Informative consumer electronics article?

Consumer electronics

Consumer electronics or home electronics are electronic or digital equipment intended for everyday use, typically in private homes. Consumer electronics include devices used for entertainment (flatscreen TVs, DVD players, DVD movies, iPods, video games, remote control cars, etc.), communications (telephones, cell phones, e-mail-capable laptops, etc.), and home-office activities (e.g., desktop computers, printers, paper shredders, etc.). In British English, they are often called brown goods by producers and sellers, to distinguish them from "white goods" such as washing machines and refrigerators. In the 2010s, this distinction is not always present in large big box consumer electronics stores, such as Best Buy, which sell both entertainment, communications, and home office devices and kitchen appliances such as refrigerators. Consumer electronics stores differ from professional audio stores in that the former sells consumer-grade electronics for private use, whereas the latter sells professional-grade electronics designed for use by audio engineers and audio technicians.

Radio broadcasting in the early 20th century brought the first major consumer product, the broadcast receiver. Later products included telephones, personal computers, MP3 players, audio equipment, televisions (first cathode ray tube TVs, then in the 2000s, flatscreen TVs) and calculators. In the 2010s, consumer electronics stores often sell GPS, automotive electronics (car stereos), video game consoles, electronic musical instruments (e.g., synthesizer keyboards), karaoke machines, digital cameras, and video players (VCRs in the 1980s and 1990s, followed by DVD players and Blu-ray disc players). Stores also sell digital cameras, camcorders, cell phones, and smartphones. As of 2016, some of the newer products sold include virtual reality head-mounted display goggles, smart home devices that connect home devices to the Internet (such as smartphone-controllable thermostats and lights) and wearable technology such as Fitbit digital exercise watches.

In the 2010s, most products have become based on digital technologies, and have largely merged with the computer industry in what is increasingly referred to as the consumerization of information technology. Some consumer electronics stores, such as Best Buy have also begun selling office and baby furniture. Consumer electronics stores may be "bricks and mortar" physical retail stores, online stores, where the consumer chooses items on a website and pays online (e.g, Amazon). or a combination of both models (e.g., Best Buy has both bricks and mortar stores and an e-commerce website for ordering its products). The CEA (Consumer Electronics Association) estimated the value of 2015 consumer electronics sales at US$220 billion.

Products

A typical CoCo 3 computer system, from the 1980s

Main consumer electronics products include radio receivers, television sets, MP3 players, video recorders, DVD players, digital cameras, camcorders, personal computers, video game consoles, telephones and mobile phones.Increasingly these products have become based on digital technologies, and have largely merged with the computer industry in what is increasingly referred to as the consumerization of information technology such as those invented by Apple Inc. and MIT Media Lab.

Trends

A modern flat panel, HDTV television set

One overriding characteristic of consumer electronic products is the trend of ever-falling prices. This is driven by gains in manufacturing efficiency and automation, lower labor costs as manufacturing has moved to lower-wage countries, and improvements in semiconductor design.Semiconductor components benefit from Moore's Law, an observed principle which states that, for a given price, semiconductor functionality doubles every two years.

While consumer electronics continues in its trend of convergence, combining elements of many products, consumers face different decisions when purchasing. There is an ever increasing need to keep product information updated and comparable, for the consumer to make an informed choice. Style, price, specification, and performance are all relevant. There is a gradual shift towards e-commerce web-storefronts.

Many products include Internet connectivity using technologies such as Wi-Fi, Bluetooth, EDGE or Ethernet. Products not traditionally associated with computer use (such as TVs or Hi-Fi equipment) now provide options to connect to the Internet or to a computer using a home network to provide access to digital content. The desire for high-definition (HD) content has led the industry to develop a number of technologies, such as WirelessHD or ITU-T G.hn, which are optimized for distribution of HD content between consumer electronic devices in a home.

Manufacturing

Gramophone factory in Hannover-Nordstadt

Many consumer electronics are built in China, due to maintenance cost, availability of materials, quality, and speed as opposed to other countries such as the United States. Cities such as Shenzhen have become important production centres for the industry, attracting many consumer electronics companies such as Apple Inc.

Electronic component

An electronic component is any basic discrete device or physical entity in an electronic system used to affect electrons or their associated fields. Electronic components are mostly industrial products, available in a singular form and are not to be confused with electrical elements, which are conceptual abstractions representing idealized electronic components.

Software development

Consumer electronics such as personal computers use various types of software. Embedded software is used within some consumer electronics, such as mobile phones. This type of software may be embedded within the hardware of electronic devices. Some consumer electronics include software that is used on a personal computer in conjunction with electronic devices, such as camcorders and digital cameras, and third-party software for such devices also exists.

Standardization

Some consumer electronics adhere to protocols, such as connection protocols "to high speed bi-directional signals". In telecommunications, a communications protocol is a system of digital rules for data exchange within or between computers.

Trade shows

The Consumer Electronics Show (CES) trade show has taken place yearly in Las Vegas, Nevada since its foundation in 1973. The event, which grew from having 100 exhibitors in its inaugural year to more than 3,600 exhibitors in its 2014 edition, features new consumer electronics and speeches by industry pioneers.

Amplifier and types of amplifier ?

Amplifier

An amplifier, electronic amplifier or (informally) amp is an electronic device that can increase the power of a signal (a time-varying voltage or current). An amplifier functions by taking power from a power supply and controlling the output to match the input signal shape but with a larger amplitude. In this sense, an amplifier modulates the output of the power supply based upon the properties of the input signal. An amplifier is effectively the opposite of an attenuator: while an amplifier provides gain, an attenuator provides loss.

An amplifier can either be a separate piece of equipment or an electrical circuit contained within another device. Amplification is fundamental to modern electronics, and amplifiers are widely used in almost all electronic equipment. Amplifiers can be categorized in different ways. One is by the frequency of the electronic signal being amplified; audio amplifiers amplify signals in the audio (sound) range of less than 20 kHz, RF amplifiers amplify frequencies in the radio frequency range between 20 kHz and 300 GHz. Another is which quantity, voltage or current is being amplified; amplifiers can be divided into voltage amplifiers, current amplifiers, transconductance amplifiers, and transresistance amplifiers. A further distinction is whether the output is a linear or nonlinear representation of the input. Amplifiers can also be categorized by their physical placement in the signal chain.

The first practical electronic device that could amplify was the triode vacuum tube, invented in 1906 by Lee De Forest, which led to the first amplifiers around 1912. Vacuum tubes were used in almost all amplifiers until the 1960s–1970s when the transistor, invented in 1947, replaced them. Today most amplifiers use transistors, but vacuum tubes continue to be used in some applications.

Amplifier categorisation

Amplifiers are described according to the properties of their inputs, their outputs, and how they relate. All amplifiers have gain, a multiplication factor that relates the magnitude of some property of the output signal to a property of the input signal. The gain may be specified as the ratio of output voltage to input voltage (voltage gain), output power to input power (power gain), or some combination of current, voltage, and power. In many cases the property of the output that varies is dependent on the same property of the input, making the gain unitless (though often expressed in decibels (dB)).

Most amplifiers are designed to be linear. That is, they provide constant gain for any normal input level and output signal. If an amplifier's gain is not linear, the output signal can become distorted. There are, however, cases where variable gain is useful. Certain signal processing applications use exponential gain amplifiers.

