Intelligent Lighting - Control

Control

Moving lights are controlled in many ways. Usually the fixtures are connected to a Lighting control console, which outputs a control signal. This control signal sends data to the fixture usually in one of three ways: Analogue (which has largely been phased out), DMX which stand's for "Digital Multiplex" (which is the industry standard control protocol), or Ethernet Control (which is still in development). The fixture then takes this signal and translates it into internal signals which are sent to the many stepper motors located inside.

The vast majority of moving heads are controlled using the DMX protocol, usually using dedicated twisted pair, shielded cable with 5-pin XLR connectors at the ends. Each fixture is assigned a block of DMX channels in one of the venue's DMX universes (a self-contained set of cables and fixtures which can operate a maximum of 512 individual channels). The central lighting desk transmits data on these channels which the intelligent fixture interprets as value settings for each of its many variables, including color, pattern, focus, prism, pan (horizontal swing), tilt (vertical swing), rotation speed, and animation.

Since moving heads did not attain prominence until DMX's predecessor, analogue, had passed the zenith of its popularity, very few moving heads use analogue control (this is also due to crippling restrictions on bandwidth, data transfer speeds and potential inaccuracy). Some of the most modern intelligent fixtures use RJ-45 or Ethernet cabling for data transfer, due to the increased bandwidth available to control increasingly complicated effects. Using the new Ethernet technology, control surfaces are now able to control a much larger array of automated fixtures. Because many devices can be connected to a single RJ-45 network, these devices have the ability to not only listen to a control signal from a lighting control board, but have the ability to transmit information back to the control board and other entities on the network. Now, it is possible for a fixture to self-diagnose any problems, announce itself on a network, or accept setting changes from any place on the network, making obsolete older versions of the system that only had one central brain, the lighting control board. Because RJ-45 (and equivalent technologies) use bidirectional digital communication, bit-checking abilities allow for lighting control networks to safely operate devices that can interfere with human safety (pyrotechnic devices, rigging mechanisms, etc.).

Moving lights are much more difficult to program than their analogue cousins because they have more attributes per fixture that must be controlled. A simple conventional lighting fixture uses only one channel of control per unit: intensity. Everything else that the light must do is pre-set by human hands (colour, position, focus, etc.) An automated lighting fixture can have as many as 30 of these control channels. A slew of products are available on the market to allow operators and programmers to easily control all of these channels on multiple fixtures. Lighting boards are still the most common control mechanism, but many programmers use computer software to do the job. Software is now available that provides a rendered preview of the output produced by the rig once fixtures are connected to the program or console. This allows programmers to work on their show before ever entering the theater and know what to expect when the lights are connected to their controller. These products usually feature some method of converting a computer's USB output to a DMX output.

The latest generation of moving heads are integrating digital projection capabilities, creating a real convergence between lighting and video projection. These new generation of heads do not only require intensity, position and focus control, but will require video content control as well.

While it is true that moving lights have, in a sense "revolutionized" the world of concert and other event lighting, to call these fixtures "intelligent" can be offensive to some people. In fact, not every person involved in the music production business feels that moving lights are intelligent, necessary or even desirable at all. While this type of technology can be used very effectively, there are many instances in which it simply distracts an audience from the lack of musical content coming from the stage. In this case, to call this lighting "intelligent" can be the source of much confusion.