Brief analysis of the evolution process of professional stage lighting system

Stage lighting is also called "stage lighting", or "lighting" for short. One of the means of stage art modeling. Using stage lighting equipment (such as lighting fixtures, slides, control systems, etc.) The external image of the stage performance and provide the necessary lighting effects.

The development of professional stage lighting equipment began with the appreciation of performances by European courts and nobles in the 15th century; later, with the invention of electricity, it has undergone a completely new change.

1. The analog world of 0 to 10 volts

Early lighting control used 0 to 10 volt analog to represent the height from 0% to 100%, and each circuit was handled by a signal line (common line). The more loops means the more lines, and the farther the transmission distance is, the more serious the problem of signal voltage drop will be.

The emergence of the 0 to -10V control method, using the positive voltage as the common ground, solves this problem and also solves the problem of signal interference.

2. Multiplexing transmission

With the development of performing arts in the 1950s and 1960s, the number of lighting control loops has continued to increase; from ten to dozens of loops to hundreds or even hundreds of loops. While the number of analog control lines used for a source increases, it also means that a more convenient and simple connection method is needed to improve the previous problems.

In the days that followed, the multiplex transmission method became the core of the professional lighting system architecture.

The methods of multiplex transmission are mainly divided into two categories - analog multiplex and digital multiplex. In the multiplexing mode, the main parameter data are the transmission rate, the maximum number of controllable loops and the type of connector used.

The following lists the multitasking protocols that have appeared in the past 30 years. Some of them have long been eliminated, some of them still exist and are used in large numbers on old-fashioned machines, and some of them are still developing and improving their functions.

3. DMX-512 protocol

Professionals who understand lighting will know this protocol, which is the most widely used lighting communication protocol today. Originated from the United States USITT Association after the Band rate in Colortran's CMX192 was raised from 153.6Kbit/s to 250Kbit/s and 192Ch was changed to 512Ch (the structure of CMX and DMX is roughly the same).

When it was first published, the Mark after Break (MaB) was 4uS. In the subsequent use, it was found that there were often signal refresh problems, so the MaB was extended to 8uS and defined as the DMX-512 (1990) version. Its wide use is due to its simple structure, low cost, and easy understanding. Major manufacturers have successively added DMX-512 interfaces to their products. Another major contributor to the successful promotion of this agreement and everyone's willingness to use it is the rapid development of computer lighting in the past few decades and its extensive use in large-scale performances.

The large number of people who use it will naturally lead to a deeper understanding of it, and more awareness of its use restrictions and its impact on the development and improvement of the entire lighting performance industry in the future.

The more controversial points are the inability to perform two-way transmission, the slow transmission rate, and the inability to load other data content (DMX only provides circuit and brightness data), etc. Seeing this, everyone can clearly know what kind of functional protocol we need tomorrow to improve the lighting control architecture.

Yes, the mature Ethernet network that has been used in the computer industry can be regarded as a direction. It is not difficult to handle and maintain the communication of the entire Ethernet network with a computer dimming console with a processing chip inside.

4. Lighting Ethernet

Around the early 1990s, Strand Lighting developed the first SMX protocol based on their original content (including bidirectional transmission, error reporting, etc.)"ethernet"Architecture and TCP/IP platform lighting network system - SHOWNET, and applied in the reconstruction project of the San Francisco Grand Theater after the earthquake.

In the past ten years, the promotion of the lighting Ethernet network has been difficult, and it is not easy to ask the lighting practitioners to accept a set of the latest computer interface. They think that lighting control only needs circuit and brightness/value changes, and other data are auxiliary; and they threaten to see that the performance in the era without these data is not the same. This is a good statement, but the times are moving forward. The advantages of a large amount of data provision, parallel platforms, full tracking backup, multiple priority control methods and resource sharing provide very convenient work in the production of complex programs and large-scale performances. platform.

In the days to come, other manufacturers launched their network systems one after another, most of them with"ethernet"Architecture and TCP/IP platform as the core, such as ETC2NET, COMPUNET, ARTNET, etc.

In the systems of many companies, no matter the platform or function is similar, a network decoding box is needed at the end of the system to restore the loop change value in the network cable to DMX format and output it. Since the current lamps and dimming silicon only accept digital or analog multiplexing protocols such as DMX-512, the advantages of the lighting network have not really been brought into play.

Moreover, the communication protocol of the Ethernet network in the system is not unified, and each manufacturer uses its own protocol code, so that lighting network products of different brands cannot be connected to each other. Speaking of this, everyone is looking forward to the emergence of a standardized and unified network communication protocol.

5. Alternative lighting ethernet

The development of professional lighting systems has reached the age of the Internet today, and in the future it will be dominated by the ACN standard. However, if some consoles are not designed to support the Internet, what will happen? And what is the possible way to achieve the Internet? Functionality? The answer depends on how ArtNet converts.

After the console outputs the DMX-512 signal, the DMX-to-ArtNet converter developed by the British Artistic License Company converts the signal into a TCP/IP network signal. Then it is distributed to various regions through general network processing methods, and finally the signal is converted from ArtNet to DMX by a converter for lamps or dimming silicon.

The so-called network signal only has lighting circuit and brightness data (converted from DMX), and can only be defined as a variant of the traditional DMX system at most; it cannot be directly upgraded to CAN specifications in the future (must replace the dimming console and cancel all DMX-ArtNet -DMX converter).

If this is considered as a transitional solution, it is still advisable. But if you want to consider the long-term system upgrade and support, this system structure does have room for negotiation.

6. ACN protocol

In 1996, the American ESTA (Entertainment Services and Technology Association) realized the changes and needs of the future common agreement (the most commonly used at that time was DMX-512), based on Strand Lighting's SMX and ShowNet (on the market The earliest lighting network product).

In November 2003, the LDI exhibition held in the United States in the exhibition hall of ESTA will display a group of lighting network systems that work with ACN. Its structure is that Strand Lighting's dimming console is connected with ETC's dimming silicon, Martin's moving lights and Pathway connectivity's ACN/DMX-512 transcoder. The purpose of this collocation is not only to show that the ACN standard has been successfully developed (published at the end of 2003), but also to let people experience that the day when different network devices can be connected to each other has arrived.

7. The competition between ACN and DMX-512A

In any case, two-way transmission is an inevitable requirement. Controlled devices such as computer lamps and dimming silicon are no longer silent. They also have the right to speak and have something to say. This is the return signal, and useful information should be returned to the dimming console. DMX-512 (1990) The protocol we are familiar with entered its tenth birthday (2000) and required further development due to limitations in its use.

The protocol update plan tentatively named DMX-512 (2000) started immediately (later renamed DMX-512A).

The first task is to add two-way transmission but also be compatible with the old system, so the transmission rate is kept at 250Kbit/S. The two-way transmission method is that the 4th and 5th pins of the original 5 pins are used as the return signal, or the original 2nd and 3rd pins are also used as the return signal, that is, the transmission and return signals are both operated in the 2nd and 3rd pins, and the StartCode is operated and switched.

In addition, add the name codes of each manufacturer to the Start Code, so that the dimming console knows the brand of the device being controlled. Since it is required to be compatible with the old DMX-512 system, the speed cannot be improved.

On the contrary, the experience on ACN can be infinitely extended and developed.

In the future, the ACN format will be accompanied by DDL language. This language format will send the information such as the nature, characteristics, brand, model, software version, and attributes of the equipment transferred by ACN to the dimming console and suggest the connection method. . All devices connected to the network can be observed and controlled from the console.