DMX and LIGHTING LIBRARY

 

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Lights and electronics

General info

The flaming touch and the campfire probably constituted early man's first use of 'artificial' lighting. Prehistoric man, used primitive lamps to illuminate his cave. Nowadays the electrical lighting is the most commonly used form of artificial lighting. The history of electrical lighting is long. In 1809, SIR HUMPHREY DAVY first demonstrated the electric carbon arc at the Royal Institution in London. The electric arc was also used for lighting at the Paris Opera. The principal of the electric arc is still used today by many older followspots and film projectors, used in entertainment facilities around the world. In 1877 Thomas Edison became interested and experimented with electric lighting. On October 15, 1878, the Edison Electric Light Company was incorporated. Edison patented more than 1000 inventions. Besides the incandescent lamp, Edison is given credit for inventing a system of electric generation. Although Edison did not invent the electric filament lamp, he did however turn theory into practicable form and was one of the first to successfully market incandescent lighting. Edison's first successful lamp used carbonized cotton thread as a filament, installed in a glass bulb, with all air evacuated. In 1880 Edison experimented with other materials for filaments, including wood, grasses, hair and bamboo. Of the over 6000 specimens tested by his laboratory, bamboo, became commonly used for filaments. In 1880, on January 17, Patent number 223,898 was issued to Edison for the T.A. Edison Electric Lamp. After the introduction of the tungsten filament, the next highly significant step in the development of the incandescent lamp, came in 1913 when the first gas-filled lamp was produced. Coiled filament gas-filled lamps in 500, 750 and 1000 watt sizes were introduced in 1913. They gave a much better light at higher efficiency with the same life as former lamps. Nitrogen gas was used in the first lamps but argon was substituted in 1914. Nowadays artificial illumination consumes more than 25% of electricity generated over the world. There are several trends in energy saving technologies for lighting industry. The first is implementation new lamps such as fluorescent, mercury, sodium, metal halide, halogen lamps. The second is associated with electronic circuit design for such lamps.

General lighting technology articles

Outside lighting information

Home and workplace lighting info

The majority of all indoor and outdoor lighting in the home today is provided by incandescent lamps, commonly referred to as conventional "light bulbs". The light bulb is the most widely used lamp in residential and many commercial and industrial lighting applications for general lighting. Halogen lamps are a type of incandescent lamp that gives "whiter" light, lasts longer, is usually small, is slightly more efficient than normal bulb and costs more.Halogen lamps are best suited for lighting areas where a direct focus of light is required.

Linear Fluorescent Tubes are the most common source of lighting in commercial facilities and can be found in many homes.Compact Fluorescent Lamps (CFL's) are of the same technology as linear tubes, but much smaller. CFLs operate with a ballast and a screw base adapter to accommodate their use in many indoor and outdoor applications. Typically, a 25 watt fluorescent lamp is supposed to give offas much light as a 100 watt incandescent bulb. Those power rating are about right, if you wait about 1 minute for the fluorescent to comeup to full brightness. When installing compact fluorescent bulbs, be sure that they do not heat too much inside the la,p. It is possible for those to fail due to excessive temperature. They don't need to reach the temperatures produced by incandescent lamps to fail after a month or two. Compact fluorescents are great, get a "name brand" for longer bulb life. Compact florescents should not be used on any circuit which is controlled by scrs or triacs (dimmers, motion detectors, security lights) unless they aredesigned for this purpose.

Low-voltage halogen lamps are becoming more popular for lighting stores, buildings, hotels, and houses. The lamps come in different configurations and wattages (typically up to 50W). Typical voltages are 6, 12, and 24V, supplied by a safety isolating transformers that are usually connected on their primary side directly to the mains power line (110 VRMS or 220 VRMS). Most typical voltage used for low voltage halogen lighting is 12V. Most of the time the safety isolating transformer feeding the lighting circuit is located in the ceiling of the room near the lights itself. In low voltage halogen lighting the most commonly used lamp types are MR 16 lamps. They are Multiple Reflector 2 inch lamps, seen as shop display lamps absolutely everywhere, available in low voltage flavour 12V (usually 20W or 50W bulbs), needs little transformer beside lamp, and mains voltage 240V flavor usually 50W or 75W and choice of beam angles. The low voltage lamps are typically very bright.

Lighting for use at a low voltage is to be considered as a power current installation since low voltages, such as 12 V, result in high currents even at moderate outputs which can generate a lot of heat. Installation must therefore be carried out carefully. The cables to the lamps must be fused in order to limit the heat generated, and they must not be twisted around one another as temperatures which are too high may then result. The core area is rough so that voltage drops which are too great do not occur, as this means that the anticipated light yield is then not achieved. Position the transformer close to the load so that the core area can be kept to a reasonable level. The following table provides guidance on the choice of cables for various loads at 12 V:

Length

1 mm2

1.5 mm2

2.5 mm2

4 mm2

6 mm2

10 mm2

1 m

120 W

120 W

200 W*

240 W*

300 W*

420 W*

2 m

80 W

110 W

200 W

240 W*

300 W*

420 W*

4 m

40 W

55 W

100 W

160 W

250 W

400 W

6 m

25 W

35 W

65 W

100 W

160 W

250 W

8 m

20 W

25 W

50 W

80 W

120 W

200 W

10 m

15 W

20 W

40 W

60 W

100 W

140 W

* Limited depending on the highest permissible fuse.

Note on light bubs and fixture power ratings have necessary meaning. You might wonder why should a mostly-metalic goosneck desk lamp say 60W? What if I put a more powerful bulb in it? 100 watt and 150 watt light bulbs radiate more heat than a 60 watt bulbdoes. More heat creates more damage to the light fixture. When the lighting fixture was designed, it was designed to accept a certain amount of heat andstill work properly over the useful lifetime of the fixture. If a fixture is designed to work properly with a 60 watt lamp in it, that means that theheat radiated by a 60 watt lamp will not destroy the fixture and the fixturewill continue to function over its useful lifetime. If a 150 watt lamp isput into a fixture rated for 60 watt lamps, the fixture will soon bedestroyed by the excessive amout of heat radiated by the 150 watt lamp andmay bread down and be the source of a fire. The designers will likely also have in mind a safe working teperature to the user, ie putting a higher wattage bulb in may raise the temperature of any metalwork on the lamp to a dangerous temperature which could cause burns to unsuspecting little fingers. The same principle applies to other lighting fitures as well. So for safety reasons NEVER exceed the wattage rating for the lamps in the fixture that they are going to go in. If you do, there may be damage, and a danger for a fire hazard! If if you need more light (lumens) from an existing fixture, a compact fluorescent rated at anything less than 60 watts of input power wouldbe ok for 60W rated lighting fixture. Typically, a 25 watt fluorescent lamp is supposed to give off as much light as a 100 watt incandescent bulb but the same amount or less heat than 25W normal light bulb. Another tip on some fixtures is to use a small reflector bulb in the lamp. Not only can you get away with a lower wattage for the same amount of lightdirected to a specific area, but for a given wattege, less heat is transferred back into the lamp. When using reflector lamp be sure to check carefully that the reflector bulb fits to it without blocking the air circulation or causing excessive hat to any place (for example getting to near to some heat sensitive part of fixture).

Suggested lighting levels (Illuminating Engineering Society (IES) Handbook)

Area:

Approximate Light Level (footcandles)

Offices:

75

Conference Rooms:

20-50

Auditoriums:

20-50

Kitchens:

50 (avg.)

Cafeterias:

10-20

Reception Areas:

25-30

Drafting Rooms:

100-200

Corridors/Restrooms:

10-20

Writing Areas:

20-50

Doctor's Treatment Areas:

200

Storage Rooms:

5-50

Stores (general):

30-100

Stores (sales displays):

50-150

The foot-candle is equal to one lumen per square foot and "the difference between the lux and the lumen is that the lux takes into account the area over which the luminous flux is spread. 1000 lumens, concentrated into an area of one square meter, lights up that square meter with an illuminance of 1000 lux. The same 1000 lumens, spread out over ten square meters, produces a dimmer illuminance of only 100 lux.

Wall hangings, retail displays, and trade show exhibits of all kinds can be very effectively lit with track lighting. Track light is a light fixture mounted on and movable along an electrified metal track. Lighting tracks are available in a variety of finishes, shapes, sizes and wattages, and with a variety of light sources and design accents. Track lighting is generally used to provide accent lighting, task lighting, and general lighting in that order. Track lighting is a very flexible lighting system. The individual track fixtures can move along the track, be swiveled or rotated while in a given position, and then aimed in any direction giving you excellent versatility to change your lighting scheme whenever the need arises. Track fixtures are available in line voltage and low voltage with a choice of incandescent, halogen, fluorescent, or metal halide light sources. Track lighting fixtures can offer an opportunity to be creative and make an aesthetic statement. Track lighting may use halogen, incandescent, fluorescent, or metal halide light sources. Track lighting can be used very successfully in any number of locations: hallways, museums, art galleries, trade show exhibits, offices, conference rooms, studies, churches, restaurants, taverns, hotel rooms, and libraries.

Here are few lighting tips for positioning lamps on some lighting applications:

There are also special decorative lights that are mostly designed for decorative purposes and the actual light output is secondary need. Examples of such are christmas light sets. They look nice, but do not give much total light output. The world glows with a colorful light at one time of the year - Christmas. Everywhere you look, Christmas lights sparkle and brighten almost every door step, window, and Christmas tree in very manu countries. Since the 17th Century, people have lit their Christmas trees to sit by its' comforting glow. The history of electrical christmas lights starts from year 1882. At year 1882 Edward Johnson, an associate of Edison's, created the first string of Christmas lights by hand wiring 80 red, white, and blue bulbs together in a string. At year 1895 President Grover Cleveland put lights on the White House Christmas tree. In 1903, the first strings of Christmas lights were sold to the masses. Strings of Christmas lights continue to evolve. Filament light bulbs are losing ground to energy-saving light-emitting-diode (LED) Christmas lights. Nowadays it is hard to imagine Christmas without bright, twinkling lights. Christmas lights are available at indoor and outdoor versions. The indoor versions are typically considerable cheaper and are only ment to be used inside. Outdoor Christmas lights are an excellent way to decorate your house and yard during the holidays. Outdoor lights are designed in such way that they are safe to use outside where enviroment can be from wet rain to freezing cold. The outside lights are designed in such way that they are safe to be on those hard environments and will last years in such enviroment (using indoor lights outside would be an electrical hazard and they would propably fail pretty quicly). Most outdoor christmas lights are based on low voltage bulbs and powered through low voltage transformer (typically 24V AC output). The low operation voltage and electrical isolation (provided by transfrer) from mains voltage provide the safety. There are also high power outside lights hat operate at mains voltage directly, those lights are constructed so that they are comptely waterproof and can withstand outside weather (because mains voltage is on this system be careful when using them, do not touch them when power is on in case insulation has failed on some place of the set).

Usually it is a good idea to select a light that is double-insulated or that has been wired with an earth conductor. Double-insulated lights will show the double box symbol. Check also the lamp rating is suitable for the enviroment they are ment to work at.

General

Wiring and installing

In many countries you can do some simple lighting related electrical wiring or light installing yourself. If you plan to do that, then check what you are allowed to do nad how to do that work properly.

Safety Alert: As with any electrical project, make sure that the power to the circuit where you are working is turned off at the breaker box. Test the wires with a tester to make absolutely certain that the power is off. It's advisable to place a note reading "electrical work in progress" on the breaker box while you are working to make sure that someone else doesn't unknowingly turn the power back on while you are working.

Safety Alert:If you feel uncomfortable or unqualified to do electrical work yourself, then you should consider hiring a licensed electrician to do the work.

Low voltage halogen lighting

Architectural lighting

Architectural lighting, the use of light in buildings, is critical to the performance of everyday activities and to the appreciation of the built environment. Using Architectural Lighting Controls, specific architectural details of an area can be enhanced and almost any effect or mood can be created. By controlling the lighting in an area, different moods can be artificially created for the desired effect, whether it be a relaxing atmosphere or to stimulate a lively response. In restaurants, for example, different scenes may be required to create a suitable atmosphere, depending on the time of day, e.g. brighter lights at breakfast time, but more subdued lighting effects at dinner. Many buildings are used for more than one purpose at different times. This creates the need for versatility & flexibility of a system. With lighting control, the mood of the lighting can be altered to reflect the mood of the activity taking place and create a suitable ambience. For example, a church may wish to change the lighting scene depending on the event which is taking place. Different scenes would be suitable for a funeral compared to a wedding. Offices are benefiting from lighting control systems. Gradually altering the levels of light throughout the day working with external lux levels, perhaps by incorporating daylight sensors maintains optimum light levels and can increase productivity in an office. In retail, lighting can be used to encourage people into shops and draw attention. Special effects can be incorporated to create interesting features.

TV studio and location lighting

In film and video lighting a constant light levels is very important. A constant exposures on the face are very important. A soft light on the face is important. Too high contrasts in the lighting are should be avoided. In TV the angle of the Key light is critical: It must light the eyes well. Most light used in TV studios are fresnels and scoops.

Central to all film and television is the Kelvin scale. The Kelvin scale is a way of measuring how orange, or how blue light is: its color temperature in other words. The color temperature used in many TV studios is around 3200 kelvins. For comparision a naked candle is 1800 Kelvins, 100W domestic light bulb is 2850 Kelvins and nominal daylight is 5600 Kelvins (direct sun can vary between 5400-6000 Kelvins). The TV studios are typically lighted with dimmable lights, and typically the light bulbs are not "full on" (this gives possiblity to adjust light levels somewhat by changing dimemr sttings, without too much altering the color temperature at the same time).

Disco lighting

The first effects in dance hall lighting appeared long before disco's started. In the 1940's it was discovered that if you shine a light on a ball covered with mirrors that you get one beam off every mirror (seen for example in 1942 film Casablanca). When disco's came along in the late sixties and early seventies the mirror ball was the first effect to adopted. Other lighting could be provided by red bulbs or other colored light bulbs. First strobo effects were generated by using a powerful spotlight with a spinning wheel in front of it (this wheel has holes in it). Soon "Ultra Violet", which made white things glow in the dark, was adopted to disco lighting (makes white clothers to shine, even underwear through clothing).

The first real dedicated disco lights were invented in about 1968 when someone decided to control lighting using electronics. The most popular effect from this era wa the light organ, that made lamps to flash to different frequencies, originally three channels (bass, middle, treble).

