One simple analogy I heard is to think of a coal train with an engine and 512 coal cars. Multiple trains are sent down a
track 44 times per second. A "device" watches to see how much coal is in car 1, or 2 or 57,
etc... and translates that (digital) information to a particular command. If it's
dimmer 57 and the car is at 28% full, then the
dimmer varies the
voltage to 28%. If it's a
color scroller the motor(s) move (the scroll of color) to a position at about 28% of travel. If a moving light, it listens to 24 coal cars per ML and uses car 1 to control position on a tilt motor, car 3 is for pan motor, car 5 might be how far to open the mechanical
shutter (
dimmer). Car 6 says move to
gobo 1.
Thus a
dimmer rack is listening to the entire
DMX data stream of 512 addresses and is typically set for
dimmer 1 to respond to
address 1, with the color scrollers and moving lights listening to that same data stream. If you have 300 dimmers,
dimmer 1 will respond to whatever the
console is telling
dimmer 1 to do, right
thru 300. If you want 10 color scrollers to function, you choose a starting "
DMX address" to be at 301
thru 310 as example (assuming the
scroller uses one
DMX addresses - some use 2) You then set
console channels to patch those
DMX addresses to appropriate channels to get the scollers to move from Home (zero value on
DMX address 301) to the end of the scoll (100% for that same
address). The
scroller moves
thru all the assorted colors on the way. If you add 2 moving lights, say High End Studio Spot
CMY Zooms, which uses 24
DMX addresses to get control of all of these features, you tell the
fixture to start listening at 311
thru 334, with the 2nd
fixture at 335 and up. Those 24
DMX addresses control the assorted functions of the
fixture,
Intensity, Pan, Tilt,
Zoom,
Iris,
Gobo 1 position,
Gobo 2 position,
dichroic color flag 1 position, flag 2 position,
etc... which is why it uses 24 addresses per
fixture.
If you screw up and put
scroller 1 at
DMX address 1, then everytime you try to bring up
dimmer 1, you will move
scroller 1 as well, because they are both configured to listen to that
address.
The use of
DMX to control things other then dimmers is one of the reasons the term
Address is in use to define a particular
DMX "coal car".
Because a single
DMX "
Universe (512 addresses) can only fit on one cable (or
track), multiple cables are run for a 2nd, or 3rd, or multiple "universes" of
DMX, each sending 512 addresses of data. Or the
DMX data streams can be combined using
Ethernet systems to allow up to 32 universes of
DMX to be run on a single
Cat5 Ethernet cables. Assorted companies use proprietary
Ethernet protocols or they can us a new standard called
ACN, for Advanced Control
Network to
send the data.
