxygen atom is more complicated. It has a nucleus of 8 protons
and 8 neutrons. thus the electrically neutral oxygen atom has 8
electrons in the space surrounding the nucleus.
ELECTRONICS - The Basics
Atomic Structure
Neutrons combine with protons to make up the nuclei of all atoms,
but they do not carry an electrical charge. In spite of the neutrons
zero charge, neutrons and protons do attract each other strongly
when they are close together in the nucleus of an atom. when this
force is overcome, as in the case when uranium atoms are split,
in nuclear reactors and atomic bombs, an enormous amount of
energy is released.
However, electrons are held much more weakly to atoms, and it is
this weakness upon which electronics is based.
ELECTRONICS - The Basics
Atomic Structure - some information about atoms
Atoms
Hydrogen
Oxygen
Copper
Silver
Silicon
Germanium
Carbon
Iron
Number of Protons
in the nucleus
Number of neutrons
in the nucleus
1
8
29
47
14
32
6
26
Number of electrons
in shells
0
8
34
61
14
40
6
30
1
8
29
47
14
32
6
26
ELECTRONICS - The Basics
Conductors, insulators and semiconductors
The reason why some materials, such as copper, are good electrical
conductors is that they contain “free electrons” which are quite
weakly bound to the nuclei of the atoms of the material. These
electrons can be moved easily by connecting the material across a
battery. Copper and Aluminium are good electrical conductors
and are used in electronics to allow electrons to flow easily between
one device and another. Electrons are more strongly attracted to
their parent nuclei in electrical insulators, which therefore do
not have any free electrons. Thus electrical insulators such as glass,
polythene and mica are used to resist the flow of electrons.
ELECTRONICS - The Basics
Conductors, insulators and semiconductors
Electronics is to with the use of semiconductors as well as the use of
conductors and insulators. Semiconductors are the basis of devices
such as transistors and diodes, heat sensors and light emitters,
integrated circuits and many other devices. as its name suggests, a
semiconductor has an electrical resistance that falls somewhere
between that of a conductor and an insulator.
Two of the most common semiconductors are Silicon and
Germanium. They are important in electronics because their
resistance can be controlled to good effect. There are 2 ways of
doing this.
ELECTRONICS - The Basics
Conductors, insulators and semiconductors
First there is applying heat on a semiconductor. At very low
temperatures semiconductors happen to be good electrical insulators
but as their temperature increases they become increasingly better
electrical conductors. This means at every day temperatures they
allow some current to pass through them.
The second way of controlling the resistance of a semiconductor is
by adding minute amounts of substances to them.
ELECTRONICS - The Basics
Silicon Atoms
Germanium is now rarely used in electronics, which is mostly based
on silicon. The picture below shows a silicon atom that has 14
`
electrons surrounding a nucleus of 14
protons and 14 neutrons. The part of
the structure that makes silicon useful
to electronics is the way in which the
electrons are arranged in the shells
surrounding the nucleus. There are 2
in the inner shell, 8 in the next and 4 in
the outer shell.
ELECTRONICS - The Basics
Silicon Atoms
The outer shell is known as the Valency Shell, which makes silicon
a pure crystalline material. In a crystal of pure silicon, each of the
4 outer electrons forms a covalent
bond with a neighboring electron.
The picture shows how the pairing uses
up every one of the outer electrons.
There are no free electrons to allow
electricity to flow so silicon is an
insulator. At least at -273 deg/c.
ELECTRONICS - The Basics
Silicon Atoms
But at everyday temperatures Silicon conducts electricity a little,
not much but enough to make silicon a bit of a problem when used
in transistors.
ELECTRONICS - The Basics
Silicon Atoms - n type and p type semi conductors
Once a very pure Crystal of silicon has been manufactured, it is
“doped” with impurity atoms! These atoms are chosen so that they
make a bad fit in the Crystal structure of silicon, due to the impurity
atoms having to many or too few electrons in their outer shells.
Depending on the impurity their are 2 types of semiconductor.
N- type and P - type semiconductors.
ELECTRONICS - The Basics
Silicon Atoms - n type semi conductors (negative).
This type of semiconductor is produced by doping silicon with for
example phosphorous. A phosphorous atom has 5 electrons in its
outer shell. The picture below shows what happens when an atom
of phosphorous is embedded in the Crystal structure of silicon.
