Reflectors

Spherical
Parabolic
Elliptical

Lenses

Concave
Convex
Plano Convex
Double Convex
Fresnel

Fixtures

Fresnel
ParNel
Ellipsoidal
Par Can
S4 Par Can
Beam Projector
Far Cyc
Follow Spot
Linenbach
Scene Machines
Pani
Wiggle Lights

Dimmers

Resistance
Auto Transformer
Triacs
SCR
SSR

Protocol

AMX-192
DMX-512

Reflectors

The Reflector: The reflector fulfills two purposes:

1. To increase the efficiency of the instrument by deflecting light that would otherwise be unused.

2. To create specific patterns and qualities by the redirection of light.

The law of specular reflection explains what happens to light when it strikes a smooth, shiny surface, such as a mirror. Light will be reflected at an angle equal to the angle which it struck, but in the opposite direction. Early stage equipment used moulded glass as reflectors, but they have been replaced by lightweight spun-metal reflectors that are coated with a highly reflective and durable surface. Stage lighting instruments use one or possibly a combination of three reflector types: spherical, parabolic, and ellipsoidal.


Parabolic Reflector: If a light source is placed in the focal point of a parabolic reflector, the rays of light will be reflected parallel to one another. This will give a great concentration of light in a tight beam, rather than an effused spread. Moving the source toward the reflector will spread the light, while moving the source away from the reflector will cause the light rays to converge. This type of reflector can be found in some floodlights, beam projectors, scoops and PAR lamps.	Spherical Reflector: If a light source is placed in the center of a spherical reflector, all of the rays will be reflected back 180 degrees of their original trajectory. This gives almost double the light output than would occur without the reflector. A spherical reflector in concert with a special Fresnel lens is used for Fresnel spotlights. This type of reflector is commonly used in Fresnels and Beam projectors. A spherical reflector will increase the efficiency of a lighting instrument by 40%.	Ellipsoidal Reflectors: The ellipsoidal reflector is more efficient than either the spherical or parabolic. By mathematical definition an Ellipsoid has two focal points. When a reflector is placed at the focal point at that end, all rays of the light that strike the reflector will be diverted through the second focal point. The result is that an enormous percentage of the light from the source is directed in a manner that makes it easily usable. Ellipsoidal reflectors are used in Ellipsoidal instruments and can improve the efficiency of an instrument by 75%.

The Housing:The housing controls the excess light that has not been reflected in the desired direction. It is generally painted black both internally and externally to contain stray light and to keep the instrument from attracting attention to itself. The housing also includes the color holder slot, or gel holder slot.

Dichorism:
Dichoric filtration refers to the ability of material to pass certain wavelengths of light through its surface while rejecting others. This principle has been applied to color filters, and is also now also used in reflectors. By reflecting the light wavelengths which are visible, while allowing the heat wavelengths to pass, the light being reflected is cooler and less likely to burn through gels, or heat the front end of a light to the point that it will burn you when you are focusing the instrument.

Lenses

Fresnel Lens

Agustin_Fresnel.htm

Concave

Convex

Plano Convex

Double Convex

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Fixtures

Fresnel

The Fresnel lens was invented by French physicist Augustin Fresnel in 1827, who used prisms to capture and concentrate 90 percent of a lamp’s light and focalizing it into an intense horizontal beam. The precise manufacturing needed produce the lens—hand-ground from perfectly molded lead crystal—required the skill of an artisan. His invention improved lighthouses’ range from a few miles to almost 20.

Parnel

Data Sheets

Ellipsoidal

Data Sheets 5’ 10’ 19’ 26’ 36’ 50’

Par Can

A par-can is a very effective flood instrument centered around the PAR (Parabolic Aluminized Reflector) lamp. A PAR lamp looks very similar to the headlight of an automobile. PAR lamps combine a parabolic reflector and a lens into one unit. The lighting instrument is just the housing and the pig tail (plug and cord). PAR lamps come with a variety of different lens configurations and part of the focusing of these types of instruments is choosing the types of lamps. PAR lamps control the spread of the light by the grooves carved into their surface causing the light refract and spread. Depending on the size, width, and how the lamps are orientated ,the light can be marginally controlled.

