1.
Lighting control system
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Lighting control systems are widely used on both indoor and outdoor lighting of commercial, industrial, and residential spaces. Lighting control systems serve to provide the right amount of light where, Lighting control systems are employed to maximize the energy savings from the lighting system, satisfy building codes, or comply with green building and energy conservation programs. Lighting control systems are referred to under the term Smart Lighting. The term lighting controls is used to indicate stand-alone control of the lighting within a space. This may include sensors, timeclocks, and photocells that are hard-wired to control fixed groups of lights independently. Adjustment occurs manually at each devices location, the efficiency of and market for residential lighting controls has been characterized by the Consortium for Energy Efficiency. The term lighting control system refers to an intelligent networked system of devices related to lighting control and these devices may include relays, occupancy sensors, photocells, light control switches or touchscreens, and signals from other building systems. Adjustment of the system occurs both at device locations and at central computer locations via software programs or other interface devices and this ability to control multiple light sources from a user device allows complex lighting scenes to be created. A room may have multiple scenes pre-set, each one created for different activities in the room, a major benefit of lighting control systems is reduced energy consumption. Longer lamp life is gained when dimming and switching off lights when not in use. Wireless lighting control systems provide additional benefits including reduced installation costs and increased flexibility over where switches, astronomical time schedules incorporate sunrise and sunset times, often used to switch outdoor lighting. Astronomical time scheduling requires that the location of the building be set, space occupancy is primarily determined with occupancy sensors. Electric lighting energy use can be adjusted by automatically dimming and/or switching electric lights in response to the level of available daylight, reducing the amount of electric lighting used when daylight is available is known as daylight harvesting. Alarm conditions typically include inputs from other building systems such as the alarm or HVAC system. Program logic can tie all of the elements together using constructs such as if-then-else statements. In the 1980s there was a requirement to make commercial lighting more controllable so that it could become more energy efficient. Initially this was done with control, allowing fluorescent ballasts. This was a step in the direction, but cabling was complicated
2.
Occupancy sensor
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Occupancy sensors are typically used to save energy, provide automatic control, and comply with building codes. Types of occupancy sensors include, Passive infrared sensor, which works on heat movement detection, inside of device is a pyroelectric sensor calibrated to detect infrared radiation radiated by human body movement. Based on the detection, the sensor operates and starts lighting load connected to it and it works on the doppler shift principle. An ultrasonic sensor will send high frequency sound waves in area, if the reflected pattern is changing continuously then it assumes that there is occupancy and the lighting load connected is turned on. If the reflected pattern is the same for a time then the sensor assumes there is no occupancy. Similar to the sensor, a microwave sensor also works on the doppler shift principle. A microwave sensor will send high frequency microwaves in an area, if the reflected pattern is changing continuously then it assumes that there is occupancy and the lighting load connected is turned on. If the reflected pattern is the same for a time then the sensor assumes there is no occupancy. A microwave sensor has high sensitivity as well as detection range compared to other types of sensors. Key-card, an energy management system used to detect when a hotel room is occupied, by requiring the guest to place their key in a slot to turn on the lights. Motion sensors are used in indoor spaces to control electric lighting. If no motion is detected, it is assumed that the space is empty, turning off the lights in such circumstances can save substantial amounts of energy. In lighting practice occupancy sensors are also called presence sensors or vacancy sensors. Some occupancy sensors also classify the number of occupants, their direction of motion, pixelview is a camera-based occupancy sensor, using a camera that is built into each light fixture. Occupancy sensors for lighting control typically use infrared, ultrasonic, tomographic motion detection, microwave sensors, the field of view of the sensor must be carefully selected/adjusted so that it responds only to motion in the space served by the controlled lighting. For example, an occupancy sensor controlling lights in an office should not detect motion in the corridor outside the office, sensors and their placement are never perfect, therefore most systems incorporate a delay time before switching. This delay time is often user-selectable, but a default value is 15 minutes. This means that the sensor must detect no motion for the delay time before the lights are switched
3.
Smart lighting
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Smart lighting is a lighting technology designed for energy efficiency. This may include high efficiency fixtures and automated controls that make adjustments based on such as occupancy or daylight availability. Lighting is the application of light to achieve some aesthetic or practical effect. It includes task lighting, accent lighting, and general lighting, 19% of energy use in the world is used for lighting, and 6% of greenhouse emissions in the world derive from this energy used for lighting. In the United States,65 percent of consumption is used by commercial and industrial sectors. Smart lighting is the way which enables to minimize and save light by allowing the householder to control remotely cooling and heating, lighting. This ability saves energy and provides a level of comfort and convenience, from outside the traditional lighting industry, the future success of lighting will require involvement of a number of stakeholders and stakeholder communities. The concept of smart lighting also involves utilizing natural light from the sun to reduce the use of lighting. The use of automatic light dimming is an aspect of smart lighting that serves to reduce energy consumption, manual light dimming also has the same effect of reducing energy use. In the paper Energy savings due to occupancy sensors and personal controls, a complete sensor consists of a motion detector, an electronic control unit, and a controllable switch/relay. The detector senses motion and determines whether there are occupants in the space and it also has a timer that signals the electronic control unit after a set period of inactivity. The control unit uses this signal to activate the switch/relay to turn equipment on or off, for lighting applications, there are three main sensor types, passive infrared, ultrasonic, and hybrid. In response to daylighting technology, daylight-linked automated response systems have developed to further reduce energy consumption. These technologies are helpful, but they do have their downfalls, many times, rapid and frequent switching of the lights on and off can occur, particularly during unstable weather conditions or when daylight levels are changing around the switching illuminance. Not only does this disturb occupants, it can also reduce lamp life, a variation of this technology is the differential switching or dead-band photoelectric control which has multiple illuminances it switches from to reduce occupants being disturbed. Smart lighting that utilizes occupancy sensors can work in unison with other lighting connected to the network to adjust lighting per various conditions. The table below shows potential electricity savings from using occupancy sensors to control lighting in various types of spaces. The advantages of devices are that they are sensitive to all types of motion and generally there are zero coverage gaps
4.
