DMX 512 Explained
Redback Dimmer
Operator Manual V1.1
7 D M X 5 1 2 E x p l a i n e d
DMX512/ 2003-A is the industry standard for the
transmission of digital control signals between
lighting equipment. It utilises just a single pair of
wires on which is transmitted the level
information for the control of up to 512 DMX
slots (addresses or channels).
The information for each slot is sent
sequentially. The level of slot 1 is transmitted,
then the level of slot 2, then 3, etc. up to a
maximum of 512 slots. This stream of data
containing the levels for all 512 DMX slots is
repeated a minimum (generally) of 44 times per
second. This provides sufficient updates of
channel information for smooth fade transitions.
As the DMX512-A signal contains the level
information for all slots, each piece of equipment
needs to be able to read the level(s) of the
slots(s) that apply only to that piece of
equipment. To enable this, the Redback dimmer
has a “SPatch” (softpatch) menu that allows you
to patch (connect) each DMX slot (address) from
your lighting controller to a Redback
dimmer
channel number.
When good quality data cables are used,
DMX512 cable runs may be up to 1,000 metres
in length. When several DMX feeds are required
(to feed different locations), DMX512 splitters
must be used. These provides multiple isolated
DMX512 feeds.
The Redback uses a high impedance DMX input
circuit allowing you to loop the DMX signal from
one Redback to the next. The last Redback in
the chain will automatically terminate the DMX
line if no cable is plugged in to the
Thru
socket.
Note:
Do not use unscreened microphone or
low speed data cables for DMX. This can cause
problems in the DMX network. Make sure the
cable conforms to the EIA485 cable
requirements by providing the following
specifications:
•
Low
capacitance
•
One or more twisted pairs
•
Foil and braid shielded
•
Impedance of 85 -150 Ohms, nominally 120
Ohms
•
22AWG gauge for continuous lengths over
300 metres
The following diagrams illustrate some simple
setups utilising DMX512.
7.1 Typical DMX Installations
In the following example, the DMX output signal
from the lighting control desk is fed to the DMX
connector of the first Redback dimmer. The
DMX cable is then looped to the following
Redback dimmers. The order of the daisy
chaining is not important as each Redback
dimmer channel can be patched to any DMX slot
number. The end of the DMX line is terminated
to prevent the signal reflecting back up the line
and causing possible errors.
Page 16
LSC Lighting Systems (Aust) Pty. Ltd
Summary of Contents for Redback 12 Channel
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