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The question is whether a surge will cooperate and just develop a
potential on a convenient path. Everything I've seen over the years
suggests these surges, most especially when induced by nearby
lightning strikes, are really bad about cooperating. So we read
stories about this wire vaporized but that one left untouched, etc.<br>
<br>
Chip's been using surface mount <a moz-do-not-send="true"
href="https://en.wikipedia.org/wiki/Transient-voltage-suppression_diode">TVS</a>
arrays. From memory I think the answer for his setup is being able
to clamp between two arbitrary conductors. I think that's six for
four wires, but (if I recall correctly, and unfortunately I can't
look it up), that's just one little package.<br>
<br>
I think it's a very good thing for you to raise this subject. In our
part of the world, in my opinion, having long wires strung around
sets up a "when" question for surges, not an "if". <br>
<br>
-Pete<br>
<br>
<div class="moz-cite-prefix">On 10/30/2017 01:57 PM, Brian via
TriEmbed wrote:<br>
</div>
<blockquote type="cite"
cite="mid:59F76815.6020900@undecidedgames.net">Hi Group,
<br>
<br>
I've been working on a design for zoned HVAC which involves having
electronics at the ends of long cables. As such, good transient
voltage suppression becomes a more important concern.
<br>
<br>
My device will be connected via Cat-5 UTP across which will be
supplied +6V, GND, and an RS-485 differential pair.
<br>
<br>
I'm wondering if anyone in the group has suggestions on the ideal
application of TVS elements. I've seen reference designs for
RS-485 that have paths to ground for each of the signal lines, but
I've also got the +6V line to worry about.
<br>
<br>
Can I just provide paths from each signal to GND, or do I need to
provide paths from every signal to every other signal? It seems
to me that theoretically, all four conductors could be floating at
different potentials relative to each other, and clamping to GND
wouldn't necessarily protect against a damaging potential between
a 485 wire and +6V.
<br>
<br>
All input greatly appreciated!
<br>
Thanks,
<br>
-Brian
<br>
<br>
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</blockquote>
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