Security alarm
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A security alarm is a system designed to detect intrusion – unauthorized entry – into a building or area. Security alarms are used in residential, commercial, industrial, and military properties for protection against burglary or property damage, car alarms likewise protect vehicles and their contents. Prisons also use security systems for control of inmates, some alarm systems serve a single purpose of burglary protection, combination systems provide both fire and intrusion protection. Systems range from small, self-contained noisemakers, to complicated, multi-area systems with computer monitoring and it may even include two-way voice which allows communication between the panel and Monitoring station. The most basic consists of one or more sensors to detect intruders. In modern systems, this is one or more computer circuit boards inside a metal enclosure. Sensors may be placed at the perimeter of the area, within it. Sensors can detect intruders by a variety of methods, such as monitoring doors and windows for opening, or by monitoring unoccupied interiors for motions, sound, vibration, alerting devices, These indicate an alarm condition. Most commonly, these are bells, sirens, and/or flashing lights, alerting devices serve the dual purposes of warning occupants of intrusion, and potentially scaring off burglars. These devices may also be used to warn occupants of a fire or smoke condition, keypads, Small devices, typically wall-mounted, which function as the human-machine interface to the system. In addition to buttons, keypads typically feature indicator lights, a small multi-character display and this may consist of direct wiring to the control unit, or wireless links with local power supplies. Security devices, Devices to detect unauthorized entry or movements such as spotlights, in addition to the system itself, security alarms are often coupled with a monitoring service. In the event of an alarm, the control unit contacts a central monitoring station. Operators at the see the signal and take appropriate action, such as contacting property owners, notifying police. Such signals may be transmitted via dedicated alarm circuits, telephone lines, when the magnet is moved away from the reed switch, the reed switch either closes or opens, again based on whether or not the design is normally open or normally closed. This action coupled with an electric current allows an alarm control panel to detect a fault on that zone or circuit. These type of sensors are very common and are found either wired directly to a control panel. The passive infrared detector is one of the most common sensors found in household
5.
Closed-circuit television
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Closed-circuit television, also known as video surveillance, is the use of video cameras to transmit a signal to a specific place, on a limited set of monitors. It differs from broadcast television in that the signal is not openly transmitted, though it may point to point, point to multipoint. Videotelephony is seldom called CCTV but the use of video in distance education, Surveillance of the public using CCTV is common in many areas around the world. In recent years, the use of body worn video cameras has been introduced as a new form of surveillance, video surveillance has generated significant debate about balancing its use with individuals right to privacy even when in public. In industrial plants, CCTV equipment may be used to observe parts of a process from a control room. CCTV systems may operate continuously or only as required to monitor a particular event, a more advanced form of CCTV, utilizing digital video recorders, provides recording for possibly many years, with a variety of quality and performance options and extra features. More recently, decentralized IP cameras, some equipped with sensors, support recording directly to network-attached storage devices. There are about 350 million surveillance cameras worldwide as of 2016, about 65% of these cameras are installed in Asia. The growth of CCTV has been slowing in recent years, the first CCTV system was installed by Siemens AG at Test Stand VII in Peenemünde, Nazi Germany in 1942, for observing the launch of V-2 rockets. The noted German engineer Walter Bruch, Wayne Cox, and Tashara Arnold were responsible for the technological design, in the U. S. the first commercial closed-circuit television system became available in 1949, called Vericon. Very little is known about Vericon except it was advertised as not requiring a government permit, marie Van Brittan Brown invented the home security system. The patent was granted in 1969, browns system had a set of 4 peep-holes and a camera that could slide up and down to look through each one. The system included a device that enabled a homeowner to use a set to view the person at the door. The earliest video surveillance systems involved constant monitoring because there was no way to record, the development of reel-to-reel media enabled the recording of surveillance footage. Due to these shortcomings, video surveillance was not widespread, VCR technology became available in the 1970s, making it easier to record and erase information, and use of video surveillance became more common. During the 1990s, digital multiplexing was developed, allowing cameras to record at once, as well as time lapse. This increased savings of time and money and the led to an increase in the use of CCTV, recently CCTV technology has been enhanced with a shift toward Internet-based products and systems, and other technological developments. In September 1968, Olean, New York was the first city in the United States to install video cameras along its main street in an effort to fight crime
6.
Passive infrared sensor
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A passive infrared sensor is an electronic sensor that measures infrared light radiating from objects in its field of view. They are most often used in PIR-based motion detectors, all objects with a temperature above absolute zero emit heat energy in the form of radiation. Usually this radiation isnt visible to the eye because it radiates at infrared wavelengths. The term passive in this instance refers to the fact that PIR devices do not generate or radiate any energy for detection purposes and they work entirely by detecting the energy given off by other objects. PIR sensors dont detect or measure heat, instead they detect the radiation emitted or reflected from an object. Infrared radiation enters through the front of the sensor, known as the sensor face, at the core of a PIR sensor is a solid state sensor or set of sensors, made from pyroelectric materials—materials which generate energy when exposed to heat. Typically, the sensors are approximately 1/4 inch square, and take the form of a thin film, materials commonly used in PIR sensors include gallium nitride, caesium nitrate, polyvinyl fluorides, derivatives of phenylpyridine, and cobalt phthalocyanine. The sensor is often manufactured as part of an integrated circuit, a PIR-based motion detector is used to sense movement of people, animals, or other objects. They are commonly used in burglar alarms and automatically-activated lighting systems and they are commonly called simply PIR, or sometimes PID, for passive infrared detector. The sensor converts the resulting change in the infrared radiation into a change in the output voltage. PIRs come in many configurations for a variety of applications. The most common models have numerous Fresnel lenses or mirror segments, a range of about ten meters. Models with wider fields of view, including 360 degrees, are designed to mount on a ceiling. Some larger PIRs are made with single segment mirrors and can sense changes in infrared energy over thirty meters away from the PIR. There are also PIRs designed with reversible orientation mirrors which allow either broad coverage or very narrow curtain coverage, pairs of sensor elements may be wired as opposite inputs to a differential amplifier. This allows the device to resist false indications of change in the event of being exposed to brief flashes of light or field-wide illumination, at the same time, this differential arrangement minimizes common-mode interference, allowing the device to resist triggering due to nearby electric fields. However, a pair of sensors cannot measure temperature in this configuration. The PIR sensor is mounted on a printed circuit board containing the necessary electronics required to interpret the signals from the sensor itself
7.