In the early seventies light sequencers came to use. The idea was to make the lights only react to the bass beat so that one light channel would turn on at time and the light bulb on would change every time the bass beat hits. This gave an easy and dramatic sound activated effect that the eye could follow easily and the Sound Sequencer or Sound Chaser was born. Over the years various variations of this technology have been used.

In the later 1970's the smoke machine arrived. Instead of just seeing the lamps flashing, provided you used the right kind of lamp, you could see the whole beam passing through the air. This heralded the reign of the "PIN SPOT" (PAR36) with a narrow concentrated beam. Sound Chasers combined with PAR36 light and smoke could be used to create qutie stunning effects. Ath the same time came motorized effects like helicopter and sweeper that turned the ligth bulb generating the light beam. Next came flower effect, that produces the multiple beams using mirror ball type (possibly colored and spinning) mirror system and force them in one direction through a lens.

Modern disco lighting nowadays is generally modern technology combined with earlier ideas. Multiple beams of the mirror ball, 3D "in air" beam projection and sound activation are the main components still nowadays. The new component on disco lighting used often nowadays are intelligent lighting instruments. Those intellinget lighing instruments send a light beam through a colour filter and a shape (called a "GOBO") then project it onto a mirror that is aimed to different directions with two electrical motors (usually stepper or servo motors). They allow selection of light color, beam shape, beam brigtness and beam direction. Those intelligent lighting instruments are generally controlled using digital DMX-512 light control interface, and the light operator runs them trough a special light control panel or computer program.

Stage and show lighting

Lighting is important in theatre and shows. Lighting allows us to see the performers. Lighting provides a tool for setting moods and tones of scenes on stage. Different type of performanced have different lighting needs. Here are some typical lighting situations:

Stage lighting is achieved by the use of a large number of powerful stage lights, or lanterns (or luminaires). There are a great variety of these, for different applications, or of different make or vintage. So there are many different types of lighting instruments used in any theatre. Each type of instrument plays an important role in the overall lighting scheme. The most common light types used in theatres are plane convex lights, freshnels, profiles, which are the generic classes of spotlights. In addition to this floods are used for various applications. Also used are PAR cans , but these offer little control and are used more in rock lighting than in theatre. Most luminaires use at least one lens, which is a piece of glass with one or both sides curved for concentrating or dispersing the light beam; this produces a variation in the beam angle and the quality of the light produced. Some luminaires utilise an attachment on the front of the unit called a barndoor. This consists of four movable metal flaps which are used to control the spill of light produced.The lamp which generates the light inside light instrument is a glass (or quartz) envelope which contains a filament or electrodes surrounded by a gas. The most common lamp types are:

Lanterns are hung (or rigged) in lighting positions and are focused (or angled) onto the stage (or anything else). If coloured or tinted light is required, as is usually the case, sheets of gel (or colour) held in special gel frames are placed in front of the lanterns.

The light color is controlled by color filters that are placed in front of the light bulb that created the white light. The filter passed through the needed wavelengths to produce the needed light color. In the early days of the electric filament lamp, gelatin color filters were used to color stage lighting fixtures. Gelatin filters dissolved when wet, and could not withstand the high heat from the tungsten halogen lamp. Next filter technology was Cinemoid. Cinemoid used a colored acetate sheeting, with inherent self-extinguishing properties. 'Cinemoid' is no longer produced and has been replaced by polyester based materials, such as 'Roscolux' and 'Lee' filters. All Lee's light control and color effect filters are made from a tough polyester film base, which is impervious to water, is totally transparent and has a high melting point. This base is then coated with specially prepared lacquers. The lacquer coating is applied to both sides of the film, is also tough and flexible and has a high resistance to water and heat. This kind of filters may scratch and the surface color may actually vaporize from the surface, through atmospheric contact. 'Roscolux' filters are designed to withstand the high temperatures of stage and studio lighting fixtures. Roscolux filters are colored when the plastic is in the resin stage before the polymer is cast into film. This results in a tough, resistant and durable filter with the color actually part of the plastic, instead of just applied to it.

The key to lighting control lies in the dimmer. Light dimmer allows the controlling of the light output (the light intensity) of different lighting instruments. Those dimers used to be resistances, autotransformers, saturable reactors and other specialist components. Nowadays light dimmers use phase control principle and use electronics switching components like thyristors, triacs, GTOs and FETs. Thyristors and triacs being the most commonly used components for dimmers in use nowadays. Dimmers are normally available in channels, which can be thought of as electrical circuits capable of handling a rated load. Standard dimming channels are offered in 600-, 1,200-, and 2,400-watt capacities, which correspond to electrical loads of 5, 10, and 20 amps in 120V AC system. In 230V AC systems most the channels are most often offered with 4A (920W) or 10A (2300W) power. In large dimming setups all the dimmer are usually located in the central dimming room or other central location. The lanterns are usually tailed and plugged up to dimmer outlets via a patch board. Various types of cabling and connectors are used to connect lighting instruments to dimmers. Often times, permanent theatre installations will have special outlet strips along the lighting battens to connect the instruments. In less permanent installations movable breakouts are used. Breakouts connect normal single light connectors to a multi-conductor cable usually terminated with a Socapex connector. Using multi-conductor cables the amount of separate wires coming from dimmers to lights can be reduced (=easier to manage). In small set-ups the lights are just directly wired to the dimmer outlets. In distributed dimming systems the dimmers with few channels of outputs are rigged together with lighting instruments to lighting setup, and then all separate dimmer devices are controlled using one lighting console through DMX-512 bus.

Typical theatre stage lighting setup has tens of dimmer channels and lots of lights conected to them. A lot of pub venues just use a dimmer pack, small programmable DMX control desk, and a few PAR cans, usually on 4 or 6 channels. This can be a very versatile arrangement for a relatively small investment.

The light dimmers are most often controlled remotely using light control desk which communicates with the dimmers through control cable, which can carry the control information in either analogue format (usully 0-10V DC) or digital format (most often using DMX-512 protocol). The simplest lighting board one is likely to find today allows the operator to set up two scenes and cross-fade between them. These are commonly referred to as X-Y boards. An X-Y board has a number of channels associated with it, where each channel can control one or more dimmer channels. For example, twelve channels may be controlled with a small board. Levels can be set for each of these individual channels on two scenes and a -fader allows switching between scenes. Advanced lighting boards usually provide all of the same features as an X-Y board, but add the ability to store scenes, record a sequence of scenes in a cue stack, and record light chases. Control desks normally come with provision for controlling 6, 12, 18, 24, 36 or even 48 dimmers (there are also bigger desks in very large systems).

The followspot is simply a high power spotlight mounted on a stand. An operator (or stagehand) controls the lamp and is able to pan and tilt the spotlight, following an actor anywhere on stage. Today, the followspot fixture is still commonly used, for theatre, dance, opera and other entertainment events.

In addition to the normal lights controlled by light dimmers, there are a huge variety of units that fall within the general category of 'intelligent'. The most well-known type is probably that of moving lights, where the luminaire is able to control the position of the light beam, together with other aspects of the light quality. Moving lights can be considered as Moving Mirror or Moving Head units. Moving head devices physically point the whole light in different directions by using a motorised yoke. Moving mirror type units (used mostly in nightclubs and rock shows) are best suited for prolonged, fast moving lighting effects. Moving lights are generally controlled using digital DMX-512 interface.In addition to those there are also color scrollers and disco effects. Use of a colour scroller system within a theatrical lighting rig can greatly increase its potential. Instead of fitting one colour filter per luminaire, the scroller allows a row of colours to be stored and wound to the chosen colour. Scrollers are pretty simple to operate. Sending a channel percent value to the scroller will set the position in the string and thus the color. What value you will need to send will depend on how many cells you have in your string, in what oder your colors are there and what color you want. Each scroller takes one light controlling channel. Powering anc controlling color scrollers vary by brand. Scrollers, moving mirrors, and other attachments for light fixturesare typically powered by a special type of external power supply. Thescroller, etc. is connected to the power supply by a special 4-pin XLRcable that provides both the DMX signal and the power (usually 24V) to the unit. You would plug the DMX line from your console into the power supplyand not the scroller. You can buy power supplies capable of poweringmultiple scrollers, so it's the responsibility of the power supply tosplit the signal and deliver it to each of the scrollers. Generally you can think that there is a power supply that takes an AC feed (NOT a dimmed) and a DMX signal from the console and then some number(like up to 16) scrollers daisy chain on 4-pin cable out of the power supply. There are also systems where each scroller takes an AC feed and a DMX signal from the console (many intelligent lighting instruments are built like this). Disco effect are type of intelligent fitting that can be used to create the effects seen in nightclubs and at parties. There is a wide range of equipment available in this category, from simple strobes to multi-colour, multi-beam units. Most disco light effects are either controlled through DMX-512 interface or move automatically semi-randomly based on sound around them (some have built-in microphone or sound input connector for this).

There are also so called "intelligent lights". Typical intelligent light instrument allows the user to control the light color and direction the light points to, possibly also can change a gobo figure. This kind of intelligent lighting fixtures are generally controlled through DMX-512 interface (idea is that one or more channels in DMX-512 data controls each intelligent light adjustable function). There is wide variety of intelligent lighting fixtures made for different uses, from a small night club to a large rock show stage use. Here are few things to consider when selecting intelligent lighting fixture:

Often the Dj lights of 250 watts or less won't have the punch to be really visible when using fresnels, pars, or ERS's of 575/750/1000 wattages forwashes. The Dj gear is OK for smaller events like home parties, small low ceiling clubs, but do not work on large stage applications. SO before getting anything you need to know what purpose do you want them for: club, arena rock, corporatebooths/parties and how much money do you have for units and then buying bulbs. All these factors are issues to add when buying intelligent lighting.

Typical small "rock and roll" club stage setup few sets of PAR can bars connected to dimmer pack (6 ot 12 channels) and some moving lights.PAR lamps stand for Parabolic Aluminised Reflector. The PARABOLIC ALUMINIZED REFLECTOR (or PAR lamp) is a sealed beam type of lamp, similar to an automotive headlamp. The filament, reflector and lens are all optically aligned at the factory, and sealed into a single lamp - resulting in a highly efficient source. As the PAR lamp is a complete lighting unit, fixtures for them are very simple indeed. The PAR lamp is also sometimes known in Europe as the 'pressed glass reflector lamp'. PAR cans come in many versions (PAR 56, PAR64 etc.). Today, PAR lamps are available in various diameters (4.5" to 8"), and various wattages (75-1000 w.) The highly efficient PAR64 lamp (8' lens) is extensively used by the theatre and entertainment industry and the fixtures are often referred to as 'PAR cans'. The bigger the number with a par can is the bigger its size. Electric lamps used in PAR lamps are sized by multiples of 1/8 inch. Therefor a PAR-8 (if such exists) would have a 1 inch diameter glass envelope.A PAR-64 is 8 inched in diam. To convert PAR number to inches divide lamp number by 8. Some common PAR lamp types:

Today, the ellipsoidal reflector spotlight is still one of the basic tools of the stage lighting designer for spot-lighting applications. In Britain the 'ER' is referred to as a 'profile spotlight' or a 'mirror spot'. In its simplest form, the ER fixture consists of a housing, a light source, an ellipsoidal reflector and a plano convex lens. The light beam produced by an ER fixture is round (or 'conical') with a sharp defined cut-off edge. The fixture is actually a simple projection device and will optically project the image of anything placed at its focal point. The typical ER fixture has 4 integral framing shutters or an iris - to provided limited beam shaping. In addition, and of particular importance the ER fixture will also accept and project the design of a metal pattern, commonly known as a template or gobo. The typical ER spotlight uses a tungsten halogen type of lamp. Fixtures are available in lens diameters from about 4" to 10" and with wattages from 500 to 2000 watts. The typical stage and studio ER fixture has a lens diameter of 6 inches and a 1000 Watt lamp. The ER spotlight is selected by beam spread. Fixed beam spreads are available as follows: 5, 10, 15, 20, 25, 30, 35, 40, 50 degrees. Formerly in North America (1950's-1980's) beam spread was designated by specifying first the diameter and then the focal length of the lens. Example: a 6x9 (pronounced 6 by 9) was a fixture with a 6" diameter lens and a 9" focal length. In order to determine the spread in degrees of any particular fixture, the designer still needed to consult the manufacturers data sheet as the designation did not accurately identify the beam spread of the fixture. Today spotlights are specified in 'degrees' only. The following table shows approximate beam spread of several common ER spotlight fixtures:

Profiles are the light instruments that produce the narrowest beam. They operate on a similar principle to a slide or film projector in that they have a focal plane (the "gate") and the image of anything placed in that focal plane will be projected by the lens. The lens can be moved to sharpen or soften the focus. Generally, of course, there is nothing at the focal plane so you get a very sharp edged circular beam of light. These lanterns, however, have beam-shaping shutters (four of them) which can be pushed into the focal plane so that you can change the shape of the beam to square, rectangular or triangular. You can also place a gobo in the focal plane. Incidentally, it is also possible to get an iris diaphragm which can adjust the size of the circle of light projected by the lantern from the full width to a pin-spot. There are two types of profile: fixed beam and zoom. A fixed beam profile produces a beam of fixed spread, whereas you can vary the beam spread of a zoom. The most commonly profile to be found has a beam angle of 23 to 25 degrees. Zoom profiles are described by the extremes of their beam angle: a 16/30 profile, for example, has a beam which is 16 degrees at its narrowest and 30 degrees at its widest.

Diffrent kind of filters are used to change the color of light that goes out of the lighting instrument. The idea of a color filter is that it is on the way of the lighting beam. The filter only lets the wanted combination of different colors (light wavelengths) through and stops everythign else (absorbs or reflects other color). The most typical way to control the ligth instrument color is to usea normal absorbing filter. It passes through the wanted light and absorbs other lighting.

