1) Whad Wi & Whad Fi?

The name is coined from the terms Wireless & Fidelity. It is a direct descendant of the term Hi-Fi used for audio recording and playback equipment. Fidelity(in communication systems) refers to the degree to which the output is an exact replica of the input. It has nothing to do with sound quality, as most people think. Wi-Fi, in fact, has little to do with Fidelity. So I wouldn’t really agree that the name is justified. In fact, The name don’t mean shit. It’s just called so because it is… called so.

So, the fact is that Wi-Fi is a stuphid name and has nothing to do with fidelity. It’s not even supposed to be a short for Wireless Fidelity.

2) How it Works

Wi-Fi allows us to browse the internet without wires, using multiple devices, at high speeds. It uses radio signals in the unlicensed frequency bands(see 5 Kickasscular Facts About Bluetooth)-using particularily the frequencies 2.4 GHz & 5 GHz. The radio signal comes from the antenna to a Wi-Fi Router that decodes the signal to stuff your Wi-Fi device can understand(0’s & 1’s, that is). The digital goes to the device-the cell phone, laptop, xbox, or your desktop-anything that supports Wi-Fi. Most laptop’s come with an inbuilt Wi-Fi card. A card can also be installed and used via USB or using the PCI slot. Most coffee shops & restaurants have Wi-Fi networking-these are called hotspots.

Though, the new “Wi-Fi Direct” will allow Wi-Fi usage without the needs of hotspots-allowing direct interaction b/w devices-somewhat like Bluetooth-with a greater range-and higher speeds.

3)802.11? That’s Wi-Fi for you.

Wi-Fi is often referred to as 802.11 technology-this is because it is based on the IEEE 802.11 standard. The standard further has the following sub-standards which can be used for Wi-Fi communications:

802.11a-uses high frequency-hence, high speed but cannot penetrate walls.
802.11b-slower; about 11 mbps, lacks range but can penetrate walls.
(802.11c-not used for Wi-Fi)
Most commonly used-802.11g-54 mbps.
The future-801.11n-150mbps.

4)Spread Spectrum

Wi-Fi transmission makes use of The Spread Spectrum-which spreads the signal in the frequency domain to occupy higher bandwidths. More presicely, it emplys the single-carrier direct-sequence spread spectrum radio technology. This increases the reliability and security of the transmitted signals. (More info)

5)Wi-Fi won’t kill you… Or maybe it will?

All around you-wherever you go-the em waves follow. They are everywhere. Coming from antennas-going to cellphones-to more cellphones-to radio sets-to television sets-to walkie-talkies and so forth. And you can pretty much do nothing about it. The waves from WiFi devices are however of very low power and this power further drops as it follows the inverse square law(with distance). Perhaps, the effect they have on you is negligible compared to the effect cell phones have on you. And we’re definitely not going to stop using the cell phone, then why not use Wi-Fi?

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Any subject you learn, you first start with the fundamentals of the subject and later use them to make bigger concepts-a cluster of fundamentals. The concepts grow in size until you completely master the subject. Any subject can hence be divided into a set of layers of abstraction.

The most basic concepts form the lowest layers of abstraction and the resulting devices form the higher layers of abstraction. The lower levels require the maximum effort and time while the higher levels are easy-depending only upon how well you understand the lower ones.

Electronics Engineering begins with Basic Physics all the way to the Microprocessor. Like any other subject, it can be summarized and over-viewed using such a set of abstraction layers.

Level 1 – The Physics/The Electron

The Atom

Electronics emerges from the basics of electricity-the flow of electrons & the fact that charge exists on the electron. We then take a look at the atomic view-the nature of the atom. This includes the study of energy levels and energy radiation from the atom. Once we know that elements can conduct-we can make use of the knowledge. As you may notice-this abstraction layer can further be divided into sub-levels(the electron, the atom & conducting elements)

Level 2 – The Semiconductor/The Holes

Once we start noticing and studying the various elements-we come across the “gifted” elements of Group 4. The gift they have is a unique energy gap-one that lies between the conductors & the insulators. They appear harmless at 0K-but do wonders under room temperature or when doped with another element from the 3rd or the 5th group. This classifies the semiconductors as Extrinsic & Intrinsic.

a)conductor b)insulator c)semiconductor

Level 3-The P-N Junction/The Diode/Rectifiers

Once we learn about doping & the extrinsic semiconductors, we make use of the fact. The p-n Junction results. Here, we introduce a concept called “recombination”. We expand the concepts of electricity to incorporate the conduction by holes-which are considered as physical positive charges. We play around with the junction-we bias it with an external voltage. It allows current only through a particular direct-it has directionality!

