Today, shows can employ tens to hundreds of moving light fixtures and other multi-parameter devices. This reality has created a need for a much more powerful communication tool, than DMX , of transmitting data between the
console
and the fixtures. For complicated multi-venue systems like theme parks , cruise ships, TV studios and performing art centers, control capability of a few thousand channels is not an unusual requirement. The network should support the ability to communicate with larger building management systems or park-wide control systems .
Lighting control methods have made some impressive advances by adapting hard ware/software tools from the computer industry. Control consoles became PC-based computers driving Ethernet network, with the ability to do much more than previous systems at a fraction the cost of older systems. To illustrate these changes we will discuss the task of designing cable layout for a new
lighting control
of a theatre. 10 years ago it took senior theatre consultant weeks of work to:
Define all
remote control
locations around the theatre (left stage, right stage, bridge…)
Specify what parameters may be controlled from each location (DMX 1, DMX2.., Video, Remote)
In comparison, today the consultants role ends after step 1 (i.e. defining control locations).The rest of the process is a routine job of laying out a standard office network.
Ethernet is a standard communication protocol embedded in software and hardware devices intended for building a local area network (LAN).
A basic hardwared LAN consists of the following components:
Two or more computers to be linked together or networked
A Network Interface Card (NIC) in each computer with an assigned unique address
Ethernet cable that connects to each computer
A networking
switch
or networking hub to direct network traffic
Networking software
In comparison, today the consultants role ends after step 1 (i.e. defining control locations).The rest of the process is a routine job of laying out a standard office network.
Ethernet is a standard communication protocol embedded in software and hardware devices intended for building a local area network (LAN).
A basic hardwared LAN consists of the following components:
Two or more computers to be linked together or networked
A Network Interface Card (NIC) in each computer with an assigned unique address
Ethernet cable that connects to each computer
A networking
switch
or networking hub to direct network traffic
Networking software
Ethernet cable runs from each NIC to the hub. The hub acts as a relay, receiving and directing packets of data across the LAN. Thus, Ethernet networking creates a communication system that allows sharing of data and resources including printers, disks, converters, etc
Most of the Ethernet networks used in lighting systems are of composite topology in which star topology is implemented at different sites (stage, dimmer room, lighting cabin, etc) and bus topology implemented between these sites.
The Ethernet networking hardware is based on market products(hubs, cables, etc .), and only the nodes (devices) are for
lighting control
purposes.
Ethernet is a general name referring to LANs (Local Area Network) protocols that use SMA/CD (Carrier Sense, Multiple Access, and Collision Detection) technologies. This means that the network access method is based on users “listening” to network transmissions and beginning their own
transmission
whenever they need the network’s management. This prevents collisions between multiple users’ transmissions. The term Ethernet describes only
transmission
management methods and network’s physical architecture (kinds of wires, topology, and distances). It does not specify what those transmissions include.
Ethernet offers a number of advantages:
The ability to connect multiple devices to a single network, regardless of the information interchange relationship between the devices Ethernet allows all devices in the network to communicate.
Ethernet operates at 10 Mb/s or 100 Mb/s, whereas DMX 512 operates at 250 Kb/s
Less cable is required, i.e. on a single cable you can transmit data from a variety of outputs (DMX 512, video, audio, etc.)
Real time bi-directional synchronization between control desks and integral back-up system.
Centralized file server stores all shows and rehearsal data
Data can be loaded from any control desk on the network
Readily available, mass market of network components hardware and software
Readily available installers and industry standards for installation
Easy configuration and monitoring of networked equipment
The wide- spread adoption of Ethernet technology continues to drive the cost of networking devices and components lower, increasing the options for smaller theaters with limited budgets
Ethernet has also some disadvantages:
Maximum cable length between 2 devices to 100 meters, compared with 250m for
DMX 512. In longer installations, where very long cables are required, it is necessary to use fibre–optic cabling.
RJ45 connectors used in Ethernet networks are not suitable for heavy-duty use in industrial or touring conditions.
Data collisions can occur on the network which slows down the data transfer between devices
The building blocks of Ethernet Network (based on Compulite hardware -CEN )
CEN consists of 3 main Ethernet workstations: CompuLINK, VideoLINK and EMIX-2
The workstations provide various functions from converting VCs into standard DMX 512 and vice versa, to remotely controlling the consoles and viewing their different displays.
Compulite File Server and Net Administrator provide remote server file access and a network configuration.
Consoles
The Ethernet software is written in TCP/IP language, but as of today (2006) there is no standard on how the control data (currently DMX 512) is being transmitted.
The lack of standard Ethernet protocol forced the larger control companies like Compulite to develop their own protocol and a complete set of supporting hardware.
ESTA has formed a committee that has been working for several years to define a new standard CAN (Advanced Control Network) that could be run over Ethernet.
