Re: Cause of some major X10 problems found

["Robert Green" <ROBERT_GREEN1963@xxxxxxxxx>]

"Dave Houston" <nobody@xxxxxxxxxxxx> wrote in message
news:46e70a52.1631096125@xxxxxxxxxxxxxxxx
> "Robert Green" <ROBERT_GREEN1963@xxxxxxxxx> wrote:
>
> >"Dave Houston" <nobody@xxxxxxxxxxxx> wrote in message
> >
> ><stuff snipped>
> >
> >> >I seem to recall postings that indicated a device like a noisy PS
could
> >> >never generate a signal randomly capable of triggering an X-10 device
but
> >> >your experience seems to indicate that's not so.
> >>
> >> The probability that a noise source will create valid X-10 PLC codes
(1110
> >> followed by manchester encoded data synchonized to powerline
half-cycles)
> >> out of whole cloth is near zero - it ain't gonna happen. However, there
> >> are other explanations for the unwanted ONs & OFFs - see the link I
cited
> >> in my response to Bruce.
> >
> >Maybe the devices were made by the same 50 monkeys and typewriters that
are
> >claimed to be able to reproduce the works of Shakespeare if given
sufficient
> >time.  (-:
> >
> >There could be a number of reasons for the Stargate not seeing anything.
The
> >power supplies' noise signal could be too weak to activate anything
except
> >nearby lights. Certain lights nearby would be affected, but the Stargate
> >would not be within range.  Since Bruce uses an XTB, one might suspect
that
> >weak signals don't propagate far in his house.  There's not enough info
to
> >know for sure.
>
> The SG uses a TW523 which reports powerline commands on a delayed basis,
> after validating them. When transmitting, it reports the first copy of the
> code 22 half-cycles later during the transmission of the second copy so it
> can send and receive at the same time.

Are we certain that Bruce's setup actually uses the TW523?  I thought he was
using the XTB-II in the TW523 emulation mode.  I don't think it's relevant,
though because I don't believe it's the culprit in any way.  What does the
TW523 report to the log when it only sees a single frame of the two in each
X-10 command?  That could have some bearing on whether a noise-created
command is ever logged.  Distance to the source of the signal could also
effect that.  Jeff can probably explain how the XTB-II reacts to orphaned
single frame commands.

> A controller using it can detect
> collisions by comparing the received copy with the earlier transmitted
code.
> It only reports valid codes so it does not report anything that doesn't
have
> valid manchester coding following the 1110.

That doesn't prohibit a lamp module from reacting to something that wouldn't
be "accepted" as a valid command by the TW523 or an emulator.  A lot of how
a device reacts to non-standard or corrupted X-10 signals, at least
according to Jeff's explanation of how he rejects noise, would seem to
depend on the smarts embedded in the firmware.

> While there is no way to disprove your wildly imaginative theories,

I would hesitate to say "no way" because that's what we're talking about
here: Very unlikely, but still non-zero probabilities.   Since Jeff has
actually observed such beasts in the wild, I'd say we're closer now to "way"
then we were to "no way" before he made his observations.  It's only until
he gets his hands on Bruce's Bad Boy PS that I would feel comfortable in
concluding there's "no way" such a supply could not generate a noise that an
X-10 switch would react to as good code.  I'm even more certain that such a
flakey PS could seriously corrupt any valid X-10 codes transmitted while
it's putting noise on the line.

When doing PC tech support work for several hundred very technically
inclined users I would often find myself saying "There's no way for what you
are describing to happen" when responding to the trouble call only to go to
their offices and find out that their PC was indeed displaying an upside
image or whatever other bizarre condition they were reporting.  That's why I
am reluctant to discount the numerous reports we've seen over the years of
phantom activations.

> I can  report, based on watching with an oscilloscope, that there was
absolutely
> nothing on the powerline that in anyway resembled X-10 activity when my
> living room lamp would turn off following a manual switching off of the
> non-X10 controlled fluorescent in one of my bathrooms. (I have since
> replaced the LM14A with an Icon dimmer module and replaced the manual
switch
> on the bathroom fluorescent with an Icon switch and no longer have any
> problem.)

You know that one case does not an ironclad proof make, particularly when
you're saying that random code creation is impossible.  However, the
converse is not true.  All it takes to disprove the hypothesis that random
noise can't create a valid code is one exception.  (-:  I'm inclined to
believe that Jeff's already proved that noisemakers can create valid X-10
codes, but it would be nice to have it in irrefutable black and white screen
shots.  The case you describe above could indeed fall under the "Bloom
Theory" of spike induced activations.  But that doesn't mean all cases are
so caused.

> Most of the anecdotal reports are like Bruce's, repeated random ONs of
> multiple addresses on multiple housecodes (usually in the middle of the
> night) and there are seldom any logged commands (logged commands usually
> point to a traceable source). Noise spikes acting directly on the switches
> and modules explain these episodes with no need to "monkey" with the laws
of
> probability.

Actually, I believe that the laws of probability are being very accurately
represented by what we're seeing.  The odds of creating lots of simply
random noise are quite high.  The odds of creating noise that the Monterey
reports as BSC's - the right start pattern followed by garbage - are much
lower.  The odds of creating a valid code out of random bits are very, very
much lower.  But I don't believe they equal zero and that's based on the
reports we see of lone activations in the middle of the night.  Based on the
X-10 propagation speed, and the length of a day, the occurrence rate might
be one in 10,000 or even 100,000.  I feel that sort of "once a day"
probablity lines up better with the random code generation theory than the
Bloom theory, which should have lights turning on faster than one could turn
them off.

BTW, I don't agree that these commands are never logged because I've found
more than a few "spirit codes" that have shown up in user's logs.  Oddly
enough, they're the codes that you postulated (M and J status requests)
could be created at random by the nature of the Manchester bit patterns.
I'll try to search Google and post a few of the messages where people
reported seeing random codes appear in the Activehome or other controller
logs.

> Ignoring the address, any ON code requires the sequence 0101100110 at the
> manchester level. A noise source is not going to generate that sequence
> repeatedly. And no X10 PLC code will affect multiple housecodes
> simultaneously.

Maybe the light switches that are misbehaving don't know the theory of one's
complements.  (-:  It will be interesting to see what happens when Bruce
sends his PS out to you guys for analysis.

--
Bobby G.