DMX help

[Shawncfer]

What is it?

I've googled it, and I've looked in the control booth Wiki (but neither really helped).

I know this is a stupid question, but I've rigged lights, cut gels, and operated a board. I've never had to set a whole system up, or fix one.

I'm assuming from what I've read that a DMX just carries the signal from the board to the dimmers. So is that right? Or am I making myself look more stupid?

and Second: Ive ran lights at a club that were already set up. I didnt have to rig them or change gels out or anything, just the board. And now Im also doing some work at my schools theatre for band/choir/dance preformances. And I've noticed that where ever the lights are theres a chanel number with a 1 foot cable hanging down from there. And obviously you run the lights through there to the dimmer and yah. BUT, Ive noticed at some theatres they dont have that little box that drops the cables down. So do they hang lights where they need them and just run a REALLY long extention cable all the way to the dimmers? or is there another box they plug it in located in the center of the lights where they just run extentions to there and then run it to the dimmer? (sort of like what I thought a DMX was in the first question)

I'm sorry for being annoying, I'm just intrigued!

[NickJones]

Not a stupid question, I have had to explain this to a few people in the past, DMX is a protocol. Its the language that makes your console talk to your dimmers, LEDs & MLs. It's that simple, I can see why the Wiki wouldn't help.

DMX may also reffer to DMX cable, the cable that carries the DMX data, like a ethernet cable (Cat5) does for your computer.
Hope I cleared it up,
Nick

[soundlight]

DMX is the control protocol for controlling dimmers, moving lights, and dmx accessories for lights such as color scrollers and gobo rotators. The wiki should help here.

When you bring up a fader on a lighting console and the appropriate dimmer comes up, the information link between the console and dimmer that carries the information that tells the dimmer rack what dimmer to bring up is the DMX protocol.

Circuits (the actual thing you plug the light in to) are sometimes on pigtails (those 1' extension cables), sometimes actually on a raceway (big long box with plugs in it that runs the length of a pipe/batten), and sometimes in boxes near the lights, but you need short extension cords to get to them. For some smaller theatres, they do actually run cable from the dimmers, but this is only for low-budget theatres with smaller houses where it's at least semi-practical. These are often semi-permenant but sometimes taken down between shows to re-run elsewhere.

[Shawncfer]

Thats exactly what we have, pigtails on a raceway.

Now back to the DMX, yall both helped me understand what it is, but I just wanna check, the lightboard doesnt run straight into the dimmers, it runs into a DMX first correct?

And the DMX allows the board to communicate with the dimmer telling which dimmer to come on at what percent. right?

[porkchop]

You have really good questions, there's no shame in asking. It sounds like you have a good idea of the basics you just need a few more details.

First of all DMX is the signal. Basically there is a 5-pin XLR cable (could be 3-pin but it's supposed to be 5-pin) running from the board to the dimmers and to any intelligent fixtures you have. It transmits 512 values between 0 and 255. I believe it does this 40 times a second but I could be wrong. The 0 to 255 value represents the intensity of any light plugged into the respective dimmer, or if the cable is plugged into an intelligent fixture is a data instruction to make the light do something (this is the only data source so all light functions are communicated this way). This can be expanded upon if you search for DMX you will probably find some very in depth information.

As far as the numbers they are the number dimmer controlling that plug. If you plug a light into dimmer 42 say and then send the DMX signal to the dimmer rack that you want dimmer 42 at full you will see your light come on (Or at least that's what's supposed to happen).

What you will probably notice is that channel 42 on your lighting console may or may not control dimmer 42. This is because of something called the patch. Which is stored on your lighting console. The best way to think of the patch is like a giant spreadsheet where the first column is the channel number and the second column is the dimmer(s) that the channel controls. Other things that you will see on different boards are: universe number (if you don't type that in with dimmer number), a maximum level to send to that dimmer, and a profile for an intelligent fixture. I'm sure there's others but that's what I can think of off the top of my head. The presentation of this varies widely from manufacture to manufacture and even between the same company's consoles but with that idea you at least get the idea.

Hope that covers it, feel free to ask more if it doesn't

[len]

I usually explain what dmx is this way:

imagine puppets, the kind with strings (marionettes). Each string represents a data channel or address. Typically, a control console has 512 channels (strings), or multiple sets of 512 channels (universes). You as the puppet master control each string and as you raise and lower the fader, twiddle the knob, press the preset, etc., it raises and lowers the string, and makes the puppet do what it's supposed to. The difference is that dmx is done with electrons, not actual string. The other difference is that instead of raising an arm on a puppet, you're sending commands to a fixture and the microprocessor in the fixture (even dimmer racks have them) translates that into some mechanical action (activating a dimmer, spinning a color wheel, etc.).

[TimmyP1955]

Originally Posted by Shawncfer

Thats exactly what we have, pigtails on a raceway.

Now back to the DMX, yall both helped me understand what it is, but I just wanna check, the lightboard doesnt run straight into the dimmers, it runs into a DMX first correct?