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S4 Par Can

Data Sheets

Beam Projector

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Far Cyc

A cyclorama instrument or cyc light is an instrument designed to provide a colored wash on a cyclorama. A cyclorama is a large cloth drop used to surround the stage. The cyc lights (pronounced "psych" light) a designed to be hung approximately 8 feet from the cyclorama. One cyc light, hung 8 feet from the cyclorama, will light an area approximately 16 feet high and 12 feet wide. Cyc lights use a hybrid-reflector which is shaped like a curly-Q. cyc lights are a single purpose instrument, and are rarely used for anything other than lighting cycloramas.

Border/Strip Lights

Strip lights are long troughs with a series of lamps in them. The lamps are circuited together so that they can be lit in a colored sequence. These instruments can be placed at the front edge of the stage and called footlights, or they can be placed at the back edge of the stage and called the electric ground row (EGR). Strips can also be used to illuminate a cyclorama or hung with chain or a C-clamp to provide down light.

There are different types of strip lights. The most common form use PAR lamps and are wired with either 3 or 4 circuits. A newer type of strip lights are called mini-strips and use specialty lamps called MR16s. These are low voltage lamps which put out as much light as PARs and take up half the space

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Follow Spot

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Linenbach

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Scene Machines

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Pani

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Wiggle Lights

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Resistance Dimmers

This is an older obsolete type of dimmer where excess power is bled off into heat. The biggest disadvantage to this type of dimmer is that there is always a load on the dimmer--as soon as the dimmer is turned on the dimmer will use 100% of its power. If the circuit attached to the dimmer is set to 20% then 80% of the power is bled off into heat coils. If the circuit is set to 0% then 100% of the power is bled off into heat. Another problem with resistance dimming is that in addition to having a maximum load (the maximum amount of power which a dimmer can safely take) a resistance dimmer also has a minimum load. In order to get effective dimming these dimmers must have at least their minimum load. Often in order to make these minimum loads resistance dimmers were loaded with "Ghost Loads" or extra electrical equipment offstage in order to make these minimum loads. This is a huge disadvantage because of how wasteful the system was as well as how difficult it was to control.

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Auto Transformer

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Triacs

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SCR
Silicon Controlled Rectifier

A diac is a form of solid-state switch used to switch AC voltage; it belongs to the class of switches known as thyristers. It is like a junction transistor without a base lead (it is a two-lead device) and accomplishes its switching action by breakdown at a certain voltage. There are also four layer devices with a similar mode of operation known as four-layer diodes.

The triode AC switch (TRIAC) is a power-switching device as is the SCR. The TRIAC conducts currents in both directions while the SCR allows current in only one direction. A common application is for lighting controllers. In response to a trigger, the triac conducts until the AC voltage applied reaches zero, then blocks flow until the next trigger occurs. Since a trigger can cause it to trigger current in either direction, it is an efficient power controller from essentially zero to full power.

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SSR
Solid State Relay

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AMX-192
AMX192 - Analog Multiplex Data Transmission

AMX192, (a USITT standard) was devised to multiplex up to 192 analog dimmer levels down a four wire cable. The four wires are ground, analog level, and a differential clock. The USITT standard is now quite old, having been last revised in February 1987, and is probably now mostly of historic interest, although there are many thousands of installations out there which use this protocol every day, there won't be many more newly installed systems. DMX512 is now the protocol of choice for multiplexed lighting control. The AMX192 standard document is bundled in from USITT with the DMX512 standard document

The standard says...:

2.0 Applicability

This Standard is intended as a guide for:

Equipment manufacturers and system specifiers who wish to integrate systems of dimmers and controllers utilizing analog multipled control.
Equipment manufacturers seeking to adopt a basic controller-dimmer analog multipled data transmission protocol

It is important to note that the origins of this standard come from a control protocol originally developed by Strand Lighting (Strand Century Inc.). This protocol is used by a large installed base of equipment manufactured by Strand and many other manufacturers. One of the objectives of the Standard is to describe a protocol that will sucessfully communicate with most of this existing equipment. Because the original protocol has undergone many slightly different versions, this Standard is broken down into two major areas:

Receive Timing. Dimmers or other receiving devices that adhere to these timing requirements should be able to successfully communicate with most existing consoles that use different variations of the original Strand protocol.
Transmit Timing. Controllers or other transmitting devices that adhere to these timing requirements should be able to communicate with most existing dimmers that use the different variations of the original Strand protocol.

