Anyone who wants to learn about automated lighting programming must study and master one very important task: Patching. Without this ability, the data within the desk will not be able to communicate properly with the connected fixtures and other devices. Patching requires an understanding of a console’s specific methodologies, DMX fundamentals and intimate details of the lighting rig layout. No matter the show or the console, a programmer must properly patch the system to actually control lighting units.
Patching Purpose
In simple terms, patching assigns fixture numbers within the console to unique DMX addresses via various connection types and locations. Once this association is in place, the programmer can simply select a fixture via a user number (or on-screen icon), and it will activate the correct unit within the lighting rig. When no patching exists, then no control is possible. With incorrect patching, abundant errors can occur, ranging from lack of control to out-of-control fixtures.
Often, the lighting designer, crew chief or another person will provide a lighting plot with a plan of how the fixtures will be connected. Since the very nature of DMX limits the number of possible fixtures on a universe, multiple cable runs may be necessary. This information is as important to the patch as is the unique DMX address of each fixture. Typically, the plot will include not only the cable routing, but also the DMX start addresses for all fixtures.
Patching Protocols
Generally speaking, all lighting fixtures and products connect via DMX in some format. The simplest method is through an XLR connector, where each line equates to a specific universe. In more complex systems, network protocols such as Art-Net, sACN and others, distribute DMX information through Ethernet cables. With these systems, multiple universes can be sent to devices and each device must then be configured to listen to the correct universe. Other network systems such as MA2-Net, Pathport and more work in a proprietary methodology, similar to DMX.
When preparing to patch, the programmer must configure the console to output data via the appropriate connections and protocols. This can vary from console to console, so be sure to check the user manual on your desk for the specifics. You may have to activate protocols and/or assign universes to their desired output method. It is imperative that the data output type matches what is being used beyond the lighting console.
Procedures, Please
The basic procedure for patching a console is to first add in the fixtures used in the show from your console’s fixture library. The library profiles will hold all the specific DMX protocols (or mapping) of which DMX channels control which functions for a particular lighting product. It is essential that you select the correct library for your fixture that matches the make, model, and mode of the light you are using. Next, you will specify how many of these fixtures you plan to use in your show.
Then you will want to assign the custom “user” numbers to the fixtures. These will vary depending upon the rig, the LD, the show and other factors. Hopefully you have a list of how you plan to number the lights, as this will become the language that everyone on the show uses to refer to each and every fixture.
Now these user numbers need to be associated with specific real-world fixtures. This is where you actually assign the patch information. You will select a fixture number (101 for example) and then enter its DMX universe and DMX start address (101 @ 2/27). In this example, this would patch fixture 101 to universe 2 and a DMX start address of 27. The syntax may differ depending on your desk, but the purpose is always the same. This same process must be accomplished for all devices that will be attached to the lighting console.
Batch Patch
Luckily, many tools exist within lighting consoles to assist when patching. Usually, you do not have to select your fixtures one at a time to enter the data. There will be syntax that allows you to select multiple fixtures and patch them via a range. For instance, you could enter 101 through 121 @ 3/1, and the console will patch these 20 fixtures sequentially, starting at DMX address 1 on universe 3.
You will often find other syntax or tools to ease the patching process. Some consoles display the patch graphically, and you can touch the starting address, or even drag fixtures around a grid of available DMX address slots. Furthermore, some consoles allow importing of the patch data from visualizers, drafting programs, or other lighting designer applications.
RDM to the Rescue
Remote Device Management (RDM) is a sub-protocol within DMX that allows two-way communication with fixtures. There are many things that can be accomplished with RDM, but one of the most useful is to patch fixtures. With RDM, fixtures can be “discovered,” and your console can then tell you what fixtures are connected to which output. This allows you to patch them to your user numbers with ease. RDM even allows you to change the DMX start address on the fixtures from your console. This provides the ability for the patch in the desk to be sent directly to the fixtures without human interaction at the fixture.
Some consoles can actually use RDM to identify a fixture and automatically select the proper profile from within the console’s library. This is pretty close to auto-patching! Additionally, some desks will even build a library on the spot if one does not already exist. Using RDM, the fixture tells the desk what its features are, and on which channels, and the desk will create a library to match. A note of caution: many consoles and fixtures have not fully implemented RDM functionality yet. It’s a good idea to take the time to learn how the elements of your show are RDM capable before you make any plans to use RDM.
Patch is the Problem
The majority of problems between a console and fixtures tend to be patch-related. Either the wrong information is in the console patch, or the fixture is assigned to the incorrect DMX address or universe. These must match in order for proper operation.
When the patching is complete and the rig is connected, it is very important that the programmer confirm that everything is working as expected. Generally, this means selecting each fixture one at a time and seeing that it corresponds correctly between the user number and the fixture in the rig. The best way to accomplish this is to use a highlight type feature and run through each fixture using the NEXT key on the desk. If you simply select groups of fixtures, you may not realize that two fixtures are set to the same DMX address. Always test each fixture individually to ensure the patching data matches up correctly.
Perfect Patchwork
As I stated at the beginning, patching is an essential requirement for programmers to master. Without a proper patch in the desk, no control of lighting fixtures is possible. In order to achieve a good patch, programmers must understand DMX addressing, universes and various protocols as well as specific syntax and processes of their console. Importing data, RDM abilities and other tools can simplify the patching procedures, but in the end, it all comes down to aligning numbers. Always test your patch and be open to correcting any mistakes. For most shows, once the patch is set and confirmed it can almost be forgotten. This allows you to concentrate on the fun and creative programming that we all love.
