Re: Understanding X10 Dims???

[nobody@xxxxxxxxxxxx (Dave Houston)]

ddl@danlan.*com (Dan Lanciani) wrote:

>In article <ZtidnVUsO8aJx2XfRVn-gQ@xxxxxxx>, ROBERT_GREEN1963@xxxxxxxxx (Robert Green) writes:
>| "Charles Sullivan" <cwsulliv@xxxxxxxxxxxx> wrote in message
>| news:pan.2005.08.08.21.58.32.976197@xxxxxxxxxxxxxxx
>| > Robert,
>| > Thanks for your response.  Yes, Dave's post is clear, but it
>| > doesn't answer my questions.
>| >
>| > I can direct the CM11A to send the same dims multiple times
>| > (with a few seconds delay in between) but the dims reported by
>| > another CM11A (looking at the actual byte reported, not converting
>| > to a percentage) vary by 1/210, occasionally 2/210. Why the
>| > variation?
>|
>| Sorry it didn't help.  I thought what you had been describing was that if
>| you had a pause in the stream, the CM11A now thinks you're sending microdims
>| so DIM_DIM without a gap gives a 6% dim whereas a DIM DIM with a gap is read
>| as a two microdims which are 2/210 or 1.2%.
>
>Although a lot of references use this description I do not believe that
>it is correct.  I think the initial DIM or BRI always results in a micro
>step regardless of whether it is followed without a gap by additional
>commands.  See:
>
>http://groups-beta.google.com/group/comp.home.automation/msg/0e3445aee7941493
>
>So the original poster's '+ X' would always be at least + 1.

I don't recall seeing the post you cited but I can confirm (at least
partially) your insight. See my earlier post to this thread which gave a
quick and dirty analysis.

I think that any Dim/Bright _preceded_ by a gap is interpreted as a
microstep. That agrees with what I observe on the powerline with a scope and
also with the watt readings using my Kill-A-Watt. It doesn't explain the
apparently random 'noise' reported by the CM11A. I don't understand why the
CM11A docs use 0-22 when transmitting and say there are 210 possible steps
when describing what it reports when receiving. Actual lamp modules only
respond with about 150 steps. I think it was PCS who said 180. Uncle Phil
said 128. X-10 says 210. My measurements say ~150.

I would refine my initial analysis to say...

The LM465 seems to respond differently to contiguous dims sent by the CM11A
in a single command and the same number of dims sent as doublets (2 standard
dims with no gap) followed by gaps.

A single CM11A command requires 21 dims to go from full bright to full dim.
This is borne out by the Kill-A-Watt reading which only reaches minimum
after 21 contiguous dims.

Doublets require 18 dims to go from full bright to full dim. This is borne
out by the Kill-A-Watt reading which only reaches minimum after 18 doublets.
However, to the naked eye, the typical lamp will appear off after 17
doublets. You have to look right at the filament to see the faint glow after
17. This is probably why most experts have said there are 16 standard dim
levels.

Assuming the first 4% of each half cycle is always chopped and the first dim
after any gap is interpreted as a microstep...

96/150=0.64 (approximate microstep)
95.36/20=4.768 (approximate standard step) 1st of 21 contiguous is a
microstep.

18 doublets: 18*0.64+18*4.768=97.344
21 contiguous: 0.64+20*4.768=96.000

That could explain both the PLC o'scope screenhots and the Kill-A-Watt
readings.

It would be nice to have a wattmeter with 1/10W resolution which might
further refine the analysis.