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Topic: automation question about DMX dimmers.
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Dave Macaulay
Film God
Posts: 2321
From: Toronto, Canada
Registered: Apr 2001
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posted 07-03-2014 12:04 AM
Yes, what is actually controlling the fixtures - the question is where is the DMX data being generated?
DMX is an addressable control protocol. Each DMX512 data signal ("universe") can control 512 dimmers each with 256 dimming steps from 0 to 100%. The control data signal is daisy chained through lighting fixtures in a simple system, repeaters and splitters are needed for larger installations. Each fixture has a way to set its channel or channels used, the controller continuously sends out address and level data. Most fixtures shut down on DMX signal loss.
Nowadays, all modern stage lighting worldwide uses DMX. A big stage show or concert lighting system will have many separate DMX512 universes and thousands of control channels available. Architectural lighting is now usually DMX: the advantage is that control is separated from power, so the extensive power wiring to connect the fixtures to a central dimmer bank is eliminated. Dimming LED lights is difficult with power dimmers, with DMX LED fixtures the dimming control is perfect and adding colour effects is trivial.
A channel can control just about anything, they aren't only used for dimming. The popular "robo light" fixtures each use many channels for dimming, aiming, focus, colour, iris, gobos, etc. Stage effects like fog or moving scenery are DMX controlled.
There is no way for a server or a Jnior to control DMX fixtures directly. There are interface units controlled by a PC that generate DMX and DMX preset boxes that "play back" prerecorded DMX signals on command... but a DMX universe only has one controller spitting out the continuous data stream of all 512 channels, and your system already has a controller somewhere. It's possible to use DMX combiners to have multiple controllers on a universe but that gets very complicated very quickly: you have to program the combiner with the rules for what controller is in charge of which channel when.
You likely have Lutron "Grafik Eye" lighting with a DMX output module. If so, you just need a Lutron control module that accepts dry relay closures to activate your lighting scenes, it basically acts like a Grafik Eye control pad. The module is not cheap but it's the way to go with Lutron. Call the people who installed or maintain the lighting system.
If you have something other than Lutron, you will need to get the maker to tell you (or sell you) what you need.
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Dave Macaulay
Film God
Posts: 2321
From: Toronto, Canada
Registered: Apr 2001
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posted 07-17-2014 12:43 AM
James - yes, DMX is standard in just about every live venue everywhere. I haven't seen a venue with house lights purely DMX, since that would mean the lighting board would need to be on to have the house lights on (most fixtures will blackout on DMX signal loss). They use something like the Grafik Eye system with wall box manual controls. It can be triggered via DMX so the lighting board is able to do houselight control.
There is maybe one live venue with D-cinema out of every thousand D-cinema installations. The automation systems are understandably made with the other 999 in mind.
Normal cinema practice is to use dimmers with dry relay closure control for off, dim, and bright houselight presets. This is economical and effective, doing what's needed without frivolous "whistles and bells".
Many larger multiplexes use site dimmer systems (usually Grafik Eye) so they can centrally control the lighting - that lets them turn all the lights off at the end of the day without marching through the complex. In Grafik Eye sites a module is installed at each screen with relay contact inputs to select the off/dim/bright "scenes".
I haven't come across any "normal" cinema that uses DMX lighting for house lights. Many multiplexes do have various DMX systems for fancy lighting effects with moving fixtures etc - usually non-functional now since nobody budgeted for maintaining them.
There's some way to interface the Doremi server to your lighting system, I don't know exactly what that is. You need to talk to the lighting system people about that and explain that you can give them RS232, TCP/IP, or dry relay closures to control the lighting. You can use a relay/RS232/TCP/IP to DMX interface but, as far as I know, without doing some fancy footwork you can only have one controller in a DMX universe - and something somewhere is already controlling your lights.
Note that the Doremi scheduling week is configurable, you can have it start on any day you like. I agree it would be better if the factory default week started on Friday.
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