Lighting Control: What to Know About 3 Protocols

Lighting Control: What to Know About 3 Protocols

In the world of lighting control, there are quite a few different control protocols and systems. Many of them however, take a huge influence from the DMX protocol.

The best lighting design is only as good as its network. A single point failure in a system can turn into a huge distraction, one that can pull the congregation out of worship.

Control protocols are the central nervous system of any lighting setup.

It is important for us as leaders in worship lighting, to not only consider our visual design, but also the technical design.

A superb technical design makes for an incredible visual design that can function without flaw.

In the world of lighting control, there are quite a few different control protocols and systems. Many of them however, take a huge influence from the DMX protocol.

DMX is a standard for digital communication, specifically designed to create interconnectivity within lighting equipment. Within the DMX 512 standard, there are 512 channels of control that can be managed with 256 distinct values. Further, this protocol can be extended with the use of multiple DMX universes. These universes essentially act as multiple control systems within a larger control scheme. 

DMX is typically transmitted over 5-pin XLRs connected to 120 ohm 2-pair cable. It can also be run over 3-pin cable as well. Many times, mic cable is used to transmit DMX data. This is not suggested, however, because mic cable does not have the same impedance rating and changes the wave properties of the signal. This can cause glitches, dropouts, and unexplainable data issues. When using long lengths of such cable, or you opt to configure a great number of fixtures on a single line, this can hold especially true.

The DMX protocol also calls for termination at the end of each run. A terminator is a resistor that helps to eliminate defects and minimize noise in the data line. It is best practice to use resistors, however in situations with shorter cable runs and low fixture counts, it is not always necessary.

Part of the appeal of DMX is its robust qualities and flexibility. Under correct use, DMX can transmit data over a span of 3,800 feet. Unlike many other past protocols, up to 32 fixtures can be wired to a single DMX output. The originating DMX line can also be split, with the use of an Opto-Splitter. This enables multiple runs of 32 fixtures to exist in a single DMX universe.

Opto-Splitters make copies of the original DMX source and duplicate it to multiple outputs. Each bit of data transferred through the output of an Opto-Splitter is internally transferred as a light wave and received by a light receiver, to be translated into DMX data.

Since light cannot travel out of the receiver, it makes it impossible for interference, or bad data to pass backwards past this point. This fail safe can be a huge asset in any lighting network plan.

Since Opto-Splitters create a copy of the DMX universe, you can split up data distribution to parts of the rig. This helps to ensure that any issues that may occur can only effect a certain area. In the case that a singular fixture fails, it may insert bad data into your DMX stream. When this happens on a system setup with multiple Opto-Splitter outputs feeding the rig, you will only have the fixtures on that line affected. I typically try to limit my total fixture count per Opto-Splitter output to 10 fixtures. This provides a good solid backbone for my network, and limits issues.

In addition to the DMX protocol, there are Ethernet-based protocols that take the DMX architecture to a new level. One of the largest is ArtNet, a protocol that packages and transmits multiple universes of DMX over typical Ethernet network components. With a universe limit of 32,768 universes, that can be used within the ArtNet protocol, there are few applications where this would not be a suitable solution.

Each device within an ArtNet network is assigned and operates with a unique IP address. Most devices are configurable by simply opening a web browser to their specific IP address. These devices often operate in the 192.0.0.1 or 2.0.0.1 IP ranges.

In a typical setup, a lighting console sends ArtNet data over the network to multiple nodes. These nodes are units that translate ArtNet into standard DMX, and output it over 5-pin connectors. Many of these nodes can also be set up in a backwards fashion, allowing them to act as DMX inputs, as well as outputs. The use of DMX nodes can create the ability to spread universes across large areas, without the need for extensive runs of cable. They also make it practical to change universes easily.

Beyond just ArtNet and DMX, another complimentary control protocol called RDM gives further functionality to systems. This protocol can be used to update IP addresses, update DMX addresses, give real-time feedback on errors, and show the type of fixture being controlled. This protocol is designed to complement, and not replace DMX or ArtNet.

Control protocols are the central nervous system of any lighting setup.

Knowing the ins and outs of control networks will help you to create a solid control network. Creating a system that is robust and serves the needs of the design well, will serve you well for years to come.

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