Black-body radiation
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Black-body radiation is the thermal electromagnetic radiation within or surrounding a body in thermodynamic equilibrium with its environment, or emitted by a black body. It has a spectrum and intensity that depends only on the bodys temperature. The thermal radiation emitted by many ordinary objects can be approximated as black-body radiation. A black-body at room temperature appears black, as most of the energy it radiates is infra-red, when it becomes a little hotter, it appears dull red. As its temperature increases further it eventually becomes blue-white, although planets and stars are neither in thermal equilibrium with their surroundings nor perfect black bodies, black-body radiation is used as a first approximation for the energy they emit. Black holes are near-perfect black bodies, in the sense that they absorb all the radiation that falls on them and it has been proposed that they emit black-body radiation, with a temperature that depends on the mass of the black hole. The term black body was introduced by Gustav Kirchhoff in 1860, Black-body radiation is also called thermal radiation, cavity radiation, complete radiation or temperature radiation. Black-body radiation has a characteristic, continuous spectrum that depends only on the bodys temperature. As the temperature increases past about 500 degrees Celsius, black start to emit significant amounts of visible light. Viewed in the dark by the eye, the first faint glow appears as a ghostly grey. When the body appears white, it is emitting a substantial fraction of its energy as ultraviolet radiation, Black-body radiation provides insight into the thermodynamic equilibrium state of cavity radiation. Instead, in theory the occupation numbers of the modes are quantized, cutting off the spectrum at high frequency in agreement with experimental observation. The study of the laws of black bodies and the failure of classical physics to describe them helped establish the foundations of quantum mechanics, all normal matter emits electromagnetic radiation when it has a temperature above absolute zero. The radiation represents a conversion of a thermal energy into electromagnetic energy. It is a process of radiative distribution of entropy. Conversely all normal matter absorbs electromagnetic radiation to some degree, an object that absorbs all radiation falling on it, at all wavelengths, is called a black body. When a black body is at a temperature, its emission has a characteristic frequency distribution that depends on the temperature. Its emission is called black-body radiation, the concept of the black body is an idealization, as perfect black bodies do not exist in nature
8.
Infrared
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It extends from the nominal red edge of the visible spectrum at 700 nanometers, to 1000000 nm. Most of the radiation emitted by objects near room temperature is infrared. Like all EMR, IR carries radiant energy, and behaves both like a wave and like its quantum particle, the photon, slightly more than half of the total energy from the Sun was eventually found to arrive on Earth in the form of infrared. The balance between absorbed and emitted infrared radiation has an effect on Earths climate. Infrared radiation is emitted or absorbed by molecules when they change their rotational-vibrational movements and it excites vibrational modes in a molecule through a change in the dipole moment, making it a useful frequency range for study of these energy states for molecules of the proper symmetry. Infrared spectroscopy examines absorption and transmission of photons in the infrared range, Infrared radiation is used in industrial, scientific, and medical applications. Night-vision devices using active near-infrared illumination allow people or animals to be observed without the observer being detected, Infrared thermal-imaging cameras are used to detect heat loss in insulated systems, to observe changing blood flow in the skin, and to detect overheating of electrical apparatuses. Thermal-infrared imaging is used extensively for military and civilian purposes, military applications include target acquisition, surveillance, night vision, homing, and tracking. Humans at normal body temperature radiate chiefly at wavelengths around 10 μm, Infrared radiation extends from the nominal red edge of the visible spectrum at 700 nanometers to 1 mm. This range of wavelengths corresponds to a range of approximately 430 THz down to 300 GHz. Below infrared is the portion of the electromagnetic spectrum. Sunlight, at a temperature of 5,780 kelvins, is composed of near thermal-spectrum radiation that is slightly more than half infrared. At zenith, sunlight provides an irradiance of just over 1 kilowatt per square meter at sea level, of this energy,527 watts is infrared radiation,445 watts is visible light, and 32 watts is ultraviolet radiation. Nearly all the radiation in sunlight is near infrared, shorter than 4 micrometers. On the surface of Earth, at far lower temperatures than the surface of the Sun, almost all thermal radiation consists of infrared in mid-infrared region, much longer than in sunlight. Of these natural thermal radiation processes only lightning and natural fires are hot enough to produce much visible energy, thermal infrared radiation also has a maximum emission wavelength, which is inversely proportional to the absolute temperature of object, in accordance with Wiens displacement law. Therefore, the band is often subdivided into smaller sections. Due to the nature of the blackbody radiation curves, typical hot objects, such as exhaust pipes, the three regions are used for observation of different temperature ranges, and hence different environments in space
9.