Amplifiers are usually designed to function well in a specific application, for example: radio and television transmitters and receivers, high-fidelity ("hi-fi") stereo equipment, microcomputers and other digital equipment, and guitar and other instrument amplifiers. Every amplifier includes at least one active device, such as a vacuum tube or transistor.

Active devices

All amplifiers include some form of active device: this is the device that does the actual amplification. The active device can be a vacuum tube, discrete solid state component, such as a single transistor, or part of an integrated circuit, as in an op-amp).

Transistor amplifiers

Transistor amplifiers (or solid state amplifiers) are the most common type of amplifier in use today. A transistor is used as the active element. The gain of the amplifier is determined by the properties of the transistor itself as well as the circuit it is contained within.

Common active devices in transistor amplifiers include bipolar junction transistors (BJTs) and metal oxide semiconductor field-effect transistors (MOSFETs).

Applications are numerous, some common examples are audio amplifiers in a home stereo or public address system, RF high power generation for semiconductor equipment, to RF and microwave applications such as radio transmitters.

Transistor-based amplification can be realized using various configurations: for example a bipolar junction transistor can realize common base, common collector or common emitter amplification; a MOSFET can realize common gate, common source or common drain amplification. Each configuration has different characteristics.

Vacuum-tube amplifiers

Vacuum-tube amplifiers (also known as tube amplifiers or valve amplifiers) use a vacuum tube as the active device. While semiconductor amplifiers have largely displaced valve amplifiers for low power applications, valve amplifiers can be much more cost effective in high power applications such as radar, countermeasures equipment, and communications equipment. Many microwave amplifiers are specially designed valve amplifiers, such as the klystron, gyrotron, traveling wave tube, and crossed-field amplifier, and these microwave valves provide much greater single-device power output at microwave frequencies than solid-state devices.Vacuum tubes remain in use in some high end audio equipment, as well as in musical instrument amplifiers, due to a preference for "tube sound".

Magnetic amplifiers

Magnetic amplifiers are devices somewhat similar to a transformer where one winding is used to control the saturation of a magnetic core and hence alter the impedance of the other winding.

They have largely fallen out of use due to development in semiconductor amplifiers but are still useful in HVDC control, and in nuclear power control circuitry to their not being affected by radioactivity.

Negative resistance devices

Negative resistances can be used as amplifiers, such as the tunnel diode amplifier.

Amplifier architectures

Amplifiers can also be categorised by the way they amplify the input signal.

Power amplifier

A power amplifier is an amplifier designed primarily to increase the power available to a load. In practice, amplifier power gain depends on the source and load impedances, as well as the inherent voltage and current gain. A radio frequency (RF) amplifier design typically optimizes impedances for power transfer, while audio and instrumentation amplifier designs normally optimize input and output impedance for least loading and highest signal integrity. An amplifier that is said to have a gain of 20 dB might have a voltage gain of 20 dB and an available power gain of much more than 20 dB (power ratio of 100)—yet actually deliver a much lower power gain if, for example, the input is from a 600 ohm microphone and the output connects to a 47 kilohm input socket for a power amplifier. In general the power amplifier is the last 'amplifier' or actual circuit in a signal chain (the output stage) and is the amplifier stage that requires attention to power efficiency. Efficiency considerations lead to the various classes of power amplifier based on the biasing of the output transistors or tubes.

Unique article on free convolution?

Free convolution

Free convolution is the free probability analog of the classical notion of convolution of probability measures. Due to the non-commutative nature of free probability theory, one has to talk separately about additive and multiplicative free convolution, which arise from addition and multiplication of free random variables (see below; in the classical case, what would be the analog of free multiplicative convolution can be reduced to additive convolution by passing to logarithms of random variables). These operations have some interpretations in terms of empirical spectral measures of random matrices.

convolution graphs

The notion of free convolution was introduced by Voiculescu.

Free additive convolution

Let {\displaystyle \mu } \mu  and {\displaystyle \nu } \nu  be two probability measures on the real line, and assume that {\displaystyle X} X is a random variable in a non commutative probability space with law {\displaystyle \mu } \mu  and {\displaystyle Y} Y is a random variable in the same non commutative probability space with law {\displaystyle \nu } \nu . Assume finally that {\displaystyle X} X and {\displaystyle Y} Y are freely independent. Then the free additive convolution {\displaystyle \mu \boxplus \nu } \mu \boxplus \nu  is the law of {\displaystyle X+Y} X+Y. Random matrices interpretation: if {\displaystyle A} A and {\displaystyle B} B are some independent {\displaystyle n} n by {\displaystyle n} n Hermitian (resp. real symmetric) random matrices such that at least one of them is invariant, in law, under conjugation by any unitary (resp. orthogonal) matrix and such that the empirical spectral measures of {\displaystyle A} A and {\displaystyle B} B tend respectively to {\displaystyle \mu } \mu  and {\displaystyle \nu } \nu  as {\displaystyle n} n tends to infinity, then the empirical spectral measure of {\displaystyle A+B} A+B tends to {\displaystyle \mu \boxplus \nu } \mu \boxplus \nu .

In many cases, it is possible to compute the probability measure {\displaystyle \mu \boxplus \nu } \mu \boxplus \nu  explicitly by using complex-analytic techniques and the R-transform of the measures {\displaystyle \mu } \mu  and {\displaystyle \nu } \nu .

Rectangular free additive convolution

The rectangular free additive convolution (with ratio {\displaystyle c} c) {\displaystyle \boxplus _{c}} \boxplus _{c} has also been defined in the non commutative probability framework by Benaych-Georges and admits the following random matrices interpretation. For {\displaystyle c\in [0,1]} c\in [0,1], for {\displaystyle A} A and {\displaystyle B} B are some independent {\displaystyle n} n by {\displaystyle p} p complex (resp. real) random matrices such that at least one of them is invariant, in law, under multiplication on the left and on the right by any unitary (resp. orthogonal) matrix and such that the empirical singular values distribution of {\displaystyle A} A and {\displaystyle B} B tend respectively to {\displaystyle \mu } \mu and {\displaystyle \nu } \nu  as {\displaystyle n} n and {\displaystyle p} p tend to infinity in such a way that {\displaystyle n/p} n/p tends to {\displaystyle c} c, then the empirical singular values distribution of {\displaystyle A+B} A+B tends to {\displaystyle \mu \boxplus _{c}\nu } \mu \boxplus _{c}\nu .

In many cases, it is possible to compute the probability measure {\displaystyle \mu \boxplus _{c}\nu } \mu \boxplus _{c}\nu  explicitly by using complex-analytic techniques and the rectangular R-transform with ratio {\displaystyle c} c of the measures {\displaystyle \mu } \mu  and {\displaystyle \nu } \nu .

