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Question About DMX Universes

Discussion in 'Lighting and Electrics' started by wemeck, Oct 24, 2003.

  1. wemeck

    wemeck Active Member

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    Anyone in the mood to Clearly explain the issues and reasons for DMX universes?
    What are they?
    Why do they exist?
    Especially with regard to Colors Scrollers and how the forerunner box when plugged into a dmx input is in the second universe.
     
  2. DMXtools

    DMXtools Active Member

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    DMX-512 (Digital MultipleX-512 channels), as the name implies, can put control for up to 512 functions (the brightness of a dimmer, the mirror pan or tilt of a scanner, etc.) on one circuit (the daisy-chain from device-to-device). All of the devices on the same circuit out of a controller are referred to as a "universe." Many of the bigger, usually PC-based, controllers have outputs for more than one universe to allow control of more than 512 functions. Because DMX-512 is designed to have only one controller, a second controller would require a second universe, even if you need fewer than 512 channels total. I'm not familiar with "the forerunner box," but if it's a controller for the color scrollers, meant to work in tandem with an existing light board, it needs to put the color scrollers into a second universe to avoid conflicts between its scroller-specific signals and those from the main board. Hope that helps.

    John
     
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  3. wemeck

    wemeck Active Member

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    Ok, so lets see if I truly have a grasp of this system.

    1.) The forerunner box is only needed to provide power over DMX to the fans and scrollers in the color scrollers, and possibly providing signal amplification. Just like a hub with power over LAN features for the computer network people.

    2.) Since our ETC Insight 2x has the ability to handle 1024 channels the scrollers are auto negotiates by the console and set to channels starting at 513, because I plugged the DMX cable from the forerunner box into the second universe output. The console can auto negotiate between universes?

    3.) Now here is a good question. Do the scrollers have to be on the second universe or could I just you use all the addressing diodes on the back of the scrollers to assign the scroller channel numbers in universe one? The one caveat being the channel numbers must be assigned higher then my dimmer numbers?

    4.) You could also address the scroller to the channel number of the instrument, pointless, but possible to do? So when you dimmed the light the colors would also changed, and depending your percentage of dimming you wiould also be affecting the color out put?

    If (4.) was possible, which I think it is, it would be a crazy theater representation of a second degree differential equation.
     
  4. Josh

    Josh Member

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    1.) The forerunner box is only needed to provide power over DMX to the fans and scrollers in the color scrollers, and possibly providing signal amplification. Just like a hub with power over LAN features for the computer network people.

    The power supply provides power to the scrollers and maintains the signal strength of the data.


    2.) Since our ETC Insight 2x has the ability to handle 1024 channels the scrollers are auto negotiates by the console and set to channels starting at 513, because I plugged the DMX cable from the forerunner box into the second universe output. The console can auto negotiate between universes?

    Each DMX cable hypothetically only carries 512 channels of DMX. Now here comes the confusing part. Everything on the second universe would be addressed as if it were on the first universe. Only the board sees the difference. SO, DMX channel 513 on your console, is transmitted as DMX channel 1 to the scroller.

    So, you have two DMX cables coming to your desk. Both wires have units addressed between DMX channel 1 and 512. What makes one the first universe, and one the second universe, is which hole you plug them into in the back of the console. To program DMX channel 1 on the second universe, you pull up channel 513 on the console.



    3.) Now here is a good question. Do the scrollers have to be on the second universe or could I just you use all the addressing diodes on the back of the scrollers to assign the scroller channel numbers in universe one? The one caveat being the channel numbers must be assigned higher then my dimmer numbers?

    Lets say you have 96 dimmers. You can run a wire from the second DMX port on your console to the scroller power supply and address the scrollers starting at channel 97. NOW, on your console, you can change the DMX strarting address of the second port to 97. You are using TWO DMX cables, but only one "Universe"

    You could also just daisy chain the DMX out of your dimmer pack and into the scroller power supply, or Vice versa, out of your console, into your scroller power supply, back to the wall plate that leads to your dimmers. (Since your dimmers are most likely set to terminate)


    4.) You could also address the scroller to the channel number of the instrument, pointless, but possible to do? So when you dimmed the light the colors would also changed, and depending your percentage of dimming you wiould also be affecting the color out put?

    This could hypothetically cause problems, but yes, you could get it to work like that. Especially if you wanted to drive an electrican nuts at 3 am the night before tech. :)


    Does that help? Ujiall (SP?) has a great DMX 512 site explaining everyting. Do a search on Google and t shoudl come up towards the top.
     
  5. Inaki

    Inaki Member

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    Although DMXtools' explanation was great, let me make it simpler for you, a universe not only has a "numerical" value (512 channels), but also a physical one. Basically every XLR plug one the back of your desk is a universe. Thereby if you desk has 2 XLR outputs it most probably (although not necessarily) handles 2 DMX universes. Some desks have 2 outputs which spit out the same infrormation. Its a weird concept, but as DMXtools said, in Ujaal's page you'll get all you need to know on DMX and then it'll become easier.
     