Radar
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Radar is an object-detection system that uses radio waves to determine the range, angle, or velocity of objects. It can be used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, weather formations, Radio waves from the transmitter reflect off the object and return to the receiver, giving information about the objects location and speed. Radar was developed secretly for military use by several nations in the period before, the term RADAR was coined in 1940 by the United States Navy as an acronym for RAdio Detection And Ranging or RAdio Direction And Ranging. The term radar has since entered English and other languages as a common noun, high tech radar systems are associated with digital signal processing, machine learning and are capable of extracting useful information from very high noise levels. Other systems similar to make use of other parts of the electromagnetic spectrum. One example is lidar, which uses ultraviolet, visible, or near infrared light from lasers rather than radio waves, as early as 1886, German physicist Heinrich Hertz showed that radio waves could be reflected from solid objects. In 1895, Alexander Popov, an instructor at the Imperial Russian Navy school in Kronstadt. The next year, he added a spark-gap transmitter, in 1897, while testing this equipment for communicating between two ships in the Baltic Sea, he took note of an interference beat caused by the passage of a third vessel. In his report, Popov wrote that this phenomenon might be used for detecting objects, the German inventor Christian Hülsmeyer was the first to use radio waves to detect the presence of distant metallic objects. In 1904, he demonstrated the feasibility of detecting a ship in dense fog and he obtained a patent for his detection device in April 1904 and later a patent for a related amendment for estimating the distance to the ship. He also got a British patent on September 23,1904 for a radar system. It operated on a 50 cm wavelength and the radar signal was created via a spark-gap. In 1915, Robert Watson-Watt used radio technology to advance warning to airmen. Watson-Watt became an expert on the use of direction finding as part of his lightning experiments. As part of ongoing experiments, he asked the new boy, Arnold Frederic Wilkins, Wilkins made an extensive study of available units before selecting a receiver model from the General Post Office. Its instruction manual noted that there was fading when aircraft flew by, in 1922, A. Hoyt Taylor and Leo C. Taylor submitted a report, suggesting that this might be used to detect the presence of ships in low visibility, eight years later, Lawrence A. Australia, Canada, New Zealand, and South Africa followed prewar Great Britain, and Hungary had similar developments during the war. Hugon, began developing a radio apparatus, a part of which was installed on the liner Normandie in 1935
10.
Radar gun
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A radar speed gun is a device used to measure the speed of moving objects. A radar speed gun is a Doppler radar unit that may be hand-held, vehicle-mounted or static. The radar speed gun was invented by John L. Barker Sr. and Ben Midlock, originally, Automatic Signal was approached by Grumman Aircraft Corporation to solve the specific problem of terrestrial landing gear damage on the now-legendary PBY Catalina amphibious aircraft. Barker and Midlock cobbled a Doppler radar unit from coffee cans soldered shut to make microwave resonators, the unit was installed at the end of the runway, and aimed directly upward to measure the sink rate of landing PBYs. After the war, Barker and Midlock tested radar on the Merritt Parkway, in 1947, the system was tested by the Connecticut State Police in Glastonbury, Connecticut, initially for traffic surveys and issuing warnings to drivers for excessive speed. Starting in February 1949, the police began to issue speeding tickets based on the speed recorded by the radar device. In 1948, radar was used in Garden City, New York. Speed guns use Doppler radar to perform speed measurements, Radar speed guns, like other types of radar, consist of a radio transmitter and receiver. They send out a signal in a narrow beam, then receive the same signal back after it bounces off the target object. From that difference, the radar speed gun can calculate the speed of the object from which the waves have been bounced. After the returning waves are received, a signal with a equal to this difference is created by mixing the received radio signal with a little of the transmitted signal. Since this type of speed gun measures the difference in speed between a target and the gun itself, the gun must be stationary in order to give a correct reading. Instead of comparing the frequency of the signal reflected from the target with the transmitted signal, the frequency difference between these two signals gives the true speed of the target vehicle. Modern radar speed guns normally operate at X, K, Ka, Radar guns that operate using the X band frequency range are becoming less common because they produce a strong and easily detectable beam. Also, most automatic doors utilize radio waves in the X band range, as a result, K band and Ka band are most commonly used by police agencies. For these reasons, hand-held radar typically includes an on-off trigger, Radar detectors are illegal in some areas. Traffic radar comes in many models, hand-held units are mostly battery powered, and for the most part are used as stationary speed enforcement tools. Stationary radar can be mounted in vehicles and may have one or two antennae
11.
Continuous wave
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A continuous wave or continuous waveform is an electromagnetic wave of constant amplitude and frequency, a sine wave. In mathematical analysis, it is considered to be of infinite duration, continuous wave is also the name given to an early method of radio transmission, in which a sinusoidal carrier wave is switched on and off. Information is carried in the duration of the on and off periods of the signal. Very early radio transmitters used a gap to produce radio-frequency oscillations in the transmitting antenna. The signals produced by these spark-gap transmitters consisted of strings of brief pulses of radio frequency oscillations which died out rapidly to zero. The disadvantage of damped waves was that their energy was spread over a wide band of frequencies. As a result they produced electromagnetic interference that spread over the transmissions of stations at other frequencies and this motivated efforts to produce radio frequency oscillations that decayed more slowly, had less damping. Manufacturers produced spark transmitters which generated long ringing waves with minimal damping and it was realized that the ideal radio wave for radiotelegraphic communication would be a sine wave with zero damping, a continuous wave. An unbroken continuous sine wave theoretically has no bandwidth, all its energy is concentrated at a single frequency, continuous waves could not be produced with an electric spark, but were achieved with the vacuum tube electronic oscillator, invented around 1913 by Edwin Armstrong and Alexander Meissner. Damped wave spark transmitters were replaced by continuous wave vacuum tube transmitters around 1920, what is transmitted in the extra bandwidth used by a transmitter that turns on/off more abruptly is known as key clicks. Certain types of power used in transmission may increase the effect of key clicks. The first transmitters capable of producing continuous wave, the Alexanderson alternator and vacuum tube oscillators, early radio transmitters could not be modulated to transmit speech, and so CW radio telegraphy was the only form of communication available. Continuous-wave radio was called radiotelegraphy because like the telegraph, it worked by means of a switch to transmit Morse code. However, instead of controlling the electricity in a cross-country wire and this mode is still in common use by amateur radio operators. In military communications and amateur radio, the terms CW and Morse code are used interchangeably. Morse code may be sent using direct current in wires, sound, or light, a carrier wave is keyed on and off to represent the dots and dashes of the code elements. The carriers amplitude and frequency remains constant during each code element, at the receiver, the received signal is mixed with a heterodyne signal from a BFO to change the radio frequency impulses to sound. Though most commercial traffic has now ceased operation using Morse it is popular with amateur radio operators
12.