Free multiplicative convolution

Let {\displaystyle \mu } \mu  and {\displaystyle \nu } \nu  be two probability measures on the interval {\displaystyle [0,+\infty )} [0,+\infty), and assume that {\displaystyle X} X is a random variable in a non commutative probability space with law {\displaystyle \mu } \mu  and {\displaystyle Y} Y is a random variable in the same non commutative probability space with law {\displaystyle \nu } \nu . Assume finally that {\displaystyle X} X and {\displaystyle Y} Y are freely independent. Then the free multiplicative convolution {\displaystyle \mu \boxtimes \nu } \mu \boxtimes \nu  is the law of {\displaystyle X^{1/2}YX^{1/2}} X^{{1/2}}YX^{{1/2}} (or, equivalently, the law of {\displaystyle Y^{1/2}XY^{1/2}} Y^{{1/2}}XY^{{1/2}}. Random matrices interpretation: if {\displaystyle A} A and {\displaystyle B} B are some independent {\displaystyle n} n by {\displaystyle n} n non negative Hermitian (resp. real symmetric) random matrices such that at least one of them is invariant, in law, under conjugation by any unitary (resp. orthogonal) matrix and such that the empirical spectral measures of {\displaystyle A} A and {\displaystyle B} B tend respectively to {\displaystyle \mu } \mu  and {\displaystyle \nu } \nu  as {\displaystyle n} n tends to infinity, then the empirical spectral measure of {\displaystyle AB} AB tends to {\displaystyle \mu \boxtimes \nu } \mu \boxtimes \nu .

A similar definition can be made in the case of laws {\displaystyle \mu ,\nu } {\displaystyle \mu,\nu} supported on the unit circle {\displaystyle \{z:|z|=1\}} \{z:|z|=1\}, with an orthogonal or unitary random matrices interpretation.

Explicit computations of multiplicative free convolution can be carried out using complex-analytic techniques and the S-transform.

Applications of free convolution

Free convolution can be used to give a proof of the free central limit theorem.

Free convolution can be used to compute the laws and spectra of sums or products of random variables which are free. Such examples include: random walk operators on free groups (Kesten measures); and asymptotic distribution of eigenvalues of sums or products of independent random matrices.

Through its applications to random matrices, free convolution has some strong connections with other works on G-estimation of Girko.

The applications in wireless communications, finance and biology have provided a useful framework when the number of observations is of the same order as the dimensions of the system.

What is electronic component OPTO COUPLER or OPTO ISOLATOR?

Opto-isolator

Schematic diagram of an opto-isolator showing source of light (LED) on the left, dielectric barrier in the center, and sensor (phototransistor) on the right.

In electronics, an opto-isolator, also called an optocoupler, photocoupler, or optical isolator, is a component that transfers electrical signals between two isolated circuits by using light. Opto-isolators prevent high voltages from affecting the system receiving the signal. Commercially available opto-isolators withstand input-to-output voltages up to 10 kV and voltage transients with speeds up to 10 kV/μs.

opto isolator

A common type of opto-isolator consists of an LED and a phototransistor in the same opaque package. Other types of source-sensor combinations include LED-photodiode, LED-LASCR, and lamp-photoresistor pairs. Usually opto-isolators transfer digital (on-off) signals, but some techniques allow them to be used with analog signals.

History

The value of optically coupling a solid state light emitter to a semiconductor detector for the purpose of electrical isolation was recognized in 1963 by Akmenkalns,et al. (US patent 3,417,249). Photoresistor-based opto-isolators were introduced in 1968. They are the slowest, but also the most linear isolators and still retain a niche market in audio and music industry. Commercialization of LED technology in 1968–1970 caused a boom in optoelectronics, and by the end of the 1970s the industry developed all principal types of opto-isolators. The majority of opto-isolators on the market use bipolar silicon phototransistor sensors. They attain medium data transfer speed, sufficient for applications like electroencephalography.The fastest opto-isolators use PIN diodes in photoconductive mode.

Operation

An opto-isolator contains a source (emitter) of light, almost always a near infrared light-emitting diode (LED), that converts electrical input signal into light, a closed optical channel (also called dielectrical channel), and a photosensor, which detects incoming light and either generates electric energy directly, or modulates electric current flowing from an external power supply. The sensor can be a photoresistor, a photodiode, a phototransistor, a silicon-controlled rectifier (SCR) or a triac. Because LEDs can sense light in addition to emitting it, construction of symmetrical, bidirectional opto-isolators is possible. An optocoupled solid state relay contains a photodiode opto-isolator which drives a power switch, usually a complementary pair of MOSFETs. A slotted optical switch contains a source of light and a sensor, but its optical channel is open, allowing modulation of light by external objects obstructing the path of light or reflecting light into the sensor.

Electric isolation

Planar (top) and silicone dome (bottom) layouts - cross-section through a standard dual in-line package. Relative sizes of LED (red) and sensor (green) are exaggerated.

Electronic equipment and signal and power transmission lines can be subjected to voltage surges induced by lightning, electrostatic discharge, radio frequency transmissions, switching pulses (spikes) and perturbations in power supply.[8] Remote lightning strikes can induce surges up to 10 kV, one thousand times more than the voltage limits of many electronic components.A circuit can also incorporate high voltages by design, in which case it needs safe, reliable means of interfacing its high-voltage components with low-voltage ones.

The main function of an opto-isolator is to block such high voltages and voltage transients, so that a surge in one part of the system will not disrupt or destroy the other parts. Historically, this function was delegated to isolation transformers, which use inductive coupling between galvanically isolated input and output sides. Transformers and opto-isolators are the only two classes of electronic devices that offer reinforced protection — they protect both the equipment and the human user operating this equipment. They contain a single physical isolation barrier, but provide protection equivalent to double isolation.[12] Safety, testing and approval of opto-couplers are regulated by national and international standards: IEC 60747-5-2, EN (CENELEC) 60747-5-2, UL 1577, CSA Component Acceptance Notice #5, etc.Opto-isolator specifications published by manufacturers always follow at least one of these regulatory frameworks.

An opto-isolator connects input and output sides with a beam of light modulated by input current. It transforms useful input signal into light, sends it across the dielectric channel, captures light on the output side and transforms it back into electric signal. Unlike transformers, which pass energy in both directions with very low losses, opto-isolators are unidirectional (see exceptions) and they cannot transmit power. Typical opto-isolators can only modulate the flow of energy already present on the output side. Unlike transformers, opto-isolators can pass DC or slow-moving signals and do not require matching impedances between input and output sides.[note 4] Both transformers and opto-isolators are effective in breaking ground loops, common in industrial and stage equipment, caused by high or noisy return currents in ground wires.

The physical layout of an opto-isolator depends primarily on the desired isolation voltage. Devices rated for less than a few kV have planar (or sandwich) construction.The sensor die is mounted directly on the lead frame of its package (usually, a six-pin or a four-pin dual in-line package). The sensor is covered with a sheet of glass or clear plastic, which is topped with the LED die. The LED beam fires downward. To minimize losses of light, the useful absorption spectrum of the sensor must match the output spectrum of the LED, which almost invariably lies in the near infrared. The optical channel is made as thin as possible for a desired breakdown voltage. For example, to be rated for short-term voltages of 3.75 kV and transients of 1 kV/μs, the clear polyimide sheet in the Avago ASSR-300 series is only 0.08 mm thick. Breakdown voltages of planar assemblies depend on the thickness of the transparent sheet and the configuration of bonding wires that connect the dies with external pins. Real in-circuit isolation voltage is further reduced by creepage over the PCB and the surface of the package. Safe design rules require a minimal clearance of 25 mm/kV for bare metal conductors or 8.3 mm/kV for coated conductors.