The P-N Junction

The device resulting from the p-n junction is the Diode. It shows certain characteristics-that of conduction with directionality-and that of breakdown when reverse biased. There are a number of types of diodes-with slight variations in structure-but a greater variation in functionality. The diode emerges as a rectifier with many other applications including clipping & clamping & peak detection.

Level 4-The Transistor/Amplifiers/Filters

The Transistor

Putting two diodes back to back give us the transistor. A device used for amplification & switching. It can be seen as a combination of two p-n junctions. This device has the directionality-but in addition -has gain. It is hence, an active device.

Consider the layers of abstraction as layers of sand piled over each other. You are still aware of the deeper & more fundamental layers-but you are now looking at the higher ones. Here, we look at the transistor and how it performs amplification/switching but we do not consider how doping results in p & n type semiconductors-that is the essence of abstraction.

Level 5-The Logic Gates

The NAND Gate

The transistors-alone-or combined with the diode and other passive devices lead to what are called-the logic families. They are used to realize the logic gates-devices which perform simple operations on digital signals. Amongst the logic gates-the NAND and NOR are the universal gates & form the basis of most of the further levels of abstraction.

Level 6-Digital Circuits/Combinational & Sequential Circuits

A Counter

A MUX

Logic gates are then combined to form circuits that establish certain logic functions-they are called the combinational circuits. These include multiplexers, demultiplex, encoders, decoders and all the logic circuits you can think of that do not use a circular logic path(no feedback).

A Flip Flop

The sequential circuits are combinational circuits with storage. They add a state to the combinational circuit-and they store it. They use feedback to store this state. The basic sequential device is a flip-flop and other devices include counters and shift registers.

Level 7-The Microprocessor/CPU/Integrated Circuits/Micro Chip

An Integrated Circuit

The Digital Circuits allow us to build Integrated Circuits. Our building blocks still being the NAND & NOR gates. We now have functionality(combinational circuits) and storage(sequential circuit)-and those are the two things a CPU does. So, we now have the CPU. We may further have all the CPU functionality on a single chip-called the Microprocessor. The digital circuits also make way for Computer Architecture which builds the Operating System-The Computer is complete. All electronic devices we see and use everyday use a microprocessor CPU-the highest level of Electronics Abstraction.

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C++, as the name suggests is a superset of C. As a matter of fact, C++ can run most of C code while C cannot run C++ code. Here are the 10 major differences between C++ & C…

1. C follows the procedural programming paradigm while C++ is a multi-paradigm language(procedural as well as object oriented)

In case of C, importance is given to the steps or procedure of the program while C++ focuses on the data rather than the process.
Also, it is easier to implement/edit the code in case of C++ for the same reason.

2. In case of C, the data is not secured while the data is secured(hidden) in C++

This difference is due to specific OOP features like Data Hiding which are not present in C.

3. C is a low-level language while C++ is a middle-level language

C is regarded as a low-level language(difficult interpretation & less user friendly) while C++ has features of both low-level(concentration on whats going on in the machine hardware) & high-level languages(concentration on the program itself) & hence is regarded as a middle-level language.

4. C uses the top-down approach while C++ uses the bottom-up approach

In case of C, the program is formulated step by step, each step is processed into detail while in C++, the base elements are first formulated which then are linked together to give rise to larger systems.

5. C is function-driven while C++ is object-driven

Functions are the building blocks of a C program while objects are building blocks of a C++ program.