There are substantial differences between the receive timing and the transmit timing. New controllers adhering to this standard must produce a signal acceptable to a wide variety of dimmers, and new dimmers must be able to listen to a number of different controller signals. As an example, note that new controllers should provide a wide "analog valid" window, but new dimmers must be able to cope with the differences in existing consoles, and use a narrow "sample window". These differences in timing between the Receive Standard and the Transmit Standard produce enough tolerance to cover worst case variations on the original Strand protocol.

Although widespread adoption of this Standard is sought by USITT, compliance with the standard is strictly voluntary. Furthermore, it is not intended as a replacement for existing protocols already manufactured, but rather as an addition to existing protocols which will broaden the installed base of controllers and dimmers that can communicate with each other.

One real gotcha with all the multiplexed analog schemes is that the cable radiates a fair amount of interference, and so wireless intercomms can get blocked if you are close by.

Pin	Purpose
1	Signal common
2	Differential clock +ve
3	Analog level
4	Differential clock -ve

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DMX-512

The U.S.Institute of Theatre Technology (hence refered to as USITT) first developed the DMX512 protocol in 1986 as a standard interface between dimmers and consoles. It was a simple concept and was easily adoptable by all concerned. Since the first standard, some improvements was made in 1990 to accomodate some problems and it is now known as the USITT DMX512 (1990) standard. Another round of discussions are on for further modifications and then it would become USITT DMX512-A. It started out as a means to control dimmers from consoles and has ended up being used to control intelligent lights, color changers, yokes, strobes, smoke machines, lasersand even confetti dispensers.

BASIC OPERATION

Although details of how USITT DMX512(1990) (hence forth refered to as DMX, unless specified othewise) is described in detail on other dedicated pages (see main page), a preamble is given below.

The DMX protocol consists of a stream of data which is sent over a balanced cable system connected between the data transmitter (usually consoles) and a data reciever (could be dimmers or any of the stuff mentioned in the above paragraph).

A single DMX port, outputting this stream, can pass magnitude value information for a maximum 512 channels (or lesser) only. This port is known as a DMX universe. For consoles catering to more than 512 channels a second universe ( and therefore a second port) is required. The following is the universe/channel table:

UNIVERSES CHANNELS

1 1-512

2 513-1024

3 1025-1536

4 1537-2048

5 2049-2560

6 2561-3072

The data stream is sent as a packet ( hence forth refered to as the DMX packet) of data which is repeated continuously. It consists of starting bits of data which informs the recievers that the packet is being refreshed and then sends out a stream of serial data corresponding to the magnitude value of each channel , starting with channel 1 and ending with 512 or a lesser channel No( depending on the design and size of the console). Each channel is separated from the other by specified bits of start and stop data.

&h01... &h02... &h03... &h04... &h05...

&h06... &h07... &h08... &h09... &h0A...

The whole system works like a city postal system. Each postman ( universe ) has a beat of 512 houses(channels). Each house(channel) has a unique address.Some houses are high risers with many individual apartments(several channels in one unit like an intelligent light). The postman goes from house to house and delivers the mail(the value data ) in individual letter boxes. Each occupant opens only HIS letterbox and takes HIS mail. Similarly each recieving unit is told it's address (one of 512 adresses) and thus ignores all other data except the one it's supposed to recieve against it's address.Some units like intelligent lights have one address as a start and go on to recieve data for that address AND several more addresses FOLLOWING it . Not unlike the lobby security receptionist who takes in the mail for every one in that building and then distributes it.

The data stream has a specific format (THE DMX512 PACKET) and has specific physical properties(DMX512 PHYSICALS) by which it is propagated .

The actual electrical method by which the digital 1s' & 0s' are spit out by your console and then recieved by all the gear on stage is also important to understand, in view of the fact that 80% of your problems are caused by distortion, in some way, of the physical DMX512 signal.

