Re: Controlling Holiday Lights

["Robert L Bass" <robertbass1@xxxxxxxxxxx>]

>> Why not use MIDI?
>
> SsssssssLlllllllOoooooooWwwwwwwww

The MIDI controlled Christmas lighting display I described earlier sequences hundreds of circuits.  Lights and motors switch on and
off, sometimes at blazing speeds, to the tune of the MIDI track.  There are several scenes where a series of lighting circuits
flashes on and off at about 10-20 times per second per circuit.  Note: I'm guessing as to the rate, but it was way too fast to
count.

> Granted, MIDI is probably 10x the speed
> (in theory) of X10, but I haven't seen a
> complete solution to know what is achievable...

I have and it's pretty darned fast.  A group of volunteers starts to build the set each year around the middle of October (it takes
seven weeks to set the whole thing up according to a notice at the entrance to the property).  I'll stop by this weekend and ask
which controller they're using.  I believe someone said they used Cakewalk software to sequence the system.  I'll check on that,
too.

> And that still means only about 10 cycles
> per second (Hertz or Hz), which still limits
> you to only basic on/off effects.  (Compare
> to 50-60Hz for a zero-crossing A.C. relay
> or way over 1000Hz for a PC parallel port.)

Controlling holiday lights that should not be much of a limitation.

> With a direct access binary I/O (eg parallel
> port or a normal digital I/O pin of a
> microcontroller such as PIC) it is trivial to
> PWM a light from dark to full on and back
> to off to create fades.  If all I wanted to do
> was turn on and off there are innumerable
> ways, and X10 is darn effective.  But once
> you add speed into the mix, it changes the
> problem dramatically.

In addition to clunky X10 and faster, more flexible MIDI, there are other options.  The DMX-512 protocol is used for modern
theatrical lighting.  It's also in use on commercial buildings where its simple topology and reliable performance are important
considerations.  One of the regular posters here has even designed a home-use DMX-512 lighting controller.  I've used DMX-512
extensively in designing theatrical lighting systems for churches and small auditoriums.

DMX-512 can run up to 512 circuits (hance the name) on a single cable.  It's fast enough to run high speed, automated spotlights and
musicians' light shows.  Controllers used to be prohibitively expensive for home use.  However, over the last few years a number of
companies have come out with PC card-based DMX-512 controllers.  Dimmers and dimming "packs" range from a hundred dollars or so to
over $2K, depending on the number of circuits and their ampacity.  Homebrew DMX-512 compatible dimmers and relays would be
significantly cheaper, though I couldn't begin to tell you how to build one from scratch.

> As for midibox, it appears to be a midi controller
> primarily, with some direct I/O capability included...

It depends on the box.  There are relatively inexpensive, multi-circuit lighting controlers (DJ's use them) that can be controlled
by MIDI, DMX-512 or 0-10 Volts DC.  DJ lights can dim and flash on/off as fast as the beat on a MIDI sequencer runs a set of Roland
digital drums.  The tempo can be blindingly fast.  If you've ever watched a rock concert on stage you've seen MIDI controlled
lighting effects.

> I don't see the direct applicability unless I
> wanted to replace to the PC as a controller,
> and then I see no obvious reason to
> introduce the complexity and delays of MIDI.

It's just one of a number of protocols you can use to control lights.  The choice shouldn't be about the protocol so much as the
available hardware and its cost.  Any one of a number of protocols can be used effectively for this project.  MIDI would work fine
(it's faster than you might realize).  That doesn't mean MIDI is best for your application but it's certainly worth investigating
IMO.

--

Regards,
Robert L Bass

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