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Earth Ground for Apartment Dwellers

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LAN_403

Tetrafluoroethane

Tue Feb 21 2006, 01:04PM

Registered Member #127 Joined: Fri Feb 10 2006, 03:36PM
Location: Cincinnati, OH - USA
Posts: 44

I am an apartment dweller looking for tips on grounding my Tesla coil properly. I have just begun to operate my first Tesla coil and I suspect I have an insufficient ground connection. So far I have had two nightly runs with a topload in place and have managed to blow a network card in my firewall. Interestingly enough a previous test of the primary circuit alone and a later test of a totally ungrounded secondary had no such effect. I only have limited access to a patch of earth and I don't know what is burried under it.

My attempt at grounding was to drive a 1/2" copper pipe 2.5' into the the flower bed in front of my patio and using a normal grounding clamp to attach to it. Running from the base of the secondary to the grounding stake is approx 10' of 12ga stranded THHN wire. The wire is attached to the secondary using a spade male connector into a blade female connector (rigged I am sure, but it seems quite solid and those were the only two semi-matching connectors I had).

In my extensive browsing of the web and reading about the entire archive for 4hv.org, I have very infrequently found any detailed mention of what other coilers are using for ground. Is solid or stranded wire better? Is 12ga too small? How do you connect it to the secondary? What length is acceptable for a ground? Should it be a very straight wire or is it okay if the wire curves around a bit? I know my stake should probably be longer, but how long is sufficient? Or have I just found a network cable that happens to be really good at picking up whatever frequency energy this coil emits (350KHz approx calculated). Should I be connecting the house ground to this ground to suppliment the house ground? Thank you all in advance for your time.

Coil Specs:
- Pimary: 14 turn, 0.25" flat spiral (tapped about 13 turns)
- Secondary: 4.5" dia., ~740 turns 21ga enameled wire
- Cap: 0.008nF MMC, 50kV
- Power: 15kV, 30mA NST
- Filters: RC between tank & NST
- Gap: 10 segment static gap, 1" copper pipe.

Michael W.

Tue Feb 21 2006, 03:33PM

Registered Member #50 Joined: Thu Feb 09 2006, 04:07AM
Location: Vernon, B.C, Canada
Posts: 324

I can't really answer your question, but DO NOT hook it to your house ground whatever you do.....

Tetrafluoroethane

Tue Feb 21 2006, 03:37PM

Registered Member #127 Joined: Fri Feb 10 2006, 03:36PM
Location: Cincinnati, OH - USA
Posts: 44

When you say don't hook it to the house ground, do you mean don't have any connection between the two? Or don't attempt to ground it ONLY through the house? The latter I know better than to attempt. The former I don't see much problem with since my grounding stake should take all the RF energy out of the line. I was just wondering if some noise was being fed back up the house ground from the NST.

Michael W.

Tue Feb 21 2006, 03:39PM

Registered Member #50 Joined: Thu Feb 09 2006, 04:07AM
Location: Vernon, B.C, Canada
Posts: 324

I mean right into mains ground....

EEYORE

Tue Feb 21 2006, 05:59PM

Registered Member #99 Joined: Thu Feb 09 2006, 06:10PM
Location: florida, usa
Posts: 637

ForceLabs wrote ...

I mean right into mains ground....

I use the mains ground all the tirme with no problems. And i live in an apartment as well(on the bottom level) It depends on your power level, and ive run at over 1kw with a drsstc with no trouble. Id say a standard SGTC would likely be worse due to the spark gap though. Perhaps you ought to think of solid state?Another idea is a counterpoise. Make a ground plane using Al foil or chicken wire...

Matt

williamn

Tue Feb 21 2006, 08:42PM

Registered Member #55 Joined: Thu Feb 09 2006, 04:56AM
Location:
Posts: 149

I just recently moved from a 3rd floor apt. I used mains ground for my DRSSTCs and SSTCs as well with no problems. I did blow out my wireless router when running my 12/30 powered SGTC. SGTCs are notoriuos for wreaking havoc with ones consumer electronics.

HV Enthusiast

Tue Feb 21 2006, 08:45PM

Registered Member #15 Joined: Thu Feb 02 2006, 01:11PM
Location:
Posts: 3068

i'd use a couterpoise ground, of course if you have wooden floors (as opposed to concrete which might contain beams, rebar, etc...) i'm not sure of the implications of how well the ground would act.

A 4x4 sheet of chicken wire should suffice for your coil.

Sulaiman

Tue Feb 21 2006, 08:56PM

Registered Member #162 Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3140

From an emi point of view;
A long wire to an external EARTH will form a transmitting element
due to rf inevitably finding power earth via building wiring.
The only way you can ensure low radiation is
to make your experimental area into a faraday cage
which goes to your mains earth, no external earth.

If you're CERTAIN that your TC will not arc to building wiring
(light fittings, wall sockets, your equipment etc.)
then a counterpoise works well
When I lived in an apartment
I too used Aluminium cooking foil in a long strip laid across the floor.
I connected it to mains earth.
Had to be able to return the room to my wife on-demand ;)

For some unknown reason
my wife still doesn't appreciate the value
of making rooms
into Faraday cages.

..... back to the shed for me.

Tetrafluoroethane

Tue Feb 21 2006, 09:52PM

Registered Member #127 Joined: Fri Feb 10 2006, 03:36PM
Location: Cincinnati, OH - USA
Posts: 44

I have always heard using the mains ground for a disruptive system is a big no-no due to the massive amount of noise introduced into the system so you don't have to worry about me attempting that.

In addition, the impedence of normal mains ground (unless you are connecting to it right at the distribution panel) is way too high for a disruptive coil.

I believe I also forgot to mention, I am actually operating the coil outside. It was about 10' away from the network cable the first time it blew the nic. The second time I had moved it 20' away.

I think am going to try a larger (maybe 8ga.) and shorter ground wire tonight, as well as a longer grounding stake. I didn't think about the long ground wire actually acting as an antenna (I was too focused on the other end of the secondary), but that makes sense. And I am thinking about ordering an EMI line filter to try to capture any additional EMI shooting back into my mains.

I only have 1 spare NIC left so if I blow it again tonight I will have to move to the garage (and hopefully not destroy the garage door openers in the other units). Man, 3 nics in 3 days would hurt.

Not to mention my highly tolerant girlfriend might start getting tired of helping me take my firewall out of the rack each night.

vasil

Tue Feb 21 2006, 10:16PM

Registered Member #229 Joined: Tue Feb 21 2006, 07:33PM
Location: Romania
Posts: 506

i used all kinds of grounding: solid and stranded, strait or with curves, clips or screws. It is ok, but the grounding wire has to be solid connected with the secondary bottom and having a sure ground connection (I was using my water pipe, for all my coils). I am thinking that the problems are related with the back EMP into the mains. I prefer to not run electronic stuff while i run my coils. Get an EM filter for the NST input. It is possible to see a bit lowering in performance.

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