The gobo has long been the lighting designer's tool to shape the light beam and project light shapes to stage. The gobo is placed to the focal plane of a suitable lighting instrument (typically profile) by the user or a set of gobos can be built into the instuments like intelligent lighting. Gobo is just a shadow mask that lets out the light at right shape and masks out the other light. Gobo is typically made from metal or metal-coated glass, or dichroic coated glass processed to have the wanted shape in it. A standard metal gobo is a piece of sheet metal with cutouts. (You canmake a crude and short-lived version with a Coca-cola can and apocketknife.) Meshed gobos are just like a normal gobo, just with a mesh so they cancarry completely cut out shapes and finer detail. The thing about mesh gobos is that you need to play with the degree of"defocusing" to blur out the mesh but not so out of focus as to make the image too blurry around the edges. A greyscale metal gobo has tiny holes of varying sizes tocreate a mesh and produce the greyscale. By careful juggling with the focus, mesh grayscale goboes will give you a greyscale image, rather than the on-off black and white image that you get fromcut-outs. Glass gobos are etched from metal caoted glass and will carry finest deatal. The gobo itself usually goes into a metal holder that slides into a slot roughly even with the shutters in the lighting instrument. Glass gobos need to be inserted with the shiny (mirrored) side facing the source; metal gobos can go either way. The image on the gobo will generally be projected reversed andupside-down from the way the gobo sits in the unit (trial and error will teach you if you are not sure). Color filter gel can be added as usual to the lighting instument if colors are needed. Taped-together piecesof different colored gels are sometimes used with patterns, but don'texpect to be able to control the color blending.

Stage lighting systems are generally controllable using some form of lighting control desk that controls the dimmers and moving lights. The simples lighting desk might have just a set of sliders that the operator manually operates. The more complicated lighting desks usually have memory options to store many lighting scenes to the memory and allows the user to recall them as needed. PCs are coming to entertainment lighting quicly with the introduction of suitable control software and DMX-512 interfaces. There has been mixed reviews how well PC performs those tasks. Maybe in simplest systems there might not need to bring in PC, but in complicated systems where the control power of traditional lighting controld desks ends, a PC based system might be a very good choise. One recomendation; do not use the same machine for sound and lighting control; in fact if you are using a PC for any entertainmentapplication; lighting, sound, video, or image playback or showcontrol it isa very good idea to use separate and 'virgin' machines and closed networks. As all of us know Windows based PCs are very prone to crashes and randumerrors; so using separate and virgin machines is always a plus; once you connect a computer to the internet and download files to it or install any applications other than what you need for the show you have comprimised theintegrity of the computer. Always be wary of multi-use computers in show applications; there is nogarauntee that the apps will work well together. Many people have experienced difficulities with standard use machines being utilized for sound playback and show control applications.

In many show lighting applications you can see two separate lighting controlling systems in use. There can be a traditional lighting desk for controlling the lights that go to the dimmers. Intelligent lights usually use a different console and protocol than the conventionals, and their control cable is run separately. Intelligent lights areoften controller with a special lighting desk optimized for intelligent lights controlling or with a suitable control software running on the PC. The use of PC gets more and more popular because there are many good control software applications that allow the light designer to make vry fancy control sequences that can be played back during the show with few keypresses, and best software even allow visualization that the lighting would look (you can design the effects in advance with just your PC without having the actual instrument or access to show location, and then then just do the fine-tuning at the show place when the instruments are installed).

The stage lighting is usually handled by a light designer and a master electrician. The responsibilities of the Master Electrician (M.E.) are to hang, patch and focus the lights as per the lighting plot provided by the lighting designer (L.D.). Master Electrician controls the lighting loadin. Master Electrician must make sure all the instruments are hung and cabled correctly. Master Electrician is often called upon to patch the lighting console, focus instruments, manage strike, and so on, depending on the demands of the lighting designer. Master Electrician will get a lighting plot from the lighting designer (LD). If necessary, also find out from the intelligent lighting designer (iLD) where those instruments are going to be hung and how they should be numbered. (Most of the time, this is on the lighting plot.) With the designers, write down which instruments go on the same channel. Often times, especially with the truss, multiple instruments go on the same dimmer, and it is important to know this before figuring out how to cable things. Many times the M.E. or L.D. will also operate the lighting console for the production.

In theatre environment the safety of foth actors and audience members needs to be considered. For actor safety all the lighting instrument must be securely put to place (so that they cannot fall, and safety cables make sure that if someting goes loose it does not fall to ground), lighting instruments must be in good condition, light away from material that can catch fire (lights can be very hot), light wiring is in good condition and proper fire extiguishers are easily available. Many theatres (most UK theaters for example), with a pros arch, have a fire curtain, also referred to as "the iron". Its mission in life is to give the audience TIME to evacuate in a safe and orderly fashion, and it should keep the smoke from an on-stage fire out of the house. Many theatres also use automatic vents above the stage, which makes sure that the smoke can get out from there easily instead of getting to audience. While these, forming a chimney, ensure that the stage becomes a raging inferno, they give the audience time to get out.

General

Glossaries

FAQs

Handbooks and training manuals

Organizations

Safety

Wiring

Building a working stage lighting system involves lots of cabling to feed the power from the power source to the lighting instruments. Different theatres provide different means for connecting equipment to be powered. Some simply provide a large number of standard mains connectors you are used at your home and some provide high-current hookups. Many venues provide some sort of combination of high-current and low-current hookups. Often some medium-capacity feeds are also available.Any venue that has been properly wired by a qualified electrician will have a circuit breaker panel that is used to shut circuits off in the event that they draw too much current. It is the current capacity of circuit breaker (in amperes) that determines how much current a circuit can supply. The breaker size is chosen relative to the type of cabling and connector used for the circuit, as each have different capacities. Stage lighting very often uses a three phase power feed which is wired to the dimmer rack, which distributed the power to different lights. There used to be some specific recommendations on some countries specific to this kind of systems. The requirement/recommendation for phase separation is no longer in the IEE regulations (currently 16th edition). There is no requirement in the 16th Edition (or the 15th) to keep sockets on different phases separate. There is a specific requirement to label 415V potential anywhere where you may not expect to find it.Once upon a time (13th edition of IEE regulations) it used to be a requirement to keep connector connected to different phases on physically separated places (two meters apart..). Many people still think it is. However it hasn't been for the last two editions of the regulations. Stage wiring can use the normal household plugs for lights or some other mains plig types (this depends on regulations and environment used). The following plugs can be seen often in stage lighting systems:

It is very nice to have different connectors for dimmed power and mains power. Most professional theatres in the USA use either stage pin (a.k.a. 2P&G) or twist lock connected to the dimmers and edison (2 parallelblades with ground) for domestic mains power. You have to actually work atconnecting something which shouldn't be dimmed to a dimmer since it willinvariably have an edison plug. When the power is fed to the dimmer packs and other similar similar system, high power electrical power connectors are used. In Europe CeeForm connectors are often used to connect three phase power to the dimmer racks. In USA cam-lok connectors are the standard for high current three phase power feeds (get a proper electrician to connect this set of five connectors right). In USA also some other connectors are used for high current feeds. NEMA "14-50" ("Harvard Standard") is commonly used connector for high current two phase power for rental dimmer packs (up to 50A per per phase). NEMA "14-60 " is sometimes to feed two phase power (125/250V) up to 60A to dimmer packs.

In addition to connectors described above there is large number of different multi-pin connectors used to connect a group of mains circuits through one connector. Those multi-pin connectors are generally used to carry the power from light dimming racks to the lighting bars. The most commonly used connectors for this are Socapex and Harting, but there are also many other multi-pin connectors in use.

Multipins connectors are often seen on the back of dimmer equipment and/or dimmer equipment racks. Sometimes separate light circuits are wired to them or out of them using an adapter that adapts the multipin connector to many separate mains single channel mains connectors or output jacks.

For the multipins connectors descibed above there are widely accepted wiring standard how those connectors should be wired. Please note that just because a connector has a wiring standard, it doesn't mean the cable you're using is following it. Please be very careful, especially with power connectors. Always check when using somebody else's kit. If in any doubt, check!

When installing lihgt dimmer systems you need to consider the needed power feed for them. When designing system (touring system or permanent installation), to think about is how many dimmers you can drive with the power available. Most dimmers this side of the pond come in multiples of 600 watts (600w 1.2kw 1.8kw or 2.4ks). Usually you don't need the amount of power that is the maximum power of dimmers connected to the mains feed. In general, you can "overload" your incoming power by a decent amount, meaning having more dimmer power and total light load than your feed can handle. You could get away with more since you will never have all channels at full even if all the dimmers are loaded to capacity (which is highly unlikely) unless you are a community theatre were untrained or inexperienced lighting people might have unsupervised access to your equipment. If you have more light instruments than your power input can handle at the same time, you need to make sure that your LDs/and or MEs understand about both the maximum loading capacity of your incoming circuits so they don't plan anything stupid.

When using three phase power feed with large dimmer packs some things need to be considered in the wiring. First it ia a good idea to distribute the dimmers among phases so that they don't get radically out of phase balance. Phase controlled dimmers are a very highly non-liner loads. Dimmers do generate a large number of odd-order harmonics (worst is third), now unlike the fundamental (50 or 60 Hz line freq.) when 3rdorder harmonics are "added up" in the neutral the magnitude increases.Usual practice is to specify the neutral conductors at 130% of phaseconductors (rated for 130% of nominal phase current).

Modern dimming systems are larger in dimmer quantity, more heavilyloaded with fixtures and more accurately fired than ever before. Electronic dimming can present many stresses on the electrical transformer that feeds thedimming system, which will make this switch gear chatter and potentiallyover-heat the wiring and the transformer. In general terms, the SCR switching distortsthe normally smooth AC waveform. This distortion is the worst in the dimming range of 35% to 70% and travels through all of the wiring involved in the system. A typical power feed to a dimmer rack would have three hot legs, one neutral anda ground wire (three-phase four wire + ground 120/208 volt servicein USA, 230V/400 volt service in Europe).In worst case (all of the dimmers are set for a 35% dimming range) more current can be carried on neutral wire than what it is rated for (unless oversized neutral is used). This can cause overheating the wire covering, wire connectionsand the transformer without main circuit breaker tripping(because the draw on the hot legs is still below their capacity).The chatter of the switch gear is an audible warning of a potentially critical problem. The chatter can also be very irritating, especially during quiet moments. This problem can then be magnified by the layout of the power feed and load wiring.

There are also considerations of the cable types to use. The wires used in stge work need to be able to take hard use, sometimes hard climate environment (in outside shows for example) and sometines need to withstand very hot conditions. The "pig tail" is a term that refers to the cord on stage instruments. Modern pig tails are made with fiberglass and other composite, heat resistant substances. In the old days these cords were coated with asbestos as a heat insulation. Unfortunately, asbestos has a nasty habit of causing cancer, so they are not allowed anymore. This by no means implies that you will never see stage instruments with asbestos (those can be found on old istruments).

You should, if buying second-hand, check that the lantern is safe and that check should include earth continuity between the plug and the case. You will presumambly be in possession of some test equipment so identifying which wire goes where shouldn't be too difficult. The simplest test is to measure the quality of the connection with a multimeter (you should get very low ohms reading between connector ground and equipment metal case). On some countries (for example in UK) you need to do PAT test that makes sure that groudn id connected and there is no breaks in insulation. Generally as long as you get the earth right, in normal lamp wiring it shouldn't really matter which of the other two is live or neutral. An incandescent lamp is passive device, it just conducts, so as long as it is between the hot and neutral, it doesn't care what color the wires are and which one is live/neutral. An exception to this is if the lamp socket is an edision screw (or equivalent) the neutral should go to the outer (neutral is less likely to cause danger if you accidentally touch it). If the lamp or wiring has a power switch that switches only one wire, then that wire should cut the live wire.

Don't rely on other people's advice blindly. Check it youself. Someone's life might depend on it.

Stage lighting design information

Well done lighting can enhance the performance very much, but badly done lighting can ruin the performance. So, first you illuminate: you make sure that the actors can be seen, but in such a way that shadows (if there are any) fall consistently. The most commonly seen lighting mistake in both school and amateur theatre is the shadow going in different directions as an actor walks across. But if you just blast light at them from in front of the stage, you will make their faces look flat and the features indistinguishable. You need to provide some modeling. There are many lighting technologies you can choose to use. The trick is to try to use the new technologies, and even the oldestablished ones, only when it does enhance the project and leave it onthe shelf when it does not. The real trick is learning to tell thedifference.

Light shows information

Lighting tips

Rigging

Rigging involves hanging things over other people. Attention to SAFETY is important. If something goes wrong, somebody can get hurt.Riggers need to know the proper methods of securing items like cable, also called as wire rope, to other objects without the possibility of slipping. Most common way to rig lights in theatrical environment is toright the lights to scaff using some suitable lighting clamp. Scaff is a 48mm steel tubing used for temporary constructions and lighting bars. Overloading a line poses a serious threat to the safety of personnel, not to mention the heavy losses likely to result through damage to material. To avoid overloading, you must know the strength of the rigging system and components used in it.This involves three factors: breaking strength, safe working load, and safety factor. Breaking strength refers to the tension at which the line will part when a load is applied. Breaking strength has been determined through tests made by rope manufacturers, and tables have been set up to provide this information. The "safe working load" (SWL) of a line is the load that can be applied without causing any kind of damage to the line. Note that the safe working load is considerably less than the breaking strength. A wide margin of difference between breaking strength and safe working load is necessary to allow for such factors as additional strain imposed on the line by jerky movements in hoisting or bending over sheaves in a pulley block. The SAFETY FACTOR of a line is the ratio between the breaking strength and the safe working load. Safety factor will vary, depending on such things as the condition of the line and circumstances under which it is to be used (safety factor is usually 4-10) .

Foggers and smoke machines

Many productions can benefit from the use of artificially generated smoke.

Commercially available machines are available that use a chemical fluid to generate smoke. The fog fluid is generally made out of glycol and water, making it relatively non-irritating and safe for use in a theatre setting. For low-lying fog effect, fog machines are often used. These machines use dry ice.

There are several types of smoke effect available, each of which will produce a slightly different result. Smoke is particularly effective at bringing the beams produced from moving lights and lasers to life, and has become an essential part of some lighting displays.

Low hanging fog on the floor consist of mist droplets. These fogs hug the floor because the air in which the mist droplets aresuspended is colder and denser than the original room air. WWater and very cold substances such as dry ice or liquid nitrogen are most often used to create the fog. However, any liquid inert gas can be used.Some of the low-lying fogs also employ chemical fog fluids in theirsystems.The low hanging fog is usually generated just by dropping "dry ice" to hot water. Low hanging fog can also be generated using a 'standard' smoke machine and coolingit's output (run through icd or use special chiller/cooler).There are also "ultrasonic mist OR fog" device which brings out fog using just normal water. There are also devices called "oil crackers", which break oil to very small droplets. This fog does not usually does notsow much, but makes the lights and lasers clearly visible.

