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40-399: A typical commercial strobe light has a flash energy in the region of 10 to 150 joules , and discharge times as short as a few milliseconds, often resulting in a flash power of several kilowatts . Larger strobe lights can be used in “continuous” mode, producing extremely intense illumination. The light source is commonly a xenon flash lamp , or flashtube , which has a complex spectrum and

80-417: A color temperature of approximately 5,600 kelvins . To obtain colored light, colored gels may be used. Strobe lights usually use flashtubes with energy supplied from a capacitor , an energy storage device much like a battery, but capable of charging and releasing energy much faster. In a capacitor-based strobe, the capacitor is charged up to around 300 V. Once the capacitor has been charged, to trigger

120-407: A fight-or-flight response in humans ; a person under this mindset will panic and either flee the perceived danger or attempt to eliminate it, often ignoring rational thought in either case. A person in such a state can be characterized as "alarmed". With any kind of alarm, you must balance between the danger of false alarms (called "false positives") — the signal going off in the absence of

160-994: A base, a LED or group of LEDs, and a cover. A solid state flash controller is located within the base, which allows the LED beacon to operate in a variety of flash patterns. Strobe lights are often used for aircraft anti-collision lighting both on aircraft themselves and also on tall stationary objects, such as television and radio towers. Other applications are in alarm systems , emergency vehicle lighting , theatrical lighting (most notably to simulate lightning ), and as high-visibility aircraft collision avoidance lights . They are still widely used in law enforcement and other emergency vehicles, though they are slowly being replaced by LED technology in this application, as they themselves largely replaced halogen lighting. Strobes are used by scuba divers as an emergency signaling device. Special calibrated strobe lights, capable of flashing up to hundreds of times per second, are used in industry to stop

200-717: A flash duration of order 0.5 μs Some strobes even offer continuous mode of operation whereby the arc is sustained, providing extremely high intensity light, but usually only for small amounts of time to prevent overheating and eventual breakage of the flash tube. A strobe beacon is a flashing electric lamp used in a variety of industries as an attention -getting device, either to warn of possible hazards , or to attract potential customers . Strobe beacons are similar to rotating beacons, but are more energy efficient , and with no moving parts, are more reliable and less likely to break. Gas strobe beacons include Xenon flash lamp and halogen varieties. Gas strobe beacons consist of

240-416: A flashing lamp to make an improved stroboscope for the study of moving objects, eventually resulting in dramatic photographs of objects such as bullets in flight. EG&G [ now a division of URS ] was founded by Harold E. Edgerton, Kenneth J. Germeshausen and Herbert E. Grier in 1947 as Edgerton, Germeshausen and Grier, Inc. and today bears their initials. In 1931, Edgerton and Germeshausen had formed

280-485: A force vector and a displacement vector. By contrast, torque is a vector – the cross product of a force vector and a distance vector. Torque and energy are related to one another by the equation E = τ θ , {\displaystyle E=\tau \theta \,,} where E is energy, τ is (the vector magnitude of) torque, and θ is the angle swept (in radians ). Since plane angles are dimensionless, it follows that torque and energy have

320-435: A form of current limiting , without which the flash tube would attempt to draw high currents from the electricity source, potentially tripping electrical breakers or causing voltage drops in the power supply line. The duration of a single flash depends on the particular strobe being used and its settings. Strobes for studio lighting often have a range of power settings. For a given strobe, higher light output corresponds to

360-413: A gas-filled tube surrounded by a lens . When electricity is applied, the tube flashes and is magnified by the lens, and a 360 degree light is emitted. The intensity of the light depends on the amount of electricity provided. These lenses come in a variant of colors, mainly clear, yellow, amber, red, blue, and green. The lens color can affect the intensity of light. LED strobe beacons consist of

