Hello everybody! We are now going to start a course on basics electronics. It is essentially
a laboratory course. We are living in an age of information technology. Electronics is
at the very foundation of information and computer age which we are living now presently.
The giant strides that we have made in the areas of communications and computers are
possible only because of the great successes that we have achieved in the field of electronics.
It is some times unbelievable how many electronics gadgets that we carry theses days in our person
for example digital wrist watch, calculator, cell phone, digital diary or a PDA, digital
camera or a video camera etc.
The different types of electronic equipments that have invaded our offices and homes theses
days are also mind boggling. Many things we use at home, offices are remote controlled.
For example television, air conditioners, audio equipment, telephone, we use a cordless
for example.
It is almost close to magic how even a small child now-a-days can switch channels or increase
or decrease the volume of sound in a TV at home by just clicking on a few buttons at
the comfort of a sofa away from the television apparently without any physical wiring or
connection.
Again we are astonished how we are able to talk to our near and dear living several thousands
of kilometers away from wherever we are at home, office, on the road in a car or in a
class room by just clicking on a few numbers on our palm sized cellular phones. Electronics
has thus made deep impact in several vital areas such as health care, medical diagnosis
and treatment, air and space travels and automobile. In short the technological developments of
several countries of the globe are directly related to their strengths in electronic design,
manufacture products and services related to electronics.
It appears as though that we have to add inevitably an "E" to the three "R's" that we
normally specify to declare a man and woman literate. That is the three R's are reading,
writing and arithmetic. Needless to add that the E I was referring to here means "Electronics".
So apart from reading, writing and arithmetic one should also have basic knowledge of E,
or electronics. Thus electronics has become surely a basic science and it is no more an
applied science.
Just as we teach physics, chemistry, biology and mathematics in our schools it is time
we start teaching our children at school electronics as a separate subject by itself. This brings
us face to face an important question how to teach the basic concepts of such an important
subject like electronics in a most efficient and effective manor. If one wants to gain
a good grip and understanding of electronics he or she should build circuits and test them
independently.
For this one should acquire a practical knowledge of the characteristics of different devices
and in constructing the various circuits let as try to learn such skills by the proven
scheme of "learning by doing".What is this? An old Chinese proverb says I read -- I
forget; I see-I remember; I do-I understand. So if you need to understand and apply whatever
knowledge you acquire then it has to be by the method of doing rather than reading or
seeing. There is only way to learn to do anything; that is just do it. That is the way we all
have learnt as a child even to talk, to walk, to ride a cycle or whatever.
Many arts and special skills like dancing, singing, swimming and martial arts are all
learnt by going to an expert or a teacher who makes us learn by doing rather than by
listening to lectures or reading books. But why "learning by doing" is so important?
It is very simple. The reason is while doing we are given an opportunity to fail. So failures
are very important in the learning process. Nobody wants fail and if one fails, one starts
wondering as to what went wrong. Thus at the point of failure there is a profound learning
taking place. That is why people say failures are stepping stones to success.
Before we go into the subject of electronics it will be nice to look at some of the historical
background of electronics. I will just mention to you few landmarks in the history of electronics.
The invention of vacuum tubes or the thermionic valve brought in the age of electronics long
time back. Many new and exciting applications were found for theses devices. Many great
names like Edison, Marconi, Ambrose Fleming, De Forest, etc., are associated with electronics.
As a mater of fact the transition from the diode to the triode which has got three electrodes
was brought about by engineer suggestion by deforest. He suggested that we can introduce
a third electrode in the vacuum tube diode to make it into a triode and that really brought
about a major change and development in the area of electronics. You can see some examples
of vacuum tube on the screen.
These are different types of vacuum tube used in those days for amplification purposes and
things like that. You can see they have a filament, which is a thermionic filament.
