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 Post subject: My Faraday Cage
PostPosted: Thu Nov 18, 2010 11:47 pm 
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This might end up a little long, but I've been preparing hardcore for the supposed EMP from a coronal mass ejection from the sun which defense experts and NASA have said will hit soon. Therefore, after much research and testing I've created my own faraday box to protect some of my electronics, i.e. my ham radios, weapon sights, etc. I do plan on getting an old beater truck and keeping it stored away with the electronics stripped and put into these faraday boxes as well. I figured I'd share my info since that is what this site is for! Sorry for the lack of pictures, I will throw some in when I have time, my pictures were too large to post here.

Disclaimer: I am not responsible for electrical shocks, fires, or any other injury/damage incurred while attempting this. If you are not comfortable with electronics DO NOT ATTEMPT THIS ALONE! That being said, this requires very little electrical knowledge.

Equipment

Heavy gauge galvanized steel trash can, 32 gallon - pick one that has a lid which seals well
12 Gauge Electrical Wire
3 Prong AC Plug
Wing Terminals
Self Tapping Screws
Toothed Lock Washers
Sand Paper
Acetone (nail polish remover)
Foil Tape
Various tools like screwdriver, wire cutter/stripper, power drill
Outlet Tester

Directions

1) Build the wire. One end should be the 3 prong AC plug **only connecting the ground, leave the other 2 blank and ensure that you leave enough space between the wire and the terminal** and the other end should be the wing terminal. Be sure that the wing terminal end is properly crimped around the ground wire braids. Cover the end with electrical tape as best as you can.

2) OK, so you have your wire built. Next thing on your list is find a spot on the bottom lip of the can.

Clean the OUTSIDE of this lip with acetone using paper towels, cotton balls, whatever you wish. Once it is clean, sand it down with coarse sand paper to make the area rough. Once you've roughened up your spot, it's time to assemble the wire to the can.

3) What I did is set the toothed washer against the bottom lip to give me an idea of where the screw needed to go in, and be sure that the heat of the screw would fit flush to the can without overlapping onto something else. I then placed the winged terminal between the toothed washer and the screw and drilled until tight. Voila! Your can now has a ground wire.

4) Alright, it is built. Now what? Well, you need an outlet tester in order to see if your outlet is properly grounded. If properly grounded, when an EMP hits, the can should take that electromagnetic energy and redirect it through the ground in your house, rather than into the contents of your can. This is the purpose of the faraday cage.

When the outlet is properly grounded, on my version of the tester, the yellow lights are on and the red is off.

5) Be sure to keep anything that is in the faraday cage in a cardboard box for insulation, because if electronic devices or batteries, etc, make contact with the energized metal during an EMP they are history. It is also recommended to be sure that the electromagnetic energy in the atmosphere is gone before opening the cage, otherwise all of your work was for none. The foil tape is used for creating an extra seal around the lid. Most believe that this is overkill, and not necessary. Obviously, if I'm preparing for something like this, I'm ok with overkill :)

I am up for any questions and/or criticism anyone has concerning my project. I am definitely not an expert in this stuff, but I've done my research and come up with a home made version of a faraday cage that seems to be useful. The test is to put a radio inside your can, if the radio loses signal you're good to go, if not you may need a thicker can.

Just one of my many preparations, I hope you enjoyed. I will post my others later (currently working on my go bag and my plate carrier molle setup).

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 Post subject: Re: My Faraday Cage
PostPosted: Fri Nov 19, 2010 12:13 am 
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Hmm, sounds easy enough. Pictures will be cool.

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 Post subject: Re: My Faraday Cage
PostPosted: Fri Nov 19, 2010 2:03 am 
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You do realize that CMEs don't present a danger to any device smaller than several miles across, right? And that a Faraday cage's protection of its contents is totally independent of it being grounded or not?