The DMX512 signal is transmitted via the industry standard interface known as the EIA485, more familiar as the RS485. This is not dissimilar to the RS232 port behind your standard desktop, but is not the same stuff exactly.

Specialised instrumentation desktops have these RS485 ports for process control jobs, but the format for communication is quite different. It's like using the same English alphabets to write two different languages.

The RS485 standard uses two/three wires to transmit the digital HIs & LOs:
1) The +signal wire (+s)
2) The -signal wire (-s)
3) The 0 wire or ground wire (0v)

A digital 1 is sent out when the +s wire is at a higher potential then the -s wire.

A digital 0 is sent out when the +s wire is at a lower potential then the -s wire.

The difference between these two data wires is what's IMPORTANT ; NOT the difference between EACH of them and the ground wire which is simply a reference point. The ground wire may not be present at all in some EIA485 installations.

The high or low potential levels are defined clearly by the RS485 interface standard.
Any of the two wires can go upto +12volts (measured to ground) or down to -7volts (measured to ground).

e.g. To transmit a digital 1 ,the +s wire is held at +5volts and the -s wire is held at -5 volts.

To transmit a digital 0 ,the +s wire is now taken to -5volts and the -s wire to +5 volts.

The DMX data stream clocks out at the rate of 250Khz which means each bit is measured at 4 micro seconds widths.

1) IDLE or NO DMX situation:
In the absence of a valid DMX packet the output of a DMX line will be a continously HI signal.

2) BREAK
The start of a DMX packet is heralded by the output going LO for a MINIMUM period of 88 microsecs. This means 22 LO bits are measured out one after the other. This is known as the BREAK. The BREAK could be longer but not less than 88 microsecs. Experience shows that slightly longer breaks (above 88 microsecs) sent from a console are better since the recieving devices are generally given the algorithm = "Is the BREAK>88 microsecs or 22 pulses". I keep it generally at 100 -120 microsecs in equipment designed by me

3) MARK AFTER BREAK (MAB)
The MAB immidiatly follows the BREAK by making the output go HI for a MINIMUM period of 8 microsecs or 2 pulses. This MAB is a bit of a problem since the difference between the original DMX512 and the current DMX512(1990) standards relate to this period of the packet. The original was set at 4 microsecs or 1 pulse. This created hassles for some recievers for being too short a MAB for detection and was upgraded to 8 microsecs or 2 pulses in 1990. The problem comes when a older console is used with newer recievers or vice versa.Wrong detection will lead to packet rejection or the wrong data going to the wrong channel. This will travel down the line leading to utter confusion. Some recievers have a dip switch to set this parameter for both timings. Again the maximum MAB lenth could be 1 sec.
My ideal timing would be 12 microsecs.

4) START CODE (SC)
The SC is next in the line. It is easier to remember that the SC is the start of the actual data stream where all individual channel data have the same format. The BREAK & the MAB were of different timings but the SC onwards all frames will have the same structure and timing of 11 pulses or 44 microsecs width. The first one can be termed as data for channel No 0 which is a non-existent channel and represents the SC.

I will first describe the general structure of these channel data frames:

-Of the 11 pulses the 1st one is always LO signifying the Start bit .

-This is followed by the actual data byte of 8 bits (which could be any of 256 values from 0 to 255).

-The frame ends with 2 bits which are HI signifying the two stop bits and end of the channel information.

Channel No '0' is the SC, which as things stand, ALWAYS has the databyte = 0 signifying that the following data is for dimmers. As per the current standard, no other value can be used. The option is left open and as and when ESTA specifies, the SC value may be used to tell the reciever that the data following it is meant for a specific type of reciever. That is the end purpose of having the SC..... to be able to segregate a packet of data, recieverwise. But, for the moment, it's zero which has been specified for dimmers by ESTA. Do remember that this also includes just about any recieving device like dimmers, moving lights or whatever !

5) MARK TIME BETWEEN FRAMES (MTBF)
The mark time between frames can be from a little more than 0 sec to upto 1 sec, but the lesser the better. Each channel frame can have the MTBF before the start bit. The MTBF is obviously HI .

