De-Mystification of Intelligent Fixtures
By Stephen EllisonIntelligent fixtures are the dream of every lighting designer. All you have to do is tell the fixture what you want to do, and voila- a great design happens! Wouldn't that be wonderful, a fixture that you could communicate with on a headset about what you want in each cue...
LD - "Ok all the Mac 2000's- go to the star Down Center in Blue."
Mac's - "How do you want us to get there and exactly what color blue man?"
LD - "Oh well, how about a wave starting upstage to downstage and make it Cobalt Blue. Oh, and make the wave a 6 count and then hold there until the next cue. Now the studio wash is on the upstage truss, I want."
If we could only have such a conversation. I have a better chance of having an intelligent conversation with my dog, Faith. The term "Intelligent Fixture" is more of a misnomer. The more accurate adjective is Moving. This new generation of fixtures has the capability of movement. No longer are you stuck with a fixed focus and color, these fixtures can move at your command.
So what exactly is intelligent about these fixtures? The intelligence is in the ability to listen to our commands and make changes based on that information. The communication between us and them is very limited, and is based on parameters laid out in the standard that was developed for communication between a lighting console and a dimmer rack. What we can do is send a signal to the fixture that provides for 256 different values. The fixture then uses this value to control a motor that changes an attribute of the fixture, such as color or movement. In the future, there are plans for limited 2 way communication, so that when you plug a fixture into the data stream it will talk back to the console and identify where it is and what it is.
In reality these "Intelligent" fixtures are better thought of as robotic in nature. The heart of the fixture is the microprocessor and the control program, the body houses all the motors and parts they control. The control program is where the intelligence lies- it controls the fixture. When the fixture is first turned on, the program initializes the fixture and performs a self test. When the program is satisfied that everything is working properly and (most importantly) it knows where everything is, then it starts to listen to the outside world.
Let's take a more in-depth look at what were actually controlling. Every fixture is composed of a number of stepper motors that control the various attributes. The term "attribute" refers to the various things that can be controlled, such as; pan, tilt, color wheel, gobo wheel etc. A stepper motor is a sophisticated motor that allows us to control it's exact position with a computer in 256 steps per byte. Simply put, we can tell the motor to move to an exact point in it's rotation out of 256 points in that circle. If you use 2 bytes to control the motor, then you have fine control with up to 65,536 values. Fortunately for us, we never have to worry about any of those numbers, all we have to do is program the lighting console.
In order to program the console, you do need to know how to talk to each motor in the fixture. The language (or protocol) that is used for communication at this time is DMX 512. DMX 512 sends information to the fixture in a stream of data that consists of 512 values of information. Each value also has an address in that stream. The fixture is set to start listening at a specific address in the data stream, then it reads the values and executes the instruction. In order to program the console, you need to know which attribute is controlled by which address. The manufacturer provides a chart that defines what attribute is controlled where in the data stream, based on a starting address of 1. Also within that chart they break down how the value, as it changes from 0 to 255, and tell you what the different values mean and how they change the attribute in question.
An example of this would be a color wheel. If that wheel has 13 colors, then you are provided with an exact range of values that correspond to each color. Oftentimes not only can you select each color but also within that same 256 range they provide some fun effects, such as color spin forward or backward, with varying speed based on a range of values.
These fixtures are easy to understand if you just view them as a bunch of motors that you control. The challenge is controlling all of those motors in all your fixtures at the same time.
Hopefully you now see that the fixtures are basically dumb robots that do whatever you tell them. You actually provide the intelligence to make them look good.
I don't want to frighten you. You may be thinking: "How do I decide what to do with all those motors?!" Not to worry though the lighting consoles today have built-in functions, so that instead of worrying about each motor, you can concentrate on the design. The consoles have the chart that I mentioned before loaded into their memory and can provide buttons that allow you to tell the fixture, with a few keystrokes, to turn on in white. You can then grab a mouse or trackball and move the fixture where you want, then push more buttons to choose the color or the pattern you want. The actual value and address is transparent to you and lives only in the console's memory. This frees you up to design the lighting instead of dealing with the mechanics of talking to the fixtures.
I hope that I have made these fixtures easier to understand, the ability to change the attributes of the fixture can geometrically increase what you can accomplish as a designer while reducing the quantity of fixtures that are required to produce the design. As a last point I should also point out that the time spent programming the fixtures to create your looks also increases geometrically compared to controlling dimmers to create a look, so when you first start to use them allow a lot of time to get used to working with them.
If you have any questions or would like more clarification on your specific requirements, please send me an email, lighting@tfwm.com. I am always looking for questions to include in this column, feel free to contact me.