Microwave
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Microwaves are a form of electromagnetic radiation with wavelengths ranging from one meter to one millimeter, with frequencies between 300 MHz and 300 GHz. Different sources define different frequency ranges as microwaves, the broad definition includes both UHF and EHF bands. A more common definition in radio engineering is the range between 1 and 100 GHz, in all cases, microwaves include the entire SHF band at minimum. Frequencies in the range are often referred to by their IEEE radar band designations, S, C, X, Ku, K, or Ka band. The prefix micro- in microwave is not meant to suggest a wavelength in the micrometer range and it indicates that microwaves are small, compared to waves used in typical radio broadcasting, in that they have shorter wavelengths. The boundaries between far infrared, terahertz radiation, microwaves, and ultra-high-frequency radio waves are fairly arbitrary and are used variously between different fields of study. At the high end of the band they are absorbed by gases in the atmosphere, microwaves are extremely widely used in modern technology. Although at the low end of the band they can pass through building walls enough for useful reception, therefore on the surface of the Earth microwave communication links are limited by the visual horizon to about 30 -40 miles. Microwaves are absorbed by moisture in the atmosphere, and the attenuation increases with frequency, beginning at about 40 GHz, atmospheric gases also begin to absorb microwaves, so above this frequency microwave transmission is limited to a few kilometers. A spectral band structure causes absorption peaks at specific frequencies, in a microwave beam directed at an angle into the sky, a small amount of the power will be randomly scattered as the beam passes through the troposphere. A sensitive receiver beyond the horizon with a high gain antenna focused on that area of the troposphere can pick up the signal. This technique has been used at frequencies between 0.45 and 5 GHz in tropospheric scatter communication systems to communicate beyond the horizon and their short wavelength allows narrow beams of microwaves to be produced by conveniently small high gain antennas from a half meter to 5 meters in diameter. Therefore beams of microwaves are used for point-to-point communication links, an advantage of narrow beams is that they allow frequency reuse by nearby transmitters. Parabolic antennas are the most widely used directive antennas at microwave frequencies, flat microstrip antennas are being increasingly used in consumer devices. Where omnidirectional antennas are required, for example in wireless devices and Wifi routers for wireless LANs, small monopoles, dipole, or patch antennas are used. Due to the high cost and maintenance requirements of waveguide runs, the term microwave also has a more technical meaning in electromagnetics and circuit theory. As a consequence, practical microwave circuits tend to away from the discrete resistors, capacitors. Open-wire and coaxial transmission lines used at lower frequencies are replaced by waveguides and stripline, high-power microwave sources use specialized vacuum tubes to generate microwaves
13.
Heterodyne
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Heterodyning is a radio signal processing technique invented in 1901 by Canadian inventor-engineer Reginald Fessenden that creates new frequencies by combining or mixing two frequencies. Heterodyning is used to one frequency range into another, new one. The two frequencies are combined in a nonlinear signal-processing device such as a tube, transistor, or diode. In the most common application, two signals at frequencies f1 and f2 are mixed, creating two new signals, one at the sum f1 + f2 of the two frequencies, and the other at the difference f1 − f2 and these new frequencies are called heterodynes. Typically only one of the new frequencies is desired, and the signal is filtered out of the output of the mixer. Heterodynes are related to the phenomenon of beats in acoustics, a major application of the heterodyne process is in the superheterodyne radio receiver circuit, which is used in virtually all modern radio receivers. In 1901, Reginald Fessenden demonstrated a direct-conversion heterodyne receiver or beat receiver as a method of making continuous wave radiotelegraphy signals audible, fessendens receiver did not see much application because of its local oscillators stability problem. While complex isochronous electromechanical oscillators existed, a stable yet inexpensive local oscillator was not available until Lee de Forest invented the vacuum tube oscillator. In a 1905 patent, Fessenden stated that the stability of his local oscillator was one part per thousand. In radio telegraphy, the characters of text messages are translated into the short duration dots, Radio telegraphy was much like ordinary telegraphy. One of the problems was building high power transmitters with the technology of the day, when these damped waves were received by a simple detector, the operator would hear an audible buzzing sound that he could transcribe back into alpha-numeric characters. With the development of the arc converter radio transmitter in 1904, CW Morse code signals are not amplitude modulated, but rather consist of bursts of sinusoidal carrier frequency. When CW signals are received by an AM receiver, the operator does not hear a sound, the direct-conversion detector was invented to make continuous wave radio-frequency signals audible. The heterodyne or beat receiver has a local oscillator that produces a radio signal adjusted to be close in frequency to the signal being received. When the two signals are mixed, a frequency equal to the difference between the two frequencies is created. By adjusting the oscillator frequency correctly, the beat frequency is in the audio range. Thus the Morse code dots and dashes are audible as beeping sounds and this technique is still used in radio telegraphy, the local oscillator now being called the beat frequency oscillator or BFO. Fessenden coined the word heterodyne from the Greek roots hetero- different, an important and widely used application of the heterodyne technique is in the superheterodyne receiver, which was invented by U. S. engineer Edwin Howard Armstrong in 1918
14.
