GenVI Dimmer
DMX Explained
Operator Manual V1.0
Page 25
5
DMX Explained
5.1
OVERVIEW
DMX512/1990-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 GenVI dimmer has a “DMX Patch” menu that allows you to patch (connect)
each DMX slot (address) from your lighting controller to a GenVI
channel number or to
multiple channel numbers.
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 GenVI
uses a high impedance DMX input circuit allowing you to loop the DMX signal from
one GenVI
to the next. The last GenVI
in the chain must have the “DMX Terminate switch”
set to TERM to terminate the line.
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
5.2
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 GenVI
dimmer. The DMX cable is then looped to the following
GenVI
dimmers. The order of the daisy chaining is not important as each GenVI
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.
DMX
Cable
GenVI
DMX Slots
61-66
GenVI
DMX Slots
49-60
GenVI
DMX Slots
25-48
GenVI
DMX Slots
1-24
Lighting
Controller
Termination
Switch set
to TERM
Summary of Contents for Gen VI
Page 4: ......
