Lighting Guide - How does DMX work?
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How does DMX work?
Every device to be controlled by DMX has to have a unique "base
address". it is this "addressing" feature of DMX
that enables it to work. The DMX address of a device is configurable
by the lighting director so he knows where in the DMX map a particular
device will be located. It also allows the devices on the network
to ignore data that isn't meant for them by examining the destination
addresses of DMX instructions and only acting if the address matches
their address. Each device is connected in a daisy-chain fashion
and the last device on the chain must be fitted with a terminator.
Consider a large rig with a mixture of conventional lights controlled
by ordinary dimmers and colour scrollers with a smoke machine thrown
in for good measure.
The console operator wishes to control all of the devices from
one desk; his first task is to work this out on paper. Once he is
happy with the addresses, he asks one of the riggers to set the
DMX addresses up as follows (all devices require only one DMX channel
in this example, but when some type of intelligent light are used,
this is not the case):
- 48 dimmers, to be based at DMX address 0 through 47
- 20 colour scrollers, to be based at DMX address 48 through
- 1 smoke machine to be based at DMX address 68
He will then have control of each individual device. It is a simple
matter for the console operator to set groups of lights and scrollers
using the console soft
patch. The smoke machine, being the last on the daisy chain,
must have either an integral terminator or a terminator fitted to
it's DMX out port.
It is possible, using opto-isolated DMX splitter units and merge
units to have separate consoles for controlling the scrollers and
the dimmers sharing the same DMX line. As long as there is no address
conflict, the system will work perfectly.
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