Re: Compact Fluorescent Noise

[nobody@xxxxxxxxxxxx (Dave Houston)]

"Jeff Volp" <JeffVolp@xxxxxxx> wrote:

>While working on the XTB-II AGC loop, I discovered it can be difficult to
>deal with nose generated by compact fluorescent bulbs.  A photo of CF noise
>in the X10 passband can be found at:
>
>http://jeffvolp.home.att.net/x10xmtbuf/cfnoise.jpg
>
>Zero crossings are at dead center of the trace, and 8.3mS on either side.
>As you can see, these CF bulbs generate a burst of noise in the X10/Insteon
>passband centered around each zero crossing.  This is exactly when Insteon
>and X10 signals are transmitted.
>
>This testing was done in my workshop, which is on a non-X10 circuit powered
>through an ArcFault breaker, and has 4 unfiltered CF ceiling lights.  The
>pulsating seen in the waveform is due to beating between the noise generated
>from the different bulbs.  As the noise pulsates, I measured up to 800mVpp,
>which lighted up two solid bars on the ESM1.
>
>The reason this noise is difficult to deal with is that it does pulsate.  So
>the point that the AGC samples the noise can be near a null, and the noise
>can rise to a peak in the middle of the X10 reception window.  In fact I can
>see extra "1"s received when that happens.  It results in a reported
>collision, and a rejected message.
>
>While the AGC in the XTB-II works fine for line transients and relatively
>constant background noise, it does have a problem with noise that pulsates
>in this manner.  I'm not sure there is a way do deal with it, and that is
>probably why some CF bulbs cause so many problems.
>
>I thought I would share this info with you.
>
>Jeff

When you posted recently about the CFL noise I was going to ask you to get a
picture but wasn't sure you had a way to do it automatically. This is a case
where the ISA Digital Sampling Oscilloscope I use would really be handy,
allowing you to zoom the horizontal axis to show more detail.

Is the spikey burst just past center screen part of the CFL noise? It
resembles a triac switching transient.

How are you determining the frequencies in the noise? Are you just relying
on the passband of the ESM1?

Since X-10, Insteon and UPB have chosen to do their signalling in the time
around ZC, this is sure to be an ongoing problem. It would be interesting to
know how well an Insteon lamp module would function in this environment.
It's also another factor to consider when considering CFLs. For those into
HA the cost of filtering CFLs really changes the economics of switching from
incandescents.

BTW, now that I have my web page up, I published several screenshots from my
scopecard showing how X-10 does gated AGC in the CM15A. Just click on the
CM15A link at the bottom of the page.

http://davehouston.net
http://tech.groups.yahoo.com/group/roZetta/
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