Power Grid and their working

Ever wondered, what actually is the mechanism that brings electricity right from the power station to your house????

Electrical power is a little bit like the air you breathe: You don't really think about it until it is missing. Power is just "there," meeting your every need, constantly.

It's only during a power failure, when you walk into a dark room and instinctively hit the useless light switch, that you realize how important power is in your daily life.

You use it for heating, cooling,cooking, refrigeration, light, sound,computation, entertainment... Without power, life can get somewhat cumbersome.

Power travels from the power plant to your house through an amazing system called the power distribution grid.

The grid is quite public -- if you live in a suburban or rural area, chances are it is right out in the open for all to see. It is so public, in fact, that you probably don't even notice it anymore. Your brain likely ignores all of the power lines because it has seen them so often.

In this article, we will look at all of the equipment that brings electrical power to your home. The next time you look at the power grid, you will be able to really see it and understand what is going on!

The Power Plant

Electrical power starts at the power plant. In almost all cases, the power plant consists of a spinning electrical generator. Something has to spin that generator -- it might be a water wheel in a hydroelectric dam, a large diesel engine or a gas turbine. But in most cases, the thing spinning the generator is a steam turbine. The steam might be created by burning coal, oil or natural gas. Or the steam may come from a nuclear reactor.

No matter what it is that spins the generator, commercial electrical generators of any size generate what is called 3-phase AC power. To understand 3-phase AC power, it is helpful to understand single-phase power first.

The Power Plant: Alternating Current

Single-phase power is what you have in your house. You generally talk about household electrical service as single-phase, 120-volt AC service. If you use an oscilloscope and look at the power found at a normal wall-plate outlet in your house, what you will find is that the power at the wall plate looks like a sine wave, and that wave oscillates between -170 volts and 170 volts (the peaks are indeed at 170 volts; it is the effective (rms) voltage that is 120 volts). The rate of oscillation for the sine wave is 60 cycles per second. Oscillating power like this is generally referred to as AC, or alternating current. The alternative to AC is DC, or direct current. Batteries produce DC: A steady stream of electrons flows in one direction only, from the negative to the positive terminal of the battery.

AC has at least three advantages over DC in a power distribution grid:

1. Large electrical generators happen to generate AC naturally, so conversion to DC would involve an extra step.
2. Transformers must have alternating current to operate, and we will see that the power distribution grid depends on transformers.
3. It is easy to convert AC to DC but expensive to convert DC to AC, so if you were going to pick one or the other AC would be the better choice.

The power plant, therefore, produces AC. On the next page, you'll learn about the AC power produced at the power plant. Most notably, it is produced in three phases.

The Power Plant: Three-phase Power

The power plant produces three different phases of AC power simultaneously, and the three phases are offset 120 degrees from each other. There are four wires coming out of every power plant: the three phases plus a neutral or ground common to all three.

There is nothing magical about three-phase power. It is simply three single phases synchronized and offset by 120 degrees.

Why three phases? Why not one or two or four? In 1-phase and 2-phase power, there are 120 moments per second when a sine wave is crossing zero volts. In 3-phase power, at any given moment one of the three phases is nearing a peak. High-power 3-phase motors (used in industrial applications) and things like 3-phase welding equipment therefore have even power output. Four phases would not significantly improve things but would add a fourth wire, so 3-phase is the natural settling point.

And what about this "ground," as mentioned above? The power company essentially uses the earth as one of the wires in the power system. The earth is a pretty good conductor and it is huge, so it makes a good return path for electrons. (Car manufacturers do something similar; they use the metal body of the car as one of the wires in the car's electrical system and attach the negative pole of the battery to the car's body.) "Ground" in the power distribution grid is literally "the ground" that's all around you when you are walking outside. It is the dirt, rocks, groundwater, etc., of the earth.

Transmission Substation

The three-phase power leaves the generator and enters a transmission substation at the power plant. This substation uses large transformers to convert the generator's voltage (which is at the thousands of volts level) up to extremely high voltages for long-distance transmission on the transmission grid.

