What is Electronics

What is electronics

The branch of physics and technology concerned with the design of circuits using transistors and microchips, and with the behavior and movement of electrons in a semiconductor, conductor, vacuum, or gas

Basic Electronics   

    

The goal of this chapter is to provide some basic information about electronic circuits. We make the assumption that you have no prior knowledge of electronics, electricity, or circuits, and start from the basics. This is an unconventional approach, so it may be interesting, or at least amusing, even if you do have some experience. So, the first question is ``What is an electronic circuit?'' A circuit is a structure that directs and controls electric currents, presumably to perform some useful function. The very name "circuit" implies that the structure is closed, something like a loop. That is all very well, but this answer immediately raises a new question: "What is an electric current?" Again, the name "current" indicates that it refers to some type of flow, and in this case we mean a flow of electric charge, which is usually just called charge because electric charge is really the only kind there is. Finally we come to the basic question:

Current   

Charge is mobile and can flow freely in certain materials, called conductors. Metals and a few other elements and compounds are conductors. Materials that charge cannot flow through are called insulators. Air, glass, most plastics, and rubber are insulators, for example. And then there are some materials called semiconductors, that, historically, seemed to be good conductors sometimes but much less so other times. Silicon and germanium are two such materials. Today, we know that the difference in electrical behavior of different samples of these materials is due to extremely small amounts of impurities of different kinds, which could not be measured earlier. This recognition, and the ability to precisely control the "impurities" has led to the massive semiconductor electronics industry and the near-magical devices it produces, including those on your Robot Board. We will discuss semiconductor devices later; now let us return to conductors and charges

What is Direct Current

Direct current electronics involves working with electrical systems where the flow of electrical current is constant through a conducting medium, generally a wire. Current and voltage in a direct-current circuit are conserved according to Kirchhoff's Current & Voltage Laws

Major Innovations

For years, electricity was used as part of parlor tricks, creating impressive showers of sparks. Benjamin Franklin is known as perhaps one of the earliest experimenters in electricity, whose invention of the lightning rod was one of the first practical applications. Throughout the 1800's the practical and theoretical concepts of electrical circuitry were developed

Electronic Engineering involves the design, manufacture and application of electronic components, in particular, semiconductor microchips. It also is central to industrial automation and encompasses areas such as robotics, artificial intelligence and satellite launching and position control. The knowledge required for a job in the field of electronics is very special and includes a good grounding in the fundamentals of electricity and electronics with their application to computer systems, communications systems, modern automobiles (including Formula One!), aerospace, and many other fields.

The modulation process

The modulation process

As discussed earlier, the purpose of a communication system or to deliver a message signal from an information source in recognizable form to a user destination, with the source and the user being physically separated from each other.

To do this the transmitter modified the message signal into a form which is suitable for transmission over channel. This modification is achieved by means of a process as modulation, which involves varying some perameter of a carrier wave in accordance with the message signal. Also the receiver recreate the original message signal from a degraded version of the transmitted signal after propagation through the channel. The recreation is achieved by using a process called as demodulation.

Modulation may be defined as the process by which some characteristic of a signal called carrier is varied in accordance with the instantaneous value of another signal called modulation signal.

Signal containing information or intelligence are referred as modulation signal. This information bearing signal is also called baseband signal. The carrier frequency is greater them the modulation frequency. The signal resulting  from the process of modulation is called modulation signal.

Classification of Communication

Classification of communication

(i)                Line Communication

(ii)             Wire or Radio Communication

Line communication

In line communication the medium of transmission is a pair of conductor called transmission line. This is also called as line channel. This means that in the communication, the transmitter and the receiver are connected through a wire or line.the installation and maintenance of a transmission line is not only costly and complex but also over crowds the open source. Apart from this its message transmission capability is also limited.

Wire or Radio Communication

In Wireless or radio communication, a message is transmitted through open space by electromagnetic  waves called a radio waves. Radio Waves are radiated from the transmitter in open space through a device called antenna. A receiving antenna intercepta the radio waves at the receiver. All the radio, TV and satellite broadcasting are wireless or radio communication. The advantage of wireless communication are cost effectiveness, possible long distance communication and simplicity.

Communication Process

The Communication Process

1.      Information Process

 We know that a communication system serves to communication a message or information. This message or information originates in the information source. In general   there can be various messages in the form of words, group of words, code, symbols, sound signal etc. however out of these messages only the desired message is selected and conveyed or communicated.