There are three main types of smoke/fog machines widely used:

There are also smoke effects that use liquid carbon dioxide (CO2) or liquid nitrogen to generate smoke effects. When those devices spray out liquid cardbon diodide or nitrogen, the coolign effect of it causes the water in the air to turn to visible moke together with the CO2. Liquid CO2 or liquid nitrogen used for example for generating "fog burst" effects. I have also heard that CO2 fire extinguishers are used on some places to generate fog effect (those needs to be separate for ones recerved for real firefighting purposes).

When using fog effects be warned of some potential healt effects. Smoke and vapour effects can give rise to a variety of hazards depending on the substances used. Manufacturers and suppliers must provide information about the hazards which may arise from their products. This information should be obtained and used when carrying out risk assessments. The following general hazards may need to be considered:

Dry ice generated fog, is almost all water vapor, but also does have anappreciable quantity of CO2 in it. Used in areas with adequate ventilation/airflow is perfectly safe. If you put too much thistype of fog to a closed room it can get very hard to breathe (toomuch CO2 in air and too little oxygen). Carbon dioxide is toxic and can causeunconsciousness in a few minutes at levels above 7 percent.

Water Base Fog technology is achived by pumping Glycol/Water mixture through a heat exhanger (simeitmes called heat chamber). The heat exhanger has been heated to the point where at the fog fluid mixture will vaporize. The fluids own vaporization forces the hot mixture through the output nozzle where, when mixed with the ambient ear, it form an opaque aerosol (fog). The fog is made up of tiny droplets of glycol that form around the small particles in the air. The suspended droplets reflect the light, thus make the illumination visible. The normal components used in this type of fogger are a solenoid pump to push the liquid in, and a fibreglass lagged heater block based on a sandwich of aluminium plates, a heating element and a long piece of copper capillery tubing snaked around between the heater plates. In some units the heater is tubular with the capillery tubing wound round it, but the effect is the same. At switch on the unit will not pump liquid until the heating block has come up to the correct temperature, whereupon the pump can run and squirt the fluid into the block. When it does, the fluid evaporates very quickly and the resultant increase in pressure not only causes it to form a dense superheated vapour, but forces it out of the front of the machine via the exit port, which can be as simple as the end of the capillery tubing being poked out, or in some cases a small pinhole orifice to make sure that the internal pressure is kept high. The resultant dense vapour exits the front of the machine and upon contact with the cool air it forms a dense cloud that is a very close relation to real fog.

In relative terms the ingredients used in smoke fluid are pretty safe, but there is always an ongoing debate in the entertainment industry about whether the output of a smoke machine is safe or not. When exposed to strong concentrations of the fog many people tend to get watery eyes and dry throats and noses. Persons suffering from asthma or allergic sensitivity may experience irration, discomfort or allergic symptoms when exposed to heated fog effects. It's a good policy to ensure that where smoke is being used in the vicinity of performers it is kept to the minimum required to achieve the desired effect. When using fogger machinces (glycol fog) it s a good idea to worry about the asthmatics. Some asthmatics can get a a dangerous reaction out of the fogger fog. Most (90% ?) of 'asthmatics' as we all know cough & splutter in stage smoke because of the psychological effect, not the actual effect. So most of the people are fine with stage smoke, but there will always be some who do genuinely not get on with the stuff. When using fogger on show it could be a good idea to put a warning that fog is used. Safety hazards: Smoke can condense back to fluid near the nozzle of the machine. This can cause a slipping hazard. The nozzle of the machine is very hot and can cause burns. Large amounts of smoke can cause panic and disorientation in an audience.

Fogger is not the only type of smoke/fog effect that has been used. There has been also some checmical fog techniques used in some applications. One is called Sal ammoniac. Sal ammoniac is ammonium chloride. When heated it decomposes into ammoniaand HCl both of which are vapours. These recombine at lower temperaturesto form a fine dispersion of ammonium chloride particles in the atmosphere,with the appearance of a dense white fog. You get the same effect if youopen bottles of ammonia solution and hydrochloric acid and bring themtogether - where the fumes mix a white cloud of ammonium chloride is formed. According to the data sheet those chemicals are harmful by inhalation and irritating to eyes. Another common chemical fog used in the film industry was titaniumtetrachloride. This fumes strongly in air by reaction with atmosphericmoisture to form titanium dioxide and HCl. Not very pleasant stuff: Causes burns to skin and eyes. If ingested causes internal irritation and damage. Vapour is irritating to eyes an respiratory system.'This kind checmical fog is not according today's safety standards and should not be used nowadays. When making smoke / fog, stick to modern smoke fluids and dry ice (and similar safe technologies)!

You should test any smoke machine(s) and hazer(s) in the venues you plan to use it in. If the locations have smoke detectors then there is a very distinct possibility that a smokemachine could set them off. This should be checked before the show. There are many places where smoke machine / fogger can't be used because of the fire alarm systems those places have. This kind of devices are now banned in many venues (or you have to pay a fortune per performance to have fire dept. standing by on site). So check the venue before using this kind of devices in them. Beware of smoke detectors in the venue; if possible disable them during the effect, if this is not possible a test run is advisable. If in doubt, don't use the smoke, evacuation of the venue during the show is not the effect you are after.

General safety notes: Smoke can cause psychosomatic effects in certain members of the audience; some people may believe the smoke causes them difficulty in breathing or makes them cough, so they have these symptoms. There is no evidence that smoke actually causes these problems but you would be wise to use the minimum smoke required and get rid of it by ventilation as soon as the effect is complete.

Discussion forums for lighting designers

Black Light

A UV / Black Light effect is where certain dyes and pigments fluoress in the visible spectrum when illuminated by light out of the visible spectrum. This enables for example floating scenes whereby animators, puppeteers dressed in black can be completely invisible.You can also use black light effect to haveconcealed text or other figures revealed when the black light is applied. Black light is also used in some application just to get nice shining text, by painting the text with fluorencing paint and shining black light to it. Black light fittings produce light that is just beyond the blue end of the colour spectrum. The light is most often put to use by using fluorescent fabrics and paints, which respond to the light to give vibrant colours. Non-fluorescent materials do not respond to this wavelength of light, and so remain dark (or invisible). Simply, fluorescence is due to the absorptionof light at one wavelength, relaxation of the absorbing material to a lowerenergy (the energy difference normally being converted to heat) and thenre-emission of light with this lower energy and hence a longer wavelength.The process is not limited to UV excitation, but this is the waveleght that is most often used (invisible light source, visible light out).The useable wavelenght range depends upon the absorption and emission processes of a material.Blacklight is an ultra-violet light from which the most harmful part of UVradiation (shortest wavelengths) have been filtered. The UV light used in black light effects is not in normal use a danger to eyes. But do not look directly at the black light tube very nearly and avoid very much exposure to strong black light, because very strong black light can still be dangerous to eyes and skin. There are actually two different commonly used types of black light, but they work in basically the same way: A tube black light and incandescent black light bulb. The conventional black light design is just a fluorescent lamp with a couple of important modifications. A tube black light is a basically a fluorescent lamp with a different sort of phosphor coating. This coating absorbs harmful shortwave UV-B and UV-C light and emits UV-A light. UVA light has wavelength of 320-400 nanometers (typically around 360 nanometers). Typically about 2% of the total input power of fluorescent black light lamps can be emitted in the visible 380 - 760 nm band.The only way to create a real blacklight effect is with realUV sources. UV tubes, UV cannons, whatever. An incandescent black light bulb is similar to a normal household light bulb, but it uses light filters to absorb the light from the heated filament. It absorbs everything except the infrared and UV-A light (and a little bit of visible light). In practice this kind of black light bulb does not work well, because they usually put out much more visible light than useable UV. Some people have used some stage lights with suitable color filters to get effect which resembles somewhat black light effect. Some people have used dark blue color filters (like Lee 181 Congo Blue) to emit dark blue light, which is not well visible, but can cause some flurescense on some materials. All trials with normal bulbs and filter emit some light in the visible spectrum and practically no UV. The reason for this is that standard theatre lamps cannot produce light in the non-visible UVspectrum therefore cannot produce a good UV / Black light effect. The reson for no UV on theatre lamps is a result that normal incandescent bulbs do not practically give out any UV and the some amout of UV produced by some halogen bulbs is filtered out by the lenses in the lamp. By using gels like Congo Blue (L181) or Tokyo Blue (L071) one cansimulate a UV sequence but there will be visible dark blue light inthe scene therefore you cannot have invisible puppeteers or operatorsbut you can have concealed text revealed. Most UV stimulated pigments will fluoresce brightly well into the blueregion of the spectrum. It's a common trick to get a quick UV styleeffect by using a deep blue gel.Using gel is not the same effect nor is it as effective as using black light tubes. That's a "UV style effect" not actual UV wavelengths. Nowadays there are also UV LEDs which can emit suitable wavelength for black light applications. Safety notice: Longwave UV and the shorter visible violet wavelengths are not completely safe to the human eye. If the lens of the eye is subjected to ultraviolet exposure comparable to that of bright daylight, it is possible for "nuclear cataracts" to form or get worse. This is a dull brown tint in the lens, and is permanent.

Fiber optic lighting

Build your own lights

Its really hard (i.e. expensive) to create really convincing lightning, but its easy to build some basic lighting devices. There is no reason to put together a concert lighting system, since those sorts of places tend to have a very good lighting system already in place and crew to work them for you. If you need is something that allows you to play anywhere, any time and have your own lights, then constructing your light system can be an useful idea. When building your own lighting systems, it is nowadays a good idea to shop around, because nowadays there are lots of cheap lighting equipment available, and building your own does not make sense in most cases. In most cases combining cheap readily available parts in a creative way and maybe adding some homebuild extra features is the most sensible solution instead of trying to build every lighting device in your system from ground up. You can buy for example get cheap flood lights for less than 10 US dollars per lamp, connectors and switches cost only few dollars cheapest, house light dimmers less than 20 US dollars per channel and wire is quite cheap. Hardware stores and electronics parts shops are places where you can easily find the most parts. By the time you have built the controller, light poles and made the cables, you will probably have spent $200.00 for a basic system.

If you want a dimmer system with several dimmers cheaply, then using a few wall plug light dimmers to control your lights (remeber to use dimmers that are designed to handle the light load you plan to control). There are also cheap dimmers that can ble instelled "in-line" on the lamp cable (designed to replace switches on lamp cables). One idea to build a simple lightboard is to use dimmer switches designed to replace normal wall light switches. Using several such dimmer switches you can quite cheaply control several light channels. In this system want to put a dimmer switch inline between a plug and an outlet. The whole board is then plugged into the outlet for the power. Each outlet is similar to normal wall outlets (you control you lamps here). When building the device get some electrical boxes where you install those components. One wire (live wire, usually white in USA or brown in Europe) goes straight from the plug to one side of the outlet. The neutral wire (usually black in USA or blue in Europe) goes from the plug, through the dimmer, to the outlet. The easiest kind of box to use are regular plastic or metal switch boxes. Plastic is a little nicer and safer. Ground all your outlet boxes (if they're metal) and dimmers and outlets properly. You can put multiple dimmers and outlets on one plug, so long as you don't pull more than a total power alloved (1800-2400W in USA, typically 2300-3600W in European countries). If you don't know how to wire a household dimmer, you could be asking for trouble in taking this on yourself. For many applications it is a good idea to build dimmer boxes that contain four dimmers each. If you need 8 dimmers, build two identical units. Probably you don't want your fire marshall see it.

When building or using your homemade lights, be very careful that nothing goes wrong as a result of faulty wiring or other mistakes. Please note that the use of home made gear in public venues can be a liability nightmare. When you use commercial purpose made kit which has been properly maintained you are in a more legally defensible position if something goes wrong. Faulty lighting equipment can start a fire or damage to the venue's electrics.

Photographing stage lighting

Photographics stage performances well is a hard taks. Photographs of stage scenes seldom do justice to thelighting or the set in many cases. It's an age-old tussle, especially atamateur shows between the lighting designer and a photographer, because what's likely to be great for the audience is seldom half right for the snapper. Genrally it is pretty dark on stage. To ger good results on low ligt condition you'll need a fast lens (f2.8 - any faster then depth of field becomes an issue) and a fast film (at least 400, if not 800 or 1600). You also need to take into consideration that the stage lighting colour temperature is much lower than daylight. You will either need a tungsten-balanced film (seriously limiting your choices)or an 80 series blue correction filter. The specs say you want to beusing 80A for tungsten to daylight, but 80B or 80C is a bettercompromise between getting something that can be printed neutrally, andnot losing too much light. If you tell them to correct it in theprinting, you can shoot unfiltered on daylight film, but the results arepretty hit-and-miss.Theatre photography is a bit of an art, and one that few can say reflectsthe 'real' live viewpoint. A good quality SLR with tungsten balanceslide film usually gives the best results. If it is not staged forphotography in a special photo call(when you can freeze the actors inplace) then you need a reasonably brisk film, a 200-800 ASA. The fasteryou go, the grainier the image. Slide film is often used because its colour saturation is far beyond that ofprint film (for example Fuji 640 tungsten balanced slide film). Slide film is very fine for slides. Yf you want prints consider a print film. The reason for this is that what you gain in glowing saturation on illuminatedtransparencies is mostly lost when you print them. Also, slide film ismuch less forgiving of exposure errors. Ideally you'll be spot meteringso this won't be a problem, but most metering systems get confused bylarge areas of black onstage. Slide film will probably also cost youmore to develop and print, and comes in a much narrower selection,especially of fast speeds. Looking lighting photographs can be positively depressing, as the contrast range is very sensitive to uniformity. A photo can show up dark spots andpatchiness that you never noticed in the live performance. If you just look at the photographs of the performance, then you may get a totally wrong impression of the quality of thelighting. Digital cameras, if you play with the settings, can give nice results on lighting photographing. Color correcting on the computer can help a lot but can be pretty tricky. his is especially true if you have have a stage split into areaswith strongly different color highlights or you are going to print the photographs.

Link pages

Fun

Intercom system used by show people

Unsorted links

Special place lighting

Art of lighting

Lighting and health

Misc

Light switch wiring

Light bulbs

A "normal light bulb" is also known as an incandescent light bulb. These bulbs have a very thin tungsten filament that is housed inside a glass sphere. They typically come in sizes like "60 watt," "75 watt," "100 watt" and so on. The basic idea behind these bulbs is simple. Electricity runs through the filament. Because the filament is so thin, it offers a good bit of resistance to the electricity, and this resistance turns electrical energy into heat. The heat is enough to make the filament white hot, and the "white" part is light. The filament glows because of the heat -- it incandesces.