400-526: A longer flash duration. For example, the Flashpoint Rapid 1200 HSS Monolight has a flash duration as long as 5.6 ms (1/180 sec) at its highest output setting, or as short as 68 μs (1/14,814 sec) at its lowest output setting. Strobes with significantly shorter flash durations are commercially available, some with flash durations less than 1 μs. For example, the SPOT strobe by Prism Science Works provides

440-530: A mark on the flywheel on the engine's main axle . The strobe-light tool for such ignition timing is called a timing light . Strobe lighting has also been used to see the movements of the vocal cords in slow motion during speech, a procedure known as video-stroboscopy. Strobelights are often used to give an illusion of slow motion in nightclubs and raves , and are available for home use for special effects or entertainment. The origin of strobe lighting dates to 1931, when Harold Eugene "Doc" Edgerton employed

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480-502: A partnership to study high-speed photographic and stroboscopic techniques and their applications. Grier joined them in 1934, and in 1947, EG&G was incorporated. During World War II, the government's Manhattan Project made use of Edgerton's discoveries to photograph atomic explosions; it was a natural evolution that the company would support the Atomic Energy Commission in its weapons research and development after

520-591: A problem — or an alarm failing to signal an actual problem (called a "false negative"). False alarms can waste resources expensively and can even be dangerous. For example, false alarms of a fire can waste firefighter manpower, making them unavailable for a real fire, and risk injury to firefighters and others as the fire engines race to the alleged fire's location. In addition, false alarms may acclimatise people to ignore alarm signals, and thus possibly to ignore an actual emergency: Aesop 's fable of The Boy Who Cried Wolf exemplifies this problem. A false alarm

560-487: A self-contained domestic smoke detector to a sophisticated alarm system that can operate building fire fighting systems automatically to extinguish fires with water or inert gases. Many industries have developed standards for alarm devices, and the colours red, blue and amber are generally recognized as alarm device-related colours, with flashing lights often indicating urgent conditions. Human reactions to an alarm will often depend on upbringing, psychological training, or

600-412: A stroboscopic light can give the illusion that white light is tinged with color, known as Fechner color . Within certain ranges, the apparent color can be controlled by the frequency of the flash. Effective stimuli frequencies go from 3 Hz upwards, with optimal frequencies of about 4–6 Hz. The colours are an illusion generated in the mind of the observer and not a real color. The Benham's top demonstrates

640-458: Is a mechanism that gives an audible, visual, combination, or other kind of alarm signal to alert someone to a problem or condition that requires urgent attention. The word alarm comes from the Old French a l'arme meaning "to the arms", or "to the weapons", telling armed men to pick up their weapons and get ready for action because an enemy may have suddenly appeared. The word alarum

680-446: Is also equivalent to any of the following: The joule is named after James Prescott Joule . As with every SI unit named for a person, its symbol starts with an upper case letter (J), but when written in full, it follows the rules for capitalisation of a common noun ; i.e., joule becomes capitalised at the beginning of a sentence and in titles but is otherwise in lower case. The cgs system had been declared official in 1881, at

720-631: Is an archaic form of alarm . It was sometimes used as a call to arms in the stage directions of Elizabethan dramas . The term comes from the Italian all'armi and appears 89 times in Shakespeare's First Folio . Often explained as the off-stage sounds of conflict or disturbance, recent research suggests a bell or drum may have been used to rouse soldiers from sleep. Early alarm devices were often bells , drums , other musical instruments, or any items which made unusual loud noises that attracted

760-408: Is an integer and ω the angular frequency ), the marked point will appear to not move. Any non-integer flash setting will make the mark appear to move forward or backward, e.g. a slight increase of the flash frequency will make the point appear to move backward. A common use of a strobe flash is to optimize a car engine 's efficiency at a certain rotational period by directing the strobe-light towards

800-533: Is equal to (approximately unless otherwise stated): Units with exact equivalents in joules include: In mechanics , the concept of force (in some direction) has a close analogue in the concept of torque (about some angle): A result of this similarity is that the SI unit for torque is the newton-metre , which works out algebraically to have the same dimensions as the joule, but they are not interchangeable. The General Conference on Weights and Measures has given

