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DMX & Moving Lights In ETC 48/96

Discussion in 'Lighting and Electrics' started by Smatticus, Jan 13, 2004.

  1. Smatticus

    Smatticus Active Member

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    I thought I would move my questions out of the new member board since I got on the subject of moving lights. The fixture patch in our Express console has been one of the things I've been unable to explore because we have no budget for moving light fixtures. From my understanding you devote a certain number of console channels to a single fixture to control its individual attributes (pan, tilt, color, etc). I was curious as to how that relates then to dimmers and actually plugging in the fixture; does that mean you need a separate dimmer for each channel or attribute. I atleast assumed this but I really don't know anything about the DMX protocol or how it works. If I need a separate dimmer for each attribute does that mean there is a stage plug coming off the fixture for every one of its attributes? :?: I was just curious as to how this works as I have not worked with it before and if that were true we have a 96 dimmer system so we wouldn't be able to support very many moving fixtures. Thanks!
     
  2. jrlang

    jrlang Member

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    typically you only need one channel or one power source for each insturment. Then the channels for the attributes are virtual. So, if you have 96 channel house, with 12 moving lights with 6 atrributes each, then you need a board that can handle 168 channels.

    Hope this helps
     
  3. cruiser

    cruiser Active Member

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    as jrlang said, you will generally give them one power source, which is a power point. As moving lights cannot be "dimmed" they have a dowser which simply covers the light as the fixtures take to long to respark fi you dimmed the lamp right out.

    To patch it to the desk, you create a "dmx daisy chain" where you link all your dimmers together, then you put the dmx of your moving fixtures into the "dmx out" on your last rack, then keep linking the moving lights.

    Each light has a little menu on it, where you select what channels you want it to go from, so say your first fixture was 1-24 you could patch your second one as 25-36 or 48-60 if you wanted to have some static fixtures in between!
     
  4. Smatticus

    Smatticus Active Member

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    I understand that each fixture only needs one power source but I guess I don't understand how the board controls its different attributes. I've been looking at some resources online trying to understand DMX protocol and in general how digital signals work. Our theatre has a ETC dimmer rack off the stage with 96 dimmers that are distributed to the three pin outlets along the electics or directly to a set of house lights or strip lights. If a moving light is the same three pin connection I just don't understand how it controls the attributes of the moving light through that connection. I could be thinking about it entirely wrong though so I don't really know. Thank you for all of your information. It may be a hopeless pursuit to try and understand how it works right now as I don't have alot of experience in the technology and how it operates but thank you for all of you help!
     
  5. jrlang

    jrlang Member

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    first,
    you are getting power and DMX cables confused. Yes you can power the fixtures on stage pin (3 pin) connectors. Just make sure they are switched to non-dimm and remain on during the time slot you want.

    Second
    DMX cable uses cable like mic cable or XLR cable. Only rather then 3-pin it uses 5 pins. That is what is used to transer or send the data signals to each fixture.
    Hope this helps
     
  6. DMXtools

    DMXtools Active Member

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    Power (the 3-pin connector) isn't the only thing going to the mover - it also gets a connection to the 5-pin (or 3-pin on cheap units) XLR, taking the DMX signals directly. The DMX signals are just numbers. If you send them to a dimmer, they tell it how bright it should be. If you send them to a mover, they tell the servos where to aim the light, or which gobo or color to select. Typically, if all your board has is faders, one fader/DMX channel will be pan, another tilt, another color, another gobo and so on - it usually takes several DMX channels/faders to control a mover. Some boards provide a joystick to control pan and tilt - it's just a pair of faders and a fancy mechanical linkage to let them both be worked by one lever.

    Because the mover has its own DMX connection and is controlled by the DMX signals directly, it doesn't need to be powered through you dimmer rack... as a matter of fact, it's a bad idea to do so. The mover wants to see clean power direct from the breaker box.

    Hope that helps.

    John
     
  7. Smatticus

    Smatticus Active Member

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    Those last two messages really helped alot, I was definitly getting stage pin and the DMX cable confused, I understand stage pin is purely for power and in our system's case they run directly to the dimmers, or from the dimmers rather. My assumption is then that the DMX cable that runs from the board (labeled 1-512) goes to the dimmer control module? I'm starting to get an idea how it is supposed to work but I don't think we could configure our system to run moving lights then. And I don't know of a way that we could power the fixtures without using the stage pin and just use the dimmer at maximum output. My understanding is gradually expanding, thanks for your information! :D
     
  8. jrlang

    jrlang Member

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    [​IMG]
     
  9. Smatticus

    Smatticus Active Member

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    I'm currently reading the manual for our Sensor CEM, it is definitly helping me to understand what goes on with the DMX signal and the dimmers, thanks for all of your help!
     
