Chauvet Tiger DMX 60 Betreibershandbuch PDF herunterladen (Seite 62)

Page 54 - 12. Introduction to intelligent lighting

Pearl 2008 Manual - 16th July 2007

goes back to channel 1 again. All the units connected to the DMX

receive all the channels, and you tell them which channels to respond

to by setting the “base channel” or “DMX address” on each unit. The

computer inside the fixture waits for the correct channels to come up,

then reads in the levels for those channels.

Dimmers can also understand DMX; some dimmers can read it directly,

others use a demultiplexer or “demux” to convert the DMX into the

normal 0 to 10 volt analogue signals they are used to.

12.5 Moving light control desks

Sliders are ideal for controlling dimmers. More complicated dimmer

control desks have memories to record the level of all the dimmers, so

you can recall a setting without having to set all the sliders again during

a show.

However, once you start controlling lights that move and change colour,

sliders become less ideal, because it is the movement rather than the

end level which is important. Dedicated moving light desks such as the

Pearl include many helpful functions which makes the programming of

intelligent lighting much easier, such as palettes of pre-programmed

colours and positions, and a shape generator to create movements.

12.6 A few cautions about using DMX

DMX is a robust system which normally works very well, but sometimes

it can be problematic. Here are a few tips for making DMX work well.

• DMX cabling should be twisted-pair data cable. Microphone cable is

not recommended because it doesn’t transmit the signal as well.

You will probably get away with it, but equally you might have

problems.

• Always ensure the last fixture in the DMX line is terminated. On

some fixtures this can be done by flipping a switch, others are self-

terminating, but often you will have to fit a terminating plug into

the vacant socket on the last unit. This has a 120 ohm resistor

across the DMX line and prevents data interference on the line. It

might work without but…

• Don’t split the DMX cable. Loop it from one unit to the next. If you

have to split it, use a proper active splitter unit.

• The DMX specification says that you should not run more than 32

fixtures from one DMX line unless the fixtures are buffered or

optically isolated. Either use several DMX lines (the Pearl has four)

or use a DMX repeater unit. In practice, most fixtures do not put

maximum loading on the DMX line and you will probably get away

with using more if you have to, but the DMX signal may be weaker

than it should be.

• Don’t run your DMX lines near high voltage cables or neon. They

may pick up interference which will stop the system working, or

worse, blow up the receiver electronics in the fixtures (this really

does happen, and usually at the most inconvenient moment).

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