Typical voltages for long distance transmission are in the range of 155,000 to 765,000 volts in order to reduce line losses. A typical maximum transmission distance is about 300 miles (483 km). High-voltage transmission lines are quite obvious when you see them. They are normally made of huge steel towers like this:

All power towers like this have three wires for the three phases. Many towers, like the ones shown above, have extra wires running along the tops of the towers. These are ground wires and are there primarily in an attempt to attract lightning.

he Distribution Grid

For power to be useful in a home or business, it comes off the transmission grid and is stepped-down to the distribution grid. This may happen in several phases. The place where the conversion from "transmission" to "distribution" occurs is in a power substation. A power substation typically does two or three things:

• It has transformers that step transmission voltages (in the tens or hundreds of thousands of volts range) down to distribution voltages (typically less than 10,000 volts).
• It has a "bus" that can split the distribution power off in multiple directions.
• It often has circuit breakers and switches so that the substation can be disconnected from the transmission grid or separate distribution lines can be disconnected from the substation when necessary.

Distribution Bus

The power goes from the transformer to the distribution bus:

In this case, the bus distributes power to two separate sets of distribution lines at two different voltages. The smaller transformers attached to the bus are stepping the power down to standard line voltage (usually 7,200 volts) for one set of lines, while power leaves in the other direction at the higher voltage of the main transformer. The power leaves this substation in two sets of three wires, each headed down the road in a different direction:

What actually is Faraday cage?? And how does it work??

Electricity is the lifeblood of many aspects of our world. Without volts and amps, many of our technological innovations would cease to exist. Even our bodies wouldn't function without an electrical charge zipping through our cells. But what electricity gives, electricity can take away.

Although this form of energy is vital to so much of our lives, it's one of those things that are only good in the right amounts. Too much electricity can electrocute people. Likewise, it can kill our modern electronics and machines.

But thanks to Michael Faraday, the brilliant 19th-century scientist, and one of his namesake inventions, the Faraday cage, we humans have developed plenty of ways to control electricity and make it safer for our computers, cars and other inventions -- and for us, too.

Faraday cages shield their contents from static electric fields. An electric field is a force field surrounding a charged particle, such as an electron or proton.

These cages often look distinctly, well, cagelike. Some are as simple as chain-link fences or ice pails. Others use a fine metallic mesh. Regardless of their exact appearance, all Faraday cages take electrostatic charges, or even certain types of electromagnetic radiation, and distribute them around the exterior of the cage.

Electromagnetic radiation is all around us. It's in visible and ultraviolet light, in the microwaves that cook our food and even in the FM and AM radio waves that pump music through our radios. But sometimes, this radiation is undesirable and downright disruptive. That's where Faraday cages come in.

As a Faraday cage distributes that charge or radiation around the cage's exterior, it cancels out electric charges or radiation within the cage's interior. In short, a Faraday cage is a hollow conductor, in which the charge remains on the external surface of the cage.

That basic function has plenty of fascinating uses in our electrically cluttered and technology-packed world. And although Faraday would eventually have his day, the backdrop for his invention actually has its roots in earlier times. So, where did the idea for these ultra-useful cages come from?

Franklin's First Findings

It was Ben Franklin who helped inspire many of the ideas behind Faraday cages. Franklin, of course, spent part of his illustrious career flying kites in thunderstorms in attempts to attract lightning and thus was already somewhat acquainted with the vagaries and concepts of electricity.

In 1755, Franklin began toying withelectricity in new ways. He electrified a silver pint can and lowered an uncharged cork ball attached to a non-conductive silk thread into it. He lowered the ball until it touched the bottom of the can and observed that the ball wasn't attracted to the interior sides of the can. Yet when Franklin withdrew the cork ball and dangled it near the electrified can's exterior, the ball was immediately drawn to the can's surface.

Franklin was mystified by the interplay of electricity and the charged and uncharged objects. He admitted as much in a letter to a colleague: "You require the reason; I do not know it. Perhaps you may discover it, and then you will be so good as to communicate it to me."

Decades later, an English physicist and chemist named Michael Faraday made other pertinent observations -- namely, he realized that an electrical conductor (such as a metal cage), when charged, exhibited that charge only on its surface. It had no effect on the interior of the conductor.

Faraday reaffirmed this observation by lining a room with metal foil and then charging the foil with the use of an electrostatic generator. He placed an electroscope (a device that detects electrical charges) inside the room, and, as he anticipated, the scope indicated that there was no charge within the room. The charge just moved along the surface of the foil and didn't penetrate the room at all.