When I pass a current through that thermionic electrons are develop which are collected
by an electrode, called the plate and you have another electrode the third electrode
which is the control grid which is in between these two electrodes and any voltage impinched
on them will alter the flow of electrons between the two main electrodes- the cathode and the
anode. So that is responsible for the amplification and such things. After the war in 1948, the
transistors were invented in the Bell laboratories in the USA by the three great people Bardeen,
Bratain and Shockely and that brought in much greater miniaturization and applications in
the area of radio electronics and things like that.
On the screen you can see some of the examples of transistors, different types of transistor
are shown in the photographs and the major development in electronics came up with the
introduction of integrated circuits. This invention is one of the major developments
in the area of electronics.
Here transistor have become already common place in everything from radios to phones
to computer and therefore the manufactures wanted some thing even better, some thing
which is much smaller and much more powerful. Two people are associated with invention of
integrated circuits. They are Jack Kilby of Texas instruments and Robert Noyce of Fairchild
semiconductors and Jack Kilby were awarded the noble prize in 2000 for his development
of integrated circuit. Robert Noyce was no more at that time and therefore Jack Kilby
alone was given for the partial development of the integrated circuit ideas.
Integrated circuits can be now found in almost every modern electrical device such as computers,
cars, television sets, CD players, cellular phones, etc. I will show you some photographs
of that. The basic idea here is the semiconductors are used for preparing the transistors. But
other devices like the resistors and capacitors have to be independently made by discrete
methods. It was the idea of Jack Kilby and Noyce whether the same semiconductors can
be used to also prepare diodes, resistors and capacitors.
Resistors can easily be developed by doping the semiconductor suitably and the capacitors
can be developed by using a p-n junction diode in a reverse bios mode and therefore diodes
can be made; resistors can be made; capacitors can be made out of semiconductor therefore
Jack Kilby and others started to make the whole circuit, which involves different devices,
completely using semiconductors. That is how the whole idea of integrated circuits came.
You integrate the different components like transistors, diodes, resistors and capacitors
all made of basic semiconductor material on the same substrate. The bulk resistivity of
the semiconductor and its diffusion doped layers could be exploited for fabricating
resistors, p-n junctions, diode, etc., and that I already mentioned. So this is one of
the fast integrated circuit idea which was implemented by Jack Kilby in his lab. You
can see that it is very crude and it has got no resemblance to the modern, well refined,
design of integrated circuit which I will show you in the next graph.
One of the integrated circuits with its memory chip is shown here and the other picture here
shows different integrated circuits. They have different packages. In all of these you
can see enormous number of transistors being prepared side by side and few of resistors
and very few capacitors and no inductances at all.
So integrated circuits are characterized by very many numbers of transistors, few resistors,
very few capacitors and almost no inductances. Therefore the whole idea of integrated circuits
completely modified the concept of circuit design. Instead of going for the distribution
of various devices, in olden days circuits will have more of resistors, capacitors, etc.,
and less number of active devices like transistors but with the introduction of integrated circuits
the situation reversed. That is we have more number of active devices like transistors,
etc and less number of resistors, capacitors and things like that. So this is generally
the background of the brief history of the electronics. Now I will move over to the table
to show you some real transistors, vacuum tubes and integrated circuits.
Here you can see the vacuum tubes. This is a vacuum tube which is used for power electronics.
You have number of pins; you will have a base into which these pins will go and the corresponding
voltages will be applied.
These are characterized by very high voltages of the order of 200-300 volts and you require
a separate power supply for energizing the filament and therefore you require large number
of power supplies and they will dissipate enormous amount of energy and therefore you
will find that they have to be cool if large big circuit are built with vacuum tube diodes
and triodes you require very efficient cooling system. Whereas when you come to the transistors,
these are semiconductor transistors. You can see this is smallest one; very small three
terminal device just as you have triode where you have plate, control grid and cathode,
here you have three electrodes -- emitter, the collector and the base. Here again you
have a slightly bigger one; this is for higher current or higher power. This one is much
higher power and this one very large power of several watts. I will just perhaps take
it out and show it you. You have two terminals only here. They correspond to the emitter
and base and the casing becomes by itself one of the other electrodes which is the collector
which takes the brunt of current in any given circuit. So these are transistors of different
type, all made of semiconductors.