There have been several threads on this general subject already; searching for CME will probably find them in pretty short order. The salient points are that geomagnetic storms can't directly harm anything that isn't either in space or connected to miles of uninterrupted wire, and while damage to the power grid might cause voltage spikes at the outlet, anything that's not plugged in is abso-freaking-lutely invulnerable to their effects. Even your ham HF rig plugged in to the 160m half-wave dipole you wish you had space for won't give two ass hairs and a dingleberry about a CME. All indications to the contrary (and yes, I've read them) are the result of scientifically illiterate reporters twisting, mutilating, and sensationalizing the science to the point of outright falsehood.

Your Faraday cage isn't useless -- it's most of the way to protecting your gear against the things that actually can damage appliance-sized devices (i.e. a nuclear EMP, very nearby lightning strike, or possibly even a non-nuclear EMP weapon) -- but you'd want to improve the electrical contact around the lid-to-can interface if you're worried about those.

Also, all NASA has said is that a big CME is more likely in the next few years than it was in the last few years, and that our new-found dependence on satellites makes us more vulnerable than we used to be. Small to moderately large CMEs happen every few weeks to every few years, and we mostly don't give a damn. Big ones happen less frequently, and they're pretty damn random, so this solar max presents roughly the same 10-20% chance of a nasty CME as any other solar max. The "Horrendous Space Kablooie Certain to Destroy Everything" headlines are just more sensationalism (though a few of the scientists are complicit in this, because they can get more funding that way).


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 Post subject: Re: My Faraday Cage
PostPosted: Fri Nov 19, 2010 9:26 am 
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Quote:
1) Build the wire. One end should be the 3 prong AC plug **only connecting the ground, leave the other 2 blank and ensure that you leave enough space between the wire and the terminal** and the other end should be the wing terminal. Be sure that the wing terminal end is properly crimped around the ground wire braids. Cover the end with electrical tape as best as you can.


Red or blue wire? That is really important around here.

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 Post subject: Re: My Faraday Cage
PostPosted: Fri Nov 19, 2010 9:52 am 
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Do you have a test protocol for verifying that your device attenuates RF?

I mean, the design seems pretty foolproof, but one thing I commonly see is that people don't have any way to /test/ their devices.

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 Post subject: Re: My Faraday Cage
PostPosted: Fri Nov 19, 2010 10:28 am 
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Thanks for the post! Welcome to the forum.

If you have some pictures that would be very helpful.

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 Post subject: Re: My Faraday Cage
PostPosted: Fri Nov 19, 2010 2:29 pm 
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crypto wrote:
Do you have a test protocol for verifying that your device attenuates RF?

I mean, the design seems pretty foolproof, but one thing I commonly see is that people don't have any way to /test/ their devices.



First thing that popped into my head was a picture of somebody crawling inside and waiting for the voices to stop... lol!

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 Post subject: Re: My Faraday Cage
PostPosted: Fri Nov 19, 2010 2:46 pm 
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Save some of that there aluminum foil for yer hat! :lol: Cool project. I play guitar so I learned about using Farady cages for the electronics inside to reduce hum and feedback.


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 Post subject: Re: My Faraday Cage
PostPosted: Fri Nov 19, 2010 3:47 pm 
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Hey guys, working a 24 on the ambulance so I figured I'd hop on here and reply to some stuff. I will try to get some pics up ASAP tomorrow when I'm off.
Bunsen, yeah like I said I'm not an expert in any of that by any means, all I know for sure is that everyone who has published documents has mixed feelings, and I'd rather be prepared for the worst. I've heard that CME EMP's would generally only affect the electrical grid, which I hope is the case, and yeah I would rather protect from a nuclear EMP as well, since one that is detonated 400mi above either coast of the U.S. would wipe out the electrical grid of half the country from what I've heard. And, in any case, my stuff is all nearby incase the zombies hit! You seem to know a bit about it, do you have any recommendations other than the foil tape for securing the seam around the lid?
Blacksmith, I hate to say it, but GREEN wire. :( I hope that's not too complex. I don't want to throw everyone off.
Crypto, from what I've read (again I am no expert) if you stick a radio or a low GHz portable phone and lose signal, you're good.
Lugnut, the voices DID indeed stop.