6. C++ supports function overloading while C does not

Overloading means two functions having the same name in the same program. This can be done only in C++ with the help of Polymorphism(an OOP feature)

7. We can use functions inside structures in C++ but not in C.

In case of C++, functions can be used inside a structure while structures cannot contain functions in C.

8. The NAMESPACE feature in C++ is absent in case of C

C++ uses NAMESPACE which avoid name collisions. For instance, two students enrolled in the same university cannot have the same roll number while two students in different universities might have the same roll number. The universities are two different namespace & hence contain the same roll number(identifier) but the same university(one namespace) cannot have two students with the same roll number(identifier)

9. The standard input & output functions differ in the two languages

C uses scanf & printf while C++ uses cin>> & cout<< as their respective input & output functions

10. C++ allows the use of reference variables while C does not

Reference variables allow two variable names to point to the same memory location. We cannot use these variables in C programming.

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Image By NASA(who else could take it?)

I had been visiting a lot of hill stations since i was a kid. I even lived in Nainital for a few years when i was little. Television was never so common at all those places until the DTH services gained popularity in India. I recently made a visit to Arunachal Pradesh and saw a DTH signal receiver at every house. I wondered how it worked so effectively at all those places, and why our cable TV did not.

TV technology could be analog or digital. The usual cable broadcast TV use land-based antennas that transmit a radio signal(using the Vestigial Sideband Technique) . Now, to avoid interferences and provide HD picture and sound quality, the receiver antenna must be in the line of sight of the transmitter.  However, the shape of our planet does not provide for it.

But, this line of sight could be increased significantly if we were to send the signals from somewhere high above-from the satellite. Now, the signal from the satellite reaches directly without any obstacles-and, to a larger number of customers. There is just one problem if you may think-the satellite is in its orbit, so do we keep aligning our antennas to its direction?

Well, that is taken care of by using geostationary satellites. By “geostationary”, we mean satellites that are stationary with respect to the earth(geo-stationary). And by the way, these satellites orbit in space in a region we humans call The Clark Belt or The Clark Orbit.

geostationary orbit

Now, there is another additional advantage of using Satellite TV. We can use a DVR(Digital Video Recorder) to record live TV shows with our satellite TV. This is easy as the signal is already a digital signal. While in analog TV(cable TV) we must first convert the signal to digital if we want to record it for later viewing.

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Image Credit-Amy Wong

In any audio communication, we first need the sound signal in the form of an electrical signal. Hence, we need the microphone in all our communication systems. It is the very first stage of any audio communication.

It acts as the (input) transducer for a system. A transducer is any device that converts a form of energy to another. The microphone converts a speech signal(sound energy) to an electrical signal(electrical energy). The function of a speaker is exactly the reverse of the microphone. The speaker is hence used as the output transducer to convert the electric signal back to a sound signal.

Now, this conversion of energy can be achieved by various means depending on the type of microphone. Largely, we can classify microphones as dynamic and condenser microphones. In either type, we have an element called the diaphragm(analogous to the biological diaphragm).

The diaphragm of the microphone vibrates when it is struck be the sound waves. This vibration is converted to an electric signal using either the principle of a capacitor storing energy as charge(the condenser microphone) or the principle of electromagnetic induction(dynamic microphones).

In condenser microphones, the diaphragm acts as a capacitor plate and when it vibrates back and forth, the distance between plates varies. Its like moving a capacitor plate back and forth with the incoming signal vibration. When the distance varies, the capacitance varies(since the capacitance is inversely proportional to the plate distance). This variation in the capacitance appears as variation in Voltage(C=Q/V but charge remains almost constant as the time frame for which the capacitance varies is very small). This variation in voltage is nothing but the desired electrical signal.

In a dynamic microphone, a coil is attached to the diaphragm.As the diaphragm vibrates, the coil moves back and forth. A permanent magnet produces a field that cuts the coil causing electric current to flow through it. This current signal is in accordance with the coil vibration-and hence the diaphragm vibration-and hence the speech signal. This is hence, the required electrical signal.