Then we come to the integrated circuits. You have here a very tiny one which has got eight
pins on either side. These are called dual in line package and you have much larger one
slightly larger one which has got fourteen or sixteen pins on either side; eight on either
side or seven on either side. This one is the much larger integrated circuit which has
got about forty pins; twenty on one side and twenty on the other. So these are integrated
circuits which have got several transistors.
For example this will have easily about twenty transistors; this will be much larger and
this will have thousands of transistors inside and the actual semiconductors will be some
where very small, few millimeter squared and to make them easy to handle they are put on
bigger package with number of pins so that they can be connected into a real circuit
outside.
So these three are the modern integrated circuits. The latest integrated circuits in the computer
that you see will have much larger number of pins of the order of 396, 400 and things
like that and some of resistors, capacitors also have to be used along with these for
building different circuits which have come in; something very similar to intergraded
circuits and are called surface mountable devices. So along with these things the miniaturization
is complete. Therefore you have enormous number of applications coming out of them including
the things that you know of like the cell phone and things like that. They have enormous
number of very tiny circuits built with several integrated circuit and several small devices
like transistors, capacitors, resistors, etc all found in one. They are all wired on one
single printed circuit board; the circuit board itself will be printed with the all
the wiring pattern and the whole thing in modern times is all automated and therefore
large number of such things can be manufactured very quickly and very efficiently and these
devices they also increase in the order of efficiency and performance. The vacuum tubes
are not all that good because they have enormous amount of heat generated. These are good but
these are much better. Here the transistors are very close to each other and therefore
the performance and reliability is enormously improved in these integrated circuits
Now let us see what we will discuss in this course on basic electronics. We have components
and devices which go into the building of circuits; we have measuring instruments like
different types and we also have circuits to learn. For example if we take the components
and devices you can classify them basically into two; one is called passive component
devices. The examples of passive components are resistors, capacitors, diodes, inductors,
etc. If you look at active components there are transistors, operational amplifiers, etc.
The passive components cannot amplify; they will only attenuate. If a signal or voltage
or current is given to them there will only be reductions if at all after passing through
this component. Therefore they are called passive. Whereas if you take the active components
like transistors or op amp, there can be an enhancement of the voltage or current or whatever
and therefore they are called active components.
Now if we look at measuring instruments one has to know something about the digital multimeters.
Most of them are digital multimeters. There are a very few occasions when you come across
analog multimeters. Power supply is very essential for the powering the different circuit for
working; voltage sources and current sources, oscilloscopes for observing the different
wave forms and function generators which are basically to generate different kinds of wave
forms or signals. When you come to the circuit, you find different types of circuit like rectifiers,
amplifiers, oscillators, filters and so many different types of circuits.
What is the prerequisite of this course? The basics prerequisite we assume for this is
that you have a general understanding of the principles of electricity and magnetism. That
is all that is required to know from your side. Once you know that we will be able to
build on that foundation the whole subject of basic electronics with a practical ...... We
will attempt here to learn the basic principles of electronics by the scheme outlined namely
"learning by doing".
So what I am going to do is I will try to explain the principles of operation of the
various devices, the measuring instruments and the circuits that was outlined a little
ago. I will also then demonstrate the working principles by actually performing that part
of the theory which we learnt by actually going over to a laboratory table and performing
those experiments on a bread board side by side. This I believe will enable you to get
greater confidence in the principles and working of electronic devices and circuits and therefore
at a later time you will be able to build different circuits on your own and learn from
them. Before we proceed further it is important to understand how and where the different
circuits will be built and tested.
We will use what is known as a breadboard for constructing the different circuits and
for testing. This is very useful here as we do not have to solder the different components
while we build the circuit. The normal scheme is to take those components and solder them
together on what is known as a group board by soldering them. By soldering, I mean you
will use lead and then use a soldering iron which is hot iron and then join the different
components into various configurations of the circuit. If we do such soldering then
you can imagine the components will have to be cut into different sizes to match the circuit.