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 Post subject: Re: My Faraday Cage
PostPosted: Fri Nov 19, 2010 4:55 pm 
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Do you think coating the inside with plastidip would help at all?

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 Post subject: Re: My Faraday Cage
PostPosted: Fri Nov 19, 2010 5:00 pm 
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I had considered lining the inside with something for insulation, I'm not real sure how effective it would be. Some sources have said just place the items in a cardboard box, I don't know why they aren't saying to line the inside with insulating material. It's definitely something to think about though.

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 Post subject: Re: My Faraday Cage
PostPosted: Fri Nov 19, 2010 5:08 pm 
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Haha! All in good fun.

Maybe you could toss a cell phone in there then try to call it and see if the call connects?

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 Post subject: Re: My Faraday Cage
PostPosted: Fri Nov 19, 2010 5:16 pm 
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Decadron wrote:
I had considered lining the inside with something for insulation, I'm not real sure how effective it would be. Some sources have said just place the items in a cardboard box, I don't know why they aren't saying to line the inside with insulating material. It's definitely something to think about though.
you have to insulate the inside of the metal for it to work, if any of your items are touching the metal walls, it will not work,
putting your items in a cardboard box inside your setup would work just fine.
the plastic dip may be enough, but it is kind of thin and cardboard is likely better.
the ideal thing to line it with would be something a little thick, like 3/8 closed cell foam,


and the grounding of the metal box is not needed.
you do not need to ground a Faraday cage for it to work,
I just don't know why everyone keeps bothering to ground it and tell others that you need to,
it will not hurt it to ground it, but it is totally pointless.

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 Post subject: Re: My Faraday Cage
PostPosted: Fri Nov 19, 2010 5:22 pm 
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Lugnut wrote:
Haha! All in good fun.

Maybe you could toss a cell phone in there then try to call it and see if the call connects?


Here has been my dilemma. I haven't found a definitive sources saying what RF range we're talking with EMP. I've heard EMP in the VHF range was the most common, but I really don't know. Cell phones work from inside the container because from what I understand they are a UHF signal, and the galvanized steel is not adequate enough to block that strong of a signal. Certain other wireless devices with weaker signals, however only receive static from inside the container so I am convinced (enough) that everything should be safe.

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and the grounding of the metal box is not needed.
you do not need to ground a Faraday cage for it to work,
I just don't know why everyone keeps bothering to ground it and tell others that you need to,
it will not hurt it to ground it, but it is totally pointless.


Yes, I know the faraday cage works without grounding, but here is how it was explained to me. You rub your feet across the carpet, generating static. You are now energized just like the faraday cage would be following an EMP. You hold that energy until it is released somewhere. When you touch another metal object, it becomes your ground, the energy is now lost from you. That is the theory of grounding the faraday cage. Is it overkill? Sure, maybe, but I want to ensure that when I open it after shtf the residual charge isn't going to fry my components inside. This is how I understood it, anyway.

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 Post subject: Re: My Faraday Cage
PostPosted: Fri Nov 19, 2010 6:17 pm 
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I looked up the frequency range once, and can't find it again,
and it started at about 10 MHz for real power and got more power up till about 100MHz where it tapered off quick,
so there should not be anything over 150MHz,
so if I calculated that right, then you don't want more than a 6 inch gap electrically on your box,
and a 3 inch gap is about the most you would want to bother with, past that it is totally pointless.

the steel is not the best conductor, but most electronics are made to deal with some electrostatic zapping, and the steel will stop almost all of an EMP, so it should be just fine.

as to the grounding thing,
once you touch the metal to open it,
then you are at the same voltage as your electronics,
so you can't hurt it then,
so there will be no residual charge at all,
plus an EMP is not a DC field,
it is an AC field,
so it will not have any charge left over anyway.