4 of the 5 outer phosphorous electrons
form covalent bonds with neighboring
silicon atoms, leaving a fifth free to
wander about. Phosphorous is said to be
p
a donor impurity since each atom of
phosphorous can donate an electron.
ELECTRONICS - The Basics
Silicon Atoms - p type semi conductors (positive).
This is produced by doping silicon with atoms such as Boron which
have 3 electrons in their outer shell. As you can see from the picture
3 of its outer electrons have paired with silicon leaving an unpaired
silicon electron. This electron is not able
to conduct but will allow another
electron to pair with it. The vacancy
created by the electron is called a hole
and since it attracts electrons it behaves
b
as if it had a positive charge. Boron is
said to be an acceptor impurity.
ELECTRONICS - The Basics
Electricity - Voltage (V).
Consider electricity as water, it will behave in a similar manner.
Consider a garden hose with water flowing out. The pressure of the
water will determine how far the water will travel out of the hose.
High pressure will cause the water to go a long way. The spark plugs
in a petrol engine work when the voltage supplied to the plug has a
high voltage (1,000’s of volts) and then the spark will jump from the
centre electrode to the earth electrode.
ELECTRONICS - The Basics
Electricity - Amperage (A).
A small garden hose will only allow a small flow of water. A
fireman’s hose will allow a greater flow of water due to the fact that
the bore of the hose is greater. A tap at either end of the hose could
reduce the flow of water.
ELECTRONICS - The Basics
Electricity - Wattage (W).
Consider a water wheel, it will have a great deal of power when the
water pressure is high i.e.. after rainfall. If the flow of water or
pressure is reduced then the amount the water wheel turns will be
reduced also.
ELECTRONICS - The Basics
Electricity - Ohms .
Consider a garden hose that has a kink in it. This will cause a
resistance that will reduce the flow and the pressure. Battery
terminals often develop corrosion that causes resistance to the
electrical flow. As a result of the resistance the starter may not turn
as fast or not at all.
ELECTRONICS - The Basics
Switch
is open
Lamp
The lamp acts
as a resistance
in the circuit
measured in
ohms.
Voltage
is electrical
pressure
-
+
Battery
Chemical action to produce electricity
ELECTRONICS - The Basics
Switch
is now closed
Lamp
The lamp acts
as a resistance
in the circuit
measured in
ohms.
Voltage
is electrical
pressure
The flow
of electricity
measured in
Amperes
-
+
Battery
Chemical action to produce electricity
TECH 2000
Please identify these symbols. Use Crocodile Clips to help you.
ELECTRONICS - The Basics
Exercise
Using crocodile clips please design a circuit containing the
following:A battery
A bulb
A bulb holder
A Switch
To activate crocodile clips click on the icon.
ELECTRONICS - The Basics
Resistors control current and are usually found between a good
conductor and a good insulator.
Their resistance is rated in ohms and heat-withstanding rating is
expressed in watts. Low wattage resistors, are small, high wattage
resistors, normally called power resistors, are larger.
Unit of resistance = ohm
1 Kilohm = 1000 ohms
1 Megohm= 1,000,000 ohms
Types: Fixed and Variable
Before wiring into a circuit, check:
1. Resistance in ohms 2. Tolerance as a percentage.
3. Power rating in Watts.
ELECTRONICS - The Basics
Symbols - resistors
Fixed
or
Variable
or
ELECTRONICS - The Basics
CARBON RESISTORS
2W
1W
0.5W
WIRE WOUND RESISTORS
8.2 OHM
100 W
ELECTRONICS - The Basics
Most resistors you see have four coloured
bands to indicate their resistance and
tolerance. How do you know which way
round to read the resistor? The gold or
silver band features last in the code.
ELECTRONICS - The Basics
BANDS 1
2
3
TOLERANCE
ELECTRONICS - The Basics
COLOUR NUMERAL MULTIPLIER
TOLERANCE
1st and 2nd
multiplier
tolerance
BLACK
BROWN
RED
ORANGE
YELLOW
GREEN
BLUE
VIOLET
GREY
WHITE
0
1
2
3
4
5
6
7
8
9
*1
10
100
1000
10000
100000
1000000
10000000
100000000
1000000000
GOLD 5%
SILVER 10%
NO BAND 20%
ELECTRONICS - The Basics
BANDS 1
2
3
TOLERANCE
BAND 1 = GREEN = 5
2 = RED
=2
3 = RED
= 00
RESISTANCE IS 5200 Ohms
ELECTRONICS - The Basics
BANDS 1
2
3
TOLERANCE
BAND 1 = GREEN = 5
To convert into Kilo Ohms.