Once you solder, the components may get spoiled. We may not be able to use the components again
later on, where as in breadboard it is very convenient because we are not going to solder
the components; you are going to just insert the components or the leads of the components
into small tiny wholes which I will show you in a moment and therefore you do not have
to solder and the components need not be cut. So the resistors and the various components
can be used repeatedly for different circuits. Let us now see how we can use the breadboard.
What is the basic principle of the breadboard? I have shown on the screen a typical breadboard
which will be used for building the different circuits. Many of you I am sure are familiar
with this type of breadboard perhaps.
You can see that a breadboard is a plastic board with number of holes on it. There is
a pattern of holes. For example you can see vertically there are five holes marked A,
B, C, D, E on the screen on side and then F, G, H, I, J on the other side. So you have
a whole row of such holes on either side with a small cavity in the center and then you
also see on either side, top and bottom between the red and the blue lines a whole range of
holes which are running parallel to the length of the rectangle. These lines which are running
at the extreme ends between the two blue and red lines are called power lines or rail lines.
They are generally used for connecting the power supply lines for the various circuits.
The other holes which are marked A, B, C, D, E, etc., are basically five holes in a
node. They all correspond to one single node. Most of the times when you build circuit,
you find you require many points to be connected together. Here we have five holes. That means
five different components or wires can be connected together to one single point. That
is what we mean by the five holes node here.
How is it done? For knowing this let us look at the figure that we have on the screen where
you can see for example below that holes in the breadboard that I showed, you have a set
of clips, metal clips in the form shown in Figure a. This is basically a metal clip which
has got very narrow hole at the point where I show and when you insert a component, for
example here in Figure b a resistor is shown, and when I insert the resistor inside the
clip, the clip expands a little bit and grips the lead of the resistor at this point.
So that is how the connection to resistance is made at these two points and this clip
is actually very long as it is shown in Figure c which will actually align below the five
holes that we saw on the breadboard. So by connecting different components through different
holes corresponding to the one set of five holes you would find, you will be all inter
connecting them because all of them have got individual clips below them which are all
connected by a single metal frame. Let us look in some greater detail the scheme of
things on a breadboard. This is actually a cut screen cut view of the breadboard.
You can see the five clips one, two, three, four, five which will come under these five
holes A, B, C, D, E and you also see on the sides which I called the power supply channel
or the rail voltage channel you would see there is one single metal clip running all
the way down for the entire length and these holes therefore will provide one connection
for the power supply. So for example if I connect this hole or this clip to the + 5
volts of a power supply and on this side I connect it to the ground or the minus terminal
then you can see that I can get the 5 volts and the ground from any other points along
the length for wiring to my circuit which is going to be formed between these two rows
of five holes each on either side. I hope you get the picture.
Now how do we check? I mentioned all those things. But unless we check that the pattern
of wiring or connections provided below the breadboard is the way I just mentioned to
you, we will not to be able to understand the building of different circuits. So we
have to try and measure or find out whether connectivity is there in the breadboard as
mentioned by me few minutes ago. How do we check that? For that we have to simply use
what is knows as a digital multimeter, the DMM and a couple of wires. You insert, for
example, two wires in which the insulations are removed and insert the metal wires into
two of the holes between which you want to check whether there is connectivity or not.
That is electrical continuity; that is what we call. Now choose the resistance mode of
the multimeter. So what you are doing is measuring the resistance between the two wires you have
inserted into the breadboard. If the resistance shown is zero that means there is no breakage
in the circuit; there is continuity or there is connection below these two wires and if
the digital multimeter in the resistance mode reads infinite resistance that corresponds
to open that means the two points are not electrically connected or they are open or
disconnected as we call. Let us look at a typical image of a multimeter.
You can see on the screen a multimeter. So a multimeter basically measures. It is multimeter
because it measures different things. It can measure for example voltage, AC voltage or
DC voltage in different ranges, resistances in different ranges, currents-AC and DC currents
as well as it can measure continuity as I was just mentioning to you.
