Automated Fixtures - The Science of MLs

[photoatdv]

I've done some shows with a very good ML programmer/designer. One of the things he really emphsized was understanding how the equiptment works (Which I always am interested in anyway.). I was looking for some more information about how different types MLs work. Does anybody know of a good website(s)?

[Thomas]

First prize is to attend a basic service training course- Martin do some really awesome ones around here. Once you've got one manufacturer figured out, the others are all applying very similar principles. There's some basic stuff in most user manuals as well- changing gobos and lamps etc.

Otherwise, assuming you have access to some moving lights, get a screwdriver and dissassemble them. With the power off, and carefully. Don't lose stuff and photograph every step so you don't get lost when you're putting it back together.

I won't say any more because I'll be attacked for it, but that's one place to start.

[derekleffew]

For websites, obviously those of Vari*Lite, Martin, High End, Robe, etc. The best book one can buy currently is Automated Lighting, by Richard Cadena. Focal Press, 2006. (More information about servo motors than anyone needs to know!)

[JD]

The science of moving lights has a very unusual family tree! They grew from a most unusual seed... The computer floppy disk drive! Floppy drives used a special two phase motor called a stepper motor. Unlike a regular motor, the stepper motor had two inputs. Using the two inputs, you could "step" the motor to very specific points which were the tracks on the floppy disk. A disk controller would keep track of how many steps the motor had taken since it left its home position, and move the head to a new position by adding or subtracting steps.

Movers kind of do the same thing. There is a "home" position with a sensor. The micro controller may get a signal to move to the 3rd color. It will then step the motor the known number of steps to get to that color. When it gets then next command, it will then send a specific number of forward or reverse steps to take it to the new color. All of the other features, gobos, pan, tilt, prism, iris, and the rest work the same way. The micro controller keeps track of how many steps have been taken since the last time it saw the "home" sensor. This is why movers will sometimes get "out of sync" with each other. Usually a 0,0,0 blackout, or reset will allow them to find home and start over.

Fun stuff!

[porkchop]

JD makes a very good point, the one thing to always remember about MLs is that they are a computer and computers are only as smart as the people that program them. They may have been very smart people but they still got confused from time to time, therefore MLs will get confused from time to time. Knowing how to reset the particular ML you're using from the board will save many many hours in the air and at the repair desk.

That being said there is no substitute for first hand experience. Only experience can tell you that the 4.5mm bolts that hold all the goodies together in a Clay Paky will sometimes get stuck so hard in their hole that the only way to get them out is to take a Dremel tool and turn the bolt into a flat head screw drive bolt. A repair manual and a class or two will teach you many useful things and the basic ideas that went into construction and go into repair of a light, but there are lots of other things that can only be learned by experience.

One last example that is a lot less straight forward than the 4.5mm bolt one. Our Alpha Wash 1200 HPEs have one static gobo wheel and two rotation wheels. We noticed that the rotating wheel closest to the static wheel wasn't rotating all the way into position. We bring the light down everything checks out, it runs the test sequence fine, no noticeable problems the rotating wheel looks and runs as well as ever. What's the problem you ask? There is one static gobo that gets a lot of use, this causes it to bend, once it's bent about 1/8" it interferes with the rotating wheels motion and causes the problem we were seeing. Why did the wheel pass the test sequence? Because all of our work space is flat so the fixture was sitting upright on its base where in the air its hanging downward from the clamps attached to the base. Gravity pulls the wheel slightly into the rotating wheel when its upside down and away when its right side up. Would have eventually happened right side up too but not in the relatively little time we had the static wheel in on the test bench. Now that fix takes 30 minutes but you never would have found that in the Clay Paky repair manual.

[indyLD]

Funnily enough, I am just prepping some articles on this subject for On Stage Lighting. Pop over and sign up the RSS feed and you won't miss them.

It is important to understand the mechanics of fixtures (once you understand the basics, a quick glance at the user manual or fiddle with the console shows what the different types can do). Then the op knows all the possible ways to acheive an effect. So good advice - and the Richard Cadena book is worth a read.

Cheers

Rob