Opto-isolators rated for 2.5 to 6 kV employ a different layout called silicone dome. Here, the LED and sensor dies are placed on the opposite sides of the package; the LED fires into the sensor horizontally. The LED, the sensor and the gap between them are encapsulated in a blob, or dome, of transparent silicone. The dome acts as a reflector, retaining all stray light and reflecting it onto the surface of the sensor, minimizing losses in a relatively long optical channel. In double mold designs the space between the silicone blob ("inner mold") and the outer shell ("outer mold") is filled with dark dielectric compound with a matched coefficient of thermal expansion.

Types of opto-isolators

Device type Source of light Sensor type Speed Current transfer ratio

Resistive opto-isolator

(Vactrol) Incandescent light bulb CdS or CdSe photoresistor (LDR) Very low <100%[note 6]

Neon lamp Low

GaAs infrared LED Low

Diode opto-isolator GaAs infrared LED Silicon photodiode Highest 0.1–0.2%

Transistor opto-isolator GaAs infrared LED Bipolar silicon phototransistor Medium 2–120%

Darlington phototransistor Medium 100–600%

Opto-isolated SCR GaAs infrared LED Silicon-controlled rectifier Low to medium >100%

Opto-isolated triac GaAs infrared LED TRIAC Low to medium Very high

Solid-state relay Stack of GaAs infrared LEDs Stack of photodiodes driving

a pair of MOSFETs or an IGBT Low to high Practically unlimited

Resistive opto-isolators

The earliest opto-isolators, originally marketed as light cells, emerged in the 1960s. They employed miniature incandescent light bulbs as sources of light, and cadmium sulfide (CdS) or cadmium selenide (CdSe) photoresistors (also called light-dependent resistors, LDRs) as receivers. In applications where control linearity was not important, or where available current was too low for driving an incandescent bulb (as was the case in vacuum tube amplifiers), it was replaced with a neon lamp. These devices (or just their LDR component) were commonly named Vactrols, after a trademark of Vactec, Inc. The trademark has since been genericized, but the original Vactrols are still being manufactured by PerkinElmer.

The turn-on and turn-off lag of an incandescent bulb lies in hundreds of milliseconds range, which makes the bulb an effective low-pass filter and rectifier but limits the practical modulation frequency range to a few Hertz. With the introduction of light-emitting diodes (LEDs) in 1968–1970, the manufacturers replaced incandescent and neon lamps with LEDs and achieved response times of 5 milliseconds and modulation frequencies up to 250 Hz. The name Vactrol was carried over on LED-based devices which are, as of 2010, still produced in small quantities.

Photoresistors used in opto-isolators rely on bulk effects in a uniform film of semiconductor; there are no p-n junctions. Uniquely among photosensors, photoresistors are non-polar devices suited for either AC or DC circuits.Their resistance drops in reverse proportion to the intensity of incoming light, from virtually infinity to a residual floor that may be as low as less than a hundred Ohms. These properties made the original Vactrol a convenient and cheap automatic gain control and compressor for telephone networks. The photoresistors easily withstood voltages up to 400 volts, which made them ideal for driving vacuum fluorescent displays. Other industrial applications included photocopiers, industrial automation, professional light measurement instruments and auto-exposure meters. Most of these applications are now obsolete, but resistive opto-isolators retained a niche in audio, in particular guitar amplifier, markets.

American guitar and organ manufacturers of the 1960s embraced the resistive opto-isolator as a convenient and cheap tremolo modulator. Fender's early tremolo effects used two vacuum tubes; after 1964 one of these tubes was replaced by an optocoupler made of a LDR and a neon lamp.To date, Vactrols activated by pressing the stompbox pedal are ubiquitous in the music industry. Shortages of genuine PerkinElmer Vactrols forced the DIY guitar community to "roll their own" resistive opto-isolators. Guitarists to date prefer opto-isolated effects because their superior separation of audio and control grounds results in "inherently high quality of the sound". However, the distortion introduced by a photoresistor at line level signal is higher than that of a professional electrically-coupled voltage-controlled amplifier.Performance is further compromised by slow fluctuations of resistance owing to light history, a memory effect inherent in cadmium compounds. Such fluctuations take hours to settle and can be only partially offset with feedback in the control circuit.

Photodiode opto-isolators

A fast photodiode opto-isolator with an output-side amplifier circuit.

Diode opto-isolators employ LEDs as sources of light and silicon photodiodes as sensors. When the photodiode is reverse-biased with an external voltage source, incoming light increases the reverse current flowing through the diode. The diode itself does not generate energy; it modulates the flow of energy from an external source. This mode of operation is called photoconductive mode. Alternatively, in the absence of external bias the diode converts the energy of light into electric energy by charging its terminals to a voltage of up to 0.7 V. The rate of charge is proportional to the intensity of incoming light. The energy is harvested by draining the charge through an external high-impedance path; the ratio of current transfer can reach 0.2%. This mode of operation is called photovoltaic mode.

The fastest opto-isolators employ PIN diodes in photoconductive mode. The response times of PIN diodes lie in the subnanosecond range; overall system speed is limited by delays in LED output and in biasing circuitry. To minimize these delays, fast digital opto-isolators contain their own LED drivers and output amplifiers optimized for speed. These devices are called full logic opto-isolators: their LEDs and sensors are fully encapsulated within a digital logic circuit.[34] The Hewlett-Packard 6N137/HPCL2601 family of devices equipped with internal output amplifiers was introduced in the late 1970s and attained 10 MBd data transfer speed. It remained an industry standard until the introduction of the 50 MBd Agilent Technologies 7723/0723 family in 2002. The 7723/0723 series opto-isolators contain CMOS LED drivers and a CMOS buffered amplifiers, which require two independent external power supplies of 5 V each.

Photodiode opto-isolators can be used for interfacing analog signals, although their non-linearity invariably distorts the signal. A special class of analog opto-isolators introduced by Burr-Brown uses two photodiodes and an input-side operational amplifier to compensate for diode non-linearity. One of two identical diodes is wired into the feedback loop of the amplifier, which maintains overall current transfer ratio at a constant level regardless of the non-linearity in the second (output) diode.[38]

A novel idea of a particular optical analog signal isolator was submitted on 3, June 2011. The proposed configuration consist of two different parts. One of them transfers the signal, and the other establishes a negative feedback to ensure that the output signal has the same features as the input signal. This proposed analog isolator is linear over a wide range of input voltage and frequency. However linear opto couplers using this principle have been available for many years, for example the IL300.

Solid-state relays built around MOSFET switches usually employ a photodiode opto-isolator to drive the switch. The gate of a MOSFET requires relatively small total charge to turn on and its leakage current in steady state is very low. A photodiode in photovoltaic mode can generate turn-on charge in a reasonably short time but its output voltage is many times less than the MOSFET's threshold voltage. To reach the required threshold, solid-state relays contain stacks of up to thirty photodiodes wired in series.

Phototransistor opto-isolators

Phototransistors are inherently slower than photodiodes. The earliest and the slowest but still common 4N35 opto-isolator, for example, has rise and fall times of 5 μs into a 100 Ohm load and its bandwidth is limited at around 10 kilohertz - sufficient for applications like electroencephalography or pulse-width motor control. Devices like PC-900 or 6N138 recommended in the original 1983 Musical Instrument Digital Interface specification allow digital data transfer speeds of tens of kiloBauds.Phototransistors must be properly biased and loaded to achieve their maximum speeds, for example, the 4N28 operates at up to 50 kHz with optimum bias and less than 4 kHz without it.