You have a dial with a knob which when it is kept in the position corresponding to off
the digital multimeter is off; when I switch it on by rotating the dial to different ranges
either voltage on this side, here they are different voltage ranges, or you have an AC
voltage range on this side; you have current range on this side and you have resistance
over here this is for diode testing and this is for continuity testing.
You have three holes here. One is for voltage, resistance and currents. The other one is
a common terminal. This digital multimeter can also be used to measure DC currents of
high value corresponding to ten amperes and for that we use this hole for the probe to
be connected. So this is the general structure of a normal digital multimeter. You have a
display here which could be a liquid crystal display or light emitting diode, LED display.
Then it will be some what red or green in color and LCD will be dull and perhaps you
have seen some of these multimeters in the laboratory. There are some digital multimeters
you will come across where apart from these like the voltages, currents and resistances,
you can also measure frequency of the input AC or the capacitors or the characteristics
of transistors, the 'h' parameter of the transistor.
So you can have different types of multimeters which are capable of measuring different types
of things. Apart from multimeter you also have a power supply which is very essential
for performing experiments in electronics. Every circuit requires electrical power so
the power supply will provide the necessary electrical energy. The power supply also can
have different outputs. What we are going to use for our experiments during this course
will have three different types of power supply all in one box. For example there is going
to be 0 -- 30 volts variable DC voltage source. That means I can vary the voltage output from
a range from 0 volts to 30 volts and this can provide a maximum of one ampere and there
is a display, digital display which will measure the voltage that is being set by using couple
of knobs on the panel.
You also have another power supply which can provide -15, 0, + 15. This is called a dual
supply. It has got two supplies in one. You can have both minus as well as plus outputs
in the same power supply and therefore its called a dual supply and the maximum current
that I can draw from this dual supply is 1.5 amperes.
The third power supply which is also built into the same casing is a fixed DC voltage
with a value of 5 volts. You cannot vary it. It is constant 5 volts but it can provide
you much higher current of up to 3 amperes. The dual supply -15, 0, + 15 is also almost
a fixed dual supply with very fine adjustments possible by a very small range from 15 volts
may be around 13 or 14 volts.
So this is what we have for performing the different experiments in the lab. You have
a breadboard, you have a digital multimeter which can be used to measure different quantities
like voltages, currents and resistances and you have a power supply which can be used
to apply different types of voltages. The 0 to 30 volts power supply is generally used
for a situation where you would like to change the voltages applied to different circuits
whereas the dual supply that is -15, 0, + 15 supply will be used most of the time for
circuits which we use, for example, operational amplifiers. Most of the operational amplifiers
require a dual supply. That means with reference to a common point which is a 0 or a ground
you will have both polarities of outputs both +15 and -15 and so the dual supply will be
used for powering operational amplifier circuits.
The five volts fixed DC voltage output that I talked about is usually used for performing
experiments with digital devices and digital circuits. Now let me quickly go over to the
working table and show you the breadboard and I will also try to show you how multimeter
can be used in resistance mode to detect the connectivity between different points in the
breadboard as I explained to you and then I will also show you the power supply which
we will be used for the rest of the course and that power supply as I already mentioned
to you has got three built in power supplies; independent built in power supplies, one with
the variable voltage 0 to 30 volts. Another is a dual supply +15, -15 and 0. Last one
is 0 to 5 volts for performing digital experiments. Now I quickly move over to the other table.
You can see I have a breadboard here and that breadboard is mounted here in a slanting position
for better view and you have here a digital multimeter with LCD display and you have the
dial which I showed some time ago and presently dial is in the off position.. So if I want
to switch on the digital multimeter I just have to click on the knob to the next position.
For example here you see there is a symbol which shows a loudspeaker. On the other side
we have the ohm symbol. That means this is for resistance measurement here and this is
a loudspeaker which shows that it will give a sound when it has continuity or when resistance
is zero. For example I have the two knobs here. Red one is at volts, ohm etc. The other
one is a common ground. Now I am going to take two wire parts and touch them together.