  10. DMXtools

    DMXtools Active Member

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    BINGO! We have a winner!

    As for hooking up a mover, for power, you could use the stage pin and just keep that channel up full all the time. I don't recommend it, but in a pinch, it would probably work.

    For the DMX signals, look at your dimmer rack. Somewhere near where the cable from your board plugs in, there should be another 5-pin XLR, probably labeled DMX OUT or something like that. Chances are it has a terminator plugged into it (That's just an XLR without a cable - instead, it's got a 120 ohm resistor soldered between pins 2&3 inside). Unplug the terminator (make sure the system is OFF first) and plug another 5-pin XLR cable in instead. Connect the other end of the cable to the DMX IN of your mover, then plug the terminator into the DMX OUT of the mover.

    Then comes addressing - if you've already got 96 dimmers, you may have to change the addressing on some of them so they share channels with other dimmers doing the same thing in order to free up some channels for the mover. I wish I was familiar with the board you're using, cuz right now, this is about as far as I can go with you.

    John
     
  11. Smatticus

    Smatticus Active Member

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    Thank you very much for your help. I'm currently reading online resources that explain the DMX protocol. The more I'm looking the more information I'm finding but everything you've offered is extremely helpful. I am definitely achieving a greater understanding of how everything works together! :D I'm also becoming more familiar with our Sensor dimmer rack which is helping too. Thank you again for all of your help! The way it sounds right now the board isn't really the biggest gap in understanding what is going on, I think just expanding the understanding I am will help me understand how the board controls everything. Thanks again! :D
     
  12. Nephilim

    Nephilim Active Member

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    My cliffnotes on DMX: Basically all that's happening is that zillions of times a second the control device is sending signal saying "CHANNEL X AT LEVEL Y" where X is a number between 1 and 512 and Y is a number between 0 and 255 (there's a reason for the 256 different values to do with the way numbers are represented in binary).

    So, the CME in those Sensors reads the entire datastream, looking for the channels that it knows that it owns. When it sees one, it tells the corresponding individual dimmer unit to go to that level. It passes the entire signal back out again for daisy-chaining.

    When a DMX signal hits a moving light, that one fixture is looking for a block of channels, starting at the one you select with the menu on the fixture. It then pipes the level information into its little CPU and controls all its functions based on what value the channels take.

    Side Note: Some DMX moving lights have "16-bit" pan and tilt. What this means is that they use two channels each for pan and tilt, where the first selects from 256 positions for the motor, and the second selects from 256 positions within each of the previous positions (if that makes sense) giving you much more precise focus control.

    Warning for the future: Many moving lights use "3 pin DMX". This marvel of technology is essentially AES/EBU audio cable (data grade 3-core) and is good enough to carry DMX without those nasty extra pins. Unfortunately, this means people want to use audio XLR cable in them. This will not work. Guitar Center, PSSL and just about every "pro" music/lighting retail store carries 3pin DMX because it's what all the silly DJ lights use.

    Of course, if you use NSI Microplex as a dimmer connection, then you can use audio XLR :D

    MAN. So, DMX is a very fast serial link that spits and endless stream of channels and their associated levels.

    BTW, with that 48/96, you have DMX B which is marked as "513-1024" - if you use that as a moving light feed, you'll need to do two things. First, when assigning channels on the fixture, remember that what's coming down that DMX B cable is "1-512" not "513-1024". Second, when in the fixture patch screen, you'll need to enter channels as "2/1" not "1/1" so signify the 2nd DMX output.

    Cheers!
     
  13. Smatticus

    Smatticus Active Member

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    I've been doing some reading in addition to what everyone has offered and I've found the equivalent of your cliffnotes just extremely more technical and complex, which I hope to eventually understand but you simplified the process very well. The last part you mentioned about the 48/96 was particularly useful in that I wasn't sure exactly what all of the different settings were in the fixture patch of that board but I'm beginning to understand that too. I read something about having a DMX 'universe' and from what I gather a single DMX universe is like DMX A on the board and another is DMX B or (513-1024). Here is another question since I am just so full of them, from my understanding each dimmer has a 'unique dimmer #' which is also represented virtually on the board. I understand that, but how do the virtual channels on the board relate to the channels of the DMX protocol. On our EXpress 48/96 there is a limit to how many virtually channels I can create but I can create more than there are physical sliders for. Now I'm trying to understand how the DMX relates to the virtual representations in the board, mainly channels but also groups and cues, etc. Thank you for all of you help! 8)
     
  14. Nephilim

    Nephilim Active Member

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    A DMX 'Universe' is 512 channels of DMX, yes.

