Faraday Cage

All you need is a metal cabinet of any kind The charge stays to the outside of the cabinet. It can be grounded to an earth ground wire but it's not really necessary. These metal cabinets need to have a shelf liner or cardboard on the shelves. Bullets should be kept in metal ammo boxes and have cardboard or something to keep them from touching the metal.

I studied this because I have frequent lightning strikes where I live. Lightning hits the trees on my property an average of once a year. It makes life interesting.

reply to post by deloprator20000
Good ideas for future exploration, but I am not there yet. As long as I have my emergency equipment available, that will help me in the possible post emp shtf that concerns me most.

reply to post by deloprator20000


A faraday cage is not complicated. All that is required is good terminations a conductive cage and a solid earth connection to the cage. The way a faraday cage works is simple, electromagenectic radiation wants to take the path of least resistance to earth. By building a cage around an object that is connected to earth automatically makes the cage the path of least resistance as for the electromagnetic radiation to reach the item stored inside will have had to pass a route to eart to get to it. Hence the reason all electromagnetic radiation is disipated to earth at the cage.

You do not need anything special to do this.

First of all, where did this aluminum idea come from? Aluminum is diamagnetic (high resistance to a magnetic field) and therefore will not shunt the electromagnetic pulse around whatever is inside. A Faraday Cage needs to be made of something which has ferromagnetic (low resistance to magnetic fields) properties. Steel is OK, iron is pretty good, some of the shielding alloys (UltraPerm) are excellent.

A ground cable is not needed, unless you're worried about static buildup.

One of the best Faraday cages around is the trunk of a car. It's not perfect, primarily because the front is typically covered only by fabric, but it does offer a good deal of protection. If one wanted to carry a Faraday cage with them, I would simply install a piece of sheet steel across the back of the rear seat.

The problem with an EMP is that the high magnetic flux change that accompanies it will induce high voltages in any conductor it crosses. That means that inside a piece of electronics, every wire, every trace on a circuit board, every component lead will become a small battery. The combination tends to burn out the components, rendering the device useless even after the EMP has passed.

Certain components are more capable of withstanding EMPs. Coils and resistors are pretty hardy, as are switches and almost anything electro-mechanical. Capacitors are so-so, as they are sensitive to high voltages beyond their rating, but they also can absorb spikes depending on their value and the amount of energy in the voltage spike. Semiconductors are pretty susceptible in general, but those which use MOSFET technology (most semiconductor chips, power transistors, etc.) will pop at the first sign of a spike in voltage. These last devices are so sensitive, special care must be taken to put them together into a product; improper handling can cause them to blow without notice or even indication.

A Faraday cage works by channeling magnetic and electric fields around itself, keeping them from interfering with what is inside. Thus, the thicker and less resistive the material is, the more current and flux it can channel around itself. The thinner and more resistive the material, the more it will allow the fields in an EMP to travel through without diverting.

TheRedneck

I could make a sheet steel cover for my box. What about the gaps though? Does it have to be a perfect seal? I figured that if the phone didn't ring, that was a good test.

reply to post by DarthMuerte

You can actually make a Faraday cage out of steel wire mesh (like chicken wire). The effectiveness will of course be limited to the ability to conduct fields and thus the size and placement of the wire, but it will work.

TheRedneck

reply to post by Elostone


I'm not an electrical expert, but I am a amateur radio person who's familiar with transmitters!

Microwaves use a high frequency magnetron to produce electromagnetic frequencies that cause particles to vibrate rapidly. This is a non-ionizing radiation and there is no residual effect once the microwave is turned off.

A microwave oven would be safe for electronics assuming it's disabled. I couldn't guarantee it protecting anything from EMP, but it'd isolate them from certain types of RF for sure.

Originally posted by mileysubet

Originally posted by thehoneycomb
reply to post by mileysubet

 

Does it matter what kind of metal? Also how important is it to be grounded? Would that be the equivalent of say using the mini fridge and bolting it into the ground?

Copper Mesh would be the best (more affordable than gold/silver). Grounding is important to dissipate any risidual charge after a EMP event, it will also help to discharge the charge away from your electronics as the event(s) take place.

I dont know how effective a mini fridge would be for a Faraday cage, but as long as it is metal on the out side then it may just work, also it has a built in ground, just clip the two flat prongs off and plug in the ground section.

Edit: As an after thought, removing most of the paint from the exterior of the fridge may also help to absorb and disparate the charge, also check to see if the ground on the plug is indeed grounded to the exterior metal of the fridge, I am not sure if that is the case of a mini fridge. Also do not use your mini fridge for cooling your electronics (computer), as this may cause unwanted and damaging condensation on your electronics.

edit on 29-5-2012 by mileysubet because: (no reason given)

your mini-fridge wouldn't make a good faraday cage without modifications, as lots of them are made from plastic. Even if you find a metal one, the seal of the door is rubber. The best one is the microwave oven. It keeps all RF in, therefore it will also keep the RF out (but not magnetic fields). Just make sure the doorseal is intact (rubber with ingrained silver/copper particles) that conducts when it is compressed. No soldering required. (just make sure you cut of the power lead, as you don't want somebody to switch it on with your sensitive electronics in it.

Else, you can make your own walk-in Faraday cage, but that is really, really expensive .....

Or just take a tin can, throw your stuff in it, and solder the lid on, making sure if there are any hinges, they get soldered up too.... Just make sure you have a cutter to cut open the box when you want your stuff..., and don't worry, if there was really a terrible EMP event, unless you have a short-wave radio in your sealed box, your cellphone would be quite useless.

