Re: Steel wire carrying twelve volts ?

On Sat, 26 Apr 2008 19:09:04 +1200, grumpyoldhori
<grumpyoldhori@xxxxxxxxx> wrote:

Stephen Robinson wrote:

What is the application and estimated amount of use per day?

Running a Linksys wireless router on a hop for a
microwave link.
The output power is only 100mw. but the router draws
five watts on average to power it's board etc.
Running 24/7.
Looked at solar and running copper wire, both came
to around NZ $600
Which is why I am keen on using the steel wire if
possible.

To get the distance at lower voltage drop, use 50 Hz or 60 Hz AC
dropped down from mains power - I would start the experiment with a 24
VAC input using the top (#1) wire as a "guard wire" grounded lightning
sink, with a ground lead going down the back side of the post to
ground rods at all the high points along the route. If lightning is
going to hit, you want to try and divert it from your power leads.

Make the #2 and #3 wires from the top your power leads, taken loose
from the fenceposts and mounted on ceramic insulators, and see how the
voltage is at the far end under load. The insulators will cost a bit,
but increase efficiency a lot - especially with the existing wire
stapled to wooden posts, when it rains the power will /all/ go away as
it leaks between the wires at 200 high-resistance shorts. When you
are only starting with 50 VA or less at the feed end it doesn't take
much loss at each post to suck it all up.

Anything below 50V with a current limited source is considered Class
2 Wiring in the US, and IIRC the rest of the world is about the same.
It will give the cows and sheep a tingle if they touch it, but that's
about it - much lower voltage than a fence shocker generator, but you
still want to use only enough voltage to get the job done.

At the feed end, my best guess for a starting point would be a 240V
to 24V at 50VA transformer meant for running Air Conditioning
controls, they are reasonably cheap. Fuses on both sides, and a
healthy lightning arrestor tied to a good ground rod.

Telephone lightning arrestors should work perfectly for that voltage
and be reasonably priced, they have about a 150V strike-over because
ringing voltage is around 120V AC 20 Hz. And the newer three terminal
gas-tube arrestor devices form a plasma and clamp both lines of the
pair to ground at once, to avoid sneak current failures.

If your area gets nailed by lightning often, you could also put
arrestors at all those mid-run ground rod locations. But due to added
expense you might want to wait till the first time it all gets "blowed
up good" and you realize it wasn't enough. Your call...

Wherever there is a gate, bury a length of PVC Plastic conduit with
the long sweep ells between the fence posts and under the opening.
Take the two power and one ground lead and convert to heavy gauge
stranded copper wire for the short run, then back to fence wires.
Might be a good location for a ground rod.

At the top of the hill you attach another healthy lightning arrestor
across the two power leads connected to a ground rod, then rectify and
regulate to the 12V DC the Ethernet repeater is going to want. And
put a healthy crowbar zener on the 12V DC output, to try and save the
repeater from a lightning strike or regulation failure.

If it all works as planned, go to a local print shop and have simple
warning signs made up - Print them two-up on A4 Goldenrod or Red paper
and cut in half (5" x 8") then heat laminated with a large border, and
staple them to every fourth or fifth fence post through the laminated
border. They will last several years if the paper remains sealed off.

"Warning - avoid contact with insulated fence wires. 24 VAC Class II
Current Limited power for Wi-Fi Ethernet repeater system on top of
hill for the (Name) residence. Safe for accidental contact. Please
do not short or ground fence wires. Enquires contact Hori at
(address/phone)."

Nothing fancy, but keeps the kiddies from playing with it, the local
loons from inventing UFO conspiracy theories (Yeah, as if that would
be enough to stop them...) ;-) and the local Law Enforcement/ Fire/
Wildlife authorities from freaking out about exposed wires.

--<< Bruce >>--

.

Relevant Pages