PLC

Hi friends, today I’m going to give info about PLC. 

A PLC is the acronym of Programmable logic controller. The advent of the PLC began in the 1970s and today in the world of automation; the PLC has become a standard for control. Control engineering has evolved over a long period of time. In the past, humans were the main for controlling a system. As the technology developed electricity has been used for control. One such is relay which allows power to be switched ON & OFF without a mechanical switch. The development of low cost computer has brought the most recent revolution called PLC.

Block diagram of PLC

What a plc is?

A PLC is a user friendly microprocessor based circuit that is used to conduct multiple and complex operations. 

• A PLC is essentially microprocessor or microcontroller based. It has multiple inputs and outputs. It functions according to the software.
• PLC monitors crucial process parameters and controls the process operations accordingly. 
• The PLC replaces much complicated wiring by a single circuit. 
• The input to the PLC can also be taken from analog devices or discrete (on off) devices. 
• The PLCs have tremendous computing capacity but at the same time its size is very compact. 
• Ladder Diagram is primarily used to develop software for programmable logic controllers (PLCs) used in industrial control applications.

Now let’s see what are the advantages of the PLC system:

• PLCs are highly flexible. 
• They have compact size and reduced cost. 
• PLCs are accurate, high speed and reliable. 
• PLCs can be reprogrammed easily & quickly. 
• Data storage and logging is easier since PLCs can be easily interfaced to computers. 
• PLCs can handle large number of inputs and outputs. 
• Programming of PLCs is easier. 

Disadvantages: 

•  For small operations or one or two functions, PLCs are not cost effective. 
• PLCs use electronic devices and microprocessors. They fail sometimes in adverse environmental conditions. 
• If operation is never altered, PLCs prove to be costly.

A few examples of ladder diagrams are:

Ladder diagram for Stair case controller

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Waveguides

Today we shall concentrate on one of the Transmission media called wave guides. A hollow conducting tube to transmit electromagnetic waves is termed as wave guide. A waveguide is a hollow tube designed to carry microwave energy from one place to another place. Waveguides may be used to carry energy between pieces of equipment or over longer distances. Waveguides are made from copper, aluminum or brass. These metals are extruded into long rectangular or circular pipe

The electric and magnetic fields of electromagnetic wave are confined to the space within the guide and made to propagate down the length of the wave guide.

Characters of waveguides:

• The propagation takes place through the dielectric field.
• Propagation is in terms of electric and magnetic fields rather than voltage and currents.
• The electric and magnetic fields that exist inside the waveguide are solution of Maxwell’s wave equation.
• Each waveguide has cut off frequency that decides the dominant mode of propagation.

Coming to the types of waveguides. There are three types of waveguides namely:

1. Rectangular waveguide:

     2.circular (cylindrical) waveguide:

     3.Ridged waveguide:

Advantages of waveguides:

• The waveguides can be used at much higher frequencies than the co-axial cables.
• Easy to manufacture than co-axial cable because waveguides are hollow.
• Waveguides do not have either inner conductor or dielectric material, therefore power handling ability is improved. It is about 10 times as high as for co-axial air dielectric rigid cables.
• Power losses are less.
• There is no radiation loss.

Applications:

• They are at their supreme in microwave transmission.
• Used to connect Radar transmitter to antenna.
• Used to channel the received echo to the receiver from the antenna

INTEGRATED CIRCUIT

Hi friendz today we shall have some knowledge about integrated circuits (abbreviated as IC).Before knowing the definition of ICs we shall know why an IC was developed?

 Now a days integrated circuits are more popular. In the early days some discrete components like capacitor, resistor, diodes, were used to be connected in a definite pattern(using wires) called electronic circuit. As the technology advanced the discrete components were integrated on a single chip this is called integrated circuit.

Integrated Circuit

Now coming to the definition : An IC is one in which a number of circuit elements like resistors, capacitors, transistors, diodes etc are fabricated on a small semi conductor chip to perform a complete function.

Classification of Ics:

1. Classification by Scale of integration:

·        SSI (Small scale integration) : ICs having 0 to 12 components on a single chip. Ex: Logic gates, Flip-flops.

·        MSI (Medium Scale Integration): Ics in this category contains 13 to 99 electronic components on a single chip. Ex: Adders, registers, encoders, multiplexers.

·        LSI (Large scale integration): Ics having 100 to 9999 components in a single chip comes under this category. Ex:Microcontroller, RAMs, ROMs

·        VLSI (Very Large scale Integration): Ics in this have 10000 to 99999 components in a single chip. Ex: Advanced microprocessor, Memory chips.

