Controlling and technology of disco and stagelights

Index

Introduction

Lighting is one of the most important backstage roles especially with music. If you go and see a band all you have is a few people standing still on a stage playing a guitar or two. After a couple of songs you are fed up of just listening. Now it is the role of the lighting designer to make the performance a lot more enjoyable, setting the tone of the songs with different colours, constantly keeping the audiences attention by changing what they can see.

Stroboscope controlling

External trigger controllers

Most of the strobocopes designed for commercial use have a external trigger connectors on the back of the strobocope. Those connectors are typically 6.3 mm jacks or XLR connectors. Sometimes there is one input and one output jacks so that many stroboscopes can be easily wired to one controler by just connecting the first stroboscope to controller and wiring next strobocope to the output of the first stroboscope etc.

Typical stroboscope inputs have following characteristics (may vary from manufacturer to manufacturer):

Flash on power off

Other way how the stroboscope can work is flash on power off controlling. In this method when you apply the power to the stroboscope the stroboscope chargers it's capacitor. And when the mains power is cut off the stroboscope flashes once. This constrolling method is useful if you want to connect a stroboscope to a light organ or to a light chaser. Some stroboscopes upport this method and some don't.

Light dimmers

What can be dimmed or and what not to dim

The following light types are safe to dim:

The loads mentioned above are easy to run loads and can be dimmer with practically any light dimmer on the market.

What to dim with caution:

The light belonging to this category are somewhat inductive loads and contain a transformer.To be able to dim the lights in this catebory you must have a dimmer which can handle inductive load and works very symmetricaly on both negative and positive halves of mains current (so no DC component on output to sature transformer). Using a dimmer not suitable for this kind of use might result strange operation, damaged dimmer or burned out transformer.

What not to dim:

Dimmer controlling

For light dimmer controlling there are two widely used industry standards: DMX-512 and analogue 0-10V controlling. Modern digital dimmers typically use standard DMX-512 interface, which is the digital interface bys standard for controlling all kinds of lighting systems from dimmers to intelligent moving lights.

The older 0-10V analogue standard us typically used by small lighting systems (single dimmer packs with 1-6 chanels typically).

0-10V controlling voltage "standard"

The analogue control voltage range is 0-10V. 0V means that light is off, 10V meast that light is full on and the voltages between them mean different dimmed settings in between (more voltage means more light output).

The outpus of the light controllers are typically equipped with diodes which allow the voltege to come out of controller, but not going back to it. Diodes in controller outputs make it possible to connect multiple lighting boards in parallel and the highest voltage value wins the game.

Many small light dimmer pacs use 8 pin input connector for inputting the 0-10V control voltage to the dimmer.

There a two major "standards" for using this connector. Both of them are quite widely used, so be warned to check the wiring before making connections.

As used by Zero 88, Anytronics, Lightprocessor - 

Pin 1- 6                Channel 1-6
Pin 7           +V (dc power - typically 18-25V @ 100mA)
Pin 8           OV (reference for signal and DC power return)
This first one is the recommended standard to use if you have a choise.

As used by Pulsar / Clay Paky - 

Pin 1           +V (dc power - typically 18-25V @ 100mA)
Pin 2           OV (reference for signal and DC power return)
Pin 3-8         Channel 1-6

Light controlling equipments

The most typical instrument to control set of light dimmers is to use traditional light desk which includes set of slide potentiometers to control the brigness of the lights. Some light boards have also extra flash buttons (to turn on single channel full on with press of button) and other features like light chasers. More advanced boards can have memoryh for maultipel light settings (light scenes).

Syncing the lights with the music

For syncing light to music syncing there are few ways to do that.

One way to do that is just use a traditional light board with some kind of chase programs and just tune the chase rate to match the beat of the music manually. That is propably the most common way to do that with tradidional light controlling desks. It is not noo hard to tune using one know to approximately match the lights flashig to the beat of the music and propably change that setting between the different pieces of music. You don't even need to get the lights to match the music exactly, usually when you go close enough it gives a good effect and illusion that everything is synced. And if something special is needed, then the light operator manually reacts to the music. This is propably the most common way light the lights are operates at least with many smaller bands no with normal light light effects. With intelligent lighting usually the the operator has preprogrammed some predefined program patterns for the intelligent lights controlling and then just selects the right ones during the show and adjust the speeds of the programs to match the music.

There are some light controllers for mosly disco use which are designed to control the lights based on the music coming in. There are two marjor types of such sound to light controllers: light organs and music synced light chasers.