Faraday further examined this phenomenon with his famous ice pail experiment. In this test, he basically duplicated Franklin's idea by lowering a charged brass ball into a metal cup. As expected, his results were the same as Franklin's.

This concept has all sorts of amazing applications, but here's one that's relevant to anyone who's ever been in an airplane. Imagine flying in an airplane that's suddenly struck by lightning. This isn't a rare occurrence -- it actually happens regularly, yet the plane and its passengers aren't affected. That's because the aluminum hull of the plane creates a Faraday cage. The charge from the lightning can pass harmlessly over the surface of the plane without damaging the equipment or people inside.

It's not shocking, really. It's just science. On the next page, you'll see how this clever kind of cage design really works.

Electrostatic for the People

In order to understand how Faraday cages work, you need a basic understanding of how electricityoperates in conductors. The process is simple: Metal objects, such as an aluminum mesh, are conductors, and have electrons (negatively charged particles) that move around in them. When no electrical charge is present, the conductor has roughly the same number of commingling positive and negative particles.

If an external object with an electrical charge approaches the conductor, the positive and negative particles separate. Electrons with a charge opposite that of the external charge are drawn to that external object. Electrons with the same charge as the external object are repelled and move away from that object. This redistribution of charges is called electrostatic induction.

With the external charged object present, the positive and negative particles wind up on opposite sides of the conductor. The result is an opposing electric field that cancels out the field of the external object's charge inside the metal conductor. The net electric charge inside the aluminum mesh, then, is zero.

And here's the real kicker. Although there's no charge inside the conductor, the opposing electric field does have an important effect-- it shields the interior from exterior static electric charges and also from electromagnetic radiation, like radio waves and microwaves. Therein lies the true value of Faraday cages.

The effectiveness of this shielding varies depending on the cage's construction. Variations in the conductivity of different metals, such as copper or aluminum, affect the cage's function. The size of the holes in the screen or mesh also changes the cage's capabilities and can be adjusted depending on the frequency and wavelength of the electromagnetic radiation you want to exclude from the interior of the cage.

Faraday cages sometimes go by other names. They can be called Faraday shields, RF (radio frequency) cages, or EMF (electromotive force) cages.

No matter what you call them, Faraday cages are most often used in scientific labs, either in experiments or in product development. On the next page, you'll discover exactly how engineers put these ingenious shields to the test.

Faraday, the Modern Way

People use Faraday cages for a wide array of purposes -- sometimes in esoteric lab settings, other times in common products. Your car, for example, is basically a Faraday cage. It's the cage's effect, not the rubber tires, that protects you in case of a nearby lightning strike.

A lot of buildings act as Faraday cages, too, if only by accident. With their plaster or concrete walls strewn with metal rebar or wire mesh, they often wreak havoc with wireless Internet networks and cellphone signals.

But the shielding effect most often benefits humankind. Microwave ovens reverse the effect, trapping waves within a cage and quickly cooking your food. Screened TV cables help to maintain a crisp, clear image by reducing interference.

Power utility linemen often wear specially made suits that exploit the Faraday cage concept. Within these suits, the linemen can work on high-voltage power lines with a much-reduced risk of electrocution.

Governments can protect vital telecommunications equipment from lightning strikes and other electromagnetic interference by building Faraday cages around them. Science labs at universities and corporations employ advanced Faraday cages to completely exclude all external electric charges and electromagnetic radiation to create a totally neutral testing environment for all sorts of experiments and product development.

Intrigued? Keep reading, and you'll see other wild ways this simple cage effect is put to use for sophisticated purposes.

MAKE YOUR OWN CAGE

You don't need to spend millions or have a physics degree to make your own Faraday cage. On the Internet, you can find instructions for building a simple cage from common household products

Cutting-edge Cages

Swing by a hospital and you'll find Faraday cages in the form of MRI(magnetic resonance scanning) rooms. MRI scans rely on powerful magnetic fields to create medically useful scans of the human body. MRI rooms must be shielded to prevent stray electromagnetic fields from affecting a patient's diagnostic images.

