Page 17
SwitchBlade™ Micro User Manual Rev. A
(c) Copyright 2014 Blizzard Lighting, LLC
5. APPENDIX
A Quick Lesson On DMX
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 signals.
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” communication 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.
DMX is connected using a daisy-chain configuration where the source connects to the input
of the first device, the output of the first device connects to the input of the next device,
and so on. The standard allows for up to 32 devices on a single DMX link.
Each receiving device typically has a means for setting the “starting channel number” that
it will respond to. For example, if two 6-channel fixtures are used, the first fixture might
be set to start at channel 1 so it would respond to DMX channels 1 through 6, and the next
fixture would be set to start at channel 7 so it would respond to channels 7 through 12.
Dimensional Drawings
4.9 in
(12.4 cm)
9.4
in
(23.7
cm)
5 in
(12.7 cm)
2.4
in
(7.2
cm)
2.9 in
(7.3 cm)
4.9 in
(12.3 cm)