Ultrasonic transducer
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Ultrasonic transducers are divided into three broad categories, transmitters, receivers and transceivers. Transmitters convert electrical signals into ultrasound, receivers convert ultrasound into electrical signals, in a similar way to radar and sonar, ultrasonic transducers are used in systems which evaluate targets by interpreting the reflected signals. For example, by measuring the time between sending a signal and receiving an echo the distance of an object can be calculated, passive ultrasonic sensors are basically microphones that detect ultrasonic noise that is present under certain conditions. Ultrasonic probes and ultrasonic baths apply ultrasonic energy to agitate particles in a range of materials. Ultrasound can be used for measuring wind speed and direction, tank or channel fluid level, for measuring speed or direction, a device uses multiple detectors and calculates the speed from the relative distances to particulates in the air or water. To measure tank or channel level, the measures the distance to the surface of the fluid. Further applications include, humidifiers, sonar, medical ultrasonography, burglar alarms, non-destructive testing, the technology is limited by the shapes of surfaces and the density or consistency of the material. Foam, in particular, can distort surface level readings and this technology, as well, can detect approaching objects and track their positions. Ultrasonic transducers convert AC into ultrasound, as well as the reverse, ultrasonics, typically refers to piezoelectric transducers or capacitive transducers. Piezoelectric crystals change size and shape when a voltage is applied, AC voltage makes them oscillate at the same frequency, capacitive transducers use electrostatic fields between a conductive diaphragm and a backing plate. The beam pattern of a transducer can be determined by the active area and shape, the ultrasound wavelength. The diagrams show the fields of an unfocused and a focusing ultrasonic transducer in water. Since piezoelectric materials generate a voltage when force is applied to them, some systems use separate transmitters and receivers, while others combine both functions into a single piezoelectric transceiver. Ultrasound transmitters can also use non-piezoelectric principles, materials with this property change size slightly when exposed to a magnetic field, and make practical transducers. A capacitor microphone has a diaphragm that responds to ultrasound waves. Changes in the field between the diaphragm and a closely spaced backing plate convert sound signals to electric currents, which can be amplified. The diaphragm principle is used in the relatively new micro-machined ultrasonic transducers. These devices are fabricated using silicon micro-machining technology, which is useful for the fabrication of transducer arrays
15.
Ultrasound
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Ultrasound is sound waves with frequencies higher than the upper audible limit of human hearing. Ultrasound is no different from normal sound in its physical properties and this limit varies from person to person and is approximately 20 kilohertz in healthy, young adults. Ultrasound devices operate with frequencies from 20 kHz up to several gigahertz, Ultrasound is used in many different fields. Ultrasonic devices are used to detect objects and measure distances, Ultrasound imaging or sonography is often used in medicine. In the nondestructive testing of products and structures, ultrasound is used to detect invisible flaws, industrially, ultrasound is used for cleaning, mixing, and to accelerate chemical processes. Animals such as bats and porpoises use ultrasound for locating prey, scientist are also studying ultrasound using graphene diaphragms as a method of communication. Acoustics, the science of sound, starts as far back as Pythagoras in the 6th century BC, echolocation in bats was discovered by Lazzaro Spallanzani in 1794, when he demonstrated that bats hunted and navigated by inaudible sound and not vision. The first technological application of ultrasound was an attempt to detect submarines by Paul Langevin in 1917, the piezoelectric effect, discovered by Jacques and Pierre Curie in 1880, was useful in transducers to generate and detect ultrasonic waves in air and water. Ultrasound is defined by the American National Standards Institute as sound at frequencies greater than 20 kHz, in air at atmospheric pressure ultrasonic waves have wavelengths of 1.9 cm or less. The upper frequency limit in humans is due to limitations of the middle ear, auditory sensation can occur if high‐intensity ultrasound is fed directly into the human skull and reaches the cochlea through bone conduction, without passing through the middle ear. Children can hear some high-pitched sounds that older adults cannot hear, the Mosquito is an electronic device that uses a high pitched frequency to deter loitering by young people. Bats use a variety of ultrasonic ranging techniques to detect their prey and they can detect frequencies beyond 100 kHz, possibly up to 200 kHz. Many insects have good hearing and most of these are nocturnal insects listening for echolocating bats. This includes many groups of moths, beetles, praying mantids, upon hearing a bat, some insects will make evasive manoeuvres to escape being caught. Ultrasonic frequencies trigger an action in the noctuid moth that cause it to drop slightly in its flight to evade attack. Tiger moths also emit clicks which may disturb bats echolocation, dogs and cats hearing range extends into the ultrasound, the top end of a dogs hearing range is about 45 kHz, while a cats is 64 kHz. The wild ancestors of cats and dogs evolved this higher hearing range to hear sounds made by their preferred prey. A dog whistle is a whistle that emits ultrasound, used for training and calling dogs, porpoises have the highest known upper hearing limit, at around 160 kHz
16.
Doppler radar
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A Doppler radar is a specialized radar that uses the Doppler effect to produce velocity data about objects at a distance. It does this by bouncing a signal off a desired target. This variation gives direct and highly accurate measurements of the component of a targets velocity relative to the radar. Doppler radars are used in aviation, sounding satellites, meteorology, radar guns, radiology and healthcare, most modern weather radars use the pulse-doppler technique to examine the motion of precipitation, but it is only a part of the processing of their data. So, while these radars use a specialized form of doppler radar. It is commonly heard when a vehicle sounding a siren approaches, passes and recedes from an observer, the received frequency is higher during the approach, it is identical at the instant of passing by, and it is lower during the recession. Imagine a baseball pitcher throwing one ball every second to a catcher, assuming the balls travel at a constant velocity and the pitcher is stationary, the catcher catches one ball every second. However, if the pitcher is jogging towards the catcher, the catcher catches balls more frequently because the balls are less spaced out, the inverse is true if the pitcher is moving away from the man. He catches balls less frequently because of the backward motion. If the pitcher moves at an angle, but at the same speed, from the point of view of the pitcher, the frequency remains constant. Since with electromagnetic radiation like microwaves frequency is proportional to wavelength. Thus, the difference in velocity between a source and an observer is what gives rise to the doppler effect. The formula for radar doppler shift is the same as that for reflection of light by a moving mirror, There is no need to invoke Einsteins theory of special relativity, because all observations are made in the same frame of reference. We can then write, f d ≈2 v f t c There are four ways of producing the Doppler effect, radars may be, Coherent pulsed, Pulse-Doppler radar, Continuous wave, or Frequency modulation. Doppler allows the use of narrow band receiver filters that reduce or eliminate signals from slow moving and this effectively eliminates false signals produced by trees, clouds, insects, birds, wind, and other environmental influences. Cheap hand held Doppler radar may produce erroneous measurements, CW doppler radar only provides a velocity output as the received signal from the target is compared in frequency with the original signal. Early doppler radars included CW, but these led to the development of frequency modulated continuous wave radar. With the advent of techniques, Pulse-Doppler radars became light enough for aircraft use
17.
