Embarassing DMX Questions


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Yeah, all right, I have a confession to make: I still don't really know how that whole "DMX" thing works, even after two years of being a Lighting Director.

Hokay. First off, conventional lights. Light power -> dimmer -> console? DMX Interface? The last step is the one I don't know. I know at school we have a separate box the DMX connects to, which connects to the board, but then again my board is so antiquated that I'm not sure if this is the same with all boards. Could someone tell me basically the connections to control conventional lights?

Second off, intelligent lights. In order to run them on a board, do you basically have to connect them all in series (in the end) in order to connect them to the one or two outputs in your console?

Third off, DMX/XLR. I know that DMX is what you really should use for intel lights, but I know that we've often used XLR cable instead, and that it's the same. I'm right on this one, correct? Or am I being forgetful, and DMX has 5 pins to XLR's 3? Heh.

Yeah, I've been wondering these things, but a bit too embarassed to ask, because I'm sure the answer is simple. By the way--I don't need the whole explanation of DMX, channels, etc; I just want to know how one would hook up a setup if one was starting from scratch.

Thanks, and stuff. :oops: !
I'll start at the bottom of your post and work my way up.

Mic cable is rated at 80 Ohms and DMX cable at 120 Ohms. In limited situations, i.e. small number of fixtures or less than 100' of total cable runs mic cable will work. "Real" DMX is designed to operate on 5 pin XLRs, however, at this time only 3 of the conductors are used and many manufacturers have adopted the use of 3 pin XLRs to save money. If the future all five conductors will be utilized as the next generation of intelligent fixtures will be sending status information back to the controllers.

Yes, intelligent fixtures are daisy chained one to the next to the next with one line back to the controller. You can also use opto-isolators to split the DMX data into two or more trunks.

There are two ways to integrate conventional (or analog) fixtures for operation via a DMX console. First if you already own analog dimmers, you'll need a Black Box. A Black Box will translate the DMX signal into an analog signal the dimmers will recognize. If you don't have analog dimmers you'll need to obtain DMX dimmer/relay packs which respond to DMX to control conventional fixtures.
You can daisy chain your movers but affter about 26 devices you need to put them on another liine this inclueds dimmers one dimmer rack = 1 device.

DMX cable vs. Mic cable. Does an $5,000 show seem worth the price of getting the right cable.

Power Setup

Disconnet ->Dimmer -> Cable To Fixtures
Distro -> Cable To Movers


Console ->DMX -> If dimmers are analog (DMX to AMX convertor) -> Dimmers.

Console -> DMX -> Mover 1 -> Mover 2 -> etc. -> Terminatior on the last mover.

I'd add little "thank you's" to each of your post, but that'd get visually distracting. Thank you very much. (I finally know what isolators are for! Excellent!)

And it'd make sense that we'd need a 'black box,' we have a hard-patch system and the original board was, of course, an analog board. That makes sense, excellent.

Since you had mentioned it, JH, I have another question, about power. What do you guys mean by distros? I've heard that dimmers (unless they're back-packs) are usually powered by the rack and need special power. Then again, from what you were saying, the distro is related to moving head fixtures. I'm ah, a-very confus-ed.

Thanks again though, you've cleared up a ton of my confusion.
Distros are used to take 3 phase power and break it down to usable power for a moving light.

For example I have a 400 amp disconnect i have 20 moving lights the movers are a mixture or 20 and 15 amp, So i have differnt modules that decide which amount of power they are and they have plugs on the back they could be twist lock or soca or edison. based on what amp of power is necessary

Dimmers usualy have power put directly to them as in a sense they are there own distro they just dim the out put of power. based on a console.

check out this site for some pictures of distros
Heh, now I gotcha, thanks. What type of cable goes from the distro to the lights? Just regular AC cable? (I ask, because I don't know where/if we have a distro, we've just used our standard sockets, wall and ND's.
DarSax The cable used would be AC cable. But whether it is single run cable, ie one cable per plug outlet or a multicore cable that carries many electrical circuits in the one cable depends entirely on how they wired your theatre. It could be a combination of both. Eg mutli-cable to a lighting bar. Single cable to single side of stage points.
Gotcha, gotcha.

In the next few (probably this one) days, I'm going to try and write out the steps to hook up an intelligent light setup, if one/some of you all would be so kind, I'd appreciate it if you could tell me where/if I'm missing steps or if I'm confused about something.