Light organs take the incoming sound (through sound input connector or built-in microphone), split it to different frequency bands (like bass, middle and high freencies) and use the output of each of the filters to control the turn on/off or dimming of individual lights. This kind of arrangement makes one light to respond to the level of bass sounds (drums, bass guitatrs.etc.), other to the middle frequencies (singer, guitar) and one for high frequencies (hihat,guitar). When those light outputs are equiped with different color lights, the result is a quite nice sound responding light show. This type of light effect was quite popular in old disco systems, but works also quite well with live bands.

Music synced light chasers take the incoming sound and try to separate the beat from it more or less well (usually by analyzing the bass frequencies in music to get the bass drum from there) to generate a clock signal to a light chaser circuit. The light chaser circuit is just a sequencer which runs though a certain set of light patterns so that it goes from one step to another every time it gets the clock pulse from the music sync circuit. Many music controlled light chasers have also basic run speed which they use if there is not music coming in so the lights do not stop even then totally and the controller can be used without music input. This kind of light controlling method is the most common arrangement used in disco light controllers used restaurants, discos and mobile DJ systems.

Many lighting desks designed for live musch stage light controlling have an audio input which gets a feed from the main audio desk. The best approach for sound operator is to feed the drum set sounds (typically a feed from the kick drum) to this light desk sound input to get it in sync with the music played. For accurate beat detection in "full" music, a manual beat synchronisation is usually required, because many music beat circuits do not work very well with full music. Most of the time however, it's just the board operator's sense of rhythm (or lack thereof) to get the light operate in nice ways in sync to the music.

Fogger controlling

Foggers typically work by vaporizing a special fog fluid which consists of pure water and few chemicals added to it to make the fog last longer and be more visible. The fogger fluid is vaporized inside the heating element of the fogger where the fogger fluip pump pumps it when fog is needed. The heating element is thermostat controlled and this thermostat is connected to the pump so that the pump will operate only when the heating element is hot enough properly vaporize the fogger fluid.

Foggers have many different kind of controlling interfaces and no industry wide standards for them. Basically this means that you practically always have to use the fogger controller provided by the fogger manufacturer to be able to control them unless the fogger has some industry standard light controlling interface available (there are 0-10V or DMX-512 interfaces on some expensive foggers, but not on the cheaper ones).

The simplest form of controllign the figger is a simple on/off remote controlling using a remote switch. For example LeMaitre MiniFog has a 6.3 mm mono jack for external control switch and the external switch just shorts the tip and shield of the 6.3 mm jack when the button is pressed. This button typically feeds the low operation voltage (12V?) to the pump inside the fogger if the button is pressed and the heating element is hot enough.

There are also wide variety of other controlling schemes around. There are foggers which use 6.3 mm stereo jack, 5-pin DIN jack, IEC style mains connector etc. sof the controlling of the fogger. The controlling iself can operate on low voltgae or at mains voltage.

Light fixtures with moving mirrors

Moving mirrors are used in disco lights to move the light to different directions. Most typical of this kind of constructions are rotating reflectors which consists of many small pieces of mirrors and are used to form multiple light beams (same ideas as in classic disco mirror ball).

This kind of construction is used in many light effects, for example moonflowers, where typically those small mirrors have also a color filter integrated to them. The traditional way to rotate this kind of mirror is a mains powered syncronous motors (fre rotations per minute). Those syncronous motors have tendency to start to rotate at random direction when the power is applied, so if the power is turned on and of based on the sound input (from microphone) a nice random rotation in both directions is seen. In some light effects the motor rotates a flat mirror, which just makes the light bouch to random directions.

For more advanced lighting effects the mirrors are typically moved by microcontroller controlled stepper motors. By using two stepper motors it is possible to have controlled movement in both X and Y directions, like in typical roboscanners. This kinf of intelligent lights are typically controlled using DMX-512 interface.

Color changers

Typical color changer used with PAR36 pinspots is a color wheel which have four colors. This color wheel is typically rotated by a mains powered syncronous motor which makes it rotate at speedd of few rotations per minute. So the wheel rotaes when the color changer wheel gets power and stays on one color when no mains power is applied to it.

More advanced color changer used in theatres typically use DMX-512 controlling interface to tell the color changer which color filter to use.

Light rigging

Discolights and other quite small lighting instrument have typically a 9 mm mouting screw hole on their mounting hardware. The clamps are then crewed to the light and the lamp is then screwed to the supporting hardware (typically pipe or truss).

Standard ways of mounting: pipe mounted via an industry standard C clamp, pipe batten mounted using 2 inch U-bolts or wall mounted using the appropriate wall mounting fasteners.

