Blizzard Lighting Q Flurry(Rev C) - Manual (Page 16)

Page 16
Flurry Q Manual Rev. C Copyright (c) 2011-12 Blizzard Lighting, LLC
5. APPENDIX
A Quick Lesson On DMX
DMX (aka DMX-512) was created in 1986 by the United States Insti-
tute for Theatre Technology (USITT) as a standardized method for con-
necting lighting consoles to lighting dimmer modules. It was revised in
1990 and again in 2000 to allow more flexibility. The Entertainment
Services and Technology Association (ESTA) has since assumed control
over the DMX512 standard. It has also been approved and recognized
for ANSI standard classification.
DMX covers (and is an abbreviation for) Digital MultipleXed signals. It
is the most common communications standard used by lighting and
related stage equipment.
DMX provides up to 512 control “channels” per data link. Each of these
channels was originally intended to control lamp dimmer levels. You
can think of it as 512 faders on a lighting console, connected to 512
light bulbs. Each slider’s position is sent over the data link as an 8-bit
number having a value between 0 and 255. The value 0 corresponds to
the light bulb being completely off while 255 corresponds to the light
bulb being fully on.
DMX data is transmitted at 250,000 bits per second using the RS-485
transmission standard over two wires. As with microphone cables, a
grounded cable shield is used to prevent interference with other sig-
nals.
There are five pins on a DMX connector: a wire for ground (cable
shield), two wires for “Primary” communication which goes from a DMX
source to a DMX receiver, and two wires for a “Secondary” communica-
tion which goes from a DMX receiver back to a DMX source. Generally,
the “Secondary” channel is not used so data flows only from sources
to receivers. Hence, most of us are most familiar with DMX-512 as
being employer over typical 3-pin “mic cables,” although this does not
conform to the defined standard.