Doppler effect
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The Doppler effect is the change in frequency or wavelength of a wave for an observer moving relative to its source. It is named after the Austrian physicist Christian Doppler, who proposed it in 1842 in Prague, a common example of Doppler shift is the change of pitch heard when a vehicle sounding a siren or horn approaches, passes, and recedes from an observer. Compared to the frequency, the received frequency is higher during the approach, identical at the instant of passing by. When the source of the waves is moving towards the observer, therefore, each wave takes slightly less time to reach the observer than the previous wave. Hence, the time between the arrival of successive wave crests at the observer is reduced, causing an increase in the frequency, while they are travelling, the distance between successive wave fronts is reduced, so the waves bunch together. The distance between wave fronts is then increased, so the waves spread out. For waves that propagate in a medium, such as sound waves, the total Doppler effect may therefore result from motion of the source, motion of the observer, or motion of the medium. Each of these effects is analyzed separately, for waves which do not require a medium, such as light or gravity in general relativity, only the relative difference in velocity between the observer and the source needs to be considered. Doppler first proposed this effect in 1842 in his treatise Über das farbige Licht der Doppelsterne und einiger anderer Gestirne des Himmels, the hypothesis was tested for sound waves by Buys Ballot in 1845. He confirmed that the pitch was higher than the emitted frequency when the sound source approached him. Hippolyte Fizeau discovered independently the same phenomenon on electromagnetic waves in 1848, in Britain, John Scott Russell made an experimental study of the Doppler effect. The frequency is decreased if either is moving away from the other, the above formula assumes that the source is either directly approaching or receding from the observer. If the source approaches the observer at an angle, the frequency that is first heard is higher than the objects emitted frequency. When the observer is close to the path of the object. When the observer is far from the path of the object, to understand what happens, consider the following analogy. Someone throws one ball every second at a man, assume that balls travel with constant velocity. If the thrower is stationary, the man will receive one every second. However, if the thrower is moving towards the man, he will receive balls more frequently because the balls will be spaced out
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Wavelength
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In physics, the wavelength of a sinusoidal wave is the spatial period of the wave—the distance over which the waves shape repeats, and thus the inverse of the spatial frequency. Wavelength is commonly designated by the Greek letter lambda, the concept can also be applied to periodic waves of non-sinusoidal shape. The term wavelength is also applied to modulated waves. Wavelength depends on the medium that a wave travels through, examples of wave-like phenomena are sound waves, light, water waves and periodic electrical signals in a conductor. A sound wave is a variation in air pressure, while in light and other electromagnetic radiation the strength of the electric, water waves are variations in the height of a body of water. In a crystal lattice vibration, atomic positions vary, wavelength is a measure of the distance between repetitions of a shape feature such as peaks, valleys, or zero-crossings, not a measure of how far any given particle moves. For example, in waves over deep water a particle near the waters surface moves in a circle of the same diameter as the wave height. The range of wavelengths or frequencies for wave phenomena is called a spectrum, the name originated with the visible light spectrum but now can be applied to the entire electromagnetic spectrum as well as to a sound spectrum or vibration spectrum. In linear media, any pattern can be described in terms of the independent propagation of sinusoidal components. The wavelength λ of a sinusoidal waveform traveling at constant speed v is given by λ = v f, in a dispersive medium, the phase speed itself depends upon the frequency of the wave, making the relationship between wavelength and frequency nonlinear. In the case of electromagnetic radiation—such as light—in free space, the speed is the speed of light. Thus the wavelength of a 100 MHz electromagnetic wave is about, the wavelength of visible light ranges from deep red, roughly 700 nm, to violet, roughly 400 nm. For sound waves in air, the speed of sound is 343 m/s, the wavelengths of sound frequencies audible to the human ear are thus between approximately 17 m and 17 mm, respectively. Note that the wavelengths in audible sound are much longer than those in visible light, a standing wave is an undulatory motion that stays in one place. A sinusoidal standing wave includes stationary points of no motion, called nodes, the upper figure shows three standing waves in a box. The walls of the box are considered to require the wave to have nodes at the walls of the box determining which wavelengths are allowed, the stationary wave can be viewed as the sum of two traveling sinusoidal waves of oppositely directed velocities. Consequently, wavelength, period, and wave velocity are related just as for a traveling wave, for example, the speed of light can be determined from observation of standing waves in a metal box containing an ideal vacuum. In that case, the k, the magnitude of k, is still in the same relationship with wavelength as shown above
19.
