10. DMX General Information
The DMX512 digital communication protocol was introduced to control
stage lighting and special effects.
The DMX standard features 512 available channels, and they are
assignable in any sequence that conforms to the user's needs. Each DMX-
capable fixture requires one or more sequential channels. A starting
address, which indicates the first control channel reserved for that
particular fixture, must be assigned to the fixture before the controller can
recognize it. DMX controllable fixtures may vary in the number of
channels they require, depending on the fixtures features and/or
functionality.
Channels should never be permitted to overlap; otherwise, for example, a
fader that controls blue output on one fixture may cause strobing or
dimming on an adjacent, incorrectly assigned fixture. Multiple fixtures of
the same type that use an identical starting address will function in unison.
Fixtures assigned properly spaced starting addresses will operate
individually, but a DMX controller with sufficient channels can be
configured to run these same fixtures either combined or independently.
The sequence in which DMX fixtures are connected has no effect on how
a controller communicates with each individual lighting fixture. Although
3-pin XLR mic cables may be used to connect DMX fixtures over short
runs, longer distances will introduce data errors due to the mic cable's
incorrect impedance. For best results, Talent Sound & Lighting
recommends the use of correct 120 ohm, low-capacitance, twisted pair
cable designed for the DMX512 protocol. It is also suggested that a
termination resistor plug be used on the output connector of the last fixture
in an array of DMX instruments. This resistance ensures proper data
transmission.
Notes