There are plenty of political and military uses for Faraday cages, too. Politicians may opt to discuss sensitive matters only in shielded rooms that can block out eavesdropping technologies. All modern armed forces depend on electronics for communications and weapons systems, but there's a catch --these systems are vulnerable to aggressive EMPs (electromagnetic pulses), which can be a result of a solar storm or even man-made EMP attacks. To safeguard critical systems, militaries sometimes use shielded bunkers and vehicles.

It's for this same reason that Faraday cages are a fond subject in the survivalist subculture. These people, who preach self-sufficiency and mistrust of governmental response in the face of human-caused or natural disasters, believe in shielding all important electronics using homemade Faraday cages. In the event that anapocalyptic cataclysm strikes, they'll still have their shortwave radios and other high-tech tools that could be lifesavers.

Even if you're not particularly concerned with doomsday scenarios, Faraday cages likely play a role in your life every day. These cages harness a basic principle of physics and help people all over the planet put those principles to use -- for safety, luxury, convenience and to help further evermore exciting technological advances.

Arduino FOR DUMMIES

Are you hooked up with a zeal to start ur own ARDUINO projects, but in dilemma from where to kick off??? If it's so you have got to download this book named ARDUINO FOR DUMMIES and enjoy the contents thereby flourishing your will to become a ARDUINO savvy.....HEre's the download link for the book...It's better if u have an IDM installed in ur device...ENJOY!!!

www.earthshineelectronics.com/files/ASKManualRev5.pdf

Potentiometer

A potentiometer is a simple knob that provides a variable resistance, which we can read into the Arduino board as an analog value. In this example, that value controls the rate at which an LED blinks.

We connect three wires to the Arduino board. The first goes to ground from one of the outer pins of the potentiometer. The second goes from 5 volts to the other outer pin of the potentiometer. The third goes from analog input 2 to the middle pin of the potentiometer.

By turning the shaft of the potentiometer, we change the amount of resistence on either side of the wiper which is connected to the center pin of the potentiometer. This changes the relative "closeness" of that pin to 5 volts and ground, giving us a different analog input. When the shaft is turned all the way in one direction, there are 0 volts going to the pin, and we read 0. When the shaft is turned all the way in the other direction, there are 5 volts going to the pin and we read 1023. In between, analogRead() returns a number between 0 and 1023 that is proportional to the amount of voltage being applied to the pin.

arduino.cc (#copied)

HOW DC motors WORK??

DC Motors convert electrical energy (voltage or power source) to mechanical energy (produce rotational motion). They run on direct current. The Dc motor works on the principle of Lorentz force which states that when a wire carrying current is placed in a region having magnetic field, than the wire experiences a force. This Lorentz force provides a torque to the coil to rotate.

PCB

On opening the back cover of the motor you can have a look to the motor speed control circuit from behind.

BRUSHES

The above image shows the brushes of the DC motor which helps the motor to take input current to the coil. The brushes always remain connected with any two commutators and supplying the input current to the coil while it is rotating.

COIL ARRANGEMENT

You can have a closer look as to how the electrical coil is arranged in the permanent magnet.

COILS

When DC current is passed through the coil, it works as electromagnet. As you can see the iron plates attached around the coil helps the coil to keep in center and movable. Permanent magnet attracts these three iron plates equally; resultantly it stays in the center of the permanent magnet.

PERMANENT MAGNET

There are three commutators shown in the image. Each one is directly connected with the coil to supply the current in.

CIRCUITRY

A motor speed control IC is used to control the rotating speed of compact DC motor. The IC integrated in the circuit has an inbuilt reverse voltage protection circuit.

Working: As we have discussed, DC motor work on Lorentz force concept. When we pass the input DC current to the coil through the brushes, it directly goes to the coil inside the motor body. This makes coil to work as an electromagnet. Magnetic fields of both magnets interact with each other that results in a force which in turn produces the necessary torque required to move the coil. This torque drives the coil to move round and a shaft attached with the coil moves too.