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All of us use the Pen Drive to store data everyday. We use it like an external storage device, much like an external hard drive. A Pen drive or Flash drive or USB drive has two basic elements-

• Flash Memory (NAND Flash with a crystal oscillator)
• USB (USB Male & a Microcontroller)

The USB(or Universal Serial Bus) just allows the pen drive to communicate with the computer or any other device. Based on their construction, the USB has various versions. The ones which are at work in pen drives are USB 1.1 & 2.

The heart of the “flash” drive is the Flash Memory. This is where digital electronics comes in. There are three kinds of storage media.

• Volatile(info stored does not survive system crashes)
• Non-Volatile(info usually survives crashes)
• Stable(info is never lost-not practically possible-but can be approximated by RAID, etc)

NAND Gate

Our flash memory falls into the category of non-volatile devices. It can be implemented by using both NOR & NAND logic circuits. In flash drives, NAND gates are used.

Digital circuits can be classified into Combinational & Sequential Circuits. A combinational circuit is a combination of a number of logic gates. A sequential circuit is a combination of gates which has a state or memory associated to it. So, a sequential circuit is a combinational circuit with memory.

NAND SR Flip-Flop

Latches and flip-flops are sequential circuits which can store 1-bit of information(either 0 or 1). Further, n flip-flops could store n bits of information.

We could further use an assembly of flip-flops to store data. Such an assembly of NAND flip-flops is used as flash memory.

The crystal oscillator acts as a clock to trigger the sequential circuit. Sequential circuits that use a clock/trigger are called Synchronous Sequential Circuits.

Floating Gate Transistor(FGMOS)

The sequential logic used in the flash memory are realized using floating gate transistors. These are transistors(MOSFET’s) whose gate is electrically isolated-and hence, acts as a floating node.

We have a floating gate(represented by the bold line) and three inputs for the transistor shown.

The use of floating gate transistors makes the flash memory electrically erasable & programmable. It is hence a type of EEPROM. It is a read-only memory that can be erased and rewritten(reprogrammed) electrically-by means of voltage/current.

However, the number of times it can be reprogrammed is limited. We always loose some bit when we format our jump drives.

Put together, our flash memory and the USB configuration forms the USB Flash drive.

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(Image Credit)

For a basic idea on whats inside the iPod, how it works and how it is build, let’s try to design our own iPod. Think of the iPod as a computer that is exclusively used to play music. It can further be equipped to add more features like video playback and games.

A Summary

Hardware Needed

• Microprocessor
• Hard Drive/Flash Memory
• Audio Chip
• Added features like Video Chip(if needed)
• LCD Display device
• Rechargeable Li Battery

Software Needed

• Pixo OS 2.1
• iTunes
• iOS(for iPod Touch)

Interface

• LCD/Touch Screen
• Click Wheel

A computer works when its got two things-Hardware & Software. The hardware is the CPU-which we would refer to as a microprocessor. A microprocessor performs all the functions of the CPU on a single IC unit. It has a memory-We need RAM to run the various processes and we also need memory to store the data(music files and stuff).

Consider the RAM already chipped on to the microprocessor as microprocessor memory. We got the microprocessor, now we need memory for data storage. (Note-we can also have RAM and flash memory on our microprocessor) We now got two options for memory-

• A Hard Drive(a highly sensitive one with lots of space)
• Flash Memory(EEPROM using NAND sequential logic)

We can use flash memory if we need about 1-8 GB memory and for all other purposes, we would go for a hard drive. The iPod Classic & Mini use drives while Nano, Shuffle & Touch use Flash Memory.

So, we now got the microprocessor & memory for data storage. We now need an audio chip that can perform the decoding and encoding of the digital stream of data(we are dealing with digital audio here.) This could also be chipped on to the microprocessor like in iPod Shuffle which uses a SigmaTel chip. So, we now have the following-

• A Microprocessor-the heart of the iPod
• An Audio Chip that encodes/decodes audio.
• Either a hard drive or flash memory for data storage

The other hardware we would require is a display device and a controlling device. For display, we use LCD(Liquid Crystal Display) for most of our purposes except when we need a touch screen. For the controls, we use the Click Wheel.