840-438: Is one of the most significant issues with conventional alarm systems. They can be triggered for several reasons, such as the movement of pets, typing in the wrong security codes, or loud sounds from windows or doors. In the case of fire alarms, aerosol sprays, smoking, or burning food can all lead to a false alarm. Many avoid the risk of false alarms by ensuring their alarms are secured in an appropriate location, such as placing

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880-655: Is the unit of energy in the International System of Units (SI). It is equal to the amount of work done when a force of one newton displaces a mass through a distance of one metre in the direction of that force. It is also the energy dissipated as heat when an electric current of one ampere passes through a resistance of one ohm for one second. It is named after the English physicist James Prescott Joule (1818–1889). In terms of SI base units and in terms of SI derived units with special names ,

920-417: The appearance of motion of rotating and other repetitively operating machinery and to measure, or adjust, the rotation speeds or cycle times. Since this stop is only apparent, a marked point on the rotating body will either appear to move backward or forward, or not move, depending on the frequency of the strobe-flash. If the flash occurs equal to the period of rotation (or an even multiple, i.e. 2*π*n/ω, where n

960-508: The attention of the surrounding population. Whistles were used by police in the 19th century. Steam whistles have been used on locomotives, ships, and in factories as alarm devices. With the advent of electricity, a variety of other alerting devices have been invented, such as buzzers , klaxons , sirens , horns , flashing and coloured lights, and other all-purpose alarms. Alarm devices can be fitted to buildings as well as vehicles. Many buildings are fitted with fire alarms , ranging from

1000-457: The behavior of others in the environment. Consequently, the ability to test an alarm and hold regular drills to practice an appropriate response may be provided as part of an alarm system. Alarm devices that are intended to cause the evacuation of an occupied building, such as fire alarms, may be deliberately designed to make remaining in the space difficult or even painful in order to encourage occupants to leave. Some alarms may startle and cause

1040-405: The effect.     Sometimes strobe lighting can trigger seizures . Several public incidents of photosensitive epilepsy have occurred. Most strobe lights on sale to the public are factory-limited to about 10–12 Hz (10–12 flashes per second) in their internal oscillators , although externally triggered strobe lights will often flash as frequently as possible. Studies have shown that

1080-549: The effects of LSD trips. Ken Kesey used strobe lighting in coordination with the music of the Grateful Dead during his Acid Tests . In early 1966, Andy Warhol 's lights engineer, Danny Williams, pioneered the use of multiple stroboscopes, slides and film projections simultaneously onstage during the 1966 Exploding Plastic Inevitable shows, and at Bill Graham 's request, Williams built an enhanced stroboscopic light show to be used at Fillmore West . Rapid flashing of

1120-532: The first International Electrical Congress . The erg was adopted as its unit of energy in 1882. Wilhelm Siemens , in his inauguration speech as chairman of the British Association for the Advancement of Science (23 August 1882) first proposed the joule as unit of heat , to be derived from the electromagnetic units ampere and ohm , in cgs units equivalent to 10  erg . The naming of

1160-419: The flash a small amount of power is diverted into a trigger transformer , a small transformer with a high turns ratio. This generates the weak but high-voltage spike required to ionize the xenon gas in a flash tube. An arc is created inside the tube, which acts as a path for the capacitor to discharge through, allowing the capacitor to quickly release its energy into the arc. The capacitor's energy rapidly heats

1200-743: The joule is defined as J =   k g ⋅ m 2 ⋅ s − 2 =   N ⋅ m =   P a ⋅ m 3 =   W ⋅ s =   C ⋅ V {\displaystyle {\begin{alignedat}{3}\mathrm {J} \;&=~\mathrm {kg{\cdot }m^{2}{\cdot }s^{-2}} \\[0.7ex]&=~\mathrm {N{\cdot }m} \\[0.7ex]&=~\mathrm {Pa{\cdot }m^{3}} \\[0.7ex]&=~\mathrm {W{\cdot }s} \\[0.7ex]&=~\mathrm {C{\cdot }V} \\[0.7ex]\end{alignedat}}} One joule