Thanks so much for all of your help, again!
All right, I included a diagram of how to hook up intelligent fixtures, to the best of my knowledge. Is this correct/could someone answer the questions that are in the image? Thanks :!:

To control moving lights with a board such as the Maxxyz, you need to have the profiles for the lights loaded in. A profile is a set of parameters and channels that correspond to the fixture so that you can program colors, gobos, positions, movement, etc. from the board with the encoders.

For example: without a profile, you just have a bunch of DMX channels. Their values can be changed. But you don't know what that channel exactly does at the console without checking the manual and DMX chart for the moving light. A fixture profile (or library, as it's sometimes called) is loaded into the console. That way, you say that you want fixture X to start on channel 1. Any fixture you add after X should automatically set itself on the right starting channel (at least on some boards). On the boards that I've worked on, you can select what fixture you want from a drop-down menu. Once you load the profile, many boards have a joystick and specific buttons for certain functions (movement, gobo, color, focus), and you can use those now because the fixture profile lets the console know what each channel means.

Most ML consoles have a large number of fixture profiles already loaded in, so you may have all of the ones that you need on your console.

I tried really hard to put that into easy terms, and it took me forever to figure it out when I first learned it. Kinda hard to explain.
Oh yeah...dip switch addressing. Many fixtures do it in weird ways, so look in the manual, but most have binary addressing. This means that, using the dip switches, you basically add up the numbers until the channel with which you want to start.

But many fixtures these days have RDMX, which is remote DMX addressing. This means that, if you have the right board, you can address the fixtures from the board.

So, you can set the starting channel from the fixture (and from the board if you have RDMX fixtures), and then you tell the board what channel the fixture starts on so that the fixture profile lines up right. The board then automatically lines up the fixtures that you add in order (just make sure that you have them addressed in the same order that you add them to the board).
Lessee. To the first soundlight post, that actually made a lot of sense, so uh, thanks, and good job. (I'm not a complete stranger to the process, so I had a sort of leg-up, but that still was very easy to understand. Thanks.)

To the BillESC/second soundlight. I think I understand what you're both saying; so you have to go into the on-board computerthing in the fixture, and tell it what channel to start on? (So when it gets data on the DMX, it knows that it's supposed to either do something or ignore the data?)

And gotcha on the opto-isolator, I had seen those in rental catalogs and had no idea what they were.

Thanks so much, again, I've always stressed that one day someone's going to ask me how to hook up these things and I'll have no idea D:
You address the fixture on it's internal computing to tell it on which channel it should start pulling it's data from. It pulls data from that channel on until it gets to the end of it's control channels.

Example: if you have a 17 channel fixture, and you set the starting address to 128, the fixture pulls data from channels 128-144. You have to tell your board which channel you set as the starting channel so it knows on what channel to start sending control commands for that fixture.

Gel scrollers would work the same way, correct? You'd have to address on the thing what channels it should respond to, and then you have to load the thing from the library on the board, and assign it channels on the board? You do have a different channel for each color, correct, so you can program in specific colors?
Sorta you have one DMX channel per scroller, But DMX uses the values 0 to 255. So when you take controll of a scroller on say dmx adress 01 you then set it between at lets say 123 and that happens to be green.

you then have the option on most high quality lighting consoles, Such as my perferd console the MA Lite. you can creat an Attribute preset. In this case colour. So when you want that scroller or any scroller you have programed into the preset to be green you just push the pallet that says green. This is a great time saver you can do universal pallets for all your fixtures so you can grab all your fixtures and set them all to green instantly with out any fussing with wheels or numbers.

Also when you travel a show you can update presets (presets can be postion, focus, colour, beam, and universal which means it records everything listed except timings. ) thus not needing to re do you whole show.

Now to your comment about you might have to set up a rig, the best way to learn is by being thrown into it. If someone hands you a rental package thats costing them 6 grand for the week you will find a way to make it work.

Ah! Thanks a lot JH, that makes a lot of sense (and I had no idea, heh.)

And about the thrown into it, fair enough. I was supposed to have already had that done to me last year, but a more knowledgeable guy came in and did everything so that I learned nothing. D:
Yes, Terminator is the term for an XLR male cable with a 120 Ohm resistor across pins 2 and 3.

Some fixtures also have built in terminators, so you may not need one on the end of every data branch, just check the fixture manuals ... e.g. there may be a second row of dip switches (not used for DMX addressing) that can be used for testing and standalone modes etc ... sometimes, one of these dip switches acts a "terminator".

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