Re: mystery signal

["Robert Green" <ROBERT_GREEN1963@xxxxxxxxx>]

"Marc F Hult" <MFHult@xxxxxxxxxxxxxxxxxxxxx> wrote in message

> Did you recently download or install X-blocker? Could be one that is
> malfunctioning and working on only one phase. You may not know that it may
> have been reported elsewhere that these are being distributing to
neighbors
> of folks that have claimed that "X10 can be highly
> reliable if you understand the various gotchas."  </joke>

Been to Dave's hometown lately, Marc?  (-:

> Dave understands the various gotchas (and has an oscilloscope with a
> specialized interface connected for monitoring the AC line.  So in his
case,
> does "reliable" encompass being "reliably blocked" ?

RF has similar issues.  I recall reading that lots of people living close to
some military bases could not get their remote car lock openers and security
systems to function because of the interference:

http://www.washingtonpost.com/ac2/wp-dyn/A28217-2004Jul4%3Flanguage=printer

[Keyless Remotes To Cars in Waldorf Suddenly Useless]

"Car entry systems, they have no rights at all," said Bruce Romano, who
works in the office of engineering and technology at the FCC. "If they get
interference, that's too bad for them."

IMHO, these car owners are in a lot worse shape than Dave, who could solve
his problem with some $$$, an electrician and a couple of whole-house
blockers.  RF interference is a *lot* harder to block than powerline
interference.  In many cases, it's simply impossible.

> There are not applicable enforced standards for powerline quality in the
US,
> so the AC powerline is becoming a free-fire war zone with increasing
random
> fatalities.  This is a problem faced by all powerline carrier (PLC)
> technologies including X-10, INSTEON and CEbus.

Even though RF standards are allegedly defined and enforced by the FCC, RF
controls suffer the same problems as PLC protocols.  Every bit of the RF
spectrum is getting more and more crowded.  If military transmitters can
overwhelm remote car openers, they probably can do a number on any RF home
automation protocol.  I'm assuming that even mesh networks like ZigBee will
fail in the presence of a strong enough RF signal.

You and I share the belief that the only truly reliable system is a
hardwired one.  It's why the military still has wire-guided munitions in the
arsenal.  Pretty damn hard to jam.  Most of the newer stuff is laser guided,
but even that is not as reliable and immune from interference as wire-guided
devices.

Some Sovs still think we blew up the Kursk by triggering one of their
torpedoes inside the ship remotely.  Modern torpedoes don't explode on
impact anymore.  It's much more effective to detonate directly below the
enemy's keel and let the explosion bubble break a ship in half.

I have a great set of Powerpoint slides of a Brit test that show how
effective it is.  They show a torpedo detonating directly under the hull of
a decommissioned destroyer.  First, there's a giant black blast that blows
out all the loose soot from the ship's funnels as the undership explosion
moves upward.  Then you see the black smoke turn grayish-brown from high
explosive gases along with water spray as the ship lifts up in the water and
its keel breaks.  Within a very few minutes, the bow half sinks and the
stern soon follows.  Much, much more effective than simply blowing a hole in
the side.  To score such a precise hit requires complicated electronic
triggering devices.  But I digress.

Oddly enough, as more and more RF devices come on line, the interference
problem will only become worse.  My wireless cams, microwave oven, cordless
phones and wireless network all step on each other in different ways.
What's the name of that old disaster movie?  "The Crowded Sky?"  That's what
we're looking at here;  pollution of both the powerline and the RF spectrum.

> INSTEON reliability is increased by signal repetition) with increasing
> number of INSTEON devices which simultaneously _decreasing_  X-10
> reliability by lowering the impedance of the AC line at 120khz ("signal
> sucking'). This may not be a "friendly-fire" fatality ...

I think Insteon is just a bridge that will allow people to perform a phased
implementation of the new technology rather than dumping everything at once.
In that respect, it's a good idea but, as you point out, it has its own set
of issues.

> But back to the question:
>
> Unlike the ubiquitous TRIAC-based lighting dimmers that turn the AC off
> during the AC cycle and are turned back on again only at the
zero-crossing,
> dimmers based on IGBT (Insulated Gate Bipolar Transistors)  devices can
turn
> the AC on *and* off during the cycle, not just at zero crossing. IGBT
> dimmers are becoming more prevalent.

Well, thanks for answering my question about why a triac-based problem would
appear to be random.  What are the advantages of using IGBT's?  Are the
cheaper?  More efficient?  And why wouldn't they sync with the zero
crossing?  It still seems odd that a lamp dimmer of any kind would output
such random interference.  I guess I'll have to Google IGBT's and learn more
about how they work.

> As best I know, there is no reason why a manufacturer of a dimmer has to
> avoid 120khz (X-10) or 130khz (INSTEON) when choosing a frequency to
control
> ("dim") an IGBT. And 120khz _is_ the maximum frequency reported for some
> popular IGBT devices.

There's still hope!  I've recently bought two switching power supplies that
not only don't attenuate the X-10 signal, but appear to boost it slightly
(the GBC video MUX PS's).  It may be that customer feedback will initiate
design changes.  All it may take is a number of product returns marked
"knocked out my home's X-10 system."  I've returned quite a few items with
just that information on the return form.  It's possible that those forms
might even make it back to engineering design.  In this bean-counter
society, manufacturers are falling all over themselves to prevent returns,
especially to places like Wal-mart that will simply drop a vendor that has
too many returns.  They did that to a Chinese manufacturer whose name
escapes me (Apex, I think) when the quality became an issue and return rates
spiked.  It nearly killed Apex.

You may have noticed that lots of new equipment comes with admonitions
everywhere to "Please do not return this unit before you call
1-800-555-5555."  From what I've read, that's part of the campaign not to
get blacklisted by the big box retailers who simply despise having to deal
with returns.

Returns cost stores *lots* of money in lost sales and employee time and
vendors are being forced to strongly discourage them.  Look at Smarthome and
their "we've never seen THIS problem before."  Uh-huh.  That's one method of
discouraging returns although it's a pretty poor strategy in light of
internet users being able to compare notes.

> So Dave's new-found dependability may be from a newer, IGBT-based dimmer
> running at about 120khz for light dimming or motor control. Doesn't bode
> well for PLC in general.

Well, it's not the end of the world.  Dave's in a peculiar situation where
blocking the noise entering his dwelling is much more difficult than it
would be for the average X-10 user.  But it's not impossible as in the case
of the poor folks who have to deal with military RF interference rendering
their car key fobs useless.  Dave's X-10 problem is just going to be a royal
PITA.  I'd rather have the PITA than an "impossible to correct" situation.

You're certainly right when you imply that X-10 users may have to face the
fact that to keep things running smoothly, they'll have to fork out for a
whole-house blocker.   And you're certainly right when you say that the most
reliable approach is hard-wiring.  Israel obliterated almost all of Egypt's
tanks during the Seven Day war and they did it with wire-guided anti-tank
missiles.  Friends tell me you can still find places in the Sinai where
there the spent wires can be found.

If it was good enough for them, it's good enough for me, at least for
security.  Hardwiring my house for hardwired lighting control ex post facto
would be incredibly hard.  X-10 isn't as good as hardwire, but by God it's a
hell of lot easier to install and uninstall and is usually cheaper than any
hard-wired alternative.

--
Bobby G.