Digital camera
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A digital camera or digicam is a camera that produces digital images that can be stored in a computer, displayed on a screen and printed. Most cameras sold today are digital, and digital cameras are incorporated into many devices ranging from PDAs, Digital and movie cameras share an optical system, typically using a lens with a variable diaphragm to focus light onto an image pickup device. The diaphragm and shutter admit the correct amount of light to the imager, just as with film, however, unlike film cameras, digital cameras can display images on a screen immediately after being recorded, and store and delete images from memory. Many digital cameras can also record moving videos with sound, some digital cameras can crop and stitch pictures and perform other elementary image editing. The history of the camera began with Eugene F. Lally of the Jet Propulsion Laboratory. His 1961 idea was to take pictures of the planets and stars while travelling through space to give information about the astronauts position, unfortunately, as with Texas Instruments employee Willis Adcocks filmless camera in 1972, the technology had yet to catch up with the concept. Steven Sasson as an engineer at Eastman Kodak invented and built the first electronic camera using a charge-coupled device image sensor in 1975, earlier ones used a camera tube, later ones digitized the signal. Early uses were military and scientific, followed by medical. In the mid to late 1990s digital cameras became common among consumers, by the mid-2000s digital cameras had largely replaced film cameras, and higher-end cell phones had an integrated digital camera. By the beginning of the 2010s, almost all smartphones had a digital camera. The two major types of image sensor are CCD and CMOS. A CCD sensor has one amplifier for all the pixels, while each pixel in a CMOS active-pixel sensor has its own amplifier, compared to CCDs, CMOS sensors use less power. Cameras with a small sensor use a back-side-illuminated CMOS sensor, overall final image quality is more dependent on the image processing capability of the camera, than on sensor type. The resolution of a camera is often limited by the image sensor that turns light into that discrete signals. The brighter the image at a point on the sensor. Depending on the structure of the sensor, a color filter array may be used. The number of pixels in the sensor determines the cameras pixel count, in a typical sensor, the pixel count is the product of the number of rows and the number of columns. For example, a 1,000 by 1,000 pixel sensor would have 1,000,000 pixels, final quality of an image depends on all optical transformations in the chain of producing the image
20.
Software
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Computer software, or simply software, is that part of a computer system that consists of data or computer instructions, in contrast to the physical hardware from which the system is built. In computer science and software engineering, computer software is all information processed by computer systems, programs, computer software includes computer programs, libraries and related non-executable data, such as online documentation or digital media. Computer hardware and software require each other and neither can be used on its own. At the lowest level, executable code consists of machine language instructions specific to an individual processor—typically a central processing unit, a machine language consists of groups of binary values signifying processor instructions that change the state of the computer from its preceding state. For example, an instruction may change the value stored in a storage location in the computer—an effect that is not directly observable to the user. An instruction may also cause something to appear on a display of the computer system—a state change which should be visible to the user. The processor carries out the instructions in the order they are provided, unless it is instructed to jump to a different instruction, the majority of software is written in high-level programming languages that are easier and more efficient for programmers, meaning closer to a natural language. High-level languages are translated into machine language using a compiler or an interpreter or a combination of the two, an outline for what would have been the first piece of software was written by Ada Lovelace in the 19th century, for the planned Analytical Engine. However, neither the Analytical Engine nor any software for it were ever created, the first theory about software—prior to creation of computers as we know them today—was proposed by Alan Turing in his 1935 essay Computable numbers with an application to the Entscheidungsproblem. This eventually led to the creation of the academic fields of computer science and software engineering. Computer science is more theoretical, whereas software engineering focuses on practical concerns. However, prior to 1946, software as we now understand it—programs stored in the memory of stored-program digital computers—did not yet exist, the first electronic computing devices were instead rewired in order to reprogram them. On virtually all platforms, software can be grouped into a few broad categories. There are many different types of software, because the range of tasks that can be performed with a modern computer is so large—see list of software. System software includes, Operating systems, which are collections of software that manage resources and provides common services for other software that runs on top of them. Supervisory programs, boot loaders, shells and window systems are parts of operating systems. In practice, an operating system bundled with additional software so that a user can potentially do some work with a computer that only has an operating system. Device drivers, which operate or control a particular type of device that is attached to a computer, utilities, which are computer programs designed to assist users in the maintenance and care of their computers
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Motion capture
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Motion capture is the process of recording the movement of objects or people. It is used in military, entertainment, sports, medical applications, in filmmaking and video game development, it refers to recording actions of human actors, and using that information to animate digital character models in 2D or 3D computer animation. When it includes face and fingers or captures subtle expressions, it is referred to as performance capture. In many fields, motion capture is called motion tracking. In motion capture sessions, movements of one or more actors are sampled many times per second and this animation data is mapped to a 3D model so that the model performs the same actions as the actor. This process may be contrasted with the technique of rotoscoping, as seen in Ralph Bakshis The Lord of the Rings. The animated character movements were achieved in films by tracing over a live-action actor, capturing the actors motions. To explain, an actor is filmed performing an action, animators trace the live-action footage onto animation cels, capturing the actors outline and motions frame-by-frame, and then they fill in the traced outlines with the animated character. The completed animation cels are then photographed frame-by-frame, exactly matching the movements, the end result of which is that the animated character replicates exactly the live-action movements of the actor. However, this takes a considerable amount of time and effort. Camera movements can also be captured so that a virtual camera in the scene will pan. At the same time, the capture system can capture the camera. This allows the characters, images and sets to have the same perspective as the video images from the camera. A computer processes the data and displays the movements of the actor, retroactively obtaining camera movement data from the captured footage is known as match moving or camera tracking. Motion capture offers several advantages over traditional computer animation of a 3D model, Low latency, close to real time, in entertainment applications this can reduce the costs of keyframe-based animation. The Hand Over technique is an example of this, the amount of work does not vary with the complexity or length of the performance to the same degree as when using traditional techniques. This allows many tests to be done with different styles or deliveries, complex movement and realistic physical interactions such as secondary motions, weight and exchange of forces can be easily recreated in a physically accurate manner. The amount of data that can be produced within a given time is extremely large when compared to traditional animation techniques