If I touch them together you can see there is a sound coming from here. That is why the
loudspeaker symbol is shown here. That means there is zero resistance in the circuit because
I have not connected any thing. When I take them out there is very large infinite resistance
do to the air dielectric. Therefore it shows a blinking display here. That shows it is
infinite resistance. If I connect them together there is a sound which shows there is continuity
in the circuit. Now this is the way I am going to test the breadboard as I mentioned. For
example I am inserting one of the wires in one of the holes at the bottom. So immediately
when I push the wire, the clip expands and receives the connecting wire and when I connect
the next wire in one of the other holes for example here I have put in F and J. Now you
can see the multimeter is giving a sound. That shows the resistance between J and F
is zero. There is continuity which is what we saw because there is one single metal clip
which is aligned parallel to the five holes that we see here.
Now if I put this into the next column of holes, now I have done that, one of the wires
I retained in the same place; another wire I connected to the next column of holes. Immediately
you find that the display is blinking and there is no sound. Because the display is
blinking and there is no sound that shows this is infinite resistance; that means there
is no connectivity or there is no continuity between these two. That means all these five
holes are independently together but the neighbouring ones are separated by infinite resistance.
So they can be used for building different types of circuits. I also mentioned that the
two rows that you see on the top here and at the bottom here they are meant for power
supply lines and also I mentioned that all of them in a given row are all connected together
completely from this end to this end. That we can now verify. For that I put one of the
leads to the first hole on the top and the other wire I am going to connect anywhere
in between. Now you can see that these two wires are on the same row and the sound is
coming. That means there is continuity.
So wherever I put it, I remove it and put it near the end again you see there is sound
coming; wherever I put that means the entire row is one single connection. If I put the
same wire in the next row just below that, you would find there is no sound and the display
is blinking.
That shows there is no continuity between the first row and the second row at the top.
A very similar exercise will tell you the situation is identical with reference to the
bottom row also. There are two rows at the bottom; there are two rows at the top which
are normally used for powering the power supply lines in a given circuit. So this is about
breadboard. Once you know about the breadboard, it becomes very easy for you to construct
different circuits.
Now let us quickly move on to the power supply. I will switch this power supply on and you
can see in the power supply there are three knobs here. This is red in color, green and
black. This corresponds to plus; this corresponds to minus and if you see the display here it
is 0 to 30 volts and the maximum of two amperes. There are two knobs here; there are two knobs
here. You can see that by varying these knobs I can vary the voltage here. The voltage is
read here and this is for fine control.
The voltage here can be changed very slowly by using the second knob which is called fine
control. This is coarse control which is used for varying the voltage by larger extent and
similarly you have two more knobs here and there is a display here which is for measuring
the current. So I can change the current limits; that means what is the maximum current I can
apply using this power supply. I can limit it by using this knob and I can increase by
using these two knobs. Again you have the coarse control and the fine control for the
current. So this forms the first block of power supply that I mentioned to you 0 to
30 volts with the maximum of two amperes and then if you come to the other side, you have
here red and black knobs which is marked five volts, five amperes for this is generally
used for digital circuit and at the end you have three knobs once again.
The plus, the zero and the minus corresponding to red, green and black and this is basically
the dual supply that I mentioned to you about +15, 0, -15 and the range can be slightly
modified by using this knob from 12 volts to 15 volts both sides. That means if I change
the knob, the voltage can be +12, 0, -12 or +15, 0, -15. One single knob will vary the
output on both sides so that is what we have here.
So having got the multimeter, now let us try and see whether we can measure the voltages
from the multimeter. So I will remove the clips and I have the simple test probes and
I will change the knob position here so that I can measure the DC volts. So I move over
to the DC volts. I press this knob because this is in yellow. I should press yellow button
because I want to measure now the DC volts as shown here.
So now I have selected the DC volts measurement using the multimeter and I have the two probes.
I am going to connect it to the two outputs; the black and the red and this display shows
it is around 15 volts and you can see the display on the multimeter is also close to
15 volts. So if I now change the fine control or the coarse control, you can see the voltage
is changed. For example now it is around 8 volts.