Design with transistor opto-isolators requires generous allowances for wide fluctuations of parameters found in commercially available devices. Such fluctuations may be destructive, for example, when an opto-isolator in the feedback loop of a DC-to-DC converter changes its transfer function and causes spurious oscillations, or when unexpected delays in opto-isolators cause a short circuit through one side of an H-bridge.Manufacturers' datasheets typically list only worst-case values for critical parameters; actual devices surpass these worst-case estimates in an unpredictable fashion. Bob Pease observed that current transfer ratio in a batch of 4N28's can vary from 15% to more than 100%; the datasheet specified only a minimum of 10%. Transistor beta in the same batch can vary from 300 to 3000, resulting in 10:1 variance in bandwidth.

Opto-isolators using field-effect transistors (FETs) as sensors are rare and, like vactrols, can be used as remote-controlled analog potentiometers provided that the voltage across the FET's output terminal does not exceed a few hundred mV.[38] Opto-FETs turn on without injecting switching charge in the output circuit, which is particularly useful in sample and hold circuits.

Bidirectional opto-isolators

All opto-isolators described so far are uni-directional. Optical channel always works one way, from the source (LED) to the sensor. The sensors, be it photoresistors, photodiodes or phototransistors, cannot emit light. But LEDs, like all semiconductor diodes, are capable of detecting incoming light, which makes possible construction of a two-way opto-isolator from a pair of LEDs. The simplest bidirectional opto-isolator is merely a pair of LEDs placed face to face and held together with heat-shrink tubing. If necessary, the gap between two LEDs can be extended with a glass fiber insert.

Visible spectrum LEDs have relatively poor transfer efficiency, thus near infrared spectrum GaAs, GaAs:Si and AlGaAs:Si LEDs are the preferred choice for bidirectional devices. Bidirectional opto-isolators built around pairs of GaAs:Si LEDs have current transfer ratio of around 0.06% in either photovoltaic or photoconductive mode — less than photodiode-based isolators, but sufficiently practical for real-world applications.

Aerospace engineering with extensive concepts?

Aerospace engineering

Aerospace engineering is the primary field of engineering concerned with the development of aircraft and spacecraft. It has two major and overlapping branches: aeronautical engineering and astronautical engineering. Avionics engineering is similar but deals with the electrical side of aerospace engineering.

assembly of equipments

Aeronautical engineering was the original term for the field. As flight technology advanced to include craft operating in outer space (astronautics), the broader term "aerospace engineering" has largely replaced it in common usage. Aerospace engineering, particularly the astronautics branch, is often colloquially referred to as "rocket science".

Overview

Flight vehicles are subjected to demanding conditions such as those produced by changes in atmospheric pressure and temperature, with structural loads applied upon vehicle components. Consequently, they are usually the products of various technological and engineering disciplines including aerodynamics, propulsion, avionics, materials science, structural analysis and manufacturing. The interaction between these technologies is known as aerospace engineering. Because of the complexity and number of disciplines involved, aerospace engineering is carried out by teams of engineers, each having their own specialized area of expertise.

History

Orville and Wilbur Wright flew the Wright Flyer in 1903 at Kitty Hawk, North Carolina.

The origin of aerospace engineering can be traced back to the aviation pioneers around the late 19th to early 20th centuries, although the work of Sir George Cayley dates from the last decade of the 18th to mid-19th century. One of the most important people in the history of aeronautics, Cayley was a pioneer in aeronautical engineering and is credited as the first person to separate the forces of lift and drag, which are in effect on any flight vehicle. Early knowledge of aeronautical engineering was largely empirical with some concepts and skills imported from other branches of engineering. Scientists understood some key elements of aerospace engineering, like fluid dynamics, in the 18th century. Many years later after the successful flights by the Wright brothers, the 1910s saw the development of aeronautical engineering through the design of World War I military aircraft.

The first definition of aerospace engineering appeared in February 1958. The definition considered the Earth's atmosphere and the outer space as a single realm, thereby encompassing both aircraft (aero) and spacecraft (space) under a newly coined word aerospace. In response to the USSR launching the first satellite, Sputnik into space on October 4, 1957, U.S. aerospace engineers launched the first American satellite on January 31, 1958. The National Aeronautics and Space Administration was founded in 1958 as a response to the Cold War.

This section needs expansion with: newer history, including recent events. You can help by adding to it. (November 2009)

Elements

Wernher von Braun, with the F-1 engines of the Saturn V first stage at the US Space and Rocket Center

Soyuz TMA-14M spacecraft engineered for descent by parachute

See also: List of aerospace engineering topics

Some of the elements of aerospace engineering are:

A fighter jet engine undergoing testing. The tunnel behind the engine allows noise and exhaust to escape.

Radar cross-section – the study of vehicle signature apparent to Radar remote sensing.

Fluid mechanics – the study of fluid flow around objects. Specifically aerodynamics concerning the flow of air over bodies such as wings or through objects such as wind tunnels (see also lift and aeronautics).

Astrodynamics – the study of orbital mechanics including prediction of orbital elements when given a select few variables. While few schools in the United States teach this at the undergraduate level, several have graduate programs covering this topic (usually in conjunction with the Physics department of said college or university).

Statics and Dynamics (engineering mechanics) – the study of movement, forces, moments in mechanical systems.

Mathematics – in particular, calculus, differential equations, and linear algebra.

Electrotechnology – the study of electronics within engineering.

Propulsion – the energy to move a vehicle through the air (or in outer space) is provided by internal combustion engines, jet engines and turbomachinery, or rockets (see also propeller and spacecraft propulsion). A more recent addition to this module is electric propulsion and ion propulsion.

Control engineering – the study of mathematical modeling of the dynamic behavior of systems and designing them, usually using feedback signals, so that their dynamic behavior is desirable (stable, without large excursions, with minimum error). This applies to the dynamic behavior of aircraft, spacecraft, propulsion systems, and subsystems that exist on aerospace vehicles.

Aircraft structures – design of the physical configuration of the craft to withstand the forces encountered during flight. Aerospace engineering aims to keep structures lightweight and low-cost, while maintaining structural integrity

Materials science – related to structures, aerospace engineering also studies the materials of which the aerospace structures are to be built. New materials with very specific properties are invented, or existing ones are modified to improve their performance.

Solid mechanics – Closely related to material science is solid mechanics which deals with stress and strain analysis of the components of the vehicle. Nowadays there are several Finite Element programs such as MSC Patran/Nastran which aid engineers in the analytical process.

Aeroelasticity – the interaction of aerodynamic forces and structural flexibility, potentially causing flutter, divergence, etc.

Avionics – the design and programming of computer systems on board an aircraft or spacecraft and the simulation of systems.

Software – the specification, design, development, test, and implementation of computer software for aerospace applications, including flight software, ground control software, test & evaluation software, etc.

Risk and reliability – the study of risk and reliability assessment techniques and the mathematics involved in the quantitative methods.

Noise control – the study of the mechanics of sound transfer.

Aeroacoustics – the study of noise generation via either turbulent fluid motion or aerodynamic forces interacting with surfaces.

Flight test – designing and executing flight test programs in order to gather and analyze performance and handling qualities data in order to determine if an aircraft meets its design and performance goals and certification requirements.

