Beware, stray ground currents and lightning strikes may be an issue.


Isaac


Em 30/1/2012 14:21, Steve Willoughby escreveu:
> On 30-Jan-12 05:50, Carl Denk wrote:
>> I have 200' to a natural gas well with one 3/4" conduit for heating the
>> enclosure. I wanted to add communications to a PIC for pressure and
>> temperature readings. It was felt to run any communications wired cable
>> in the same conduit would result in crosstalk and garbage messages. I
>> settled on 62.5/125 um fibe optic which has been working great for 6
>> years. Today I probably would do it with X-10.
>>
>> This is an overkill for the application below, but running signal and
>> power close together is a concern and needs investigation before
>> committing to the work. Have you considered X-10 and it's successors?
>> Checkout Smarthome.com
> Even here, I think X10 wouldn't be practical since these aren't powered=20
> by mains current.  Each of the bricks is an 8-pin PIC driving a few=20
> high-brightness LEDs which light fiber optics to the surface, powered by=
=20
> 5V DC.  I think crosstalk is less of an issue with DC power, but there=20
> is the issue of stray RF interference, although having the cables=20
> underground may help (still need to look into that).
>
>> On 1/30/2012 4:55 AM, Mike Harrison wrote:
>>> In a situation like this, where you don't have noise or long-distance i=
ssues, probably your main
>>> risk is problems caused by the shift in the level of the ground caused =
by the power draw of the
>>> lighting.
>>> Another potential risk is damage caused by shorts from your supply duri=
ng installation - RS485
>>> transceivers will typically take 12V without damage.
>>> A 75176  RS485 transceiver is not exactly expensve
> True, although the main cost I'm concerned about is PCB real estate--I'm=
=20
> trying to make these things as tiny and trouble-free as possible, since=20
> most likely they'll end up buried permanently in the walkway, with just=20
> a DC power connection and RS485 line from the house to the first brick.=20
>   The question is whether to keep the RS485 going from brick to brick or=
=20
> switch to something simpler at that point.  Might be just as well to=20
> spec in a bunch of 75176s anyway.
>
>

--=20
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