#COPIED...ENGINEERSGARAGE.COM

Zener VS Avalance diode

"'Zener diode' and 'avalanche diode' are terms often used interchangeably, with the former much more common.  Both refer to breakdown of a diode under reverse bias.  Specifically, when a diode is reverse biased, very little current flows, and the diode is to a first order approximation an open circuit. As the reverse voltage is increased, though, a point is reached where there is a dramatic increase in current.  Equivalently, there is a dramatic reduction in the dynamic resistance (slope of the V-I curve) that can be as low as 1- 2 W in this region.This voltage is called the reverse breakdown voltage and it is fairly independent of the reverse current flowing.This property makes it ideal as a voltage reference.
"Avalanche breakdown is caused by impact ionization of electron-hole pairs.While very little current flows under reverse bias conditions, some current does flow.The electric field in the depletion region of a diode can be very high. Electron/holes that enter the depletion region undergo a tremendous acceleration. As these accelerated carriers collide with the atoms they can knock electrons from their bonds, creating additional electron/hole pairs and thus additional current.As these secondary carriers are swept into the depletion region, they too are accelerated and the process repeats itself.This is akin to an avalanche where a small disturbance causes a whole mountainside of snow to come crashing down. The efficiency of the avalanche effect is characterized by a so-called multiplication factor M that depends on the reverse voltage (Equation 1).
  Equation 1: Multiplication Factor "Here n is in the range 2 - 6, V is the applied (reverse) voltage, and V_br is the breakdown voltage.This is an empirical relationship, as are many of the relationships used to describe both Zener and avalanche breakdown.
"Avalanche breakdown occurs in lightly-doped pn-junctions where the depletion region is comparatively long.The doping density controls the breakdown voltage.The temperature coefficient of the avalanche mechanism is positive.That is, as the temperature increases, so does the reverse breakdown voltage.The magnitude of the temperature coefficient also increases with increasing breakdown voltage.  For example, the temperature coefficient of a 8.2 V diode is in the range 3 - 6 mV/K while the temperature coefficient of an 18 V diode is in the range of 12 - 18 mV/K.
"Zener breakdown occurs in heavily doped pn-junctions.The heavy doping makes the depletion layer extremely thin.  So thin, in fact,Ýcarriers canít accelerate enough to cause impact ionization.With the depletion layer so thin, however, quantum mechanical tunneling through the layer occurs causing current to flow.The temperature coefficient of the Zener mechanism is negative the breakdown voltage for a particular diode decreases with increasing temperature.However, the temperature coefficient is essentially independent of the rated breakdown voltage, and on the order of -3 mV/K.
"In a 'Zener' diode either or both breakdown mechanisms may be present.  At low doping levels and higher voltages the avalanche mechanism dominates while at heavy doping levels and lower voltages the Zener mechanism dominates.At a certain doping level and around 6 V for Si, both mechanism are present with temperature coefficients that just cancel.  It is possible to make Zener diodes with quite small temperature coefficients.
"Neither Zener nor avalanche breakdown are inherently destructive in that the crystal lattice is damaged.However, the heat generated by the large current flowing can cause damage, so either the current must be limited and/or adequate heat sinking must be supplied."

MICROCONTROLLER vs MICROPROCESSOR

Micro controllers versus Microprocessors

Micro controller differs from a microprocessor in many ways. First and the most important is its functionality. In order for a microprocessor to be used, other components such as memory, or components for receiving and sending data must be added to it. In short that means that microprocessor is the very heart of the computer. On the other hand, micro controller is designed to be all of that in one. No other external components are needed for its application because all necessary peripherals are already built into it. Thus, we save the time and space needed to construct devices.

What is a microcontroller??

What IS a "Microcontroller" ?

If you ever took a very introductory computer course, you probably learned about the major components of ANY computer:

• A Central Processing Unit or CPU. The part that actually performs logic and math
• Memory. Where the computer stores data and instructions
• Input and Output or I/O. How the computer moves data between its other components and the real world.

A microprocessor uses microelectronic fabrication techniques to shrink the CPU to a very small size; usually a single "chip."

A microcontroller uses the same techniques to shrink the entire computer to a single chip (or very small module.) CPU, Memory, and I/O all in a little package as small as a grain of rice. Just connect up power and it starts doing its thing; computing and talking to the world. Usually the I/O on a microcontroller is aimed at "low level" hardware like talking to individual switches and LEDs instead of keyboards, internets, and displays (like your desktop computer.) A microcontroller is just the thing you want, if you want to talk to individual switches and LEDs...