The basis of most of these elements lies in theoretical physics, such as fluid dynamics for aerodynamics or the equations of motion for flight dynamics. There is also a large empirical component. Historically, this empirical component was derived from testing of scale models and prototypes, either in wind tunnels or in the free atmosphere. More recently, advances in computing have enabled the use of computational fluid dynamics to simulate the behavior of fluid, reducing time and expense spent on wind-tunnel testing. Those studying hydrodynamics or Hydroacoustics often obtained degrees in Aerospace Engineering.

Additionally, aerospace engineering addresses the integration of all components that constitute an aerospace vehicle (subsystems including power, aerospace bearings, communications, thermal control, life support, etc.) and its life cycle (design, temperature, pressure, radiation, velocity, lifetime).

Degree programs

Main article: List of aerospace engineering schools

Aerospace engineering may be studied at the advanced diploma, bachelor's, master's, and Ph.D. levels in aerospace engineering departments at many universities, and in mechanical engineering departments at others. A few departments offer degrees in space-focused astronautical engineering. Some institutions differentiate between aeronautical and astronautical engineering. Graduate degrees are offered in advanced or specialty areas for the aerospace industry.

A background in chemistry, physics, computer science and mathematics is important for students pursuing an aerospace engineering degree.

In popular culture

The term "rocket scientist" is sometimes used to describe a person of great intelligence since "rocket science" is seen as a practice requiring great mental ability, especially technical and mathematical ability. The term is used ironically in the expression "It's not rocket science" to indicate that a task is simple. Strictly speaking, the use of "science" in "rocket science" is a misnomer since science is about understanding the origins, nature, and behavior of the universe; engineering is about using scientific and engineering principles to solve problems and develop new technology. However, the media and the public often use "science" and "engineering" as synonyms.

Concepts of electronic engineering?

Printed circuit board

Electronics engineering, or electronic engineering, is an electrical engineering discipline which utilizes non-linear and active electrical components (such as semiconductor devices, especially transistors, diodes and integrated circuits) to design electronic circuits, devices, microprocessors, microcontrollers and other systems. The discipline typically also designs passive electrical components, usually based on printed circuit boards.

Electronics is a subfield within the wider electrical engineering academic subject but denotes a broad engineering field that covers subfields such as analog electronics, digital electronics, consumer electronics, embedded systems and power electronics. Electronics engineering deals with implementation of applications, principles and algorithms developed within many related fields, for example solid-state physics, radio engineering, telecommunications, control systems, signal processing, systems engineering, computer engineering, instrumentation engineering, electric power control, robotics, and many others.

The Institute of Electrical and Electronics Engineers (IEEE) is one of the most important and influential organizations for electronics engineers.

Relationship to electrical engineering

Electronics is a subfield within the wider electrical engineering academic subject. An academic degree with a major in electronics engineering can be acquired from some universities, while other universities use electrical engineering as the subject. The term electrical engineer is still used in the academic world to include electronic engineers. However, some people consider the term 'electrical engineer' should be reserved for those having specialized in power and heavy current or high voltage engineering, while others consider that power is just one subset of electrical engineering, as well as 'electrical distribution engineering'. The term 'power engineering' is used as a descriptor in that industry. Again, in recent years there has been a growth of new separate-entry degree courses such as 'information engineering', 'systems engineering' and 'communication systems engineering', often followed by academic departments of similar name, which are typically not considered as subfields of electronics engineering but of electrical engineering.

Electronics

In the field of electronic engineering, engineers design and test circuits that use the electromagnetic properties of electrical components such as resistors, capacitors, inductors, diodes and transistors to achieve a particular functionality. The tuner circuit, which allows the user of a radio to filter out all but a single station, is just one example of such a circuit.

In designing an integrated circuit, electronics engineers first construct circuit schematics that specify the electrical components and describe the interconnections between them. When completed, VLSI engineers convert the schematics into actual layouts, which map the layers of various conductor and semiconductor materials needed to construct the circuit. The conversion from schematics to layouts can be done by software (see electronic design automation) but very often requires human fine-tuning to decrease space and power consumption. Once the layout is complete, it can be sent to a fabrication plant for manufacturing.

For systems of intermediate complexity engineers may use VHDL modelling for programmable logic devices and FPGAs

Integrated circuits, FPGAs and other electrical components can then be assembled on printed circuit boards to form more complicated circuits. Today, printed circuit boards are found in most electronic devices including televisions, computers and audio player.

Subfields

Electronic engineering has many subfields. This section describes some of the most popular subfields in electronic engineering; although there are engineers who focus exclusively on one subfield, there are also many who focus on a combination of subfields.

Signal processing deals with the analysis and manipulation of signals. Signals can be either analog, in which case the signal varies continuously according to the information, or digital, in which case the signal varies according to a series of discrete values representing the information.

For analog signals, signal processing may involve the amplification and filtering of audio signals for audio equipment or the modulation and demodulation of signals for telecommunications. For digital signals, signal processing may involve the compression, error checking and error detection of digital signals.

Telecommunications engineering deals with the transmission of information across a channel such as a co-axial cable, optical fiber or free space.

Transmissions across free space require information to be encoded in a carrier wave in order to shift the information to a carrier frequency suitable for transmission, this is known as modulation. Popular analog modulation techniques include amplitude modulation and frequency modulation. The choice of modulation affects the cost and performance of a system and these two factors must be balanced carefully by the engineer.

Once the transmission characteristics of a system are determined, telecommunication engineers design the transmitters and receivers needed for such systems. These two are sometimes combined to form a two-way communication device known as a transceiver. A key consideration in the design of transmitters is their power consumption as this is closely related to their signal strength. If the signal strength of a transmitter is insufficient the signal's information will be corrupted by noise.

Control engineering has a wide range of applications from the flight and propulsion systems of commercial airplanes to the cruise control present in many modern cars. It also plays an important role in industrial automation.

Control engineers often utilize feedback when designing control systems. For example, in a car with cruise control the vehicle's speed is continuously monitored and fed back to the system which adjusts the engine's power output accordingly. Where there is regular feedback, control theory can be used to determine how the system responds to such feedback.

Instrumentation engineering deals with the design of devices to measure physical quantities such as pressure, flow and temperature. These devices are known as instrumentation.

The design of such instrumentation requires a good understanding of physics that often extends beyond electromagnetic theory. For example, radar guns use the Doppler effect to measure the speed of oncoming vehicles. Similarly, thermocouples use the Peltier–Seebeck effect to measure the temperature difference between two points.

Often instrumentation is not used by itself, but instead as the sensors of larger electrical systems. For example, a thermocouple might be used to help ensure a furnace's temperature remains constant. For this reason, instrumentation engineering is often viewed as the counterpart of control engineering.

Computer engineering deals with the design of computers and computer systems. This may involve the design of new computer hardware, the design of PDAs or the use of computers to control an industrial plant. Development of embedded systems—systems made for specific tasks (e.g., mobile phones)—is also included in this field. This field includes the micro controller and its applications. Computer engineers may also work on a system's software. However, the design of complex software systems is often the domain of software engineering, which is usually considered a separate discipline.

VLSI design engineering VLSI stands for very large scale integration. It deals with fabrication of ICs and various electronics components.

