Tesla coil RF ground

Discussion in 'The Projects Forum' started by amilton542, Jun 1, 2011.

  1. amilton542

    Thread Starter Active Member

    Nov 13, 2010
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    For my next college project I have decided I am going to build a tesla coil. I have done some research and excluding the tuning of the tank circuit it seems a potential project to attempt. I always like to do a demonstration of my project in my college presentation and I want it safely grounded. So far my research on the RF ground has highlighted it cannot be connected to the building earth because of voltage spikes, it must must have it's own electrode 6ft in the ground. Could I use a big plant pot filled with compost and an earth electrode for an RF ground?
     
  2. SgtWookie

    Expert

    Jul 17, 2007
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    1,728
    Ah, no. :)

    Standards here in the States call for TWO 8-1/2 foot long copper clad rods driven into the planet earth at least 6 feet apart.

    While I don't see Tesla coils expressly prohibited in the rules or Terms of Service on the Board, be advised that high (dangerous) voltages can be involved, and Tesla coils can and do emit broadband RF, and in the States will quickly result in the FCC (Federal Communications Commission) hunting one down like a rabid dog, issuing large ($10,000 USD) fines, along with confiscation of equipment and imprisonment. I don't know what the laws are in the UK, but I can imagine that they are rather strict as well.

    There are many far more safe projects that don't involve such safety considerations. Why not attempt a low voltage project instead?
     
  3. beenthere

    Retired Moderator

    Apr 20, 2004
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    Absolutely not. The earth in the pot is not in electrical contact with the earth (the planet). See if this link helps - http://en.wikipedia.org/wiki/Ground_(electricity)
     
  4. amilton542

    Thread Starter Active Member

    Nov 13, 2010
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    I have come across the FCC during my research about RF interference, my presentation would no doubt be in a large computer room, I am pretty sure the argument would still hold, the demo will have to be outside. My last project was a drill powered generator made from a shaft with pillow block bearings and soil pipe with internal windings, it generated 4v :). Ive had my mind set on this for weeks
     
  5. amilton542

    Thread Starter Active Member

    Nov 13, 2010
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    Is there not another means of adaquate earthing or is an earth electrode the only option?
     
  6. DerStrom8

    Well-Known Member

    Feb 20, 2011
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    How big will your Tesla Coil be? I have built a few myself, and if they are small enough, they may not need one at all (though not advised). Also, again if they're small enough, I have read that a large metal plate on the floor (as long as the floor is concrete) may work as well. Another idea would be to use a faraday cage, to protect external electronics from the harmful RF.
    Der Strom
     
  7. amilton542

    Thread Starter Active Member

    Nov 13, 2010
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    For the spark gap to function correctly I have read it should be 5kv or more. The NTS transformer with no GFI I am looking for is an old model rated at 9kv. The secondary dimensions are 4" by 20", thus for safety I may just have to make a small one out of a cardboard kitchen roll tube.
     
  8. Kermit2

    AAC Fanatic!

    Feb 5, 2010
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    You can investigate the grounding of the building before hand to help you out. Check the resistance reading between earth ground in an outlet and some metal superstructure or water pipe(if the building has any nearby) If there is more than 2 or 3 ohms resistance you could use the metal as your ground, if the readings show they are bonded to each other you'll have to find another way.

    Also with the card board tube, I suggest placing it in an oven overnight on very low heat(160F to 250F). The lowest your oven has. This will dry out the paper completely. Immediately upon removing the cardboard from the oven, cover it with SHELLAC. You can find it at the big box stores. This will give you maximum possible electrical insulation, and prevent the paper from re-absorbing water which I'm sure you know can be a big problem with high voltage type experiments. The shellac is also good to use between and on top of all your windings. PVC pipe is an excellent substitute for a transformer form if you don't want to mess with insulating and moisture proofing the paper. Most of the internet viewable coils use the PVC.
     
  9. beenthere

    Retired Moderator

    Apr 20, 2004
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    Uh, have you got a large insurance policy that will cover replacing the network, servers and all? Plus sundry odd computers?

    Any Tesla coil can throw a spark a surprising distance. I would not care to imagine what damage it might cause in a computer lab. Do your demo in a gym.
     
  10. CDRIVE

    Senior Member

    Jul 1, 2008
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    Please tell me this is meant to be a joke??????
     
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