Re: X-10 WARNING

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

Original poster: "K. C. Herrick" <kchdlh-at-juno-dot-com> 

Yes, it just feeds the computer; nothing else.  As to dirtier dc, I don't
know about that.  The supply outputs are pretty well isolated from the 2
1/2%-or-so glitches on the mains.  At any rate, I find no problem.

KCH

On Mon, 24 May 2004 13:20:17 -0600 "Tesla list" <tesla-at-pupman-dot-com>
writes:
 > 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
 >  >
 >  >
 >  >
 >
 >
 >