Education and training

Electronics engineers typically possess an academic degree with a major in electronic engineering. The length of study for such a degree is usually three or four years and the completed degree may be designated as a Bachelor of Engineering, Bachelor of Science, Bachelor of Applied Science, or Bachelor of Technology depending upon the university. Many UK universities also offer Master of Engineering (MEng) degrees at undergraduate level.

Some electronics engineers also choose to pursue a postgraduate degree such as a Master of Science (MSc), Doctor of Philosophy in Engineering (PhD), or an Engineering Doctorate (EngD). The master's degree is being introduced in some European and American Universities as a first degree and the differentiation of an engineer with graduate and postgraduate studies is often difficult. In these cases, experience is taken into account. The master's degree may consist of either research, coursework or a mixture of the two. The Doctor of Philosophy consists of a significant research component and is often viewed as the entry point to academia.

In most countries, a bachelor's degree in engineering represents the first step towards certification and the degree program itself is certified by a professional body. After completing a certified degree program the engineer must satisfy a range of requirements (including work experience requirements) before being certified. Once certified the engineer is designated the title of Professional Engineer (in the United States, Canada and South Africa), Chartered Engineer or Incorporated Engineer (in the United Kingdom, Ireland, India and Zimbabwe), Chartered Professional Engineer (in Australia and New Zealand) or European Engineer (in much of the European Union).

Some trained physicists may also choose to become Electronic Engineers.

A degree in electronics generally includes units covering physics, chemistry, mathematics, project management and specific topics in electrical engineering. Initially such topics cover most, if not all, of the subfields of electronic engineering. Students then choose to specialize in one or more subfields towards the end of the degree.

Fundamental to the discipline are the sciences of physics and mathematics as these help to obtain both a qualitative and quantitative description of how such systems will work. Today most engineering work involves the use of computers and it is commonplace to use computer-aided design and simulation software programs when designing electronic systems. Although most electronic engineers will understand basic circuit theory, the theories employed by engineers generally depend upon the work they do. For example, quantum mechanics and solid state physics might be relevant to an engineer working on VLSI but are largely irrelevant to engineers working with macroscopic electrical systems.

Apart from electromagnetics and network theory, other items in the syllabus are particular to electronics engineering course. Electrical engineering courses have other specialisms such as machines, power generation and distribution. This list does not include the extensive engineering mathematics curriculum that is a prerequisite to a degree.

Electromagnetics

Elements of vector calculus: divergence and curl; Gauss' and Stokes' theorems, Maxwell's equations: differential and integral forms. Wave equation, Poynting vector. Plane waves: propagation through various media; reflection and refraction; phase and group velocity; skin depth. Transmission lines: characteristic impedance; impedance transformation; Smith chart; impedance matching; pulse excitation. Waveguides: modes in rectangular waveguides; boundary conditions; cut-off frequencies; dispersion relations. Antennas: Dipole antennas; antenna arrays; radiation pattern; reciprocity theorem, antenna gain.

Network analysis

Network graphs: matrices associated with graphs; incidence, fundamental cut set and fundamental circuit matrices. Solution methods: nodal and mesh analysis. Network theorems: superposition, Thevenin and Norton's maximum power transfer, Wye-Delta transformation. Steady state sinusoidal analysis using phasors. Linear constant coefficient differential equations; time domain analysis of simple RLC circuits, Solution of network equations using Laplace transform: frequency domain analysis of RLC circuits. 2-port network parameters: driving point and transfer functions. State equations for networks.

Electronic devices and circuits

Electronic devices: Energy bands in silicon, intrinsic and extrinsic silicon. Carrier transport in silicon: diffusion current, drift current, mobility, resistivity. Generation and recombination of carriers. p-n junction diode, Zener diode, tunnel diode, BJT, JFET, MOS capacitor, MOSFET, LED, p-i-n and avalanche photo diode, LASERs. Device technology: integrated circuit fabrication process, oxidation, diffusion, ion implantation, photolithography, n-tub, p-tub and twin-tub CMOS process.

Analog circuits: Equivalent circuits (large and small-signal) of diodes, BJTs, JFETs, and MOSFETs. Simple diode circuits, clipping, clamping, rectifier. Biasing and bias stability of transistor and FET amplifiers. Amplifiers: single-and multi-stage, differential, operational, feedback and power. Analysis of amplifiers; frequency response of amplifiers. Simple op-amp circuits. Filters. Sinusoidal oscillators; criterion for oscillation; single-transistor and op-amp configurations. Function generators and wave-shaping circuits, Power supplies.

Digital circuits: Boolean functions (NOT, AND, OR, XOR,...). Logic gates digital IC families (DTL, TTL, ECL, MOS, CMOS). Combinational circuits: arithmetic circuits, code converters, multiplexers and decoders. Sequential circuits: latches and flip-flops, counters and shift-registers. Sample and hold circuits, ADCs, DACs. Semiconductor memories. Microprocessor 8086: architecture, programming, memory and I/O interfacing.

Signals and systems

Definitions and properties of Laplace transform, continuous-time and discrete-time Fourier series, continuous-time and discrete-time Fourier Transform, z-transform. Sampling theorems. Linear Time-Invariant (LTI) Systems: definitions and properties; causality, stability, impulse response, convolution, poles and zeros frequency response, group delay, phase delay. Signal transmission through LTI systems. Random signals and noise: probability, random variables, probability density function, autocorrelation, power spectral density, function analogy between vectors & functions.

Control systems

Basic control system components; block diagrammatic description, reduction of block diagrams — Mason's rule. Open loop and closed loop (negative unity feedback) systems and stability analysis of these systems. Signal flow graphs and their use in determining transfer functions of systems; transient and steady state analysis of LTI control systems and frequency response. Analysis of steady-state disturbance rejection and noise sensitivity.

Tools and techniques for LTI control system analysis and design: root loci, Routh-Hurwitz stability criterion, Bode and Nyquist plots. Control system compensators: elements of lead and lag compensation, elements of Proportional-Integral-Derivative controller (PID). Discretization of continuous time systems using Zero-order hold (ZOH) and ADCs for digital controller implementation. Limitations of digital controllers: aliasing. State variable representation and solution of state equation of LTI control systems. Linearization of Nonlinear dynamical systems with state-space realizations in both frequency and time domains. Fundamental concepts of controllability and observability for MIMO LTI systems. State space realizations: observable and controllable canonical form. Ackermann's formula for state-feedback pole placement. Design of full order and reduced order estimators.

Communications

Analog communication systems: amplitude and angle modulation and demodulation systems, spectral analysis of these operations, superheterodyne noise conditions.

Digital communication systems: pulse code modulation (PCM), Differential Pulse Code Modulation (DPCM), Delta modulation (DM), digital modulation schemes-amplitude, phase and frequency shift keying schemes (ASK, PSK, FSK), matched filter receivers, bandwidth consideration and probability of error calculations for these schemes, GSM, TDMA.

Professional bodies

Professional bodies of note for electrical engineers include the Institute of Electrical and Electronics Engineers (IEEE) and the Institution of Electrical Engineers (IEE) (now renamed the Institution of Engineering and Technology or IET). Members of the Institution of Engineering and Technology (MIET) are recognised professionally in Europe, as Electrical and computer (technology) engineers. The IEEE claims to produce 30 percent of the world's literature in electrical/electronic engineering, has over 430,000 members, and holds more than 450 IEEE sponsored or cosponsored conferences worldwide each year. SMIEEE is a recognised professional designation in the United States.