6) CHANNEL DATA (CD)
The CD frames follows the SC frame in a logical manner from 1 to 512 (or less) in the form described above.

7) MARK TIME BETWEEN PACKETS (MTBP)
After the last valid CD stopbits are sent, one full packet is completed and the next packet can start with a fresh BREAK & MAB. However an idle (HI) can be inserted between packets (MTBP), the lenth of which may be a little more than 0 sec to upto 1 sec. It is upto the console designer to design the architecture of the console and the software powering it in such a manner that the data thruput time is at a minimum.

IMPORTANT

The happy part of DMX is that you DONT send the CHANNEL NUMBER AT ALL!!

The 1st byte AFTER the STARTCODE(SC) is AUTOMATICALLY taken as the datavalue for Channel 1...next, datavalue for Channel 2....next, datavalue for Channel 3...and so on...upto 512 OR less channels. That is how the recievers...be they intelligent lights or whatever...will decode them. Actually a channel counter is set up in the reciever...either in the software itself or as a hardware counter. This counter will be automatically reset to point at channel 0 when a valid BREAK and a valid MAB is detected. Subsequently with every LAST stop bit in each frame, this counter is incremented by ONE. Thus, DURING the SC frame, the counter output reads zero. At the end of the SC (last stop bit of the SC frame)the counter output becomes one, thus telling the processor that the next frame contains the data for channel 1 and so on. So the reciever knows which channel the current data is valid for ....Thus when you set a start address in an MARTIN 812 at say 50 (+6 channels) it simply takes the 6 databytes from when the internal channel counter reaches 50....counting upto 55 !! The moment you start a fresh BREAK ...etc sequence (a new packet ,that is) this counter is reset !! So it is fully legal for a console or software to generate upto valid 100 databytes after the SC for 100 channels and then generate a BREAK,etc. Thus you don't HAVE TO generate all 512 bytes !! The LSC ATOM, for instance, has the capacity to drive 99 channels; thus at the end of the 100th frame or a count of 99(remember, we have an SC frame to count,too, at the count of zero) the console starts sending a BREAK + MAB and so on. This concept is vital in order to understand the one to one relation between channel nos and their respective data.

The DMX data stream clocks out at the rate of 250Khz which means each bit is measured at 4 micro seconds widths.

1) IDLE or NO DMX situation:
In the absence of a valid DMX packet the output of a DMX line will be a continously HI signal.

I will first describe the general structure of these channel data frames:

-Of the 11 pulses the 1st one is always LO signifying the Start bit .

-This is followed by the actual data byte of 8 bits (which could be any of 256 values from 0 to 255).

-The frame ends with 2 bits which are HI signifying the two stop bits and end of the channel information.

6) CHANNEL DATA (CD)
The CD frames follows the SC frame in a logical manner from 1 to 512 (or less) in the form described above.

IMPORTANT

The happy part of DMX is that you DONT send the CHANNEL NUMBER AT ALL!!

The DMX data stream clocks out at the rate of 250Khz which means each bit is measured at 4 micro seconds widths.

1) IDLE or NO DMX situation:
In the absence of a valid DMX packet the output of a DMX line will be a continously HI signal.

I will first describe the general structure of these channel data frames:

-Of the 11 pulses the 1st one is always LO signifying the Start bit .

-This is followed by the actual data byte of 8 bits (which could be any of 256 values from 0 to 255).

-The frame ends with 2 bits which are HI signifying the two stop bits and end of the channel information.

6) CHANNEL DATA (CD)
The CD frames follows the SC frame in a logical manner from 1 to 512 (or less) in the form described above.

IMPORTANT

The happy part of DMX is that you DONT send the CHANNEL NUMBER AT ALL!!

The DMX data stream clocks out at the rate of 250Khz which means each bit is measured at 4 micro seconds widths.

1) IDLE or NO DMX situation:
In the absence of a valid DMX packet the output of a DMX line will be a continously HI signal.

I will first describe the general structure of these channel data frames:

-Of the 11 pulses the 1st one is always LO signifying the Start bit .

-This is followed by the actual data byte of 8 bits (which could be any of 256 values from 0 to 255).

