Re: Controlling Holiday Lights

[Marc_F_Hult <MFHult@xxxxxxxxxxxxxxxxxxxxx>]

On Sat, 21 Oct 2006 17:31:24 -0600, sylvan butler
<ZsdbUse1+noZs_0610@xxxxxxxxxxxxxxxxxxxxx> wrote in message
<slrnejlbec.c53.ZsdbUse1+noZs_0610@xxxxxxxxxxxxxxx>:

>On Sat, 21 Oct 2006 02:13:08 -0400, Robert L Bass <robertbass1@xxxxxxxxxxx>
wrote:
>> sylvan wrote:
>>> I'm talking about the hardware, and you are talking about the protocols
>>> to talk to the hardware.
>>
>> I don't see why you consider MIDI too slow to accomplish the task.
>
>I'm wanting the hardware to control TRIAC or SSR switches, eg a parallel
>binary I/O port.  With that I can turn on and off a light (or anything
>else) at a rate over 1000 times per second.
>
>This allows all kinds of creative fades to On, Off, or anywhere in
>between at 100% the whim of my self-written software.

1000 on-offs per second controlling 60 hz AC lighting yields:

(1000/sec) /(120 zero-crossing/sec) = 8.33 control choices per second.

As a practical matter, about one-third of those possible on-off signals will
fall so early in the AC cycle that they wouldn't produce enough current to
make visible light (although they would use up electricity).

So as a practical matter, unless you first convert the AC to DC, you might
have as few as 5 distinct illumination levels.

This is probably completely adequate for most scene-control purposes where
slow, smooth transitions from scene to scene are unimportant, but you are
touting this "1000hz" approach as being as providing "all kinds of creative
fades" and "anywhere in between" when as a practical matter, your "1000hz"
approach is much cruder than even the simplest X-10 dimmer.

And it pales in comparison to DMX-512 with 255 distinct values and the dimmer
curves and pre-heat values (i.e, non-linear relationship between input
control value and phase value) are part and parcel of even moderately
sophisticated implementations.

Are you doing more work and accomplishing less with this technique? Or do I
misunderstand something quite completely  -- wouldn't be the first or last
time ;-)

... Marc
Marc_F_Hult
www.ECONtrol.org