·        ULSI (Ultra Large Scale Integration): The components in the Ics of this type are more than 100000. Ex: Single chip Microprocessors, memory chips.

    

2. Classification by Structure:
• Monolithic
• Film Passive : Thick film and Thin film ics
• Hybrid Ics

3. Classification of Ics by function:

•           Analog Ics

Analog IC

• Digital Ics

Digital IC

Advantages of Integrated Circuits:

• Smaller weight.
• Low cost
• Highly reliable
• Low power consumption
• Easy replacement

Disadvantages of Integrated circuits:

·        Transformers, inductors can’t e fabricated.

• Large values of capacitance > 30pF can’t be built.
• The components in the IC can’t be repaired instead whole IC should be replaced.
• Not possible to modify circuit parameter

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Power Electronics

Hi guys it’s been a long time to know about one more topic. Today we shall see what power electronics meant by? First of all we shall see the basics of Power electronics. Power electronics is one of the important branch of electronics and electrical engineering. It deals with conversion & control of electric energy.

Power electronics can be defined as the application of the solid state electronics for controlling & conversion of electric power. To understand the topic we should go through the basic power electronic system.

Power electronic system:

power electronic system

We all know that the AC current and voltage from the mains has always fixed frequency and this supply can not be used directly ( for example computer needs SMPS for its working) so in order to convert one form of energy into other form of energy the power electronics system is used. Thus a Power Electronic system performs the conversion and controlling of electric energy. For instance rectifier is a good example because a rectifier converts AC into DC.    

Applications:

The power electronics is used in:

1. UPS and Standby power supplies
2. Power control in resistance welding induction heating, electrolysis etc.
3. Speed control of motors
4. Solid state power compensators, static contactors etc.
5. High voltage supplies for electrostatic precipitators and x-ray generators.
6. Power supplies for communication systems, telephone exchanges, satellite systems etc.

Advantages:

1.      Fast dynamic response due to static devices.

2.      High efficiency of conversion due to low losses in electronic devices.

3.      Compact size and light weight of the controllers due to electronic devices.

4.      Increased operating life and reduced maintenance.

5.      Their operation is highly flexible.

Disadvantages:

1. These generate harmonics.
2. power factor of some electronic controllers is very low.

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Computer Network

Hi viewers today I am going to share some information about data/computer network which is widely used all over the world. Before going to the topic of Computer network it is necessary to know some basic knowledge about a communication network and its components.

The first thing which every one should know is “What is a Network?” and what is it made up of, A network can be defined as the group of nodes interconnected, through which the entity flows.

The network consists of several components which can be named as: Node & Branch.

Network

 First of all Node is the basic component of a communication network and can be defined as a point where two or more branches meet. The general communication network may have infinite number of nodes but it’s not necessary that each one of them is to be interconnected to every node.

In the case of Data communication the ‘Packet switch’ acts as node. Next coming to the next component Branch, Branch can be defined as the transmission medium through which the data or entity flows.

The branch may be of wired or wireless medium..

Computer network:-

Computer network is a group of computers which are interconnected together using links or branches.

Computer network

The computer/Data network including the Internet carries digital data from source to destination. The switches used in the network are packet switches which use “Store & Forward” mechanism. The switches present in the network receive the data in the form of packets and stores them in the memory and then transmits them to the appropriate link which is free from congestion problem and is in working condition according to the address of the packet. The packet switches can also be called as routers.

Internet is a network of networks which was used to carry text messages, but now a days the advancement in technology has made possible to support the multimedia and even web facility also.

A computer network:-

·  Is primarily a digital network

·  Supports variable bit rates/bandwidth as data is bursty in nature.

·  Was originally designed carry non-real time traffic.

·  Is generally non-interactive.

·  Is full duplex.

·  Has to have switches with buffers.

According to ARPA the switches earlier were called as IMP (Interface Message Processors). Now they are called as PSE (Packet Switching Exchanges). While with respect to internet they are termed as routers.

                         

Necessity of the computer network:-

1. Resource sharing
2. High reliability.
3. Saving money and time.
4. It provides a powerful communication medium which enhances human-to-human communication.

Advantages:-

1. Reduces cost through sharing of data between users.
2. It allows sharing of resources.
3. It provides standardization of applications.
4. It enables efficient communication and scheduling.
5. Facilitates electronic access to remote computers.

Disadvantages:-

1. The fault in server penetrates in the user’s computer, which disturbs the running of users computer.
2. Fault on networks can cause loss of user’s data.
3. Internet makes it possible to find information quickly, but a lot of it can be misleading.
4. Electronic junk mail (spam) can be annoying.
5. E-mails containing active content can contain viruses.
6. Identity theft is a serious problem.

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