1240-457: The majority of people that are susceptible to the strobing effects can have symptoms, albeit rarely, at 15 Hz-70 Hz. Other studies have shown epileptic symptoms at the 15 Hz rate with over 90 seconds of continuous staring at a strobe light. Many fire alarms in schools, hospitals, stadiums, etc. strobe at a 1 Hz rate. Joule The joule ( / dʒ uː l / JOOL , or / dʒ aʊ l / JOWL ; symbol: J )

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1280-490: The same dimensions. A watt-second (symbol W s or W⋅s ) is a derived unit of energy equivalent to the joule. The watt-second is the energy equivalent to the power of one watt sustained for one second . While the watt-second is equivalent to the joule in both units and meaning, there are some contexts in which the term "watt-second" is used instead of "joule", such as in the rating of photographic electronic flash units . Alarm system An alarm device

1320-611: The successor organisation of the International Electrical Congress) adopted the " Giorgi system", which by virtue of assuming a defined value for the magnetic constant also implied a redefinition of the joule. The Giorgi system was approved by the International Committee for Weights and Measures in 1946. The joule was now no longer defined based on electromagnetic unit, but instead as the unit of work performed by one unit of force (at

1360-434: The time not yet named newton ) over the distance of 1 metre . The joule was explicitly intended as the unit of energy to be used in both electromagnetic and mechanical contexts. The ratification of the definition at the ninth General Conference on Weights and Measures , in 1948, added the specification that the joule was also to be preferred as the unit of heat in the context of calorimetry , thereby officially deprecating

1400-452: The unit in honour of James Prescott Joule (1818–1889), at the time retired but still living (aged 63), followed the recommendation of Siemens: Such a heat unit, if found acceptable, might with great propriety, I think, be called the Joule, after the man who has done so much to develop the dynamical theory of heat. At the second International Electrical Congress, on 31 August 1889, the joule

1440-414: The unit of energy the name joule , but has not given the unit of torque any special name, hence it is simply the newton-metre (N⋅m) – a compound name derived from its constituent parts. The use of newton-metres for torque but joules for energy is helpful to avoid misunderstandings and miscommunication. The distinction may be seen also in the fact that energy is a scalar quantity – the dot product of

1480-422: The use of the calorie . This is the definition declared in the modern International System of Units in 1960. The definition of the joule as J = kg⋅m ⋅s has remained unchanged since 1946, but the joule as a derived unit has inherited changes in the definitions of the second (in 1960 and 1967), the metre (in 1983) and the kilogram ( in 2019 ). One joule represents (approximately): 1 joule

1520-540: The war. This work for the Commission provided the historic foundation to the Company's present-day technology base. Internally triggered Strobotrons (light-output optimized thyratrons ) were available as well as flood-beam-CRT -type, grid-controlled Vacuum stroboscopic light sources with fast phosphors . The strobe light was popularized on the club scene during the 1960s when it was used to reproduce and enhance

1560-406: The xenon gas, creating an extremely bright plasma discharge, which is seen as a flash. A strobe without a capacitor storage device simply discharges mains voltages across the tube once it's fired. This type of strobe requires no charging time and allows for much quicker flash rates, but drastically reduces the lifetime of the flash tube if powered for significant periods of time. Such strobes require

1600-529: Was officially adopted alongside the watt and the quadrant (later renamed to henry ). Joule died in the same year, on 11 October 1889. At the fourth congress (1893), the "international ampere" and "international ohm" were defined, with slight changes in the specifications for their measurement, with the "international joule" being the unit derived from them. In 1935, the International Electrotechnical Commission (as

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