The click wheel is an interesting part of the iPod. It’s plastic when we look at it. But inside it is a metal channel in the form of a grid. The grid hold charge and acts as a capacitance equivalent. Our fingers act as conductors that vary this capacitance. These capacitance variations are interpreted by a control chip that translates the variations into instructions for the microprocessor.

(Image Credit)

We now add a rechargeable lithium ion battery to supply power to our iPod. Well, we are done with the iPod hardware but to make sense of the hardware, we need a platform or software or host-the Operating System is the host-a bridge between the user and the hardware.

The iPod uses the Pixo OS 2.1(found by Paul Mercer after he left Apple to create his own company-Pixo!). The Pixo OS framework uses C++(if you care).  And as everyone would agree,  iTunes would be our desired jukebox/media player software. Now, we all know about iTunes, don’t we?

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1) Start with the name. Bluetooth got its name from a Danish king! A king called Harald Blåtand (which is Bluetooth when anglicised-converted to English) who united Denmark and a part of Norway into a single kingdom. Bluetooth technology can now be thought as to unite two electronic devices.

Some really cool myths-

• The king wore a blue crown.
• The founders wrote notes with blue ink.
• It sends out waves of “blue” frequency.

2) Bluetooth uses the ISM(industrial, scientific and medical) band which are reserved for scientific and medical purposes-and are not supposed to be used for communication. In this band, it occupies the frequency range 2402-2480 MHz. Wi-Fi also uses the ISM band.

3) Bluetooth can connect up to 8 devices at a time without any interference. This is possible because Bluetooth makes use of FHSS-which stands for Frequency Hopping Spread Spectrum.

In this method of transmitting radio signals, the carrier is switched rapidly amongst multiple frequency channels.

So there’s hardly a chance that two devices will be transmitting signals at the same frequency. Even if they do-they do it only for a very short instant as the frequency is continuously hopping/changing values. Also, The device sending the information(master) switches between the receivers(slave devices) using a kind of Round Robin scheme.

4) Now comes the reason for Bluetooth’s short range. The usual Bluetooth devices work in about 10 m or 32 feet. It’s short range comes from the fact that it sends out signals of low Power(about 1 mW-goes to a limit of 3 mW). And the reason for using low power signals is to avoid interference with other signals using the ISM band.

5) Bluetooth uses a combination of modulation processes. By far, the most favorable modulation for Bluetooth transmission is Frequency Shift Keying(FSK). FSK identifies a positive deviation from the center frequency representing a binary one and a negative deviation from the center frequency representing a zero. The image below illustrates the method.

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Silicon - "It's All Sand!"

Before you begin reading..

This is not about-

• People trying out stuff they made in their basements.
• People fighting over patents.
• Inventions of gadgets like the Toshiba Satellite Pro S300.
• Time, Dates and Weather Reports of days in electronics history.

This is about-

• Inventions that changed the electronics industry forever.
• Inventions that form the very basics of modern electronics.
• Inventions that every electronics engineer should know.

J.J. Thomson

1897

Electronics is the ability to control electron flow. It is nothing without the electron. The discovery of the electron marks the birth of electronics itself. If we waive off the Greeks, the Latin & the German, then its safe to say that the electron was discovered by J.J. Thomson when he was playing around in the interiors of the atom. He first discovered the cathode rays. He conceptualized them to be made up of particles smaller than the atom-which were then called the electrons.

1904

The First Thermionic Valve was invented in 1904 by John Fleming. The thermionic diode is slightly different from the semiconductor diode. Though both perform the same function-allowing current to pass through in one direction-The thermionic diode has a cathode and an anode just like the semiconductor diodes have the p and the n junctions. Even before the invention(since 1874), certain crystals were known to have rectifying abilities. Diodes were initially just referred to as rectifiers.

Rectifier Valves

Lee De Forest

1906

The diode valve and the triode valve are both thermionic valves-the diode valve has two electrodes and the triode vale has three. The first triode valve was invented by Lee De Forest in 1906. These valves were the major components of radios for many years(were later replaced by transistors). For this reason, the guy is called ‘The Father Of Radio’. As a matter of fact, he gave himself the title but was never really recognized by the people as ‘The Father Of Radio’. This was largely due to the controversies surround him.