    Inside the 48/96, there are a whole honking lot of channels, which you patch to DMX channels in the Patch screen. So, the DMX channels are the 'unique dimmer number' and the Express 'channels' are the physical faders plus whatever else you enter with the keypad.
     
  15. Smatticus

    Smatticus Active Member

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    So if the DMX channels are the 'unique dimmer numbers' I can control essentially 512 dimmers just on DMX A. But whenever I try to specify the number of virtual channels on the board it doesn't let me go above a specific number, I would assume because of available memory? But those virtual channels can either send DMX signals to dimmers or to specific attributes of a moving light fixture? (I just tried it in Expression Offline and it only lets me create 192 virtual channels on the board):

    I'm just kind of thinking 'out loud' here but if the DMX channels are the same as the ''unique dimmer number' and we have 96 dimmers the first 96 DMX channels are controlling the dimmers, so if I wanted to patch a moving light fixture without interfering with the dimmers and the CEM settings I could just patch the fixture starting on channel 97? Granted on the board I wouldn't have manual control of any channels above 96 b/c there are only 96 sliders but I could just record using the keypad...

    Interesting 8O
     
  16. Nephilim

    Nephilim Active Member

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    Correct. It could also be that the software limit on number of channels has been lowered. Check the manual, there's a setting in Setup for the maximum number of channels.

    Did you set EOL to emulate the 48/96 though? You are correct though, each Express channel can be sent to either a dimmer via the CME or a moving light. With the Patch screen you can have one channel control more than one DMX channel, if you want. But it gives you more control to assign submasters and leave the patch relatively one-to-one.
     
  17. Smatticus

    Smatticus Active Member

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    Sorry I edited that last message after I posted it. I do have it set to emulate the 48/96 and having 96 sliders and 96 dimmers to control for the most part it stays relatively one to one, in fact as I think about it now it makes more sense to keep everything entirely one to one, record submasters to use as washes instead of actually putting them on the same channels, and then if at some point in the future we had moving light capabilities or resources (unlikely) they could be patch starting at 97? Thanks for your help, I might be starting to get this. :)
     
  18. Nephilim

    Nephilim Active Member

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    Yes, you could start at 97, or you can use DMX B - it depends on where you want your cable to come from. It's great when it all clicks, isn't it :)
     
  19. Smatticus

    Smatticus Active Member

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    That it is. :D Thanks for all of your help! In our theatre DMX A goes to a box in the booth which goes to the Sensor rack so if I used DMX B it would have to come directly out of the board, out the window or the door, and then run a long cable to the front of the theatre and up to the electric or a tree or something, or it might be fun to set them up on top of the booth. :eek: I don't know, now I just need a moving light to play with. :D Thanks again!
     
  20. seanb

    seanb Member

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    next time you are at the board, look at the four buttons near the numbered pad. There is STAGE, BLIND, SETUP, and PATCH

    If you hit patch, you will see how softpatch works

    There are, at the most basic level, three levels of patching and numbering

    1) Circuit - a fixture is plugged into a designated circuit, the actual plug/socket where it gets its power. This will run into your dimmer room

    2) Dimmer - back in your dimmer room, you will find your circuits all coming into a patch panel. Some circuits may be hard wired to a dimmer. Some circuits might be pluggable into a dimmer as you need them, this is your hard patch. In some theatres, they will put a dimmer in for every one of the circuits to eliminate the hard patch stage. Certainly simplifies the situation!

    3) Channel - this is where you assign the actual slider on your board, in the soft patch. It's the soft patch because you aren't doing anything hard wired, just changing how the lighting board remembers what dimmers are attached to what channel sliders. For example I can put dimmers 1, 2, and 3 into channel 1. I can't go back and put dimmer 3 into channel 2 as well, though.

    Soft patch is very handy! I use it a lot when I'm building shows as it allows me to figure out the tough stuff from a poorly organized theatre once and layout my channels how I want them :) All of this refers to how the express sees traditional fixtures, I'm not really sure how it sees intelligent fixtures. Any insight?

    Correct me where I'm wrong, I'm sure I messed up somewhere :) :D
     

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