Assigning Addresses; Dmx Universes; Dmx Connectivity; Fixture Location - Chauvet Followspot 1200 User Manual

DMX Configuration (Cont.)

Assigning Addresses

DMX Universes

DMX
Connectivity

Fixture Location

Number of Fixtures

DMX Data Cabling

Making your Own
DMX Cable
DMX Cable
Characteristics
April 7, 2010
Because of the different number of DMX channels used by each fixture, assigning their
respective starting addresses may become a difficult task.
The user must carefully assign the starting addresses for each individual fixture to
avoid DMX channel overlapping. If the DMX channels do overlap, the affected fixtures
could operate erratically.
A DMX universe is the set of DMX compatible fixtures connected to the same DMX
daisy chain, which are receiving DMX data from the same DMX controller using the
same set of 512 DMX channels.
Usually, a regular size installation will have only one DMX universe. In some cases,
however, it might be necessary to define two or more universes due to distance or
number of features constrains.
Most DMX controllers support only one universe, although some DMX controllers may
support two or more universes. Each universe will have its own separated DMX daisy
chain.
A DMX compatible fixture can only be part of a single DMX universe.
Connecting the DMX fixtures to a DMX controller in small to medium installations is
usually a rather simple operation that requires a minimum of tools and some planning
(not including the actual fixture rigging and configuration).
However, in large installations it may be necessary to plan carefully the position and
cabling of each fixture to avoid unexpected problems.
The order in which the fixtures connect to the DMX controller is not important and it has
no effect on how a controller communicates to each fixture. However, the user should
always define a physical location for the fixtures that provides for the easiest and most
direct cabling.
When using a DMX controller, the combined number of channels required by all the
fixtures on the serial data link determines the number of fixtures the DMX controller has
to support. Conversely, the number of onboard sliders, page buttons and fixture buttons
limits the number of discrete DMX channels a DMX controller can support.
To comply with the EIA-485 standard, which is the base for the USITT
DMX512-A protocol, do not connect more than 32 fixtures without using a DMX
optically-isolated splitter. Doing otherwise may result in deterioration of the
digital DMX signal.
You must use DMX compliant data cables to link two or more DMX compatible fixtures.
You may purchase CHAUVET® certified DMX cables directly from a dealer/distributor
or construct your own cable.
USITT recommends limiting the total length of the DMX cable (from the first
fixture/controller to the last fixture) to 300~455 m (985~1,500 ft).
If you choose to create your own DMX cable, make sure to use data-grade cables that
can carry a high frequency signal and are less prone to electromagnetic interference.
Use a Belden© 9841 or equivalent cable, which meets the specifications for EIA RS-
485 applications.
Do not use standard microphone cables for DMX applications because they
cannot transmit DMX data reliably over long distances.
The DMX data cable must have the following characteristics:
Type:
Maximum capacitance between conductors:
Maximum capacitance between conductor and shield:
Maximum resistance:
Nominal impedance:
-27-
Appendix
shielded, 2-conductor twisted pair
30 pF/ft
55 pF/ft
20 ohms/1000 ft
100~140 ohms
Followspot 1200 User Manual Rev. 03e