-The frame ends with 2 bits which are HI signifying the two stop bits and end of the channel information.

6) CHANNEL DATA (CD)
The CD frames follows the SC frame in a logical manner from 1 to 512 (or less) in the form described above.

IMPORTANT

The happy part of DMX is that you DONT send the CHANNEL NUMBER AT ALL!!

DMX512 Standard Pinouts
The Standard connector for DMX512 is the 5 pin XLR connector [Note 1]. A female is fitted to a transmitter (eg a console), and a male to a receiver (eg a dimmer).

Pin	Usual colour	Usage	Notes
1	Screen	Interference screen, and ground reference	[Note 2]
2	Black	DMX512 Data -ve
3	White	DMX512 Date +ve
4	Green	Spare data -ve	[Note 3]
5	Red	Spare data +ve	[Note 3]

Notes

The XLR5 physical pinout is very different to a 5 pin DIN!
The body of the connectors is not connected to the screen. This is very important. If they were, and if you were to pickup two DMX connectors that have different earth potentials you could get a very nasty (or fatal) shock.
That "spare" data pair referred to hides a multitude of sins.

Scrollers - DMX512 & Power on XLR 4 pin

The 4 pin XLR is used mostly by scrollers and colour changers to deliver both control and power to a lighting accessory.

The following pinout is believed to be correct for:

Chroma-Q color changers
Wybron Forerunner

Not the Wybron ColorRam!

Pin	Usual colour	Usage	Notes
1	Screen	Interference screen, and ground reference	[Note 1]
2	Black	DMX512 Data -ve
3	White	DMX512 Date +ve
4	Green&Red	+24V DC	[Note 2]

The body of the connectors is not connected to the screen. This is very important. If they were, and if you were to pickup two DMX connectors that have different earth potentials you could get a very nasty (or fatal) shock.
The power is referenced to screen, pin 1.

DMX512 on XLR 3 pin

The 3 pin XLR is used mostly by moving lights. Of course, as the XLR3 was never standardised as a "proper" DMX512 connector, there is no "proper" pinout, so of course, both variations are used.......

Pin

High End Systems
(Cyberlight, Intellabeam)

Martin Professional
(RoboScan)

Notes

Dimmers

Protocol

Reflectors

Lenses

Fresnel Lens Agustin_Fresnel.htm

Concave

Convex

Plano Convex

Double Convex Back To Top

Fixtures

Parnel Data Sheets

Ellipsoidal Data Sheets 5’ 10’ 19’ 26’ 36’ 50’

Par Can

S4 Par Can Data Sheets

Beam Projector Back To Top

Border/Strip Lights

Follow Spot

Linenbach Back To Top

Scene Machines Back To Top

Pani Back To Top

Wiggle Lights Back To Top

Resistance Dimmers

Auto Transformer Back To Top

Triacs Back To Top SCR Silicon Controlled Rectifier

SSR Solid State Relay Back To Top

AMX-192 AMX192 - Analog Multiplex Data Transmission

&h01... &h02... &h03... &h04... &h05...

&h06... &h07... &h08... &h09... &h0A...

IMPORTANT

The happy part of DMX is that you DONT send the CHANNEL NUMBER AT ALL!!

IMPORTANT

The happy part of DMX is that you DONT send the CHANNEL NUMBER AT ALL!!

IMPORTANT

The happy part of DMX is that you DONT send the CHANNEL NUMBER AT ALL!!

IMPORTANT

The happy part of DMX is that you DONT send the CHANNEL NUMBER AT ALL!!

Notes

Scrollers - DMX512 & Power on XLR 4 pin

DMX512 on XLR 3 pin

Fresnel Lens

Agustin_Fresnel.htm

Double Convex

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Parnel

Data Sheets

Ellipsoidal

Data Sheets 5’ 10’ 19’ 26’ 36’ 50’

S4 Par Can

Data Sheets

Beam Projector

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Linenbach

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Scene Machines

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Pani

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Wiggle Lights

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Auto Transformer

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Triacs

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SCR
Silicon Controlled Rectifier

SSR
Solid State Relay

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AMX-192
AMX192 - Analog Multiplex Data Transmission