[SML] DMX/Programmable Winches/Hoists

[Michael Sauder]

On Thu, Jun 30, 2016 at 12:09 PM, Bill Conner via Stagecraft <
stagecraft at theatrical.net> wrote:

> Sorry, but can you explain how you know  "They've clearly done the
> research and installations to prove they believe it's safe."?  Have
> you seen the documentation?  Is it available?


I've not had to look into these enough to ask for any documentation. I do
know the Kinetic Lights website says "... complies with all international
security regulations to move tethered elements above people (BGV C1 now
DGUV 17, UL, CE)."

I only said that they've done enough to prove THEY (and presumably their
lawyers and insurance companies) think it is safe.

As I gather, the two main issues with using DMX is that it's open loop, and
does not contain any error correction.

Closing the loop is easy enough to do. Kinetic Lights does this by return
DMX channels.

Error in the data stream is typically transient. If you think about what
we're controlling, momentary 1/40th second blips in the data is not going
to have a large impact -- a winch that has been receiving a steady "0 feet
@ DMX value 0" is not suddenly going to drop its load 20 feet just because
it receives a single errant "20 feet @ DMX value 255." It's not a
pyrotechnic, instantaneous response is not possible. On top of that, it's
easy to write the winch code such that the winch will, for example, only
move if the height parameter changes in a continually increasing/decreasing
manner with sudden changes ignored.

Perhaps in the past DMX was not reliable enough for motion control, but it
may well be time to reconsider the knee jerk reactions against it.

--
Michael Sauder
Show Control Programming and Design
Email: michael.sauder at gmail.com
Web: www.shownet.io
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