Re: X10 AGC and Insteon

["Jeff Volp" <JeffVolp@xxxxxxx>]

I agree.  The problem isn't glitches, which only contribute a few counts.

The apparent sensitivity of the XTB-II can be varied by changing the
threshold of the comparator.  Default at power on is zero threshold, which
can detect very low signal levels.  That works well here, but I don't have
any continuous noise.  Increasing the threshold turns it into an envelope
detector, perhaps similar to the CM15A.

The XTB-II only "listens" to the powerline during the 650 uS reception
window defined by X10.  Applying AGC, it would take a burst with sufficient
amplitude in that window to be detected as a "1".

The conflict I have is what to monitor to set the threshold level.  The
various methods all have their advantages and disadvantages.  Monitoring
everything outside the Insteon/X10 window may be the best approach as long
as I ignore a few high-level transients.

As you said earlier, the real problem is continuous background noise.  All
the methods will deal with that.

Thanks again for your input.

Jeff

"Dave Houston" <nobody@xxxxxxxxxxxx> wrote in message
news:453ee9db.960742687@xxxxxxxxxxxxxxxx
> Both X-10 and Insteon chose the area around ZC on the theory there is less
> transient noise there but, if you are counting transitions (or looking for
a
> carrier phase difference) to determine logic 1 or 0, transients should not
> be that big a problem. As you say, it only causes a few pulses to be
counted
> which is unlikely to change a logic 0 into a logic 1. The problem comes
from
> continuous signals that should be present most of the time and without
being
> limited to the area around ZC.
>
> The CM15A which uses gated AGC does not count transitions. It uses a
> low-pass filter, "listens" to the powerline only during the 1mS after ZC
and
> its AGC Reset line goes low for 1/2 cycle at the end of each 22 bits (or
62
> bits for extended codes), draining the AGC capacitor. That approach makes
> sense when looking at the data envelope but not when counting transitions.
I
> don't know whether Leviton, who introduced "gated" AGC counts transitions
> but suspect not.
>
> "Jeff Volp" <JeffVolp@xxxxxxx> wrote:
>
> >Thanks for your input Dave,
> >
> >Monitoring line noise here with a scope, most noise does not occur in the
> >X10 sample window.  The most significant noise is from large transients
that
> >occur near the waveform peak.  Then there is a 200mV glitch that
> >periodically walks its way through the 60 Hz waveform.  Finally, I see an
> >occasional high frequency burst that seems to be about one cycle long.
It
> >is not periodic, so I just see it for one scan.  That signal is well down
in
> >amplitude from the X10 signals.  Only one line transient comes in the
middle
> >of the X10 signal window.  It is about 100mV, but certainly causes a few
> >pulses to be counted with the XTB-II's high sensitivity.
> >
> >Now I am using just the X10 sample window, and reducing the sensitivity
if
> >there are a series of counts above 12 cycles on multiple sequential half
> >cycles.  It seems to work pretty well for the type of noise I see here
> >except for the random high frequency burst.
> >
> >If I did open up the AGC to sample the full cycle, those large transients
> >near the peak would reduce the sensitivity more than necessary.  I'm also
> >not sure how to deal with that random high frequency burst if it really
is
> >only there for a cycle at random times.  At maximum sensitivity it could
> >look like a collision if its frequency is in the X10 range.  I'm thinking
> >about a fast attack AGC loop sampling outside the Insteon/X10
transmission
> >window, but after the glitches that occur near the waveform peaks.
> >
> >Jeff
> >
> >"Dave Houston" <nobody@xxxxxxxxxxxx> wrote in message
> >news:453cd54d.889944843@xxxxxxxxxxxxxxxx
> >> I would sample outside the X-10 and Insteon windows. Any noise that's
> >likely
> >> to be troublesome is likely to be present outside these windows. Basing
> >your
> >> threshold on the general background noise level makes more sense to me

> >than
> >> the "gated AGC" that others use.
> >>
> >> However, it might be a problem should someone encounter another system
> >using
> >> the powerlines outside of the X-10 & Insteon windows.
> >>
> >> If you haven't already done so, you might explore how X-10 does it with
> >the
> >> CM15A.
> >
>
>
> http://www.davehouston.net
> http://tech.groups.yahoo.com/group/roZetta/
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