On Oct 14, 8:37*pm, klem kedidelhopper
wrote:
On Oct 14, 7:48*pm, JeffM wrote:

klem kedidelhopper posted 3 times:
Would I be better off with building and burying
their smaller coil with more turns or[...]

nesesu wrote:
Yes, Lenny, all three posting came through okay.

Heh. *Google Groups' quasi-annual takedown for maintenance.
Roughly 10AM - 3PM today.

Impatient posters using a Web interface to Usenet
should poll ANOTHER one of those *before* posting *again*.
(Google is NOT the only game in town.)
Here are some with reasonable latency:http://www.electronicskb.com/Default...trondepot.com/

Neil
When I said "every time" I wasn't thinking of motorcycles. My wife's
business which is run out of part of our home is a gift shop catering
primarily to women. The shop is off the main road. So considering the
clientele we're really not expecting too many bikes in here, and if
the occaisional one does come through and does not get detected then
its not the end of the world. No, I was referring to the mass of a
typical automobilie. The issue is that there are sometimes long
periods of time when there is no business. she doesn't want to have to
stay down there waiting for a customer to show up. This sensor will
allow her to turn out the lights and be in some other part of the
house until the alarm sounds. She can then run downstairs, turn on the
lights and be "open for business" And so far with the loop laying on
the ground its worked every time. You were right on the money with
your idea of three turns and a 4 X 8 footprint which is the 72 feet
the book talks about. I don't have an impedance bridge.so I can't
directly measure inductance, however the instructions did mention an
operating frequency of between 30 and 60 KHZ. I suppose that I could
look at this with the scope, determine exactly what it is and then
figure out a way to determine inductance if I really want to. But for
the time being I'm going to rewind the coil for the 6 turns the
instructions call for.
So now I need to ask for your advice again. Last year I rewired my
well. I pulled up 175 feet of the old wire and replaced it. The
conductors in that wire were continuous however the insulation was
scuffed and scraped and in some cases down to bare copper and no
longer servicable for well application. However I kept it around to
use for projects, such as this one..Well wire if you've ever worked
with it is typically three twisted conductors made from 14AWG. This
wire is apparently impervious to moisture because it runs right down
the well casing throught the water to the submersible pump. My present
test coil is made from some of that old wire.unwound to single srand.
The scuffed parts were taped up in places for purposes of this test
but it is not in good enough condition to put directly into the
ground. I have a gravel driveway and ultimately I will need to bury
the final coil amidst this abrasive material.. I could get some more
of this well wire or the instructions say that you can directly bury
THHN or a similar type of wire. My concern though is the dirt, stones,
sand, etc. which would be in constant cantact and abrading this wire.
I think that I would like to encase it somehow. ideally in PVC. Then
have some kind of an underground junction box to connect my sheilded
cable to. Do you have any ideas as to how to do this? Lenny

Lenny, I think that the 'well pump wire' is stranded type TWU . In any
case it generally has a much thicker insulation intended exactly to
withstand high abrasion situations such as sliding in and out of well
casings or being directly buried in the ground. It would not survive
being shallow buried in a gravel drive for very long. If you can come
up with the needed length of normal TW or XLPE or the newer Nylon
coated wire, then I would suggest you buy some 1/2" PVC conduit,
couplings, glue, 4 90 degree sweep bends and an outlet box with two
1/2" hubs on one end and one hub on the other end as well as a blank
cover for the box. You then form the PVC pipe into the rectangular
coil form and pull in the wire around the loop the required 5 or 6
times and splice it to the shielded lead in in the box.
Please email me directly with your email address and I will send you a
sketch of how to form the pipe.
Naturally the pipe should be surrounded with coarse sand to pad it
from the stones, but since you should be staying within 3" - 4" of the
surface, you don't have a lot of margin for that.

Neil