Faraday Cage

reply to post by chr0naut


'day chronaut Thanks for your great post. Any chance of some comments on say a set of solar panels and the associated inverter and a way of making sure they still work after an EMP plz of if it happened before them being protected, what would be needed to get the panels up and running again ???
Regards

Originally posted by steve1709
reply to post by bobs_uruncle

 

G'day bobs-urunkl So how good would a steel framed house that has silver sarking all over the walls and ceiling work a a F cage plz?

If you can get access to the conductive material inside and ground each sheet and/or attach the conductive part of the sheets continuously and ground them as a group so that you had one large conductive box that is grounded, it would work quite well, but you will have holes and open seams I am sure, so that's where your leakage would be located. If there are spaces in between the sheets, these spaces will limit the maximum frequency you can be protected against. The quarter wavelength is the size you have to account for. Grady's Rule states that 1 ghz wavelength 11.808" or the speed of light is 11.78" of which the 1/4 wavelength is just under 3". You can calculate your wavelengths with this handy little TOOL.

The most important thing about Faraday Cages, apart from the grounding, is the maximum hole size in the cage which is the aperture or waveguide size. So if you have a hole or slit that is 3" high and 1/16" wide, you are still only protected to about 1ghz which is pretty low. Scanning technology as well as EMF weapons range in the 10's of ghz with weapons being at the top of scale between 75ghz and 90ghz, so really want to be protected in those ranges which have a 1/4 wavelength of about 0.033" (33 thousands of an inch) or 0.84 mm. The only way to get this kind of protection is to fold wrap all of your conductive material to make one continuous sheet that can be grounded. There should be NO holes or tears larger that the maximum aperture size you want to protect against, even holes made by screws and nails can allow leakage, it's a tricky process.

Hope this helps,

Cheers - Dave

reply to post by bobs_uruncle


Thanks for your great answer Dave. Presently, we only have the frame with the silver sarking and outer skin up, So I'm thinking I'll line either the whole inside or at least one room completely using your info. Just waiting now for a few events to happen that will give me the dollars to make this happen. Hopefully it will be sooner rather than later. Once lined and the inner walls are in place, I'll know about it and have my stuff safe but it'll look like any other normal house. Much appreciated. Have a top day.

Originally posted by steve1709
reply to post by chr0naut

 

'day chronaut Thanks for your great post. Any chance of some comments on say a set of solar panels and the associated inverter and a way of making sure they still work after an EMP plz of if it happened before them being protected, what would be needed to get the panels up and running again ???
Regards

It's all about the effectiveness of the receiving antenna. If you could break up the antenna into smaller segments and isolate them from each other sufficiently, the overall current through each would be reduced.

This is what they do with mains power grids when a CME is incoming. They throw circuit breakers that isolate bits of the grid into smaller segments rather than linking across vast areas.

Because EMP from a nuke is more like a radio wave, the antenna length would be much shorter than a ULF 'atmospheric charge' event like a CME would cause.

Silicon cells are usually small individual elements connected together by wire links, you could replace these wire links with fusible links that would burn out well before the silicon is damaged.

OK, the next bit is very "back of the envelope" and approximate because I don't have on hand the specifics of Solar Cells or of EMP conditions, but it would probably be an OK "rule of thumb" to start from.

Generally, damage occurs to silicon devices when the voltage is usually at or above 400 volts (actually, usually closer to 3kV but i'd rather err on the safe side). So, we could use standard low voltage fuses. They have to be "fast blowing" or "quick acting" fuses because an EMP is a short duration event.

As the max current you will get from a 152mm silicon solar cell is less than 8 volts at 160mA, all you have to do is find some 0.2A (200 milliAmp) fast blowing fuses and enough fuse holders to match and re-wire these in between your cells and you are set.

Should an EMP take out your solar panel, a pocketful of replacement fuses will get you up and running again in no time.

Note that the internal resistance of the fuses will also probably limit the efficiency of your panel a bit too, but it shouldn't be too bad.

Note again that you MUST have fast blowing fuses! Ionization effects can cause air resistance to drop and at very small distances, you still might get conduction through a partially blown fuse.

Protection of the inverter is a bit more of a problem.

It would be best to isolate it close to the inverter (put circuit breakers close to the inverter on both the input and output side so there's no runs of wire) and sit the whole thing in a ferrous metal box to deflect magnetic as well as electric effects.

If it's a true RMS inverter, it will likely have a large transformer which will convert a magnetic pulse to current very efficiently and will fry the rest of the power circuitry. Again, fast blow fuses might be your solution here, but they would have to be rated at just above the transformer output.

If your inverter is fully solid state, then I don't really know how you'd protect it beyond EM shielding and putting circuit breakers on all runs of wire.

(I suppose you could pray).

reply to post by chr0naut


thanks chr0 for your great answer. helped me, hope other ATSs will also benefi

regards

steve

I intend on using aluminum screening, They have used aluminum in older transformers in the early 60s due to a shortage in copper..Im not to worried about this being effective as a shield for my electronics, as it will conduct.
Though the the screening will have a thin coating for anti corrosion.. I will make sure I have an even connection
in all places.

