Blizzard Flurry 5 - A Quick DMX Lesson

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Flurry™ 5 User Manual Rev. A (c) 2013 Blizzard Lighting, LLC
DMXisconnectedusingadaisy-chaincongurationwherethesource
connectstotheinputoftherstdevice,theoutputoftherstdevice
connects to the input of the next device, and so on. The standard al-
lows 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
xturesareused,therstxturemightbesettostartatchannel1so
itwouldrespondtoDMXchannels1through6,andthenextxture
would be set to start at channel 7 so it would respond to channels 7
through 12.
The greatest strength of the DMX communications protocol is that it is
very simple and robust. It involves transmitting a reset condition (in-
dicating the start of a new “packet”), a start code, and up to 512 bytes
of data. Data packets are transmitted continuously. As soon as one
packetisnished,anothercanbeginwithnodelayifdesired(usually
another follows within 1 ms). If nothing is changing (i.e. no lamp lev-
els change) the same data will be sent out over and over again. This is
a great feature of DMX -- if for some reason the data is not interpreted
thersttimearound,itwillbere-sentshortly.
Not all 512 channels need to be output per packet, and in fact, it is
veryuncommontondall512used.Thefewerchannelsareused,
the higher the “refresh” rate. It is possible to get DMX refreshes at
around 1000 times per second if only 24 channels are being trans-
mitted. If all 512 channels are being transmitted, the refresh rate is
around 44 times per second.
In summary, since its design and evolution in the 1980’s DMX has be-
comethestandardforlightingcontrol.Itisexible,robust,andscal-
able, and its ability to control everything from dimmer packs to moving
lights to foggers to lasers makes it an indispensible tool for any light-
ing designer or lighting performer.