2 = RED
=2
Take the 5 2 0 0 Ohms and move
3 = RED
= 00
the decimal point three places to
RESISTANCE IS 5200 Ohms
the left.
ELECTRONICS - The Basics
BANDS 1
2
3
TOLERANCE
BAND 1 = GREEN = 5
To convert into Kilo Ohms.
EXAMPLE
2 = RED
=2
Take the 5 2 0 0 Ohms into Kilo
3 = RED
= 00
Ohms, move the decimal point
5 2 0 0. Ohms
RESISTANCE
IS 5200 Ohms
three places to the left.
ELECTRONICS - The Basics
BANDS 1
2
3
TOLERANCE
BAND 1 = GREEN = 5
To convert into Kilo Ohms.
EXAMPLE
2 = RED
=2
Take the 5 2 0 0 Ohms into Kilo
3 = RED
= 00
Ohms, move the decimal point
5 2 0.0
RESISTANCE
IS 5200 Ohms
three places to the left.
ELECTRONICS - The Basics
BANDS 1
2
3
TOLERANCE
BAND 1 = GREEN = 5
To convert into Kilo Ohms.
EXAMPLE
2 = RED
=2
Take the 5 2 0 0 Ohms into Kilo
3 = RED
= 00
Ohms, move the decimal point
5 2. 0 0 IS 5200 Ohms
RESISTANCE
three places to the left.
ELECTRONICS - The Basics
BANDS 1
2
3
TOLERANCE
BAND 1 = GREEN = 5
To convert into Kilo Ohms.
EXAMPLE
2 = RED
=2
Take the 5 2 0 0 Ohms into Kilo
3 = RED
= 00
Ohms, move the decimal point
5 . 2 0 0 =IS5.2Kilo
Ohms
RESISTANCE
5200 Ohms
three places to the left.
ELECTRONICS - The Basics
BANDS 1
2
3
TOLERANCE
BAND 1 = GREEN = 5
To convert into Kilo Ohms.
EXAMPLE
2
=
RED
=
2
Thethe
forth
the tolerance
Take
5 2 band
0 0 Ohms
into Kilo
3
=
RED
=
00
bandmove
is Silver.
The resistor
Ohms,
the decimal
pointhas a
5 . 2 0 0 =IS5.2Kilo
Ohms
RESISTANCE
5200
Ohms
Tolerance
ofthe
+ orleft.
- 10%
three
places to
ELECTRONICS - The Basics
BANDS 1
2
3
TOLERANCE
If you are asked to calculate the minimum
and maximum resistance this is how it is
done.
The resistance is 5.2 K Ohms + or - 10 %
ELECTRONICS - The Basics
BANDS 1
2
3
TOLERANCE
If1st
youwork
are asked
to calculate
the minimum
out 10%
of 5.2 K Ohms.
and
resistance this is how it is
Usemaximum
your calculator.
done.
5.2 * 10 then press the % button on your
The
resistance
is K5.2
K Ohms + or - 10 %
calculator
=.52
Ohms
ELECTRONICS - The Basics
BANDS 1
2
3
TOLERANCE
If1st
youwork
are asked
to calculate
the minimum
out
10%
of
5.2
K
Ohms.
Now
work out
the MINIMUM
value
of the
and
maximum
resistance
this
is
how
it
is
Use
your
calculator.
5.2
K
Ohm
resistor.
done.
5.2
*- 0.52
10 then
press
the % button on your
5.2
=
4.68
K
Ohms
The
resistance
is K5.2
K Ohms + or - 10 %
calculator
=.52
Ohms
ELECTRONICS - The Basics
BANDS 1
2
3
TOLERANCE
If1st
youwork
are asked
to calculate
the minimum
out
10%
of
5.2
K
Ohms.
The
MAXIMUM
value this
of the
5.2 KitOhm
and
maximum
resistance
is
how
is
Use
your
calculator.
resistance
is
done.
5.2
*+ 0.52
10 then
press
the % button on your
5.2
=
5.72
K
Ohms
The
resistance
is K5.2
K Ohms + or - 10 %
calculator
=.52
Ohms
ELECTRONICS - The Basics
BANDS 1
2
3
TOLERANCE
R=5.2K Ohms min = 4.68
max 5.72