Project engineering

For most engineers not involved at the cutting edge of system design and development, technical work accounts for only a fraction of the work they do. A lot of time is also spent on tasks such as discussing proposals with clients, preparing budgets and determining project schedules. Many senior engineers manage a team of technicians or other engineers and for this reason project management skills are important. Most engineering projects involve some form of documentation and strong written communication skills are therefore very important.

The workplaces of electronics engineers are just as varied as the types of work they do. Electronics engineers may be found in the pristine laboratory environment of a fabrication plant, the offices of a consulting firm or in a research laboratory. During their working life, electronics engineers may find themselves supervising a wide range of individuals including scientists, electricians, computer programmers and other engineers.

Obsolescence of technical skills is a serious concern for electronics engineers. Membership and participation in technical societies, regular reviews of periodicals in the field and a habit of continued learning are therefore essential to maintaining proficiency. And these are mostly used in the field of consumer electronics products.

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The Watt steam engine, a major driver in the industrial revolution, underscores the importance of engineering in modern history. This model is on display at the main building of the ETSIIM in Madrid, Spain

The concept of engineering has existed since ancient times as humans devised fundamental inventions such as the pulley, lever, and wheel. Each of these inventions is consistent with the modern definition of engineering, exploiting basic mechanical principles to develop useful tools and objects.

The term engineering itself has a much more recent etymology, deriving from the word engineer, which itself dates back to 1325, when an engine’er (literally, one who operates an engine) originally referred to "a constructor of military engines."[1] In this context, now obsolete, an "engine" referred to a military machine, i. e., a mechanical contraption used in war (for example, a catapult). The word "engine" itself is of even older origin, ultimately deriving from the Latin ingenium , meaning "innate quality, especially mental power, hence a clever invention."

Later, as the design of civilian structures such as bridges and buildings matured as a technical discipline, the term civil engineering[3] entered the lexicon as a way to distinguish between those specializing in the construction of such non-military projects and those involved in the older discipline of military engineering (the original meaning of the word "engineering," now largely obsolete, with notable exceptions that have survived to the present day such as military engineering corps, e. g., the U. S. Army Corps of Engineers).

Ancient Era

The Acropolis and the Parthenon in Greece, the Roman Roman aqueducts, Via Appia and the Colosseum, the Hanging Gardens of Babylon, the Pharos of Alexandria, the pyramids in Egypt, Teotihuacán and the cities and pyramids of the Mayan, Inca and Aztec Empires, cities of the Indus Valley Civilization, the Great Wall of China, among many others, stand as a testament to the ingenuity and skill of the ancient civil and military engineers.

The earliest civil engineer known by name is Imhotep. As one of the officials of the Pharaoh, Djosèr, he probably designed and supervised the construction of the Pyramid of Djoser (a Step Pyramid) at Saqqara in Egypt around 2630-2611 BC. He may also have been responsible for the first known use of columns in architecture.

Ancient Greece developed machines, both in the civilian and military domains. The Antikythera mechanism, the earliest known model of a mechanical computer in history, and the mechanical inventions of Archimedes are examples of early mechanical engineering. Some of Archimedes' inventions, as well as the Antikythera mechanism, required sophisticated knowledge of differential gearing or epicyclic gearing, two key principles in machine theory that helped design the gear trains of the Industrial revolution and are still widely used today in diverse fields such as robotics and automotive engineering.

Chinese and Roman armies employed complex military machines including the Ballista and catapult. In the Middle Ages, the Trebuchet was developed.

Middle Era

An Artuki by the name of Al-Jazari built five machines to pump water for the kings of the Turkish Artuqid dynasty and their palaces. Besides over 50 ingenious mechanical devices, Al-Jazari also developed and made innovations to segmental gears, mechanical controls, escapement mechanisms, clocks, robotics, and protocols for designing and manufacturing methods.

Renaissance Era

The first steam engine was built in 1698 by mechanical engineer Thomas Savery. The development of this device gave rise to the industrial revolution in the coming decades, allowing for the beginnings of mass production.

With the rise of engineering as a profession in the 18th century, the term became more narrowly applied to fields in which mathematics and science were applied to these ends. Similarly, in addition to military and civil engineering, the fields then known as the mechanic arts became incorporated into engineering.

The following images are samples from a deck of cards illustrating engineering instruments in England in 1702. They illustrate a range of engineering specializations, that would eventually become known as civil engineering, mechanical engineering, geodesy and geomatics, and so on.

Each card includes a caption explaining the purpose of the instrument:

Four of hearts: Sea quadrant

Nine of diamonds: Dyals (dials)

Six of diamonds: Circumferentor

Eight of diamonds: the Compass

King of spades: Spheres

Knave of hearts: Surveying wheel and chains

Knave of spades: Leavell

One of diamonds: Mathematical instruments

Queen of diamonds: Projections of the sphere

Queen of spades: Astronomical quadrant

Three of diamonds: Gauger (gauges)

Two of clubs: Theodolet and semi-circle

Modern era

The inventions of Thomas Savery and the Scottish engineer James Watt gave rise to modern Mechanical Engineering. The development of specialized machines and their maintenance tools during the industrial revolution led to the rapid growth of Mechanical Engineering both in its birthplace Britain and abroad.

The discipline of Electrical Engineering was shaped by the experiments of Alessandro Volta in the 19th century, the experiments of Michael Faraday, Georg Ohm and others and the invention of the electric motor in 1872. Electrical engineering became a profession late in the 19th century. Practitioners had created a global electric telegraph network and the first electrical engineering institutions to support the new discipline were founded in the UK and USA. Although it is impossible to precisely pinpoint a first electrical engineer, Francis Ronalds stands ahead of the field, who created the first working electric telegraph system in 1816 and documented his vision of how the world could be transformed by electricity.

The work of James Maxwell and Heinrich Hertz in the late 19th century gave rise to the field of Electronics. The later inventions of the vacuum tube and the transistor further accelerated the development of Electronics to such an extent that electrical and electronics engineers currently outnumber their colleagues of any other Engineering specialty.

Chemical Engineering, like its counterpart Mechanical Engineering, developed in the 19th century during the Industrial Revolution. Industrial scale manufacturing demanded new materials and new processes and by 1880 the need for large scale production of chemicals was such that a new industry was created, dedicated to the development and large scale manufacturing of chemicals in new industrial plants. The role of the chemical engineer was the design of these chemical plants and processes.

Aeronautical Engineering deals with aircraft design while Aerospace Engineering is a more modern term that expands the reach envelope of the discipline by including spacecraft design.Its origins can be traced back to the aviation pioneers around the turn of the 20th century although the work of Sir George Cayley has recently been dated as being from the last decade of the 18th century. Early knowledge of aeronautical engineering was largely empirical with some concepts and skills imported from other branches of engineering. Only a decade after the successful flights by the Wright brothers, the 1920s saw extensive development of aeronautical engineering through development of World War I military airc

raft. Meanwhile, research to provide fundamental background science continued by combining theoretical physics with experiments.

The first PhD in engineering (technically, applied science and engineering) awarded in the United States went to Willard Gibbs at Yale University in 1863; it was also the second PhD awarded in science in the U.S.

In 1990, with the rise of computer technology, the first search engine was built by computer engineer Alan Emtage.