Both here as well as in the multimeter. So this is the voltmeter, voltage source, which
can go up to nearly 30 volts. Now I take it out and connect it to second power supply
which is five volts, five amperes power supply and the moment I connect it this display does
not correspond to this output. This is a fixed voltage output and therefore the display there
you can see is showing 5 volts constant; that can not be varied.
This is generally used for performing digital experiments. In the last one you have three
knobs. I can take it out and connect red to the red and black to the green because this
is 0, this is +15 and so you can see output voltage on the multimeter is +15 volts right.
Now I take the red wire and connect it to the black knob on the other side. I have not
disturbed the black probe of the multimeter which is still with the green. Now you can
see that the voltage measured is -15 volts.
That voltage, as I already mentioned to you, can also be varied by using this knob. You
can see that when I change the knob, the voltage in the multimeter is changing. So when I change
the knob here the corresponding voltage in the multimeter will also change. So now it
reads something close to 12 volts. So you have here two voltage supplies with a common
terminal which is here the green. The red one gives the positive voltage and the black
one gives the negative voltage and therefore this is a dual supply. You might perhaps ask
me why do we have a green knob here which I did not use with reference to the first
power supply. So I will try to do once more. I connect one of the knobs to the red and
the other black probe to the black and you can see the voltage is 22 volts here and that
means the power supply output is only between the black and red terminals. Then why do we
have the green? If you look at the green at the bottom you would see there is a symbol
corresponding to ground, earth which is shown here. I hope you can see that.
So this is used to make this power supply either positive power supply or negative power
supply. For example if I take a wire and connect the green to the black then it becomes 0 to
whatever voltage that I get. For example this is 22 volts, it will become a +22 volts power
supply this becomes a 0. If I connect both of them together by a small wire I can either
take from green or red it becomes a ground or common terminal and this is the output
which goes up to 22 volts.
Now if I want a negative voltage then what I do is I connect the wire between the green
and the red. Then this positive end is grounded. What I have is an output from the black which
is -22 with reference to the common which is now shifted to the plus terminal and therefore
with reference to the plus terminal this will be 22 and therefore when it is 0 by connecting
them together this become -22 with reference. So this is actually a floating power supply
between plus and minus. By connecting to ground either the plus or the minus I can get a positive
supply or a negative supply. So that is about the power supply. What we have seen we have
got multimeter; we have got a breadboard and we have got a power supply and perhaps we
may need some more instruments for performing some of the experiments that we will be discussing
about.
In summary therefore what we have seen, we have seen the importance of electronics, how
one has to have some basic understanding of electronics, the various components, devices,
the various measuring instruments and the circuits. Then we also saw why learning by
doing is the best way to learn any subject, especially subjects like electronics which
is an applied subject. We also saw the plan of course with reference to different topics
that will be covered. For example the basic devices and components, the measuring instruments
like the multimeter, oscilloscope, power supply, function generator, etc and also the different
circuits like rectifiers, the amplifiers, the filters, oscillators, etc. We also saw
that it will be better to build the circuit using what is known as a breadboard.
We saw how a breadboard is constructed, its parts, how it is able to receive the different
components without having to solder them together and we also saw how a digital multimeter and
a power supply can be used for building the different circuits and components.
We also simultaneously saw by actually using the multimeter and measuring the various points
on the breadboard and then it was seen that the breadboard has got a very special type
of connectivity between the various sockets which can be used for building different circuits.
We also saw the power supply with three different output voltages starting from a single variable
supply and a dual supply and a digital power supply with 5 volts output and we also measured
some of the voltages using the multimeter and we just got basic understanding of the
various instruments and devices. Now what are we going to look at during our next lecture?
In the next lecture we will be looking in some detail about some of the components that
we will come across while building the different circuits namely resistors and capacitors,
their properties, their color codes; there are different types of resistors and capacitors
and then how the different combination of resistors and capacitors behave in different
situations in a circuit. All these things will be discussed during the next lecture.
Thank you.