The incandescent light source was introduced in 1879. It is fairly well known that Thomas Alva Edison invented the first reasonably practical incandescent lamp, using a carbon filament in a bulb containing a vacuum. Since that time, the incandescent lamp has been improved by using tantalum and later tungsten filaments, which evaporate more slowly than carbon. Nowadays, incandescent lamps are still made with tungsten filaments.In an incandescent bulb, current heats the tungsten filament, which glows white hot. To prevent the filament from rapidly oxidizing, the bulb is filled with an inert gas, mainly argon at low pressure. Much of the energy dissipated by the filament is heat; only a little is light. The filament of an incandescent lamp is simply a resistor. Inside that fragile glass envelope is a coil of wire that's as much as a metre long and less than 50 microns thick. Shrouded in an atmosphere of inert and sometimes expensive gases, this tungsten wire literally burns away the whole time it's turned on. If electrical power is applied, it is converted to heat in the filament. The filament's temperature rises until it gets rid of heat at the same rate that heat is being generated in the filament. Ideally, the filament gets rid of heat only by radiating it away, although a small amount of heat energy is also removed from the filament by thermal conduction. The filament's temperature is very high, generally over 2000 degrees Celsius, or generally over 3600 degrees Fahrenheit. In a "standard" 75 or 100 watt 120 volt bulb, the filament temperature is roughly 2550 degrees Celsius, or roughly 4600 degrees Fahrenheit. At high temperatures like this, the thermal radiation from the filament includes a significant amount of visible light. Because the filament emits only about 12% of the energy input as visible light, while converting the entire energy input into heat, conventional bulbs are roughly 10% efficient.

The color of the light coming from light bulb is typically measured with color temperature numbers. A typical 100W domestic light bulb is color temperature 2850 Kelvins (nominal daylight direct sun can vary between 5400-6000 Kelvins). The color temperature of halogen bulbs is typically soewhat higher, because their filaments run hotter. When the a light bult is run at lower than rated voltage or they are dimmed with dimmer, the temperature of the light bulb filament drops, this the color temperature. Very rough data extracted from the colour temperature conversion nomogram in the back of the Strand booklet "The Art of Light" gives esimates for a tungsten lamp:

    100%:    3200K

     80%:    2900K

     65%:    2700K

     50%:    2500K

This is just as an example to give general idea how the light bulb colro temperature varies. Don't rely on these figures as a reference.

Filament lamps have a positive temperature coefficient meaning that the resistance of the filament goes up with temperature. The resistance at the normal operating temperature is such that it would make the bulb to take the nominal power from the voltage what the bulb is designed to work at. If the temperature is less, the resistance is lower. Typically the the normal light bulb resistance when the bulb is cold is around one tenth of the resistance that it has when it is turned on. This causes that when you turn on the light bulb, it take a quie high current peak until it heats to working temperature quicly. The inrush current as the filament heats to working temperature is some seven to 15 times the steady-state current, creating circuit-protection issues. Every time you turn a lamp on, the filament rises from ambient temperature to more than 2500 degrees Celsius in a few milliseconds (or to as much as 3300 degrees Celsius for halogen types in almost same time). This temperature boost inevitably creates a thermal shock that's often sufficient to rupture depleted wire. Another favourite failure mode occurs as the element cools and passes from a semifluid state back to solid form. In either case, when you reapply power, the weakened element sometimes snaps or molten metal flows, creating a short circuit that blows fuses or trips circuit breakers.

An incandescent lamp can be easily dimmed by changing the voltage that is bed to the bulb. An incandescent lamp responds to the average (RMS) value on the input. As long as the thermal interia of the filament is greater than 1/2 the cycle time, the lamp will act as if it had a lower voltage when fed with a chopped waveform. Light dimmers use typically this kind of chopped waveform.

The fact that a bulb uses 100 watts of energy doesn't mean it gives 100 watts of light (typically only 10% or less of the energy consumed by incandescent lamps is actually used to produce light, the rest ends up as heat). The problem with incandescent light bulbs is that the heat wastes a lot of electricity. Heat is not light, and the purpose of the light bulb is light, so all of the energy spent creating heat is a waste. Incandescent bulbs are therefore very inefficient. In a 120 volt, 100 watt "standard" bulb with a rated light output of 1750 lumens, the efficiency is 17.5 lumens per watt. Some lower power bulbs produce perhaps 15 lumens per watt of input power. This compares poorly to an "ideal" of 242.5 lumens per watt for one idealized type of white light, or 681 lumens per watt ideally for the yellowish-green wavelength of light that the human eye is most sensitive to.To get most light buy the bulbs that give the highest number of lumens for every 100 watts of energy used. Most light bulbs average around 500 lumens per 60 W.A lumen is the unit of luminous flux equal to the light emitted in a unit solid angle by a uniform point source having an intensity of one candela. There is no direct correlation between lumens and watts because other variables may affect the relationship, such as lamp design life and fill pressure. Tungsten halogen lamps try to reduce filament evaporation by including small amounts of bromine in the bulb atmosphere. The bromine forces the tungsten to redeposit on the filament. Halogen lamp life is about twice that of conventional incandescent lamps.

Incandescent lamps are available in wattage ranging from 2 to 1500 watts and above. In many cases, the light level generated by a particular luminaire can be increased or decreased simple by switching to a different lamp wattage (do not exceed the maximum lamp power allowed in the luminaire). Incandescent lamps are "resistance smart." The lamp's filament is designed and sized to offer a preset amount of resistance to current flow. This controls the amount of current passing through the lamp. As long as the bulb voltage is right for applied mains voltage, it will work well. Light bulbs have changed very little over the years. They are the cheapest form of lighting product, but they are also the most expensive and inefficient light source in the long run.The bulb type has effect on the bulb live and light it gives out.Incandescent bulbs bring out warm yellow tones and are recommended for living rooms and dens. Halogen bulbs are the brightest, whitest and more expensive. They cost twice as much as incandescent bulbs but also last twice as long. Halogen bulbs give out more light per watt than "normal" incandescent bulbs (up to almost 2 times more in best cases). Typical halogen light bulbs offer a life span of 1,500 to 2,000 hours. Incandescent light bulbs are voltage-driven devices. Operating the bulb at even a few volts above test conditions quickly shortens the life of the bulb compared with its stated specification. The resistance of a tungsten filament is lower when it is cold than when it is hot so if you measure its resistance with a multimeter the result obtained is a little misleading. Once you apply voltage across it so that current flows it heats up and its resistance increases. This means that the initial current is typically few times greater than the normal running current. The high current surge and the effects of very fast filament heating are reason why light bulbs usually fail at switch-on. Dichroic lamps are special reflector floods incorporate a dichroic reflector. In a lamp with a conventional reflector, much of the infrared energy (heat) from the source is reflected into the beam. In a lamp using a dichroic reflector, some infrared energy is dissipated out through the reflector, and not into the beam, resulting in a cooler beam. Those 'cool beam' lamps are particularly useful for museum or gallery lighting applications where excess heat could damage precious artwork or artifacts. Dichroic lamps are manufactured in MR11, MR16 and in various PAR sizes to PAR38.

Here is a comparision of lumen/watt figure of some different commonly used light technologues:

Lumens/Watt

Light Source

100-190

low pressure Sodium (HID) (150 for 90W low pressure sodium lamp, clear)

50-150

High pressure Sodium (HID) (115 for 1000W dual arc-tube high pressure sodium lamp, clear)

100

Sylvania 18 watt low pressure sodium

84

32W, 48" MOL, T8 OCTRON fluorescent lamp

75

Best white LEDs announced 2004 (not available in volume)

60-65

standard F40T12 cool white fluorescent

64

250W mogul based metal halide lamp, clear

60

150W single ended compact metal halide lamp

48-60

compact fluorescents

45-55

Super bright Red/Orange LED

35-45

Super bright Green LED

17.5

Tungsten Halogen Single-End SUPER-Q Frosted Finish D.C. Bay 100Watt

17.5

100W Incandescent A19 Bulb, softwhite

14.5

60W Incandescent A19 Bulb, softwhite (standard bulb)

6

incandescent night light bulb (7w)

6

6w incandescent flashlight bulbs

The history of incandescent lamp technology is long. In 1877 Thomas Edison became interested and experimented with electric lighting. On October 15, 1878, the Edison Electric Light Company was incorporated. Edison patented more than 1000 inventions. Besides the incandescent lamp, Edison is given credit for inventing a system of electric generation. Although Edison did not invent the electric filament lamp, he did however turn theory into practicable form and was one of the first to successfully market incandescent lighting. Edison's first successful lamp used carbonized cotton thread as a filament, installed in a glass bulb, with all air evacuated. In 1880 Edison experimented with other materials for filaments, including wood, grasses, hair and bamboo. Of the over 6000 specimens tested by his laboratory, bamboo, became commonly used for filaments. In 1880, on January 17, Patent number 223,898 was issued to Edison for the T.A. Edison Electric Lamp. After the introduction of the tungsten filament, the next highly significant step in the development of the incandescent lamp, came in 1913 when the first gas-filled lamp was produced. Coiled filament gas-filled lamps in 500, 750 and 1000 watt sizes were introduced in 1913. They gave a much better light at higher efficiency with the same life as former lamps. Nitrogen gas was used in the first lamps but argon was substituted in 1914.

Most light bulbs are designed for the mains voltage operation directly. In addition there are light bulbs that are designed to operate at low voltage sources, for example 3V bulbs on some flash lights and 12V bulbs used in car lighting and low low voltage halogen lights. There are also some special applications where several low voltage bulbs are wired in series to make them all operate together directly from mains voltage. For example there are fairylights where there are tens of low voltage light bulbs wired in series. This works well when all the lamps are same type (same voltage, same power rating), their norminal operating voltage makes together the mains voltage and the whole system is built so that insulation is rated for mains voltage. The downside of this arrangement is that when one bulb goes out, the whole light system goes out. Thanks to the wonders of modern technology, a little shunt wire hasbeen added to modern fairylights. This can be seen just above theglass bead that supports the filament, and is in the form of a fewturns of wire with a low dielectric strength coating which remainsintact at low voltage, but which shunts when the lamp goes opencircuit and 110/240V is present.Modern sets are also available with electronic shunts that maintain circuitcontinuity without increasing the current through the rest of the lamps like a shunted lamp (the electronic component is in the holder which gets warm when no lamp is present).

Gas discharge lamps

Fluorescent lights

General information

Fluorescent lamps are low pressure or low intensity discharge lamps. The lamp consists of a closed tube that contains two cathodes, an inert gas such as argon, and a small amount of mercury. Typically the glass tube is filled with a mixture of argon and mercury vapor. The metal electrodes are coated with an alkaline-earth oxide. When voltage is supplied to the lamp in the correct amount, an electrical arc strikes between the two cathodes. This arc emits energy that the phosphor coating on the lamp tube converts into usable light. Commonly used phosphor coatings are zinc silicate and magnesium tungstate.

The fluorescent lamp was first introduced to the public at the New York World's Fair in the late thirties (1937). The lamps were introduced commercially in about 1938. The fluorescent lamp is a low pressure gas discharge source, in which the light is produced predominantly by fluorescent powders activated by ultraviolet energy generated by a mercury arc. Typically, a fluorescent lamp must efficiently generate 253.7 millimicron ultraviolet radiation to excite the phosphors coating the inside of the tubular glass bulb. The lamp is usually in the form of a long tubular bulb with an electrode sealed at each end.

The modern fluorescent lamp has an efficacy of approximately 65-80 lumens per watt. Today fluorescent lamps are also available in circular and 'folded' shapes. Lamps with various different color temperatures and color rendering properties are commonly available. The most common fluorescent lamp is the CW or cool white version, although new 'warmer' versions are now gaining popularity, worldwide. All fluorescent lamps require a ballast, for operation. A fluorescent lamp tube has argon combined with a minuscule amount of mercury. At the low pressure within the lamp, becomes mercury vapor, even at temperatures only slightly above room ambient. An electrical discharge ionizes the mercury vapor, which emits UV radiation. The UV radiation stimulates phosphors that coat the interior of the lamp's glass envelope, and the phosphors convert essentially all of the UV radiation to visible light.

The conversion of electrical energy to light is much more efficient than in an incandescent lamp, and a considerably smaller fraction of the input energy is converted to heat. Generally fluorescent fixings give out ~ 3 times as much light/watt as a halogen. The color of the light that a fluorescent lamp produces depends on the composition of the lamp's phosphors. Fluorescents used for general lighting purposes are nearly enoughentirely of "hot cathode" type. The mechanism for conducting electronsfrom the negative electrode to gas/vapor is "thermionic arc". The negative end of the arc, even though it is much more distended than awelding arc due to the low gas/vapor pressure, heats the electrode to atemperature such that molecules in a coating on the electrode lose theirgrip on some of their electrons. Hot cathode fluorescents are generally near or a bit over 100 mA in their smallest sizes (one popular one may oftenwork reasonably at 60 mA) and the usual sizes take generally around 220-450 mA and a few take more.

The most typical fluorecent lamp type seen in Europe is offices and homes is lamp where there is is one fluorescent bulb (or sometimes two in series) wired in series with a magnetic ballast that limit the current though the lamp to the needed range. In addition to this there is also the starter (passes power for some time though tube heaters when bulb is turned on) and usually some kind of filter capacitor (for RFI filtering and/or power phase compensation). This construction is simple and works well with mains voltages used in 220-240V countries. There the voltage is well enough for the tube to start conducting reliably and there is enough voltage range for the simple magnetic ballast work well (the tube voltage is something in 60-100V when it is on). The simplest sort of ballast, generally referred to as a magnetic ballast, works something like an inductor. It is sufficient for fluorescent lamps operating at around 230V AC or higher voltage. Different lamps require specialized ballasts designed to maintain the specific voltage and current levels needed for varying tube designs. Magnetic ballasts modulate electrical current at a relatively low cycle rate, which can cause a noticeable flicker. Magnetic ballasts may also vibrate at a low frequency. This is the source of the audible humming sound people associate with fluorescent lamps.

At countries that use 110V mains voltage this simple approach does not work, because that voltage is too low for reliably opeating a fluorescent lamp directly with simple ballast. In 110V world the fluorescent lamps need to use a more complex ballast that steps-up the voltage for the bulb to initially reliably start. This kind of ballast is much more complicated, more expensive and less energy efficient than the simple "just coil" ballast. Many fluorescent lamps operating at 110V AC nowadays use electronic ballasts that can properly power the lamp from 110V power supply with better efficiency than magnetic ballast and are not too much more expensive than those complicated magnetic ballasts. Modern ballast designs use advanced electronics to more precisely regulate the current flowing through the electrical circuit. Since they use a higher cycle rate, you don't generally notice a flicker or humming noise coming from an electronic ballast.