The 3 element vacuum tube was made by adding a control grid to Fleming’s valve. The device was called ‘The Audion’ with which we could control the electron flow. The Audion however, could not provide electronic amplification. However, it formed the basis of the electronic amplifying triode.

The Electrical Experimenter, August 1916. Volume 4.

1947

In 1947, the first transistor was made. It was a  point contact transistor which could amplify electric signals. It was invented at Bell Labs by William Shockley(”the father of the transistor”) along with John Bardeen and Walter Brattain. The term transistor was coined by John R. Pierce.

The way I provided the name, was to think of what the device did. And at that time, it was supposed to be the dual of the vacuum tube. The vacuum tube had transconductance, so the transistor would have ‘transresistance.’ And the name should fit in with the names of other devices, such as varistor and thermistor. And. . . I suggested the name ‘transistor.’

-John R. Pierce, interviewed for PBS show “Transistorized!”

1954

It was in 1954 when Gordon Teal at Texas Instruments created the first Commercial Silicon Transistor. He announced the production of the first Silicon Transistors at a presentation. He started the presentation like usual technical paper presentations without disclosing the achievement. He then amazed the crowd by playing Artie Shaw’s “Summit Ridge Drive.” on a Silicon Transistor. He first played the same music on a Germanium Transistor to bring out the difference. Gordon Teal began his research at Texas Instruments after leaving Bell Labs. Previous studies and inventions were already booming at Bell labs. But perhaps, Bell Labs did not consider it a device too fancy for commercial production.

1958

Jack Kibly was da man of 58′. He invented the first Integrated Circuit(IC) while working for Texas Instruments. He is also the daddy of the first handheld calculator & the first thermal printer. There were transistors already, and transistors needed connecting wires. To reduce the sizes further, they needed to integrate the transistor, the wires and everything else together. Jack Kibly got the idea to make all the components like the resistor, capacitor and the transistor from a single Silicon crystal. This increased performance and reduced costs. The components were close to each other and hence-required much less power supply & showed high switching speeds.

1971

In 1971, Intel introduces the first CPU on a chip-the first Microprocessor. Named The Intel 4004, it was a 4-bit CPU and was the first commercially available microprocessor. A microprocessor is a single Integrated Circuit that performs all the functions of the CPU. The invention further reduced the chip size leading to better performance and reduced costs. Microprocessors are now  apart of almost every electronic device. From small embedded systems to supercomputers-they are an essential component-the heart of all devices.

(The Intel 4004-Image Credit)

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Found this really cool tutorial on Operational Amplifiers by Dr. Holbert, Arizona State University. It includes the Op-Amp basics, a few op-amp circuits including the differentiator and integrator circuits and a few examples. Its flash-based and easy to understand. Here’s the link-http://holbert.faculty.asu.edu/ece201/opamp.html

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If you think you’re practiced them enough, its time to see their real beauty, Try solving the most “beautiful” Indefinite Integrals-the beauty comes from the flow of the solutions, the answers, the feel of the integrals-math is beautiful, just like everything else!

Note-The links/email at the end of the presentation wont work. For solutions, just leave a comment here.

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July 2010-India got its currency symbol. To decide and design the symbol, a contest was held by the Indian Government. The contest was announced on 5th March, 2009 and the symbol was finalized out of about 3000 proposed symbols on 15th July, 2010.

The symbol is given by an IITian D Udaya Kumar. It comes from the Devanagari ‘र’ and Roman ‘R’. As per the contest guidelines, the symbol depicts the cultural heritage of India and includes a national script.

The Tidle/Grave Accent Key

A font with the Rupee symbol is available for download at Foradian. There is also another version of the same that includes all letters. Once you download the font, you can type it using the grave accent(`) symbol-the one just left of the #1 key.

Previously, Rs or Re was used to denote the Indian currency. A modification of Rs was used as a former symbol(can be found at Xe.com)

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