The light mouted over places where people are oftern (like stages), security chains are used to make sure that the light does not drop to the floow (or someone's head) if the clamp fials for some reason (mechanical failure or improperly fitted to the pipe).

Lamps types

Basics

Most people just think of a light as a bulb hanging from the end of a wire in the ceiling. The lights (or luminaires) we use come in many different shapes and sizes from long and thin to short and fat, and each type has its own use.

A luminaire consists of three basic parts:

It is the way these parts are arranged that decides the type of luminaire. The bulb provides the initial source of light that is sent in all directions. The reflector then reflects all the light rays into one direction. The job of the lens it to control the spread of light ie what sort of beam it is, and how it is focussed.

Sometimes luminaires do not have a lens and these are floods and they do just that, flood an area with light. If a luminaire has a lens it is called a Spot. If we use spots we can control the light coming from it. We do this, by control the size of the beam and the 'focus' (or blurryness) of the beam.

The beam out of a light is usally a fixed shape, either a circle or oval. We can control the shape even more by using barn doors or shutters, these allow us to straighten the edges of the beam.

In addition to the three basic components of a luminaire, you will usually find a facility for colour the light. We colour the light using coloured plastic (called Gels).

At home the average light bulb is 60 watts. In a theatre the average light bulb is 1000W (15 times stronger). In disco/stage lighting the typical lights are in power range of 200-500W. Because of this increase in power a lot more light is given off, but also a lot more heat and it is common for luminaires to become to hot to touch.

To use lighting to its full effect we need to use colour. There are only so many effects we can do with white light and it soon becomes boring. But we can use colour to bring the excitement back.

Common lamp types

Incandescent lamps

Incandescent lamps are the oldest form of electrical lighting and are still in widespread use. Incandescent lamps are thermal radiators. In an enclosed bulb filled with gas, an electric current is passed through the tungsten wire of the filament to make it glow. Apart from heat, they also produce light, but light accounts for only 5 to 10% of their output.

Tungsten-halogen lamps

Conventional incandescent lamps get dimmer because vaporised tungsten from the filament is deposited as a dark coating on the inside of the glass bulb. In halogen lamps, this is prevented by adding halogens to the filler gas. The halogens ensure that the vaporised tungsten is returned to the filament. Halogen lamps are available for low-voltage operation (for which a transformer is needed) or for mains voltage as direct replacements for incandescent lamps.

Halogen lamps have a number of advantages over normal incandescent lamps, notably their brilliant light for attractive glittering effects, smaller dimensions, uniform bright light, longer lamp life and greater economy. Tungsten-halogen lamps perform a wide variety of tasks in projection, car headlights, operating theatre lighting, light guide technology and TV, film and stage lighting. The most powerful halogen lamp available is rated at 20,000 W.

Halogen lights have typically better effiency and smaller size than normal incandescent lamps.

Fluorescent lamps

A FLUORESCENT LAMP is a lamp in which a current passes through mercury vapor, generating ultraviolet energy. There is a phosphorous coating inside the bulb that transforms that ultraviolet energy to visible light. A fluorescent lamp is more energy efficient than standard incandescent lighting.

Fluorescent lamps are characterised by economy and extremely long life.They last considerably longer than incandescent lamps and consume much less electricity.

Fluorescent lamps are low-pressure-discharge lamps. An electrical field is produced between two electrodes in a gas-filled tube. This electrical field causes mercury atoms to radiate. Phosphors applied to the inside of the glass convert this radiation into visible light. As with all discharge lamps, these lamps require electronic or electromagnetic ballasts.

The low pressure mercury vapor arc in the tube emits lots of shortwave UV at 253.7 nanometers. This is the germicidal wavelength that erases EPROMS and does quite a number on the conjunctiva and the cornea of the eye. Most fluorescent tubes are coated on the inside with a phosphor to absorb this shortwave UV and emit visible light.

Fluorescent lights are not much used in disco/effect lighting except the UV fluorescent tubes. The most popular black light bulbs are 60 cm (20W) and 120 cm (36W or 40W) models which can be fitted to any normal fluorescent light fixture.

Black light tubes

Black light tubes are designed to give out some components at the extreme "violet" end of the visible light spectrum as well as emissions not visible to the eye. This gives the "purple" color to that you see from a black light source. Blacklight fluorescent tubes are coated on the inside with a phosphor to absorb shortwave UV and emit longwave UV, usually around 360 nM. The glass is a dark violet glass known as "Woods glass", which does a good job of passing longwave UV but blocking visible light. Some visible violet and a trace of visible blue gets through.