In many office building and similar places there are also fluorescent lamps that operate at higher voltages than 110V in USA and Canada. In those buildings there are usually higher voltage three-phase power in use within the ouse for power distribution. In many places the fluorescent lamps are powered with 277V AC or 347V AC that is derived from higher voltage three-phase power system (between phase wires or between phase and neutral). At those higher voltages the simple magnetic ballast lamps work well. In such building using higher voltage for lighting saves money.

In a cold cathode fluorescent lamp as well as neon glow lamps, the cathode mechanism is "glow discharge". This is a multilayer processbut in this process positive ions of the active gas/vapor ingredient(s)accelerate towards the electrode and knock electrons from atoms of theelectrode material to permit conduction from the electrode material to thegas/vapor. This is more practical and has longer life than hot cathode with lowercurrents. Miniature cold cathode fluorescent lamps have typical operatingcurrent often around 5 mA. "Neon signs" are cold cathode and frequentlyfluorescent and usually operate at 20 mA. There is a large style of coldcathode fluorescent (rare) with operating current somewhere around ormaybe a little over 100 mA. One advantage of cold cathode fluorescent is a lack of extra wear from starting. The disadvantage of glow discharge over thermionic arc is that glowdischarge has a much higher voltage drop in the cathode process (typically 55-80 volts) compared to usually 8-12 volts for thermionic arc. Cold cathode fluorescent lamps can be for example seen in applications like neon lights as used for advertisements and for example as miniature back-lights as used in laptop computer LCD screend.

Cold-cathode fluorescent tube (CCFT) / Cold-cathode fluorescent lamp (CCFL) is a special form of fluorescent tube without heaters on the cathodes. CCFL is often used as a backlight in LCD flat panel displays and also in some decorative lighting applications (for example decorating PC cases). CCFL bulbs are typically small (typical diameter 3-10 mm, lenght 10-30 cm). CCFT requires an adjustable, current-limited, high-voltage, ac-power source. Generally the tube needs quite high voltage to start operate and then operates at lower voltage (up to several hundred volts). EMI and tube-lifetime considerations practically dictate a sinusoidal waveform to be used for powering CCFT. There are also some large cold-cathode fluorescent tube systems that use high voltage mains powered transformer capable of putting out high voltage at current of around 100 mA.

Note on installing fluoresent light fixtures: Many mains powered florescent fixtures need to be grounded to work properly. Two wire fixtures might need the correct wire connected to the neutral and hot. If they are reversed, they will be hard to start. That you can touch yours andhave them start indicates you may indeed have a reversed hot andneutral.

Developed in the late 1980's the compact fluorescent lamp revolutionized the lighting industry. This lamp (also referred to as the PL lamp), is simply a folded fluorescent tube, sometimes no larger than a standard 'light bulb'. The ballast is usually mounted in the base pf the lamp. This new lamp allows most household incandescent lamps to be replaced with these new energy saving fluorescent lamps. PL lamps are available in various wattages from approximately 9 - 50 watts, and are available from all major lamp manufacturers. Compact fluorescent light bulbs, or CFLs, use fluorescent light technology in a compact size that can be used in place of standard light bulbs. Compact fluorescent light bulbs use 70 percent less energy than standard incandescent light bulbs. Roughly, roughly, a compact fluorescent lamp produces as much light as an incandescent lamp of 3-4 times as much wattage. Good compact fluorescents normally produce 4 times as much light as good incandescents, except compact fluorescents can be dimmed by non-ideal temperatures, heat buildup in fixtures, etc. CFLs come in a variety of sizes, depending on wattage and manufacturer, and will fit most standard lighting fixtures. CFLs last an average of 10,000 hours, compared to only 850 hours for a standard incandescent light bulb. Generally you can replace a norma light bulb in the fixture with a compact fluorescent lamp that mechanicaly fits to the lamp in most cases. Be prepared though that if you put a compact fluorescent in a fixture designed for an incandescent, the light may not be distributed in a less favorable manner than that of the incandescent. Some lamp fixture work better than other with compact fluorescent bulbs.

Fluorescent lamps and incandescent lamps can vary significantly in efficiency with manufacturer and model due to various issues of design and quality. "Standard" fluorescents of the more usual "shades of white", especially the 4 foot T8 (1 inch diameter) ones, are a little more efficient than compact fluorescents. Compact fluorescents with magnetic ballasts are usually less efficient than ones with electronic ballasts and they also have quality issues. Non-compact fluorescents also suffer from ballast issues. Generally fluorescent lamps with color rendering index higher than 86 or so have less photometric output than most usual ones with rated color rendering index in the range of 53 to 86.

Fluorescent lamps are not the optimum lamp types for outside lighting in freezing cold enviroment. Any fluorescent lamp will have an issue with temperature being way off it's optimum operating temperature. This creates two problems:

Compact fluorescent lamps have also the same problems as listed with normal fluorescent tubes. For outside operation in cold environment select lamps that are rated for this.

Lamp data

Other technical information

Circuits

Neon lights

The colorful neon lights used ad company logos and other advertising purposes are an another story. The history of neon lights is long. The initial color source is the inert gas which emits a characteristic color when electricity is applied. The two most common gases are neon which emits a fiery red, and a mixture of argon and minute particles of mercury which emits a subdued blue. Clear glass allows you to see the characteristic colors emitted by the gas. Fluorescent powders may be painted or baked to the inside walls of the glass tubing and the source light is then converted into a multitude of shades such as pink, turquoise, and green.

Neon lamps are typically is powered by voltages in the 2,000 to 15,000 volt range from a current limited source. The needed voltage depends on the used gas mixture and the length of the tube. Even though the current is in the milliamp range (or few tens of milliamps). If a neon piece is not properly mounted, wired, and insulated this voltage poses both a shock and fire hazard. Well made neon lights can last decades. In practical terms the expected life span is between 8 to 15 years. Neon light system components can be repaired and recharged.

The neon transformer can supply different current, voltage and frequency as needed. The voltage is typically in 4-15 kV range and the current limit is typically around 30 mA. The traditional ferrous core neon transformers work at mains frequency (50 Hz or 60Hz) and supply AC output. As a rule of thumb you can say that you need 1000 VAC per meter (about 3ft) of standard diameter tube (13 mm diameter) to make it work and for normal brightness you need 20-30mA of current. Neon sign transformers are distinguished from traditional transformers by being current limited and center grounded. Center grounded simply means that the center of the transformers output winding is electrically connected to ground. This results in both output terminals being hot with respect to ground (quite typical value is around 4 kV per output, total 8 kV per output pins). Current limited means that when the transformer's output is shorted, only a limited amount of current will flow. Current limiting is achieved by the use of a tightly coupled, magnetically saturable (usually iron) core. The iron core provides resistance to the fluctuating magnetic field which, in turn, impedes the current flow.

Many modern electronic neon power supplies supply either DC or high frequency AC (usually 20-30 kHz). The high frequency neon tranformers are quite often used nowadays. The limit on high frequency AC output models is that the output wires cannot be long (usually maximum of around 2 meters). The transformers with DC output allow longer cable runs (around 100 meters or so).

Neon transformers are failsafe, at least in most civilized countries (legal requirement). Usually this is done with ferroresonant cores. It means that the current output is constant, regardless of the load (more or less), and they can sustain this indefinetly. If you have only one meter of tube, and connect it to the 5000 VAC transformer, the output voltage of the transformer will be about 1000V and 30mA of current will flow. Since those transformers are not perfect, the current will be a bit higher with shorter tubes, and they will get hotter too. The transformer's life will be a bit shorter and also the tube's electrodes will wear out (and blacken) a bit faster. So for best performance you should be have the transformer output voltage that matches the needs of the tube. Electrical transformer have typically built-in open circuit protection and thermal protection.

There are also other kinds of neon lights in use. Special little bulb neons /neon glow lamps) are very commonly used as indicators that the mains electricity supply is on.The typical current for a baseless type such as the NE-2 is about 0.3 mA (for some other bulb types it is in 0.5-1 mA range). This kind of neon lamps typically fire at about 90volts and then sustain a voltage of around 60 once fired. Around 330 Kohm resistor is a common with the NE-2 as a 220V AC line indicator(lower resistance values like 47-100 kohms are used for 120V AC). The exact resistor size is usually not critical as long as the current is not mode than the bulb can handle. This kind of little neon bulbs are also used in "phase testers" which are used to test if some wire has mains voltage on it when you touch thewire with this instrument (sometimes this feature is built into a screwdriver).Those phase testers generally use a very high resistance (few megaohms) resistance to limit the current to a very low safe value (safe enough to touch).

Metal halide lamps

Metal Halide lamps are essentially mercury high pressure discharge lamps that have additional metal halides in their arc tubes. Metal Halide lamps provide improved efficiency and improved color rendering qualities over mercury lamps. The modern metal halide lamp has a luminous efficiency of 85-115 lumens per watt. The first metal halide lamp was developed about 1960.

HID lamps

HID lighting stands for High Intensity Discharge Lighting. Modern followspots and projectors now tend to rely on a High Intensity Discharge, (Xenon, CSI, HTI, etc.) lamps. The HID lamp group is one of the three major lamp groups used in modern lighting (other two are incandescent and fluorescent). The HID lamp group includes mercury vapor and metal halide lighting systems. The HID lamp group is by far the most important lamp group used in modern exterior and industrial lighting. HID light sources are highly regarded for their long life and high efficacy. The compactness of HID lamps also increases optical control and allows for a great deal of flexibility in the area of luminaire design. The first HID lamp introduced was the mercury lamp in 1901. Later, low pressure sodium, high pressure sodium and metal halide lamps, were developed. All of these sources consist of electric arcs, operating in a gaseous environment, sealed within a glass tube or bulb. HID light sources are all more efficient than the electric filament lamp, however they also have limited color rendering abilities, due to their 'line' spectrum (not continuous spectrum). Many HID lamps are now also provided with a phosphor coating on the inside of the bulb. This coating causes additional secondary emissions of visual radiation, providing a wider 'spectrum' of light and color. Typical applications include industrial, commercial and architectural lighting. HID lamps are "amps dumb." You can't connect them to mains directly.HID lamps do not have a built-in resistance to current flow, and must rely on an external ballast to set and limit current flow to the lamp. The wattage and voltage ratings of the HID lamp and its ballast must match exactly.

Xenon lamps

Sodium lamp

The high pressure sodium (HPS) lamp has steadily developed and gained in popularity, since its introduction 1966. It provides a more economical source of illumination than mercury, fluorescent, or incandescent and has a more natural color than low pressure sodium. The HPS sodium lamp has a luminous efficacy of approximately 80-140 lumens per watt.

HMI lamp

The HMI lamp (mercury medium arc iodides) lamps were developed by OSRAM GmbH to meet a need established by the German Federal Television System in 1969, and their use quickly spread throughout Europe and to the rest of the world. Although originally designed for television lighting, they are now used for location film lighting and as a source for many common followspot spotlights. The modern HMI lamp is highly efficient (100-110 lumens per watt), and produces a daylight type spectrum with a color temperature of 5600 degrees K. Lamp wattages currently range from 200 to more than 12,000 watts. Although not widely know in the name HMI, the H stands for mercury (Hg), M indicates presence of Metals and the I refers to the addition of halogen components (iodide, bromide). HMI is the registered trademark of Osram Lighting. The HTI lamp is a more recent version of the HMI. They area available with an integral reflector and are often used in followspots, fiber optic illuminators and in slide projectors.

Sulfur Lamp

Sulphur lamp was developed in 1994 by Fusion Lighting (USA). About the size of a golf ball, the sulfur lamp consists of a quartz bulb containing non-toxic sulfur and inert argon gas at the end of a thin glass stick. A microwave energy source of 2.45 Ghz. (magnetron) bombards the lamp while a fan cooled motor spins the lamp at 3400 rpm. The microwave energy excites the gas, which heats the sulfur, forming a brightly glowing plasma that can illuminate a very large area. The first early prototype lamps were 5.9 Kw. units with a system efficacy of 80 lumens per watt. Correlated color temperature was about 6000K with a color rendering index of 79 CRI. The sulfur lamp starts within seconds even at low ambient temperatures and can be dimmed. The surfer lamp emits no electric or magnetic fields and the light output remains constant over its life. The energy output is continuous throughout the visual spectrum (much like sunlight) however the source is low in both the ultraviolet and infrared energy. Several companies are working with Fusion lighting to develop new fixtures and equipment for the sulfur lamp.

Other gas discharge lights

Circuits

LEDs in lighting applications

The light emitting diode (LED) is p-n junction semiconductor lamp which emits radiation then biased in a forward direction. The emitted radiation may be either invisible (infrared) or in the visible spectrum. Invented in 1967, the LED had been traditionally used strictly as an indicator device. LED's are commonly used in indicator lighting applications. Due to their very long life and low operating current, they are ideal replacements for incandescent indicator lights. LEDs have come a long way from their humble beginnings as simple on-off indicators on panels and displays. Early LED's came in red only. Traditionally LED palette used to be only mostly red, followed by green and then yellow and orange, and their brightness was still only enough for indoor applications. By the mid 1990's blue and white LED's had been developed. Many of the older limitations associated with LEDs have changed dramatically in the past few years. New high-efficiency LEDs boast brightness that makes them usable in daylight and provides colors that include long-sought blue and even white.

Traditionally LEDs have only been available on different colors and the LEDs that give out white light have just became widely available just quite recently. There are different technologies to get white light out of LEDs. The very first white light LEDs used three different color LEDs inon one package to generate white light. Many so-called white LEDs actually use three color light sources, a blue LED that stimulates red and green phosphors, to simulate a white emitter. But because the blue LED is highly directional and the phosphors are omnidirectional, the effect is dependent on the viewing angle and thus is uneven. There are also LEDs that give "nearly white" light by using just one phosphor. Those LEDs use blue light generating LED and phosphor that generates yellow light (blue generated the blue, yellow color activates gree and red on eye).

