Appendix; Troubleshooting - Blizzard Lighting Weather System EXA Manual

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 flexibility. 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-
sification.
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 five 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 flows 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 defined standard.
DMX is connected using a daisy-chain configuration where the source connects to the input
of the first device, the output of the first 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.

Troubleshooting

Symptom
No Light Output
Chase Speed Too
Fast/Slow
Bad Wireless
Reception
Blown Fuse
No Response to
Audio
Fixture Not
Responding /
Responding Er-
ratically
Weather System EXA Manual Rev. A
Solution
Check to ensure fixture is operating under correct mode, IE sound
active/auto/DMX/Etc., if applicable.
Check to ensure proper setup of speed adjustment.
Make sure the antenna on fixture(s) and footswitch are swiveled to
their outward position. Improve the line-of-sight between units.
Check AC cord and circuit for damage, verify that moving parts are
not restricted and that unit's ventilation is not obstructed
Verify that the fixture is in "Sound Active" mode.
Adjust Audio Sensitivity, If Applicable.
Make sure all connectors are seated properly and securely.
Use Only DMX Cables and/or check cables for defects
Install a Terminator.
Reset fixture(s).
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