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Re: [TCML] My first Tesla Ground Questions
Simon Dodd wrote:
Hi guys,
Thanks for all your help so far, I am now using the designs set out on
deepfriedneon.com and am very close to the first test firing of my
coil!! I just have a quick question about suitable grounds...
I recently did the 17th edition wiring regulations and it stated that
you should never use water or other supply pipes as a ground. Should I
follow these guidelines for my coil and if so what else could I use?
Indeed.. never use water pipes:
1) it just puts RF in places you don't want it
2) pipes are plastic these days, even if the stub-up through the soil is
metal, it might transition to plastic in a few meters.
I
live on an industrial estate in London so I have no access to nice earth
to put a spike into. I do however have lightning conductors on the side
of buildings and there are some earth rods on concrete plates on the
ground. Which, if any of these should I be using?
None of them. (assuming you're not running a 50kVA monster coil)
You want your "ground" connection to be close to the coil. It's really a
counterpoise forming the "other plate" for the capacitor formed by the
topload on your coil.
some large conductive sheet under your coil (aviary netting, chicken
wire, or whatever they call it in the UK, works well). In rough terms,
you want the "conductive floor" to extend out about as far as your coil
is tall above it (i.e. if your topload is 1.5m from the floor, then, a
3x3 meter area would be reasonable).. It's not critical, by the way.
Why not hook to the building earthing? Think of the circuit here.. RF
current flows in the secondary inductance, into the topload, then
through the capacitor formed by topload and "surroundings", then into
some sort of wire, then into the bottom of the secondary inductance. If
that path includes a 10 meter wire to some ground rod, then the path
through the soil back to under where your coil is, you've created ample
opportunity for interference.
You DO want to connect the counterpoise to the safety earth, too.. In
case one of the HV or mains side wires falls on it and makes it "live"
with respect to your bare feet standing on the floor. But here, the
concern is at mains frequencies, not RF. I haven't tried it, but it
seems one could use a RF choke in the path to prevent putting RF into
the building's earthing/grounding/bonding system.
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