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  • 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.

Hello everybody! We are now going to start a course on basics electronics. It is essentially

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B1 中級

講義-1 基礎エレクトロニクス入門 (Lecture - 1 Introduction to Basic Electronics)

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    rachel6433 に公開 2021 年 01 月 14 日
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