Originally posted by Lil Drummerboy
I intend on using aluminum screening, They have used aluminum in older transformers in the early 60s due to a shortage in copper..Im not to worried about this being effective as a shield for my electronics, as it will conduct.
Though the the screening will have a thin coating for anti corrosion.. I will make sure I have an even connection
in all places.

Aluminium might be OK for an electrical field and environmental shield but is not so good as a magnetic shield. As an EMP most likely has a magnetic component, it probably wouldn't be too effective.

reply to post by chr0naut


Well, to protect your inverter and other things, you can find high-power TV's to put between the power-lines, and in parallel with them, gas arrestors. TV's are good for clamping the very fast waveforms, but can only absorb between 300 and 3400 Joules depending on size. Gas arrestors on the other hand react slower, but can handle a lot more power, but you can't just add these things without taking the rest of the system in consideration. It becomes quite complicated, AND very expensive. As there are only a limited amount of declassified information available as to what waveforms to expect due to EMP, you can only do your best, but there is no guarantee that it will survive an actual EMP. (It depends what type of EMP-weapon it was, the distance from your equipment, etc, etc). It is quite achievable to make electronic equipment immune to EMF-fields greater than 140kV/m, but is is very, very expensive, and only some military electronic equipment are EMP-proof, it is just not worth it. (It is not worth designing equipment selling for US$20 000 with EMP protection, as the cost due to EMP protection would greatly exceed that.) It is normally only the stuff going into bunkers, or into some airplanes that are designed in that way. (OK, I am not speaking for the US military, but I guess the same would apply there too). It is much, much cheaper to EMP-proof the bunkers, and keep lots of stock in a heavily shielded room. Another thing to think about, even if your equipment survive the EMP-effect, would you survive it if it was a nuclear device detonated close to you?

Originally posted by chr0naut

Originally posted by Lil Drummerboy
I intend on using aluminum screening, They have used aluminum in older transformers in the early 60s due to a shortage in copper..Im not to worried about this being effective as a shield for my electronics, as it will conduct.
Though the the screening will have a thin coating for anti corrosion.. I will make sure I have an even connection
in all places.

Aluminium might be OK for an electrical field and environmental shield but is not so good as a magnetic shield. As an EMP most likely has a magnetic component, it probably wouldn't be too effective.

edit on 30/5/2012 by chr0naut because: (no reason given)

And lets say I weave copper strands though the aluminum,. or steel every 1 foot for a 6x6 enclousure?

reply to post by Lil Drummerboy


then you still would have to have it surrounding a solid metal box, as any you need to make sure extremely good contact is made between all the weaves. Any opening can and will cause RF to leak in. The smaller the opening, the higher the frequency. You need to make the whole cage from something like mu-metal (google it).

and then, say that you do manage to make a cage that can protect your precious equipment from the electric and magnetic components of a nuclear EMP, how are you going to protect that from the gamma-ray components from a nuclear EMP? You will have to bury the whole thing a couple of meters deep under ground, or concrete.

great thread.

Ive just started thinking about making a Faraday cage and I have a couple of questions on what might make a good cage.

1) Would a regular garden shed make a good Faraday cage? I think ours is made of tin and sits on a concrete base, or would it have to sit on a metal base?

2) A filing cabinet? providing the items on the inside are stored inside a non conductive container

I think you need to think about what is the function of the Cage that you are building.

A Cage amid-agates the effects of EMP from

#1 Inadvertent EMP Static - Lightning

#2 Natural Disaster - Very Large Solar Flares or Earth Feild reversal

#3 Man made directed attack

You can protect

#1 People

#2 Electronics

#3 Food

The cost of doing this can be very cheep if the object is not in use or not moving.
The cost will increase if the object is moving or requires an external power source.
Nothing other than not being in use and not moving will guaranty protection.

Additionally the object of protection must have a use after the EMP event.
A working Radio sure would be nice if there was something to pick up after the EMP.
Radio Stations would be the first affected by EMP.

Thinking about what you would like to accomplish with your cage will help you focus your effort.

Each protected subject has different requirements for each EMP event described.

Example: If desired mitigation is for a flip in the Earth's Magnetic Field you would need something that would continue protecting the Subject threw multiple EMP events. Normal EMP is burst of energy not multiple events like the earth magnetic field reversal.

Thinking that connection to natural Earth Ground is a common mistake in large EMP.
The earth is an Antenna hooking to it just makes you more susceptible to ground spikes.
A Solar flare or an Airborn or Below Earth Burst causes the current flow out threw the ground coonection as the natural earth (Dirt, Water, Stone what ever) is overwelmed by the burst.

The ground connection threw a large resistor might give some protection from a large burst if power is required durring the event.

The best thing in these instances for "power on": EMP suppression is self generated individual power.
That is placed in a plastic cage along with the subject for protection.

The plastic cage is then placed inside a non grounded Faraday cage. The non grounded cage then would be placed inside another plastic cage

Then the entire protection described placed heavy Faraday cage that is itself grounded yet isolated from the inner structure.

Finally, Electronic devices that do not require clocking from an external sorce will work cheeply.
Scrap matterals would surfice.

Well goto go....

---Watcher....