2.      Input Transducer

A transducer is a device which converts one form of energy into another form. The messages from the information source may not be electrical in nature. In a case when the message produced by the information source is not the electrical in nature, an input transducer is used to convert it into a time varying electrical signal. For example in case of radio broadcasting, a microphone converts the information or messages which is in the form of sound waves into corresponding electrical signal.

3.      Transmitter

The function of the transmitter is to process the electrical signal from different aspects. For example in radio broadcasting signal obtained from signal, is processed to restrict its range of audio frequencies and is often amplified. In wire telephony no real processing is needed, however in long distance radio main function of the transmitter, in modulation the message signal processing such as restriction of range of audio frequency, amplified,  and modulation are achieved. All these processings of the message signal are done just to case the transmission of the signal through the channel.

4.      The channel and the Noise

With reference to the block diagram of a communication system the term channel means the medium through which the message travels fom the transmitter to the receiver. In other words, we can say that the function of the channel is to provide a physical connection between the transmitter and the receiver.

There are two types of channels, namely point to point channels and broadcast channels. Examples of point to point channels are wirelines, microwaves link and optical fibres . Wirelines operated by guided electromagnetic waves and they are used for local telephonic transmission. In case of microwaves links are used in long distance telephone transmission. an optical fibre is a low loss, well controlled, guided optical differently, they all provides a physical medium for the transmission of signals from one point to another point. For these channels the term point to point is used.

Source of information

Source of information.

As a matter of fact, The telecommunication environment is dominated by the following four important sources of information.

(i)                 Speech

(ii)               Television

(iii)             Facsimile and

(iv)              Personal computer

A source of nformation may be characterized in term of signal which carrier the information. Further, a signal is defined as a signal valued function of the time that play the role of the depedent variable. At every instant of time, the function has a unique value.

Speech

(a)   Production: an intended message in the speaker mind is represented by the speech signal that consist of sounds generated inside the speaker mouth and whose arrangement is governed by the rule of language.

(b)   Propagation: The siund waves propagates through the air, reaching the listener’s ears.

(c)     Perception: The incoming sounds are deciphered by the listener into a received message, and thus completing the chain of events that results in the transfer of information from the speaker to the listener.

Television

The second source of information, television refers to the transmission of picture in motion by means of electrical signal. To accomplished this transmission, each complete picture has to be sequentially scanned. The scanning process is carried out in a TV camera. In a black and white TV, the camera contains optics designed to focus an image on a photocathode consisting of a large number of photosensitive elements.

The charge pattern so generated on the photosensitive surface is scanned by an electron beam, and thus producing an output current which vaies temporally in accordance with the way in which the brightness of the original picture varies spatially form one point to another. This resulting output current is called a video signal.

The type of scanning used in television is a form spatial sampling called raster scanning. The purpose of raster scanning is basically to convert a two dimensional image intensity into a one dimension waveform.

Facsimile

The purpose of the third source of information, facsimile machine, is to transmit still picture over a communication channel a telephone. Such a machine provide a highly popular facility for the transmission of hand written or printed text from one point to another. Further, transmitting text by facsimile is treated simply like transmitted a picture.

The basic principal employed fo signal generation in a facsimile machine is to scan an original document and use an image sensor to convert the light to an electrical signal.

Personal Computer

As a matter of fact, personal computer are becoming increasingly an important part of our daily lives. We use them for electronic mail, exchange of software, and sharing of resource. It is estimated that over 30 percent of the personal computer in use today are already networked and the number is increasing rapidely. The text transmitted by a PC is usually encoded using the American standard code for information interchange, ASCII which is the first code developed specifically for computer communication.

Each character in ASCII is represented by seven data bits constituting a unique binary pattern made up of 0s and 1s. hence a total of seven power of two = 128 different characters can be represented in ASCII. The character symbols are various lowercase and uppercase letters, numbers, special control symbols, and punctuation symbols commonly used such as @,$ and %. Some of the special “control” symbols such as BS ( back space ) and CR (carriage return), are used to control the printing of characters on a page Other symbols, such as ENQ (enquiry) and ETB (end of transmission block), are used for communication purpose.

The even data bits are ordered starting with the most significant bit b7 down to the least significant bit b1.

At the end of the data bits, an extra bit b8 is appended for the purpose of error detection. This error detected bit is called a parity bit.