Stage lighting has come a long way from the days of simple candle-lit stages. Today’s sophisticated productions rely on complex systems of lighting fixtures and control equipment, which in turn depend on robust and reliable communication protocols. This article explores the evolution of these protocols, with a focus on how they benefit stage lighting operators.
The Foundation: DMX512
In the mid-1980s, DMX512 emerged as the first universal standard for controlling stage lighting equipment. Developed by the United States Institute for Theatre Technology (USITT), DMX512 was originally intended as a standardized method for controlling stage lighting dimmers. Before DMX512, lighting control relied on various incompatible, proprietary systems. DMX512 uses a multi-drop bus topology, where devices are connected in a daisy-chain. A single DMX512 controller manages a network of slave devices like dimmers, fog machines, and intelligent lights. DMX512 transmits data over a single twisted pair of wires, using a differential signal.
Benefits for operators: DMX512 provided a standardized way to control lighting devices, simplifying system design and operation. It allowed operators to control up to 512 channels, each representing a specific lighting parameter, from a single control console.
Limitations: DMX512 is a unidirectional protocol with limited error reporting and no automated configuration capabilities. Each device on the network must be manually configured with a starting address, and the same address must be programmed into the control console. The one-way communication means that the controller cannot receive any feedback about the status of the connected devices.
Enhancing Control: RDM
To address these limitations, Remote Device Management (RDM) was developed as an extension to DMX512. Approved by the American National Standards Institute (ANSI) in 2006, RDM introduces bidirectional communication to the DMX network.
Benefits for operators: RDM enables operators to remotely configure devices on the network, including setting DMX addresses and other parameters. It allows for automatic detection of devices, making setup quicker and less prone to error. RDM also enables status reporting, which allows operators to view device status, including faults like burnt-out lamps or failed motors.
How it works: RDM packets are inserted between DMX data packets using a unique start code (0xCC) that non-RDM devices ignore. RDM uses the same physical cabling as DMX512, and can be used in mixed systems.
Expanding Reach: IP-Network Protocols (Art-Net and sACN)
As lighting systems grew more complex, the need arose for protocols that could extend the reach of DMX512 control. Art-Net and Streaming ACN (sACN) emerged as the main solutions for transmitting DMX512 data over Ethernet networks. These protocols enabled the management of multiple DMX universes over a single network cable.
Art-Net
Developed by Artistic Licence, Art-Net is a royalty-free protocol for transmitting DMX512-A and RDM over UDP/IP. It allows communication between Ethernet (or Wi-Fi) nodes and a console, facilitating the control of many devices across a larger network. Art-Net also supports management functions, including detecting Ethernet nodes, updating parameters and transmitting timecodes. Art-Net 4 introduced the ability to manage gateways with more than four DMX ports without the need for multiple IP addresses.
Streaming ACN (sACN)
Also known as ANSI E1.31, sACN (Streaming ACN) uses the Root Layer and PDU format of ACN to transport DMX512 data over IP networks. It is designed to carry repetitive control data from one or more sources to one or more receivers. The protocol includes a synchronization mechanism, to ensure that multiple receivers process data concurrently. sACN also facilitates higher refresh rates when there are no DMX512 components in a system, allowing for greater flexibility. sACN is gaining popularity for data transmission, but lacks native support for device discovery, configuration, and RDM data transfer.
Benefits for operators: These network protocols significantly increase the scalability of lighting control systems, allowing for more complex designs across larger areas. Multiple universes of DMX data can be transmitted through a single cable, reducing setup complexity and costs. The use of Ethernet allows for greater distances between controllers and devices compared to traditional DMX512 cabling.
Key Differences between Art-Net and sACN
While both Art-Net and sACN transmit DMX data over IP, they have key differences. Art-Net supports device discovery, RDM, and management. sACN is designed for efficient data transport and synchronization but lacks native RDM support and device discovery. Art-Net 4 has the ability to manage sACN by selecting whether a given gateway port should convert sACN or Art-Net to the DMX output.
Looking into the Future
These modern protocols have revolutionized stage lighting, enabling the advanced lighting designs seen in today’s productions. They have become essential in live performances, concerts, corporate events, and more. Automated lighting fixtures, like moving heads, benefit greatly from the expanded capabilities of these control protocols.
The continuous evolution of lighting control protocols reflects the growing complexity of stage lighting systems. Protocols such as RDMnet, which extends RDM for network-based lighting management, help operators to achieve more precise control.
Conclusion
The evolution of stage lighting control protocols, from DMX512 to RDM, Art-Net, and sACN, has significantly improved the capabilities and flexibility of stage lighting systems. These advancements empower lighting operators with greater control, increased scalability, and more efficient management of complex lighting networks. As technology continues to advance, we can expect even more sophisticated and user-friendly solutions that further enhance the art of stage lighting.
