Re: X-10 WARNING

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Hydrogen18" <hydrogen18-at-hydrogen18-dot-com> 

I'm guessing this is just inline with your pc's switching psu and not the
whole house, a 4 volt dead band all around might wreak havoc on some things.
The switcher wont care, but it will have dirtier DC rails now.

---Eric
----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Monday, May 24, 2004 11:46 AM
Subject: Re: X-10 WARNING


 > Original poster: "K. C. Herrick" <kchdlh-at-juno-dot-com>
 >
 > Quite a while back I posted a warning about zapping household X-10
products
 > with Tesla discharges.  It's very likely I did that but I now, belatedly,
 > post a caveat.
 >
 > About the time I had that problem, I had installed a new computer (but not
 > for the reason that it, too, had been zapped), and ever since that time I
 > have been baffled by the fact that one of my X-10 locations has
continually
 > been plagued by incomplete operability, even though I have not, of late,
 > been making Tesla sparks.
 >
 > So I finally have made the connection:  Home-automation products marketed
 > by companies such as X-10 depend on power-line-transmitted rf signals
 > occurring near mains-voltage zero-crossings.  Electronic apparatus
 > incorporating switching power supplies can put EMI on the power line that
 > will interfere with those low-level signals.  I found that that's what my
 > computer was doing.
 >
 > X-10 markets a filter (their model XPPF) that is supposed to take care of
 > that kind of problem.  Finding that it did not in my case, I made up a
 > simple trap that works very nicely and which might do the same for other
 > coilers.
 >
 > The X-10 products send and receive their signals within 200 us of the
 > zero-crossings.  With the nominal 160 V peak amplitude of (U.S.) mains
 > voltage, about 4 V of amplitude is reached at 200 us.  What the trap does
 > is to keep the mains-circuit to the load essentially open for that 200 us
 > by the simple expedient of connecting a string of back-to-back diodes in
 > series with each side of the mains circuit.  I connected 3 diodes in
 > series, in each side, paralleled by another 3 reversed.  That provides the
 > "dead band" of about +/- 4 V.  I added 0.15 uF capacitors to ground at the
 > load-side of the diodes to further reduce the EMI.
 >
 > The trap is, of course, too good by half: it not only blocks the EMI
during
 > the interval but also the mains voltage itself.  But not to worry: with
 > mains voltage at nominal, most electronic equipment should not be
adversely
 > affected by the loss of 2 1/2% of the peak.
 >
 > Ken Herrick
 >
 >
 >