OR, just get yourself a valve-shortwave radio, they are sort-of EMP-proof, provided you don't have them to an antenna connected during the pulse....

reply to post by thehoneycomb

I understand that equipment using valves only and not transistors or ICs will withstand an EMP pulse. If you're expecting to run a vehicle look for an older one that has a simple engine, no injectors, no engine management systems, no fancy gizmos. Something that was built in 70's. Simple mechanics and easy to work on.

Look for books that tell you what you'll need to do. Farming, animal slaughter, survival. Build your stocks of real books up. Check out tools and manual machinery to make clothes, work on wood and basic materials.

i don't know where i saw this but, there was a man that lined a thin watch cap with thin copper wiring, and at one side of the cap, there was a long insulated wire that had only a single male fitting on it. he plugged this into the ground hole of his electrical socket next to his bed, and slept with this at night...he claimed to get a more restful sleep, as he would wake up feeling alot more alert, and he said he seemed to have a more positive attitude during the day.
i have NOT tried this, but i'm curious if anyone else has, and what results did they get from it.

of course, if you want to read how the military does it, you can download the specs here. The document also give a lot of details of EMP.

It is a large document, 44MB but it makes for interesting reading.

ELECTROMAGNETIC PULSE (EMP) AND TEMPEST PROTECTION FOR FACILITIES

(Of course, a lot is classified, but this doc, as well as the ones referred to inside, should give you an idea what is involved and what to do).

reply to post by michael1983l

Sorry I should have put more than 90% but it does not travel at light speed.

The electromagnetic wave that causes all the electronic problems is slowed down due to earths magnetic field. We can argue this if you like the answer is still at 30 miles there is NO time...

en.wikipedia.org...

reply to post by mileysubet


You would need to use multiple layers of meshes with different sized gaps in order to shield the devices from the broadest possible amount of energy induced. That's because the effectiveness of the shielding is based upon the wavelength of the induced energy. An EMP generated by the sun or from a nuclear explosion will have a wide range of wavelengths.

HERE is an interesting read.

Metal garbage can with a chunk of wood in the bottom. Cheap and effective.

Originally posted by thehoneycomb
reply to post by Elostone

 

Yes Ive heard that, but they also when turned on keep radiation in. Another suggestion was an aluminum trash can. But somehow I don't think I can justify keeping the computers in a trash can to the other half lol.

ETA: we do have a mini fridge that isn't working, but I was thinking something more portable.

edit on 29-5-2012 by thehoneycomb because: (no reason given)

The problem with a mini-fridge is that many parts are plastic, the design is for keeping things cold not providing an EM sealed enclosure.

An old microwave is the way to go.

Originally posted by bobs_uruncle
reply to post by thehoneycomb

 

Go large or go home LOL. Line all your walls and ceiling/floor with foil, crimp it together, leave no holes. Then ground the entire foil set to your water pipe. If you do it properly, with no holes, it's EMF impenetrable. I have built room sized Faraday cages before for EMF experiments and recording studios, so I know it works ;-)

One thing that will really surprise you is that once you have done this, put a cot into the room and go to sleep. It's ef'ing amazing. I had one guy in a band who was a pretty well controlled narcoleptic. He'd play all night with the band, never fall asleep, but when he went into my insulated room, he had to lay down and he was asleep in seconds. Of course I had 100 oz carpet on the floors with 3/4" underpad and 2.5 lb sound insulation on the walls are ceiling. That room was like nothing I had ever built or encountered before, it was the deadest space I have ever been inside.

Faraday cages are way cool when they are done right.

Cheers - Dave

I can vouch for that. When I worked at EMI Studios in Australia, they were faraday cages, acoustically lined, acoustically balanced in regard to resonances, properly air conditioned and the rooms floated in oil.

The rooms just felt strange but in a good way and super quiet (they went for 'live end-dead end' design so they weren't actually anechoic).

Hi-Fi reality!

Originally posted by thehoneycomb
Also before I forget there were a few other things I wanted to ask. Maybe someone knows the answers. In the event of an EMP, how long would you have say it happened 30 miles away to get your gear into a faraday cage? How long should you leave it in there?

Would all cars and electronics be useless? How would you go about restoring equipment after an EMP? Is it essentially the same as taking a magnet to a hard drive or a cassette tape?

The EMP travels at the speed of light & would hit before you knew it had happened. It's essentially a high power radio signal. Invisible & instant.

Once the source had stopped (from a nuke, probably milliseconds would be enough, but 30 seconds would be a safe margin). You could probably use a disconnected fluorescent tube which would light up to indicate if the EMP is still going.

An EMP 'over-currents' anything that can act as an antenna and has sufficient conductance. Silicon (transistors, diodes & etc) would be fried and either be totally dead or damaged to the point of reduced function. Coils and inductors could also be similarly fried, but their size probably would protect them. Capacitors would likely be unaffected but may retain residual charge if the circuit they were in suddenly went open due to the pulse.

The electronic ingnitions in most cars should actually be shielded if they were disconnected but it is the wiring through the car that makes an antenna that would fry them.

Similarly, anything connected to the mains power would be fried from the power coming in over the wires.

To be effective, your Faraday cage needs to completely enclose its contents and you can't run wires in there.

Originally posted by jimmyx
i don't know where i saw this but, there was a man that lined a thin watch cap with thin copper wiring, and at one side of the cap, there was a long insulated wire that had only a single male fitting on it. he plugged this into the ground hole of his electrical socket next to his bed, and slept with this at night...he claimed to get a more restful sleep, as he would wake up feeling alot more alert, and he said he seemed to have a more positive attitude during the day.
i have NOT tried this, but i'm curious if anyone else has, and what results did they get from it.

If you screwed up a bit, this would kill.

I wouldn't think it would be worth it.

Thanks all for the responses, trying to soak this in a bit. Theres a lot I don't know about EMP's and faraday cages so pardon me for my absence. I am reading and considering all thoughts and thank you.

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?