And the DMX allows the board to communicate with the dimmer telling which dimmer to come on at what percent. right?

DMX is not a thing, it is a communication protocol, or a "message" that is "written" in a particular "language". If you are familiar with MIDI, think of it as similar to that. The lighting console sends out a signal - a message that is written in the DMX language. This DMX signal is fed via DMX cable (basically like mic cable with less capacitance) into the dimmer pack (or LED PAR or moving fixture), which reads the message and interprets what instructions it is being given in this message. It then carries out the instructions. For a dimmer, the message might be "fade channel 3 up to 50%". For a moving fixture, the message might be "change color to gel holder 2, then fade up to 100%, then simultaneously pan 45 degrees clockwise and incline 90 degrees".

[Shawncfer]

Alright. So I got it figured out now.

DMX is just the SIGNAL that goes From the board, through the 5 pin XLR, and into the dimmer.

Now question two!

When talking about conventional fixures, the signal (DMX) goes through the 1 XLR cable, right? So after all (lets pretend our board has 30 channels) 30 channels on the board go into one xlr cable, how does it split up into each dimmer once it arrives where ever the dimmers are located?

and

When talking about moving fixtures, if we have 10 intelegents and one board for the intelegents, does each one require its own cable? Going out from the light board for intelegents?

For example, If im using a lightboard for intelegent lights, does it have 10 outputs for 10 different lights? or is there 1 output and somewhere along the lines it splits going to the different lights? or what?

[Kinkele]

DMX ( Digital Multi Plex, before that was AMX, Analog Multi Plex) can handle 512 things on one cable. On the receiving end it can pass in and out of various devices and keep going. Each device has a selectable address or a starting address that tells it which of the 512 addresses to listen to. A dimmer rack may start at DMX address 1. If it is a rack of 96 dimmers the dimmers are 1-96. if a similar rack is set for a starting address of 101 then the dimmers are DMX addresses 101 thru 196. If you continue the signal out of the rack and on to a scroller, then address the scroller as 201 then it listens to DMX 201. You can continue this on to a moving light. Each moving light has its own specific number of dmx addresses needed. If the mover is very simple it may need only 14 addresses; intensity, shutter, gobo, color, pan, tilt. ect. Each individual thing you want to control needs an address. Moving lights get compicated which is why the consoles have fixture libraries of moving lights.

Once everything has an address, then the console has a patch. In the patch you get to change the order of the DMX addresses into something that makes more sense to you, the operator. Some operators make all the front light on channels 1-10, fill on 11-20. Whatever order make it easy for you. "Patch" "dimmer" 101 @"channel" 1. Now the light plugged in to dimmer 101 will come on when you bring up channel 1 on the console.

Patches can also be defaulted 1 to 1, 2 to 2, 3 to 3....this is good to do during setup to check your lights.

Moving lights and moving light consoles get more complicated. I have done it the most basic way. Assign a moving light to DMX 301. Patch the 14 dmx addresses it needs individually; 301 @ channel 11, 302 @ 12, 303 @ 13...ect. Then on a basic console I have to figure out what function in the moving light each channel does. This is a good way of understanding what is actually happening. Sometimes a moving light responds to very specific percentages; The "control" function is on channel 14 is set to 25 % for 2 seconds, while the intensity channel is set to 0% then the fixture will reset. This is why there are moving light consoles. They just create a reset button.

I hope that was clear. I have to go. My 14 yr old is doing some CKY band with 6 movers and 24 dimmers.

[NickJones]

As for the movers, your console sends a message for example, you have a moving light with the attributes as follows (its more complex than this but it should give you an idea):

1. Move Left & Right
2. Tilt Forward & Backwards
3. Dimmer
4. Colour

So lets say your console sends a messsage to the Mover, the message is Channel 1 @ 50
Channel 2 @ 25
Channel 3 @ 100
Channel 3 @ 0

Now lets decode.
The first channel is set to 50, meaning that the moving light moves to the middle, as it is 50, and 50 is halfway between 0 and 100.
The second channel is at 25, and this is the moving forward and backwards channel, if directly up is 50% (90 Degrees), then 25% will mean that the light is at 45 degrees.
Channel 3 is our dimmer, its at 100% so its at full.
Channel 4 is at 0, that's open white, so no colour there.

Okay, so now I will confuse you.

DMX doesn't understand 0-100% instead it uses any value between 0-225, meaning 225 is full, and 0 is nothing. Most consoles allow you to enter a value in percentage, rather than the DMX value.

On most moving light consoles, typing the channel is both inaccurate and a bore, so instead, you can use encoder wheels, to move the left & right and tilt up & down, all these do is when you turn the wheel the increase/decrease the value.

It's not called up & down, its called Tilt,
It's not called left and right, its called Pan,

Most lights have 2 channels for pan & 2 channels for tilt this makes it more accurate.

Most lights have no dimmer, as the light (called a lamp) is not dimmable. So instead the have mechanical dimmers that basicly just cover up the light.

As they can't be dimmed movers have to have the lamp "struck" meaning the light turns on.

I think I covered everything.

Nick