Faraday Cage

Discussion in 'Survival & Sustenance Living Forum' started by 12fretter, Sep 26, 2012.

  1. 12fretter

    12fretter New Member

    422
    0
    0
    Since grounding is a big issue with a Faraday Cage, I was wondering if you could wire up a custom AC power cord that only has the third green wire hooked up, connect it with a big ol' ring terminal to the cage, and plug it into any outlet in the house. Is that a reasonable solution?
     
  2. scottmac

    scottmac New Member

    268
    0
    0
    Grounding is not necessary for a Faraday cage; the metal is a better path than air and guides the field around the contents.
     

  3. ellis36

    ellis36 Well-Known Member Supporter

    2,327
    129
    63
    I'm not sure about that. Check out
    http://www.endtimesreport.com/faraday_cages.html

    As for the question…it would depend on the integrity of the ground wires from the outlet back through the main breaker box out to the power company ground. Some unknowns there but a possible solution. The thing is, shielding for RF is an iffy thing. Because of the short wavelength a ground wire can actually act as an antenna under the right conditions. The ground needs to be as large, as short and as direct as possible.
    Google 'Faraday Cages.' There is lots of info there about this subject.
     
  4. JTJ

    JTJ Well-Known Member Supporter

    9,538
    136
    63
    Your best bet is an independent ground rod if you have good mineral content in the soil. I have had to dig a trench and run a bare ground cable when I could not get a sufficient ground with a rod. Sand can be iffy.
     
  5. WebleyFosbery38

    WebleyFosbery38 New Member

    7,510
    0
    0
    Ive built these for our scientists in our BIO labs, they have dedicated Grounding systems in the labs so its not an issue. The ground lug in your outlets isnt a great place to grab ground, they are often noisy and in older homes, very unreliable. The impedance is just as important as the pathway.

    The reference to the Grounding is a very important factor in the use of a Faraday cage, I agree a well placed (Damp, minerals, deep) ground rod with a dedicated strap is best. Also, the perforations, mesh in the cage should be as small as possible to minimize penetration of Higher Frequencies. I use copper cloth, its expensive and easy to solder directly too but is nearly impenetrable.
     
  6. 12fretter

    12fretter New Member

    422
    0
    0
    Did you mean it's INexpensive?
     
  7. WebleyFosbery38

    WebleyFosbery38 New Member

    7,510
    0
    0
    Unfortunately its not cheap to buy woven copper fabric but it is pretty much impervious unlike most other materials that cross conduction isn't so guaranteed. We use smaller versions for monitoring brain waves, Signals so small that any stray RF in the room would register.
     
  8. bkt

    bkt New Member

    6,964
    0
    0
    Short answer: yeah, it'll work OK if your ground on your outlet actually goes to ground. Grounding usually isn't difficult. If you're in an apartment, that might be a different deal. Buy an outlet tester and confirm ground really goes to ground. If it does, modify an extension cord and you should be OK.
     
  9. clr8ter

    clr8ter New Member

    4,015
    0
    0
    If it were me, I'd put the cage in the basement, drill a hole thru the concrete floor the size of a grounding rod, pound it into the ground under your house, and attach a big cable directly to it.
     
  10. bkt

    bkt New Member

    6,964
    0
    0
    Right, me too. But if you're living in a 5th floor apartment you might be limited doing something like that.
     
  11. clr8ter

    clr8ter New Member

    4,015
    0
    0
    True, it might be hard finding a 5 story grounding rod, LOL. If that were the case, I don't know what I'd do.....I guess I'd have to trust the building's wiring........
     
  12. scottmac

    scottmac New Member

    268
    0
    0
    It is the conduction path, not the grounding that create a Faraday cage. For example, (non-convertable) cars and flying airplanes pass lightning, protecting the contents (people) ... they are not grounded. Some newer airplanes are made with composite materials ... they explode when hit by lightning, so NASA (and others) developed and tested a copper mesh to embed in the composite skin to provide a discharge path to keep that from happening (it also provides a ground plane for the radios).

    If you watch Mythbusters, they had a cage at the top of a Van De Graaf generator used to demonstrate lightning ... the cage was not grounded, if it was the "lightning" wouldn't have been attracted to the test objects.
    Touching the inside surface of the cage has no effect, and presents no danger for the same reason ... the cage is a better, less resistive path than the objects contained within.

    I'm not saying you shouldn't ground them, I'm just saying that 99.9% of the time, it's not needed. Adding a ground would basically control where the charges are drained. If the grounding system is insufficient or inefficient (there's more to it then slamming a rod into the ground and screwing a wire to it), chances are you'd cause more problems than you think you're solving.