HOW TO CHOOSE A MICROCONTROLLER??o

How to choose a MicroController

It used to be that the number of different microcontroller chips available to the hobbyist was pretty limited. You got to use whatever you could manage to buy from the mail-order chip dealer, and that narrowed down the choice to a small number of chips.

But times have changed. Digikey lists over 16000 different line items under a 'microcontroller' search. Which one should a hobbyist with no particular prior experience choose?

Here are some hints. These are particularly aimed at someone trying to pick a microcontroller to use for the first time at least partially as a learning experience, rather than someone who wants to accomplish a particular task.

Update 2009-01-28: This Instructable was recently mentioned in some popular blogs, and is getting a bunch of new readers. Be sure to read the 'comments' made by other readers and the responses to them; there's a lot of value in those comments...

ALL about AC MOTORS

There are many different types and sizes of electric motors. Electric motors can be divided into two types: Alternating Current (AC) motors and Direct Current (DC) motors. An AC electric motor requires an alternating current, while a DC motor requires direct current.

AC motors are further subdivided into single phase and three phase motors. Single phase AC electrical supply is what is typically supplied in a home. Three phase electrical power is commonly only available in a factory setting. The most common single phase AC motor is known as a universal motor because it can also run with DC current.

This type of motor is very inefficient but can be very inexpensively made. It is also used almost exclusively for small factional horse power AC motors. The other advantage that it has is that the rotational speed of the motor can be easy changed. This type of motor is commonly found in mixers, hand drills, and any other application requiring variable speed and low cost and small size.

For larger single phase AC motors, a electrical component known as a capacitor is used to create a second phase from the single phase AC current. This type of motor is known as an induction motor, and there are two basic types: a capacitor start motor and a capacitor run motor. It is the interaction between the two phases of this type of motor that causes it to turn.

SAFETY FIRST.....

Something in u urges to u to start doing some cool electronic projects…What do u think is the first thing u need to learn??Ohms Law?? Micro controller??digital??analog??..

                                   Nothing my friend…SAFETY is the buzz word of electronics..No engineer would love to scorch up his hands or spike his hair with current and in particular beautiful girls b careful..i don’t want u to end up like sth in a humorous cinema scene getting woed with microwave oven or electric device............

Electrical shock is the response of the human body to high currents.which may range from  an intense contraction of the heart, and extremely high heat at the point of contact leading to death or disfigurement.. ..sounds like scenes from SAW? The degree of damage of course depends on your age ,but its obvious that  even the fittest cannot survive a 230v shock…..So here are some safety tips adapted from various books…if u survive even after your first project, thank this post…

1)INSULATE OPEN WIRE ENDS..

              Considering the fact that u r not stupid enuf to use naked copper wires ,make sure u insulate all exposed wires…for this the old tape reel from ur grandfathers box wont do..get a new one..just 20 bugs…don’t end up using too much ..making your project appear like a village girls hairdo with ribbons all over.

2)DO U LAUGH A LOT??

             Do u make people around u laugh?Cracking jokes and comments?all rite…just shut up wen u r with electricity.concentrate…else u wud end up dead with mouth wide open laughing…

3) WATER WATER EVERYWHERE…

             Wet places attract danger as …avoid working in wet places…If u cannot resist it ,lock yourself up till u finish ur work,,after that u can very well jump in to the pool..

 4) EVEN SIMBU DROPPED AC…WHY DO U STICK ON TO IT??

              AC supplies range from 110-220 volts..Very high…not something u can lick like what u do with ur 9V battery..Why face danger when u knw it exixts..those things can be done only in marriage and not in electronics..choose DC..safe and easy..of course with no other option use an adapter like this…

5)EVEN I AM STINGY….

       But I don’t buy adapters that short when switched on, ICs that burn easily ,etc etc just because they are cheap…be prepared to spend reasonably..

                   And this list is not exhaustive ,,these are just general views…there is more on soldering,wiring etc…Will follow up soon…

 #COPIED.....

What comes first?? THE VOLTAGE OR CURRENT??

Well, much of a seemingly stupid question- the one that matches with a very popular analogy of hen and egg.....Voltage, currents,and conductors all work together. If there is a voltage applied across a conductor, electric current flows. If you have an electric current flowing through a conductor, there will be voltage across the conductor. Bottom line: Don’t worry about which comes first.