Leds have already replaced light bulbs in virtually all indication applications. Now with the advent of super bright leds, many illumination applications are being taken over by leds also. Until recently, though, the price of an LED lighting system was too high for most residential use. The versatile LED is now bright and colorful enough to use in applications beyond simple indicators and readouts. The virtues of LEDs, compared with incandescent sources, are clear: long life plus power efficiency. LED (light emitting diode) lamps consume less than a quarter of the electricity that fluorescent lighting does, and the lamps last about ten times as long. A 1.2 watt white LED light cluster is as bright as a 20-watt incandescent lamp (bright enough to read by). The lighting quality can be comparable to that of cool white compact fluorescent lamps, with color rendering indices near 85. LED lights powered from DC source don't flicker. The light is very directional in small arrays. Most LED vendors cite an operating LED life of 100,000 hours under nominal operating conditions. LEDs maintain colour consistency when dimmed, and integrate efficiently into advanced optical systems with high illumination efficiencies.

The power savings potential with LEDs are dramatic, but you still need to understand the vendor's intentions and what you need. The common signal-integrity unit for defining the amount of light emitted compared with energy input is lumens per watt may be misleading. An incandescent bulb distributes its photons relatively evenly around its source in a non-directional, spherical mode, whereas an LED is inherently a directional source. In addition, the output of the incandescent lamp covers most of the visible spectrum, whereas LEDs are wavelength-specific. As a rule, an incandescent source is 10 to 20% efficient, but an LED is 80 to 90% efficient. Individual LEDs are designed to be driven from low voltage current limited sources. The typical operation voltage per LED is only few volts. When you have to run LEDs from higher voltages, you need to use various techniques to make it work well. Here are few circuit ideas used to drive LEDs from various power sources.

A standard LED lens without any diffusion produces a relatively narrow viewing angle of about 12? on either side of the LED center. With special techniques vendors can make the LED viewing angle spread to as much as ?35?. To get broad-area illumination using LEDs, you need an optical diffusing lens or an LED array. Many illumination systems use an array of LEDs to develop the desired overall intensity. Current LEDs are generally not a lot more efficient than light bulbs. You can generally expect light output of around 15-50 Lumens per watt. LEDs are current-driven devices. Usually, a voltage source provides this current through a current-limiting resistor at a low cost. Most LEDs, regardless of efficiency, have a nominal current drive of 20 mA; some units can use a maximum drive of 70 mA. Regardless of current level, you need to maintain the drive current within specification in all operating conditions. With LED technology you still need to grapple with issues of source drive, brightness, derating, spectral output, and viewing angle. To use LEDs in more than simple indicator applications, you need to understand LED-drive models, compensation for temperature increases, the legitimate ways of assessing brightness, and viewability factors.

When you need to drive many LEDs from higher voltage than typical LED operating voltage, it may seem simplest to just connect all your LEDs in series, which ensures that each LED has the same forward current. This topology works, but you have to make sure that your current source has enough compliance for the sum of the forward-voltage drops of the LEDs, nominally 1.4 to 3V for each LED. At the other extreme, you could run each LED from its own parallel branch for maximum redundancy and lowest compliance voltage at the source. Between these two extremes, you can use a combination of series and parallel strings to manage the trade-offs. In practice, most LED arrays use a 12 to 24V-dc source and three to six LEDs per series string to achieve a satisfactory trade-off.

White LED lamps are now available with standard screw-in bases to fit incandescent fixtures. They are much smaller than compact fluorescent and even incandescent, because instead of a bulb, there is an array of tiny diodes lining the rim of the base. The biggest limitation to LED for common residential use is the cost of manufacturing due to still-limited production runs. There is still a limited number of manufacturers, but this is changing.

Sometimes there has been discussion if pulsing a LED will help to make it to appear brighter that applying continuous power of same amount. In some special cases human eye can detect a blinking light better than steady light, but generally pulsing does not help. The human eye response peaks at about 10Hz, then begins to decline,getting pretty weak by 40Hz or so. Above 70Hz the lightappears to be continuous, with an apparent brightnessthat's equal to the average light power level, so there'sno benefit to pulsing the light. In the 5 to 15Hz regionwhere there is a benefit, you'll realize that the lightappears to be strongly flickering, which is an attention getter, especially in the peripheral vision. So pulsingat 10Hz would be a good idea for an alarm signal. A blinking LED will certainly get extra attention, but if it continues to blink without stopping, it may alsocreate some irritation. As faras our visual system is concerned, there's no advantage toshort powerful pulses vs longer ones with the same number of photons.

Other lamp types

Dimmers

In many situations, luminiares are not used constantly at full power. They are generally required to fade in and out, and to be used at different brightnesses, or intensities, at different times. A device is required to regulate the amount of electrical voltage sent to each luminaire, thereby allowing the intensity of the light to be varied: this is a dimmer. A light dimmer allows controlling of light bulb brightness. The basic idea of dimmer operation is that it limit the electrical power that gets to the light bulb. Dimmers today come in many styles to control different types of loads. In some old mains powered lighting systems variable transformer is used as light dimmers, but nowadays they are largely replaced by electronic light dimmers with operate using phase control principle (first this kind of SCR based system was publicly demonstrated in 1962 in London). There are also some other dimmer types used in some special applications (variable transformers, simple resistors for very low power bulbs and PWM controllers for DC lights).

Proper matching of control system types to the load is very important. Not all dimmers work properly with all types of loads. Using wrong type of dimmer causes that the dimming does not work well, and in worst case can damage the light dimmer and/or the lamp connected to dimmer. Normal incandescent bulbs can be dimmed with very many dimmer types, but some other light types are harder to dim. Be warned not to dim lights which have motors or control electronics in them (unless they are specifically designed to be dimmed). For example if you dim a typical disco light (one with electronics and motors) it will probably damage the electronics.

One light dimmer regulates one lighting circuit, or channel, allowing the electrical supply sent to the attached lumainire to vary between 0 and the mains voltage (230V or 110V). Each dimmer is designed to work up to a maximum electrical load, called its capacity. Any number of luminaires can be connected to a dimmer, until the capacity is reached. In stage lighting applications the dimmer systems are generally built from many dimmer packs. A dimmer pack comprises a number of individual dimmer modules, housed together for convenience.

The first dimmers used in theatrical applications used to be quite simple resistive current regulators. Tens of year ago devices like slider resistance that housed in a sheet metal casing and which is used mounted on the front of the switchboard, was used to control the ligth brightness (used to waste lots of power and heated considerably). Some very old systems even used a bucket with metal bottom and a spade with salt water in the bucket, just dip the spade further in to pass more current (wouldn't like to operate it personally). Those "water dimmers" using glass cylinders with a metal plate at the bottom were real in the theatres in the earily 1900s. In some applications those resistive dimmers were replaced with adjustable autotransformers. Those early methods worked, but the downside of them was that they are big and hard to make remotely controllable.

An effective and widely used modern method of controlling the average power to a load through a triac is by phase control. This means that a typical light dimmer circuits use a form of Pulse Width Modulation (PWM) to control the brightness of the bulb. It controls the brightness of the bulb by turning the bulb ON for part of time and then OFF for part of time. An incandescent lamp responds to the average (RMS) value on the input. As long as the thermal interia of the filament is greater than 1/2 the cycle time, the lamp will act as if it had a lower voltage when fed with a chopped waveform. Phase control is a method of using the triac to apply the ac supply to the load for a controlled fraction of each cycle. In this mode of operation the triac is held in an off, or open, condition at a time in the half-cycle determined by the control circuitry. The brightness of the bulb is a function of the ON time to the OFF time. In the on condition the circuit current is limited only by the load, i.e. the entire line voltage (less the forward drop of the triac) is applied to the load. Modern mains light dimmers use TRIACs to control the flow to the light bulbs so that only needed part of mains pulse wave enters the light bulb (the PWM operation is syncronous to mains power). This basic principle of operation of a dimmer, has remained unchanged for forty years. SCR dimmers chop the sine wave on the front end, IGBT dimmers chop it on the back end. Many times users of dimmers have noticed buzzing sound that dimmed lighting systems make. The "Buzz" is due to inadequate chokes. The choke controls the rise time when the SCR "turns on". Any resistive load, such as an incandescent filament type of lamp, simply "sees" the chopping as equal or the same as a voltage drop. Because a filament takes a measurable amount of time to "heat up" or "cool down". The on and off cycles blend into a steady degree of incandescence that we see as a "level".

Many modern dimming systems that allow curves to be set usually have a program that allows the dimmer output to be set by the "apparent" voltage level. Inductive loads are another issue entirely. In the early days of SCR dimming, motors and transformers such as those used in many slide projectors and such, either destroyed the dimmer, were destroyed BY the dimmer or both. Most, but not all, dimmers on the market today have electronic circuits to deal with the problem.

Electronic dimming using triacs or thyristors use a technique which switches on the device at certain point after the AC power has crossed the zero reference line. By nature of it's construction , the device turns off the passage of current thru it when the current is zero (at the zero crossing point). very convenient, since we can switch it on every cycle at a point very near the zero crossing or far from it. If we switch it on near the zero crosssing we get a brighter lamp since the device remains on longer before turning off t the next zero crossing. This sudden turning on of the triac or thyristor creates transients which buzz very nicely on the audio line at 50 or 60 Hz and the harmonics of those. This noise problem can be reduced by putting large inductors on the output of the triac this sudden rise can be smoothened to a certain extent, but not perfectly. Since the largest current rise is at the centre of the AC waveform (there the voltage is highest so current is highest with resistive load), you will typically find the largest amount of noise when the dimmers are at around 50%. Modern high-specification dimmers have a choke which increases the switch-on rise time from an uncontrolled 2?S to typically about 350?S, and they generally comply with standard EN55014 (representing the levels for residential electrical emission).

Besides the noise coupled to electronic circuits you can sometiems hear acoustic noise from the dimmer itself. The fast current rises on the dimmer electronics can make some components inside dimmer to make noise. Most typically this noise comes from the filtering coil, but in some cases the noise can coem from filtering capacitors, wires, circuit overload protectors and such parts. Sometimes the lamps connected to dimemr output can make noise. However, even with good quality filtering, you can in many cases clearly hear a lamp filament resonate as the intensity is altered or set to a static dimmed level. Audible noise is also often present at the dimmer device itself, caused by some choke vibrating/resonating (there are chokes inside dimmer in power input and output filters, and also on some circuit breakers that project dimmer channels against overload). Resonance in the lamp filament, colloquially called "lamp sing" is caused by the high frequency switching of power to the lamp. There are several factors which affect lamp sing, main things being the type of light bulb and the risetime of the choke. The longer the rise time, less singing. Improvements can be made using higher inductance chokes. It is now common for choke risetimes of up to 600?S to be specified for TV and concert hall installations. Although technically possible, the higher inductance adds significant weight, volume and cost to each dimmer channel in the installation. With an increased inductance in the dimmer circuit, there is a proportional loss of efficiency due to an increase in lost power which is dissipated as heat from the choke, and often causes an increase in audible .hum. from the choke windings. Singing can also be reduced with careful design of the choke and snubber capacitor combination in dimmer circuit (success is often variable with mass-produced, budget-priced dimming).

Light dimmers are quite energy efficient, although they are not ideal.As one might expect, in spite of its usefulness, phase control has some disadvantages. The main disadvantage is the generation of electromagnetic interference (EMI) in triac applications. Each time the triac is triggered the load current rises from zero to the load-limited current value in a very short time. The resulting di/dt change generates a wide spectrum of noise that may interfere with the operation of nearby electronic equipment unless proper filtering is used. For mains operated light dimmers the efficiency is usually in the rangeof 90-97% depending on dimmer load and design for a normal triac basedlight dimmer (phase control). The efficiency of a dimmer module can be determined by loading it to full capacity and then measuring the voltage drop across the dimmer module (you need at True RMS voltmeter between the Line and neutral wires to do the measurement). The SCRs (Silicon Control Rectifiers) or triac that provide current control in the power device, part of the dimmer module, drop about .75 Volt across each junction (there are two). The choke is responsible for the remainder of the voltage drop. The amount of voltage drop across the choke varies proportionally to the connected load. This means that there will always be a dimmer insertion loss of at least 1.5 volts + the voltage drop across the choke. This is true for all SCR / Choke based dimming regardless of manufacturer. This power loss in dimmer needs to be taken into consideration when calculating the amount of Heating Ventilating and Air Conditioning (HVAC) required in a dimmer room of large dimming systems.

Dimming can be used to extend lamp life in some applications where long lamp life is more important than maximum amount of light. Turn to the tungsten halogen section of most lamp manufacturers catalogues and you will find a small graph which correlates things like % of rated lamp voltage against % rated lamp life and color temperature. If you study these graphs they will show that 5% under voltage (i.e. dimming) will produce a much longer average life without significantly affecting the light output or the colour temperature. Dimming more than that usually reduces light output considerably and changes the color temperature quite much. When lamp is dimmed a lot, the light output drops very much faster than consumed power (so the efficiency of lamp drops considerably when normal lamp is dimmed). One inherent drawback of the ubiquitous thyristor dimmer is that when it is switched on, noise and harmonic disturbances are caused due to the rate of change of current. High peak currents are also generated. Resonance in the lamp filament, colloquially called "lamp sing", is generated by the abrupt, high frequency switching of power to the lamp. The solution has traditionally been to fit a large inductor (choke) to the dimmer circuit to reduce lamp sing and radiated emissions. Filter chokes used in dimmers are typically measured in micro second rise time. The usual 'conducted emissions'filter uses the rise-time inductor with a capacitor across the mains input. The cap value depends on the choke and the dimmer power rating.You can't practicably filter out the low-order mains harmonics.The most basic choke used in thratrical dimmers is typically rated at at around 350 microseconds with 500and 800 micro second rise time chokes also available.

Here is some data of dimmer choke values and rise time relationship (data is collected and adapted from document found at http://www.almag.co.uk/new22.htm (not available anymore on web). The rise time is for 10% to 90% rise time.

coil     230V AC       110V AC
 mH      risetime      risetime
         microseconds  microseconds
 0.9       50          100
 1.6      100          210
 4.3      200          420
 5.7      300          640
 7.9      420          870

Generally, the longer the rise time of the choke, the less filamentnoise it will produce. Unfortunately to achieve higher rise time,the choke requires more wire to be wound around the core.This increases the production costs; hence the dimmer will cost more.Aside from the filament hum, dimming induced noise in sound systems is alwaysa concern. Through the operation of the dimmers RFI or Radio FrequencyInterference can be produced. For example sensitive sound equipment shouldhave an isolated power feed to avoid the potential RFI produced by the dimmers. Using dimmers with higher micro second rise time filter chokes will reduce audile noise and RFI. In Europe standard EN55015 defines the noise suppression for light dimmers.