    Wikipedia has a pretty good explanation: http://en.wikipedia.org/wiki/Faraday_cage

    Another thing to consider is that a true pulse is made up of an infinite number of third-order harmonics, meaning that given a sufficiently strong pulse, some energy will penetrate a mesh of any dimension (smaller = less, solid = total).
     
  13. ellis36

    ellis36 Well-Known Member Supporter

    2,327
    129
    63
    Good post with good info. As with a lot of situations, nothing is as simple as it might appear. :)
     
  14. WebleyFosbery38

    WebleyFosbery38 New Member

    7,510
    0
    0
    SM explained it well, my experience with Faraday Cages has been purely scientific, the signals and pulses we are trying to eliminate are so small that they could not possibly damage Electronics equipment but they would provide false data in Bio Research Labs. Never considered EMP protection for survival as is being talked about here and we never had any drills or skills in Anti Armor to deal with it although we always knew it was likely if there was a nuke detonation danger close or further. Im not exactly sure what the primary shock frequencies are for a bomb of that magnitude, the Third and Fourth order harmonics are truly incalculable at the JQ Public level and I leave those calculations to the PHD's, I just build what they describe, twice if they are wrong the first time! My head hurts just thinking about the calculations but the pressure behind them is seismic.

    What he said about the density of the mesh is a real factor in effectiveness, thats why we use woven copper cloth, its nearly impervious to any frequency and the edges solder well for a closed loop on the shield. Grounding isnt important so much in an aircraft thats potential resistance is in the Millions of Meg-ohms impedance wise in a pathway to ground. As a cage sitting near ground yet not earth grounded solidly, the potential for inducement grows larger.
     
  15. clr8ter

    clr8ter New Member

    4,015
    0
    0
    At what point did this forum switch languages? LOL
     
  16. WebleyFosbery38

    WebleyFosbery38 New Member

    7,510
    0
    0
    Das Copperscplinger und der groundenkafish ist guflickin in der feiselpunkt, ist Kaput!

    Defined means, if your anywhere near an atomic detonation, bend over and kiss your arse goodbye!
     
  17. clr8ter

    clr8ter New Member

    4,015
    0
    0
    I also meant to ask, and this may be stating the obvious, if smaller mesh size copper is better, and sealing up the seams completely is better, does it follow that a box made from solid copper sheet welded at the seams would be the best? (Yes, you can WELD copper.)
     
  18. WebleyFosbery38

    WebleyFosbery38 New Member

    7,510
    0
    0
    Absolutely, solid is much better than any mesh but you might not wanna know how much thats gonna cost (unless your making a shoe box)! The real world application of shielding from Nuke radiation/ EMF is in every XRay room in the nation, Lead! It blocks almost everything you can throw at it, the very old houses like I own actually have shown less RF passthrough than new ones and thats been attributed in large part to layers of Lead paint that limit penetration naturally. Lead sheets are much cheaper than Copper and pound for pound, less penetrable than nearly any other material but certainly is not the safest substance to have a ton of in close proximity to your family.
     
  19. scottmac

    scottmac New Member

    268
    0
    0
    Solid is "best." However, you'll have to judge whether the cost differential is worth the marginally better performance.

    For a pure Faraday effect, conductivity king. If you are also looking to block radiation (all with a single layer of some metal), then you'll need to weigh one thing (conductivity) versus another (radiation shield) according to your needs.

    There's a lot of talk here about using copper or aluminum, but mu-metal is actually better for most magnetic / EMI / RFI shielding applications (http://en.wikipedia.org/wiki/Mu-metal ). It's still electrically conductive for the Faraday effect, but is more effective against most types of magnetic fields.


    We used this to shield rooms used for electron-microscopy; the 'scopes imaging ability is sensitive to stray magnetic fields.
     
  20. Jimmy

    Jimmy New Member

    134
    0
    0
    I like this disscussion. There are some gaps in explainations, but overall good info.

    There are many factors in and emp event, weither CME or bomb supplied. There are ground effects as the currents are top to bottom and bottom to top. EI: E1 and E3 currents. For me I have only nested faraday cages. Grounding may actually cause you more problems from E3 currents. Do lots of more study before making any solid plans.

    For some good reading and a lot of it, here is some from ORNL. About 14 MB of it...

    http://www.ornl.gov/sci/ees/etsd/pes/pubs/ferc_Meta-R-319.pdf

    Jimmy
     
    Last edited: Oct 4, 2012