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When considering possible projector control schemes, these things
should be weighed:
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Cost of implementation and use
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Availability of devices (consoles, PC add-in boards, devices,
software, etc.)
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Ease of installation and use
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Relative ease of creating in-house devices, i.e. designing
boards yourself
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Recordability
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Safety
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Robustness (fault tolerance and recovery)
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Usable communication distance
DMX compared with MIDI
When considering MIDI, the strongest arguments are the
availability of devices, and reasonable cost. There are several MIDI
lighting consoles and MIDI-to-analog converters available. PC-add in
boards and software are also available. The cost for these units is
quite reasonable.
On the downside is
distance of communication and system robustness. Since MIDI uses a
current loop for communication, distance is limited to around 10
meters. As far as robustness, MIDI is a "burst" protocol,
which only transmits data when something changes. It is conceivable
that a beam actuator could be left "on" if a communication
problem caused the "off" command to be missed. Clearly
this is unacceptable for laser projectors.
For DMX512, there are
many devices available. These include lighting consoles, dimmers,
DMX-to-Analog converters, PC add-in boards and software, etc. Since
there is a lot of competition in this field, these are all available
at a reasonable cost. The DMX512 protocol is simple, so proprietary
designs are possible using standard microprocessors and components.
Usable distance of communication is up to 4000 feet. And since DMX512
is a "continuous" protocol, there is no chance of
a "stuck beam" condition as with MIDI. When you consider
all of the desirable traits of a laser projector control scheme, DMX
seems superior.
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