  6. DMXtools

    DMXtools Active Member

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    Actually, it was Josh who pointed us to Ujaal. :wink: Like I said, this board is full of knowledgeable people.
     
  7. Inaki

    Inaki Member

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    OOOOOps...sorry Josh!!!!!!!!!!!!
     
  8. samiwas

    samiwas Member

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    Some of it has already been explained somewhat, but I'll try to give some info as well.

    A DMX universe is 512 channels of 256 levels. A DMX channel is not the same as a console channel/fixture.

    If you patch a dimmer to DMX address 1, that dimmer has 256 levels of control between 0 and 255 (out to full brightness). If you patch a 3-channel RGB LED fixture to DMX address 11, you will have 256 levels of red control on channel 11, 256 levels of green control on channel 12, and 256 levels of blue control on channel 13.

    Now, where do the universes come in? With the DMX universe being 512 channels, you can fit up to 170 3-channel RGB fixtures onto it (taking up 510 of those channels). So, what if your show has 250 RGB fixtures? A single DMX universe will not be able to control them all, because 250 RGB fixtures require 750 DMX channels. So, you need to add a second universe. If you have a bunch of 30-channel moving lights, you can put a max of only 17 fixtures on a universe. So again, if you have 30 of those fixtures, you will need more than one universe to control them.

    Beyond just the technical reasons for additional universes, they are often used in an organizational fashion. For instance, on my current TV show, my universes are allotted as follows:
    1 - Set Dimmers
    2 - Overhead Dimmer West
    3 - Overhead Dimmers East
    4 - Not Used
    5 - LEDs 2nd Floor South (added when 7 filled up)
    6 - LEDs 1st Floor
    7 - LEDs 2nd Floor
    8 - First Unit Fixtures​

    In pretty much every situation, the receiving fixture has absolutely no idea what universe it is on. You address the fixture to address 25, and it listens to address 25. It does not matter if it's in universe 1 or 100. It just sees a stream of 512 channels, and listens to the 25th (plus whatever range of channels the fixture uses). For instance, if I address my RGB fixture at 25, plug it into universe 2 on my console, and want to control it on channel 100 on the console, I patch fixture 100 at 2.25 in the console. If I move it to universe 4, I patch fixture 100 at 4.25. The fixture itself still just sees the 25.

    As to your question about the forerunner box being in the second universe, that's solely a matter of how it is patched into the console (unless there's something very strange going on). It could be plugged into universe 1 or 3 or 7, and you would just need to reassign the patch in the console to the correct universe.

    Hopefully, that helps some.
     
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  9. danTt

    danTt Well-Known Member

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    A great answer, but I can't imagine the OP is still watching this post for details 15 years after making it :)
     
  10. Amiers

    Amiers Lighting Phoenix 1 Lamp at a Time

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    I think this takes the cake on earliest dug up thread.
     
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  11. samiwas

    samiwas Member

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    What the heck? I didn’t go searching for a thread...it was on the general thread list! Why on earth was it displayed if it was from 2003?? Weird. I guess that’s what I get for forum-ing at 3:30am after 13 hours at work!

    Now I’m I one of those people.
     
  12. RonHebbard

    RonHebbard Well-Known Member Premium Member

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    @samiwas Welcome to the "those" club along with the rest of us.
    Toodleoo!
    Ron Hebbard.
     
  13. BillConnerFASTC

    BillConnerFASTC Well-Known Member

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    ...who did lighting before DMX...
     
  14. RonHebbard

    RonHebbard Well-Known Member Premium Member

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    @BillConnerFASTC God, Tharon Musser and Beverly Emmons. Don't you remember??
    Toodleoo!
    Ron Hebbard.
     
  15. BillConnerFASTC

    BillConnerFASTC Well-Known Member

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    It was about "one of those people" , not a question.
     
  16. samiwas

    samiwas Member

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    OH, I'm certainly in that club. My high school had a large, 12-dimmer system with slider patch...dimmer sliders were about 15" of travel as I recall. Wish I could remember the details. We upgraded to a 0-10v control system using, I believe, a 25-pin serial cable. Didn't have DMX until I was in college in the 90s.
     
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  17. derekleffew

    derekleffew Resident Curmudgeon Senior Team Premium Member

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  18. samiwas

    samiwas Member

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    Those are definitely the same manufacturer, and a search led me to this thread. This is almost the same board I started on in the late 80s as a high-schooler. Ours had 12 dimmers, 40 patchable circuits, and two large levers that swapped the dimmers from house light to stage lighting control.

    Thanks for the trip down memory lane!
     

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