The longwave UV is what makes most fluorescent dyes, inks, paints, and pigments glow. Many of these substances also glow from visible violet and visible blue. Some of these even respond to other visible wavelengths! But it is mainly longwave UV that is responsible for these glowing from a fluorescent blacklight tube.

The deep purple coating is an absorber of far UV that prevents danger to the viewer of this light for entertainment purposes, and the "black light" was specifically pioneered for entertainment and educational purposes. The small amount of near UV is low enough in energy that it is not much more dangerous than visible light.

You would NOT wish to be exposed to pure mercury fluorescent light, however, which is what is used inside the tube ! Contrary to some popular opinion, a low pressure mercury arc does not produce a lot of longwave UV. Nearly all the longwave UV from a blacklight fluorescent tube is produced by the phosphor from shortwave UV. Omitting the phosphor would greatly reduce longwave UV output.

What about incandescent bulb black lights ?

The incandescent blacklight is indeed a dark violet lightbulb. Yes, in fact the incandecent lamps give off UV light. Unfortunately an incandecent filament puts out very little UV lignt so the ratio of heat to UV light in these bulbs is very high. The violet filter passes the small amount of UV emitted by the filament, as well as most of the visible violet and some visible blue, which also excite most fluorescent paints, dyes, pigments, and inks. Most fluorescent colours don't need UV to illuminate them. Blue light is just fine, although UV is better since it offers a better contrast between the background and the fluorescent paint. Most fluorescent colours don't need UV to illuminate them. Blue light is just fine (for example "Congo Blue" filter), although UV is better since it offers a better contrast between the background and the fluorescent paint. If you want very good UV effects do need a real source of UV, because regular filament lamp just doesn't produce enough UV to mention.

Some very deep red and most of the near-infrared from the filament also pass through the violet bulb. Incandescent blacklights have no mechanism to produce longwave UV from other forms of energy. They are inefficient at producing longwave UV and do not work nearly as well as the fluorescent type of blacklight.

In some cases a powerful theatrical light fitted with a suitable color filter can produce an usable black light fluorescent effect on some materials. Here is the list of some color filters which might be usable for this (I have not tried those, only seen those mentioned in rec.arts.theatre.stagecraft newsgroup):

Compact fluorescent lamps

Compact fluorescent lamps generate their light in the same way as fluorescent lamps. By bending the glass tube back on itself the lamps are made very compact. Many of compact fluorescent lights nowadays in use have ntegrated electronic ballast. These can be used as direct replacements for incandescent lamps. They consume 80% less energy and last ten times as long. Energy-saving compact fluorescent lamps can be usually fitted straight into lampholders designed to take standard incandescent lamps.

Compact fluorescent lights are not used in effect lighting. They can't be flashed quicly (turn-on takes always some time and micth not wothstand flashing). Compact fluorescent lights are not generally disgned to be dimmed, so connecting such lamp to a dimmer can cause damages to either to dimmer ot the compact fluorescent bulb.

High-pressure-discharge lamps

High-pressure discharge lamps like for example metal halide lamps are used mainly in shop windows, large-format overhead projectors, powerful slide projection, LCD video projectotion and high power light effects such as moving light fixtures. Metal halide lamps are valued for their high luminous flux, impressive economy or good colour rendering.

The light is generated directly by an arc discharge. Electrical discharges between the electrodes cause the various filler materials in the discharge to luminesce. The light from metal halide lamps is generated by an electrical arc discharge in an atmosphere of mercury vapour and halogenides of rare earths.

The lamps need special electronic ballasts for current limitation and ignition purposes. The balast need to be selected according the lamp type used. Metal halide lamps are quite expensive compared to other lamps, but they have better effiency than normal bulbs and last longer.

PAR CANs

Par stands forParabolic Aluminum Reflector. The PAR lamp contains the reflector, filament, and lens. Hence, the lamp you choose detrmines the brightness and beam spread. Pars come in many sizes and wattage ratings as well as quartz and halogen types. These types of lamps will fit in many types of fixtures.

All PARCAN lamps produce a soft edged oval shaped pool of light. The CANisters are typically available in steel or aluminum. CANisters are fitted using yoke. The color gel is connected to color frame in front of the CAN.

Due to their simplicity and low cost, these are the most popular fixtures for illuminating a performance area such as musicians on stage, dance, festivals, shows. etc. In band lighting, the PAR 64 lamp is the most dominant breed of lantern used. The name comes from the Parabolic Aluminised Reflector, which tells you what youve got in it, and 64, which tells you how big it is (in eighths of an inch!). "Par Can" is short for "PARabolic reflector lamp in a CANister". Most road shows that use Par's for their main source of instruments because they are inexpensive and can take hard use.

