Re: X10 AGC and Insteon

[nobody@xxxxxxxxxxxx (Dave Houston)]

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/
roZetta-subscribe@xxxxxxxxxxxxxxx