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<div class="moz-cite-prefix">I'm still at work and don't have the
time to go into a long answer, but here are a couple of pointers
to help:<br>
<br>
Similar question as yours, posted on a forum:<br>
"RS485 and power on the same cable":
<a class="moz-txt-link-freetext" href="https://www.electronicspoint.com/threads/rs485-and-power-on-the-same-cable.37397/">https://www.electronicspoint.com/threads/rs485-and-power-on-the-same-cable.37397/</a><br>
<br>
A couple of great sites for RS485 are<br>
<a href="http://www.rs485.com/" target="_blank"
class="externalLink" rel="nofollow">http://www.rs485.com/</a><br>
<a href="http://www.bb-elec.com/" target="_blank"
class="externalLink" rel="nofollow">http://www.bb-elec.com/</a><br>
<br>
(warning: most of these are hawking products...)<br>
<br>
Bourns Application Note: Handling Transient Threats in RS-485
Systems<br>
<a class="moz-txt-link-freetext" href="http://www.bourns.com/docs/Products-General/Bourns_RS-485_AppNote.pdf">http://www.bourns.com/docs/Products-General/Bourns_RS-485_AppNote.pdf</a><br>
<br>
Using Isolated RS-485 in DMX512 Lighting Applications<br>
<a class="moz-txt-link-freetext" href="http://www.analog.com/en/analog-dialogue/articles/isolated-rs-485-in-dmx512-lighting.html">http://www.analog.com/en/analog-dialogue/articles/isolated-rs-485-in-dmx512-lighting.html</a><br>
<a class="moz-txt-link-freetext" href="http://www.analog.com/media/en/analog-dialogue/volume-43/number-4/articles/isolated-rs-485-in-dmx512-lighting.pdf">http://www.analog.com/media/en/analog-dialogue/volume-43/number-4/articles/isolated-rs-485-in-dmx512-lighting.pdf</a><br>
<br>
Transmit High Data Rates Over Long Distances with Murata’s
NM485D6S5MC Isolated RS485 Driver, Now at Mouser<br>
<a class="moz-txt-link-freetext" href="https://www.electronicsmedia.info/2017/03/16/transmit-high-data-rates-long-distances-muratas-nm485d6s5mc-isolated-rs485-driver-now-mouser/">https://www.electronicsmedia.info/2017/03/16/transmit-high-data-rates-long-distances-muratas-nm485d6s5mc-isolated-rs485-driver-now-mouser/</a><br>
<br>
Building a Reliable RS485 / RS422 Network<br>
<a class="moz-txt-link-freetext" href="https://www.commfront.com/pages/building-a-reliable-rs485-rs422-network">https://www.commfront.com/pages/building-a-reliable-rs485-rs422-network</a><br>
<br>
<span class="slider-title" id="slider-title-882">SCADALink
Industrial RS485 Solutions<br>
<a class="moz-txt-link-freetext" href="https://www.scadalink.com/products/data-communications/industrial-rs485/">https://www.scadalink.com/products/data-communications/industrial-rs485/</a><br>
<br>
----<br>
When I did work in Radio & Television engineering, we used
the center-taps of high-speed transformers to carry power over
the signal pairs, making sure to use transformers designed for
the extra DC bias to avoid saturation:<br>
<br>
<tt>Full Duplex RS-485 (2 pair)<br>
<br>
TX + --------}|{--------------/ /------------}|{------- + TX<br>
}|{ }|{<br>
}|{--- CT +24V ~+22V CT ---}|{<br>
}|{ }|{<br>
TX - --------}|{--------------/ /------------}|{------- - TX<br>
<br>
RX + --------}|{--------------/ /------------}|{------- + RX<br>
}|{ }|{<br>
}|{--- CT SGnd SGnd CT ---}|{<br>
}|{ }|{<br>
RX - --------}|{--------------/ /------------}|{------- - RX</tt><br>
<br>
</span><br>
You do know that my weekend "business" is Smart-Home /
Smart-Energy, don't you ?<br>
<br>
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>
</blockquote>
<p><br>
</p>
<pre class="moz-signature" cols="80">--
Scott G. Hall
Raleigh, NC, USA
<a class="moz-txt-link-abbreviated" href="mailto:ScottGHall1@GMail.Com">ScottGHall1@GMail.Com</a></pre>
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