Popular lamp types with built-in reflector: 

Lamp    Diameter  Beam spread   Power    Base    Use / comments
        (inches)  (degrees)     (watts)

PAR 36   4.3        5x5          30      Blade   Used in pinspots, typically 6V 30W
PAR 38   4.75      30,60     75,150,300  Screw
PAR 38   4.75       12           60      Screw   Special model (Osram PAR-EC special)
PAR 46   5.75       ?           200      Blade
PAR 56    7        11x25       300,500   Blade    
PAR 64    8        11x25      500,1000   Blade   Very common light in stage lighting

Here are some tips to identify different PAR lamp types:

Some notes on PAR lamps

PAR lamps (except PAR 36 and some specila version of other version) operate typically on the mains voltage which is 120V or 230V depending on the country. In PARCANs the bulbs are just directly wired to the incoming mains wire. PARCAN can be easily dimmed with practically any light dimmer.

PAR 36 pinspots are are kind of exception to other PAR lamps. Those PAR 36 bulbs typically operate on 6V AC low voltage which is usually generated by a transformer inside the lamp fixture. The transformers in this kind of lights are typically designed so that they have an internal overtemperature fuse (if the transformer is overloaded it will heat up, the fuse burns and you will toss out the lamp fixture or change transformer).

Some people say that PAR 36 fixture with transformer can not be used with a dimmer as it uses a transformer to supply the correct voltage. It is true, that using those lamps with a baddly designed dimmer might result a quicly burnt out transformer, but with proper dimmer those can really be dimmer (propably with a little loss of lamp transformer life propably because the transformer runs a little but hotter than normal when dimmed). The danger of overheating the transformer is there with PAR lamps with some dimmers and with some other poorly designed light controllers equipments (some light sequencers can generate uneven amount of positive and negative halves of mains voltage on high speed rates and this can eventually heat up the transformer quicly).

PAR 36 lamp originaltes from sealed light beam lamps used in some as aircraft landing lights and in some heavy automobiles. PAR-36 sealed light beam (General Electric Model 4596 - Aircraft Landing light) operates at around 30 volts. The 4596 is rated at 250 watts (10 degree beam). Apart from original aircraft use those lights are sometimes used with mains voltage so that there are many of such bulbs wired in series.

Common reflector lamps


     Diameter  Beam spread  Power    Base   Use/comments
       (mm)    (degrees)
R39     39       80          30 W    Screw
R60     60       80          25-100  Screw  
R80     80       80          40-100  Screw  


Concentra 80 deg  60-75W     Also known as R (reflector) lamp, type R80
Concentra 30 deg  60W        Special models (Osram has 30 degree models)

Common R (reflector) lamp produces light by applying current through a tungsten filament until it glows. An R lamp is made of a one-piece, glass bulb coated on the inside with a reflective material. Lamp is filled with the inert gas argon to help retard the evaporation of the tungsten filament.

PAR (parabolic aluminized reflector) lamp produces light by applying current through a tungsten filament until it glows. A PAR lamp has a reflector made of thicker, heat-resistant glass coated on the inside with a reflective material and sealed to a separate glass lens. Lamp is filled with the inert gas argon to help retard the evaporation of the tungsten filament.

A halogen PAR lamp is nearly identical to a common PAR lamp except that its filament is enclosed in a small, quartz capsule that contains halogens along with argon. This filament can operate at higher temperatures than one in a common PAR lamp. This increases the efficacies of halogen PAR lamps. The average rated life of these lamps ranges from 2000 to 2500 h.

Common R and PAR lamps are the most popular lamps used for floodlighting and accent lighting. A 75-W common R lamp has an efficacy of approximately 11 lumens per watt (LPW), and a 75-W common PAR lamp has an efficacy of approximately 10 LPW. Both efficacies fall below the 12.5 LPW required by EPACT for 75-W reflector lamps. The average rated life for these lamps is typically 2000 hours (h).

Popular low voltage lamp types with mirror:

            Spread    Diameter     Power    Voltage
PAR36        5x5       110mm        30W     6V used in pinspots, 12V available
Multimirror  30,12deg   51mm       20-75W   12V, also called MR-16, cool beam
Minimultimir 10,25?     35mm       10-20W   12V cool beam

Beam spread definition: The angle where the light intensity has decreased to half than what is in the center of the beam.

Connectors for cool beam multimirror bulbs (51 mm) use G 6,35 mm connector (two pins at 6.35 mm distance). The smaller buls typically use 4 base (two pins at 4 mm distance).

Tomi Engdahl <[email protected]>

 
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