Dimmers are typically designed for resistive loads in mind. With resistive loads, such as incandescent lamps, the current and voltagecurves match. This will keep every light dimmer happy.Once you start trying to work with reactive loads, such astransformers, motors, or fluorescent lamps, you may get unhappy dimmersunless you use spacial dimmer designed to handle inductive loads.When faced with an inductive load the pulse driven triac circuits oftenturn off with the back EMF from the load. Unfortunately most seem to be quite happy to conduct on one half of the phase but not the other which causes the load to be run on half wave AC (pulsed DC component).This kind of DC balance problem will saturate transformers and damagethen quickly (they overheat).With many normal dimmers and a small inductive load, a resistive ballast in parallel will usually keep the dimmer happy. But be warned that therecan still be some small DC balance problems left which can causeproblems (this varies depending on the dimmer design).For a dimmer to generate nice AC output without DC, the controllingelectronics has to have the firing pulses symmetrical. They don't have to be far out to generate a few volts DC that'll cook a transformer.

Dimmers are available in many forms. For household use dimmer switches come in four popular styles: dial, slide, touch pad, and combination light switch/dimmer slide. Since dimmer switches come in different shapes and each operates a little differently, you should always follow the instructions included with the switch for installation and operation. Theatrical applications and rock shows generally use remotely controlled dimmer packs. Each dimmer pack contains many individual remote controlled (usually 0-10V DC or DMX-512 controlled) light dimmer circuits in one case.

Typical light dimmers as discussed earlier work using forward phase control. Forward phase control is when there is a "wait" time after zerocrossing, then you fire the thyristor and it conducts current for theremainder of the half cycle (until the next zero crossing when the PNjunction that is conducting becomes reversed biased). Forward phase control turns on under load and has a choke to limitrate of current rise ("rise time") but turns off along the same slopeas a sine wave.This is not the only way you can make a mains light dimmer. Reverse phase control is when current switching component begins to conduct right at zerocrossing, and conducts through the half cycle until "some point" whenthe transistor (IGBT in the IPS case) is biased off. Reverse phase control turns on at zero crossing andhas a rate of rise that is the same as the slope of a sine wave, butturns off under load and has a "fall time". The IGBTs in the IPS stuffdissipate heat during the "fall time". There are several advantages that can be used: no flter choke needed (size, weight, cost), ability to sense current and shut down if needed (can shut down power in the middle of phase if overcurrent is detected) and this design gives you bility to change "fall time" via software (though the longer the fall time the more heat the IGBT has to dissipate). Reverse phase dimmer works also better with some electronic loads that do no work well with normal dimmer (for example electronic lamp transformers that power low voltage halogen bulbs etc.). The main disadvantage of reverse phase dimming high component count (the current stuff is better than before but there still are a bunch of parts on one of those boards) which leads to higher cost. Reverse phase control still generates harmonics like normal dimmers. Since reverse phase control is cutting off the "back end" of a sine wave at some point, right thereyou have a waveform that is something other that a sine wave and wefind ourselves back in harmonic land. The harmonic reduction in some special stuff (IPS dimmers) is achieved by firing one half ofthe dimmers in forward phase control and the other half in reversephase control. Literally (well almost anyway) half the harmonics are coming and the other half are going and now we actually do have summing that is trending towards zero.

In addition to the systems described above there are sinewave dimmers on the market. Dimmers with a sine wave output are hardly a new phenomenon. The resistance dimmer in its many forms, whether a pair of electrodes in a container of salt water, a rheostat-like slider, or a mechanically operated "grand master" system, always produced a nice clean sine wave output which varied only in amplitude. It was only the fact that these dimmers were heavy, expensive, load-dependent, produced vast amounts of waste heat, and required some form of direct mechanical operation that caused them to be bypassed for other technologies. There has been some low power home light dimmers that have used variable autotransformers (variacs) to control the voltage to the light bulb. Some high-end dimmer switches, such as the ones once commonly used in stage lighting, are built around an autotransformer instead of a triac. The autotransformer dims the lights by stepping down the voltage flowing to the light circuit. A movable tap on the autotransformer adjusts the step-down action to dim the lights to different levels. Since it doesn't chop up the AC current, this method doesn't cause the same buzzing as a triac switch. This approach works, but is expensive and bulky on large power systems.

There are a lot of other dimmer switch varieties out there, including touchpad dimmers and photoelectric dimmers, which monitor the total light level in a room and adjust the dimmer accordingly. Most of these are built around the same simple idea, chopping up AC current to reduce the total energy powering a light bulb, as the dimmers described above. Attempts have been made in the past to produce a sine wave output dimmer by using various semiconductor devices as the variable resistance, but each of these has run up against the difficulty of the available semiconductor technology not being able to handle the currents, voltages, and heat dissipation required for a robust, reliable production dimmer. The new wave of sine wave output dimmers has taken a different approach, using the switch-mode technology widely used in devices as diverse as the ballasts of many discharge luminaires and the power supplies of virtually all computers and lighting consoles. There are few companies which work on sinewave dimming field.Dynalite has been shipping the SVC (Sinewave Voltage Converter) dimmer since 1998. Bytecraft VST (Variable Sinewave Technology) won an award at PLASA 98. Jands Electronics has announced the development of a prototype of its SWDim sine wave dimmer. The principle behind all of these sine wave dimmers is very simple: The incoming mains is switched on and off between 600 and 1,000 times per mains cycle (30-50kHz) with the on time (width) of each pulse being proportional to the required output power from the load, a method known as Pulse Width Modulation (PWM). The very finely chopped output is then filtered back into a continuous waveform through an inductor similar to the choke on a phase control dimmer, but very much smaller, as the pulse frequency is higher. The shape of the filtered output waveform is almost identical to the input waveform, only its amplitude is different, precisely what happens in a resistance dimmer. Sinewave dimmer is very complicated electronic device. Only with a large number of sensors to gather data, a fast processor, and some clever software is it possible to maintain the complex dynamic equilibrium necessary for a sine wave dimmer to function. But when those are implemented properly, lot of extra function and protection technologies can be added to the dimmer. There are some dimmer technologies that has been earlier in large use but later not used anymore. One early means of lamp 'dimming' was through the use of the salt water dimmer. The dimmer consisted of a tank (or barrel) of salt water brine with a permanent electrode submerged. As a second electrode was slowly raised (or lowered) into the brine, the conductivity between the two electrodes would increase (or decrease) respectively. Lamps connected in series to the dimmer, would be dimmed accordingly. It was not uncommon for a theatre to have a large number of these dimmers and it is said that the heat from the boiling brine would often help to heat the backstage areas. Undoubtedly messy and difficult to operate and maintain, the electric salt water dimmer was soon to be replaced by the somewhat more efficient (and dryer) electrical resistance dimmer. The resistance dimmer was simply a long length of wire, usually wound in the form of a coil. A 'wiper' contact would move along the coil, usually controlled by a manual leaver (or motor control). As the contact moved along the coil, the coil resistance would decreasing or increase accordingly. This coil resistance was placed in series with one or more electrical filament lamps to provide a relatively efficient means of dimming. This type stage lighting switchboards were large and heavy. The first autotransformer was developed and patented about 1933 by General Radio Company (USA). This device was a continuously variable transformer with the trade name of "Variac". The Variac provided a much more efficient means of dimming electric lighting fixtures in theatres, than did the existing resistance and saltwater dimmers of the time. In the 1960's, the American Superior Electric Company, produced a number of autotransformer dimming systems for theatre and television applications. Autotransformers can also be motorized for remote operation. The autotransformer dimmer is still used today in some applications (recording studios & hospitals) as they do not generate radio frequency interference (RFI) as does a modern SCR type dimmer.

Domestic light dimmers usually incorporate a mechanical switch for isolation (and a minimum dim level) to ensure that an OFF light really is OFF. A typical wall switch dimmer has a clearly defined 'off' click' which corresponds to a mechanical switch. There are some remote control wall dimmers ( touch dimmers ) which perhaps dont have the physical isolation when set to off. In home dimmers some dimmer units intentional go from 'off' to directly say 20 percent to avoid any uncertainty as to whether the power was really off or not. Providing an air gap isolation when a system is aparently 'off' is a good idea in domestic systems. In a domestic or similar situation, who would be liable if someone got a shock from a light fittting, if the 'off' setting was actually causing some leakage. Where dimming is done by chopping the waveform, which is generally the case in any efficient dimmer, it is possible, with more cost, to ensure that the waveform has no time of passing current. The control circuits in cheap dimmers can't quite do that. In addition to the control accuracy problems, there can be leakage cause byl filtering components near triac (for example through "subber circuit" that is in parallel with triac). Once you are getting into scene control systems, then the cost isn't so much to get a real "off". Still, if you really want a true disconnecting off, add a switch ahead of the controller.

Theatrical dimmers use a number of different technologies to reduce the current. They also very often have an intentional feature what is called a pre-heat setting, that leaves a couple percent of the current flow even when at nominal 0% which keeps the lamp filaments warm. This reduces the warm-up time to get to the desired light level when it does come up, and is supposed to reduce thermal stress in the lamp, extending it's lifespan. So pretty much any recent manufacture theatrical dimmer system will be constantly bleeding a little power to the loads. Certainly many larger dimmer units only have isolation at the wiring hub via a circuit breaker - and not at the local control position.

Dimmers are designed to drive light bulbs and similar loads. Driving other types of loads with dimmers is not generally a good idea unless you know absolutely that this is ok. If the dimmers aren't rated for light inductive loads (which they probably weren't) then they could have fed the lights with a slight DC component due to non symmetrical triac latching on the two halves of the sine wave. This would pop the fuses. In some cases it can smoke the transformers too. Inductive loads are a nightmare to SCR or Triac dimmers. Even something a small as fan motors. A substantial resistive load (in parallel with inductive load) will often solve the problem.

Driving devices and switch mode power supplies with power from dimmer is generally not a good idea. Most poeple at one point or another have tried this, some with limited success and others with unpleasant results. For example plugging a moving light into a dimmer is bad news. Even when leaving the dimmer at FULL and turning it OFF when light needs to be powered down. The problem here is that FULL ON and FULL OFF might not be what you expect them to be, and the output between those extremes is genrally anything but sinewave. Many theatrical dimmer systems feed a low voltage through at off to keep the bulbs warm. Some theatrical dimmers are "regulated" to give the show the same look even under slight variations in supply voltage. This can mean that even when you think it's 100% on, it's not. Another danger to plugging different electronics devices into dimmers is that the DMX signal has absolutely no fault tolerance or error correction/detection. Dimmers can end up at odd levels even if the console never sent a level other than full or zero to that channel. One thing to point out too, on most dimming systems you can change the scale type on a dimmer to a non-dim or switched mode. Be careful though, this is often NOT the same as a module performing the relay function. Usually it is only changing the behavior of how the dimmer is reacting to data. If you switch a standard dimmer to non-dim in the software, you could be still clipping the waveform, which can still smoke your electronics device. The dirty secret of most digital dimmers designed before about 1995 is that they are analogue dimmers in digital clothing. In a true non-dim module, there is nothing clipping the wave at any point in the electrical path. Its just a glorified DMX switch.

When installing light dimmer systems you need to consider the needed power feed for them. When designing system (touring system or permanent installation), to think about is how many dimmers you can drive with the power available. Most dimmers this side of the pond come in multiples of 600 watts (600w 1.2kw 1.8kw or 2.4ks). Usually you don't need the amount of power that is the maximum power of dimmers connected to the mains feed. In general, you can "overload" your incoming power by a decent amount, meaning having more dimmer power and total light load than your feed can handle. You could get away with more since you will never have all channels at full even if all the dimmers are loaded to capacity (which is highly unlikely) unless you are a community theatre were untrained or inexperienced lighting people might have unsupervised access to your equipment. If you have more light instruments than your power input can handle at the same time, you need to make sure that your LDs/and or MEs understand about both the maximum loading capacity of your incoming circuits so they don't plan anything stupid.

SCR dimmers are a nightmare from a power quality perspective. At the output end the dimmer waveform is very distorted. Running at 50%, the triac or SCR pair will turn on when the voltage is at its peak, with a huge hard edge. The 'clean up' inductors slow this down a bit, but it's still largely there, and will to some extent reflect back into the incoming supply. The load the dimmer puts on the mains supply may possibly distort the supply waveform. There are cases where the supply impedance is low enough that it will just absorb the harmonics without much harm, and there are cases where sypply impedance is higher an unfortunate sound man can bear witness. The problem can be severe if the supply comes from a small generator or some sort of electronic inverter. For the usual public supply there is no real problem but the supply company may want to know if we are talking about a load of tens of kilowatts or more. Generally it is a good idea to have separate power feed directly from the transformer or house main distribution panel for audio and lights, so the place where the distortion from dimmers meet the power going to the audio dystem there is the lowerst possible network impedance (least amount of distortion gets through).

When using three phase power feed with large dimmer packs some things need to be considered in the wiring. First it ia a good idea to distribute the dimmers among phases so that they don't get radically out of phase balance. Phase controlled dimmers are a very highly non-liner loads. Dimmers do generate a large number of odd-order harmonics (worst is third), now unlike the fundamental (50 or 60 Hz line freq.) when 3rdorder harmonics are "added up" in the neutral the magnitude increases .Usual practice is to specify the neutral conductors at 130% of phase conductors (rated for 130% of nominal phase current).

General information

Technical documents

Basic dimmer circuits

A basic light dimmer is a mains voltage controlling device which controls which amount of each mains halw wave gets to lamp and which does not. This is done by controlling the conduction angle (time after zero cross) in which the mains switching element (usually TRIAC) starts to conduct. When TRIAC starts to conduct, it will conduct up to the next zero crossing of mains voltage (time when current decreases zero). An RC network delays the trigger pulses on the gate of the TRIAC. The longer the RG time constant is, the longer it takes for the TRIAC to trigger which causes less time of conduction. Less time of conduction means less power to lamp which means less light output.

This kind of simple triac based light dimmers (e.g., replacements for standard wall switches) widely available at hardware stores and home centers. While designed for incandescent or heating loads only, these will generally work to some extent with universal motors as well as fluorescent lamps down to about 30 to 50 percent brightness. Long term reliability is unknown for these non-supported applications.

Remember, that most mains powered dimmer circuits are "hot" and dangerous! Line power circuitry should be constructed only by qualified persons and enclosed into a suitable protective case before using it. A circuit that is not properly built can be a safety hazard, because baddly designed or wrongly built circuit can electrocute you, cause lots of noise to mains power and can even start a fire in your house.