Atom Operator Manual
Appendix A
LSC Lighting Systems (Aust) Pty. Ltd.
38
15.0 APPENDIX A: DMX 512
15.1 DMX512/1990
DMX512/1990 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 channels. (The Atom transmits levels for 99 DMX channels). The information for each channel
is sent sequentially. The level of channel 1 is transmitted, then the level of channel 2, then 3, etc. up to a
maximum of 512 channels. This stream of data containing the levels for all 512 DMX channels is repeated a
minimum (generally) of 44 times per second. This provides sufficient updates of channel information for
smooth fade transitions.
When good quality data cables are used, DMX512 cable runs may be up to 1,000 metres in length. Most DMX
receiving equipment (dimmers, scrollers, moving lights, etc) are provided with a DMX512 input and DMX512
output. This allows the DMX512 feed to be looped through various pieces of equipment. DMX512 splitters
may also be employed to provide multiple DMX512 feeds. If a piece of DMX equipment
regenerates
the DMX
signal, then the calculation of the 1,000 metre cable length limit begins again from the output of the
regenerating device
As the DMX512 signal contains the level information for all channels, each piece of equipment needs to be
able to read the level(s) of the channel(s) that apply only to that piece of equipment. To enable this, each
piece of DMX512 receiving equipment is fitted with an address switch. This switch is set to the channel
number to which the equipment is to respond. If the equipment is a rack of 12 dimmers, then the address
switch is set to the channel number to which the first dimmer in the rack is to respond. The other 11 dimmers
will follow on from the channel number on the address switch in numerical order.
Advantages of DMX
•
Up to 512 channels of control on a single pair of wires.
•
Up to 1,000 metres per cable run.
•
Feeds are easily distributed via DMX512 splitters and/or DMX loop through.
•
Multiple units may be set to the same address. For example,
•
By setting several dimmers to the same address, a number of dimmers in
different locations
may be
controlled by a single desk channel, or,
•
By setting several colour scrollers to the same address they will all change colour in unison under the
control of a single channel.
•
Dimmers may be
distributed
in various locations around a venue, (usually adjacent to each group of
fixtures to be controlled), and all that is required at each dimmer location is a feed of power and DMX512.
•
Patching of desk channels to dimmers is easily achieved and
altered
and it also allows a small number of
desk channels to control a large number of dimmers. The patching may be performed either in the lighting
desk (if it has a softpatch facility as in the Atom) or in a DMX patching device such as the LSC
“SOFTLINK”.
15.2 Controlling Analogue Dimmers with the Atom
The Atom has DMX512 as its standard output. However, if you are using older analogue dimmers, there are
two methods available to control them from the Atom.
1. Optional Analogue Outputs
The Atom may be fitted with
optional
analogue outputs which provide an analogue control voltage
(0 to + or -10 volts) on a one wire per channel basis. Details of connector types and pin connections are given
in Appendix B. The DMX output still operates when analogue outputs are fitted.
Using analogue outputs is most useful if either;
•
The Atom is to be located close to the analogue dimmers (hence the multi core cable lengths are short).
•
The Atom is to be located some distance from the analogue dimmers and multi-core cables
already
exist
between the Atom and the dimmers.
2. Demultiplexers (Demux)
A demultiplexer is a device that accepts a DMX512 input and produces analogue outputs to drive analogue
equipment (dimmers). By using a demultiplexer with each group of dimmers you can utilise the advantages of
DMX512 (see above) and still maintain use of your analogue dimmers. DEMUX boxes are usually located
adjacent to the analogue equipment and hence the lengths of multi core cable are kept to the minimum.
