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5. APPENDIX
A Quick Lesson On DMX
DMX (aka DMX-512) was created in 1986 by the United States Institute for Theatre
Technology (USITT) as a standardized method for connecting lighting consoles to lighting
dimmer modules. It was revised in 1990 and again in 2000 to allow more fl exibility. The
Entertainment Services and Technology Association (ESTA) has since assumed control over
the DMX512 standard. It has also been approved and recognized for ANSI standard clas-
sifi cation.
DMX covers (and is an abbreviation for) Digital MultipleXed signals. It is the most common
communications standard used by lighting and related stage equipment.
DMX provides up to 512 control “channels” per data link. Each of these channels was origi-
nally intended to control lamp dimmer levels. You can think of it as 512 faders on a lighting
console, connected to 512 light bulbs. Each slider’s position is sent over the data link as an
8-bit number having a value between 0 and 255. The value 0 corresponds to the light bulb
being completely off while 255 corresponds to the light bulb being fully on.
DMX data is transmitted at 250,000 bits per second using the RS-485 transmission stan-
dard over two wires. As with microphone cables, a grounded cable shield is used to prevent
interference with other signals.
There are fi ve pins on a DMX connector: a wire for ground (cable shield), two wires for
“Primary” communication which goes from a DMX source to a DMX receiver, and two wires
for a “Secondary” communication which goes from a DMX receiver back to a DMX source.
Generally, the “Secondary” channel is not used so data fl ows only from sources to receiv-
ers. Hence, most of us are most familiar with DMX-512 as being employer over typical
3-pin “mic cables,” although this does not conform to the defi ned standard.
DMX is connected using a daisy-chain confi guration where the source connects to the input
of the fi rst device, the output of the fi rst device connects to the input of the next device,
and so on. The standard allows 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 fi xtures are used, the fi rst fi xture might
be set to start at channel 1 so it would respond to DMX channels 1 through 6, and the next
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 (indicating 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 fi nished, another can begin with no delay if desired (usually another
follows within 1 ms). If nothing is changing (i.e. no lamp levels 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 fi 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 fi 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 sec
ond if only 24 channels are being
transmitted. 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 become the standard
for lighting control. It is fl exible, robust, and scalable, and its ability to control everything
from dimmer packs to moving lights to foggers to lasers makes it an indispensible tool for
any lighting designer or lighting performer.
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Keeping Your NorthStar As Good As New
The fi xture you’ve received is a rugged, tough piece of pro lighting equip-
ment, and as long as you take care of it, it will take care of you. That said, like
anything, you’ll need to take care of it if you want it to operate as designed.
You should absolutely keep the fi xture clean, especially if you are using it in an
environment with a lot of dust, fog, haze, wild animals, wild teenagers or spilled
drinks.
Cleaning the optics routinely with a suitable glass cleaner will greatly improve
the quality of light output. Keeping the fans free of dust and debris will keep
the fi xture running cool and prevent damage from overheating.
In transit, keep the fi xtures in cases. You wouldn’t throw a prized guitar,
drumset, or other piece of expensive gear into a gear trailer without a case,
and similarly, you shouldn’t even think about doing it with your shiny new light
fi xtures.
Common sense and taking care of your fi xtures will be the single biggest thing
you can do to keep them running at peak performance and let you worry about
designing a great light show, putting on a great concert, or maximizing your cli-
ent’s satistfaction and “wow factor.” That’s what it’s all about, after all!
Returns (Gasp!)
We’ve taken a lot of precautions to make sure you never even have to worry
about sending a defective unit back, or sending a unit in for service. But, like
any complex piece of equipment designed and built by humans, once in a while,
something doesn’t go as planned. If you fi nd yourself with a fi xture that isn’t
behaving like a good little fi xture should, you’ll need to obtain a Return Authori-
zation (RA).
Don’t worry, this is easy. Just send an email to [email protected],
and we’ll issue you an RA. Then, you’ll need to send the unit to us using a
trackable, pre-paid freight method. We suggest using USPS Priority or UPS.
Make sure you carefully pack the fi xture for transit, and whenever possible, use
the original box & packing for shipping.
When returning your fi xture for service, be sure to include the following:
1.) Your contact information (Name, Address, Phone Number, Email address).
2.) The RA# issued to you
3.) A brief description of the problem/symptoms.
We will, at our discretion, repair or replace the fi xture. Please remember that
any shipping damage which occurs in transit to us is the customer’s responsibil-
ity, so pack it well!
Shipping Issues
Damage incurred in shipping is the responsibility of the shipper, and
must be reported to the carrier immediately upon receipt of the items.
Claims must be made within seven (7) days of receipt.