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 Post subject: Re: My Faraday Cage
PostPosted: Fri Nov 19, 2010 6:48 pm 
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Thank you for doing some research on EMPs and not just posting a microwave oven. You've restored a bit of my faith in humanity. I can't tell you how infrequently that happens. :lol:

Good project and please do post some pics when you get a chance.

The frequency range on an EMP is: most power from 0-100mhz, still some (but much less) power up to 200-250 or thereabouts. Negligible amounts after that. I'd probably leave the thing unplugged and plug it in after an event. Just in case you get a ground spike (as sometimes happens with a nearby lightning impact).

I'd be interested to see how much power it attenuates at what frequencies, but don't know any easy way to test this... Bunsen?

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 Post subject: Re: My Faraday Cage
PostPosted: Fri Nov 19, 2010 6:59 pm 
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I know how to test how much it stops,
you put a receiver that checks the signal level (like something with an S meter),
then set up a transmitter on your test frequency and check,
I would likely just use a camcorder inside the setup to watch a hand held radio inside
then transmit a few hundred watts just outside it,
then repeat for each frequency range.

as you can tell, it is a pain to test it,
I will do it this weekend on 145MHz and 50 MHz because I have transmitters for that range.

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 Post subject: Re: My Faraday Cage
PostPosted: Fri Nov 19, 2010 7:47 pm 
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spacecase0, that's a great idea, though I don't have an S meter yet all I have is a handheld radio. Thanks everyone for the critiques/insight, lots of useful info.

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 Post subject: Re: My Faraday Cage
PostPosted: Fri Nov 19, 2010 8:56 pm 
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<edited out>


Last edited by ei8htx on Sat Nov 20, 2010 4:38 am, edited 1 time in total.

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 Post subject: Re: My Faraday Cage
PostPosted: Fri Nov 19, 2010 10:48 pm 
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ei8htx wrote:
I read somewhere, and it seems to make sense that, to build a simple EMP device:

1. Build an electromagnet using a 9 volt battery and a coil of wire
2. Wrap it around a (edit) (wrap the coil before you add the battery)
3. Add the battery
4. Light the fuse

I've been meaning to try this myself to test a faraday cage. Test it by placing some cheap device with a circuit (happy meal toy?) nearby, make sure your cell phone isn't in your pocket.

The concept behind this is pretty close to this:
http://en.wikipedia.org/wiki/Explosively_pumped_flux_compression_generator

My comprehension of this is that the electrons are unable to return to the ruptured return line to the power source. You're in a sense blasting the magnetic field away.


No way could you do this. (edit) are waaaay to dangerous. :wink:

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Last edited by Regulator on Sat Nov 20, 2010 10:26 pm, edited 1 time in total.

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 Post subject: Re: My Faraday Cage
PostPosted: Sat Nov 20, 2010 4:36 am 
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Regulator wrote:
No way could you do this. M-80's are waaaay to dangerous. :wink:


Perhaps so. I thought about that. I've played with fire and electicity enough to know how dangerous it is, and I think I could do it safely. However, I would feel horrible if I found out someone tried this and blew it up in there face by cooking the M80 with a hot coil.

There's some pretty gruesome images if you google m80 firecraker with safe search off.

If you wanna take out the quote I'll edit out my post.


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 Post subject: Re: My Faraday Cage
PostPosted: Sat Nov 20, 2010 10:31 pm 
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o.m.g.... I edited it out on your request ei8htx. I guess my prior post should have been in blue letters.

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 Post subject: Re: My Faraday Cage
PostPosted: Sun Nov 21, 2010 2:10 pm 
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spacecase0 wrote:
I will do it this weekend on 145MHz and 50 MHz because I have transmitters for that range.

ok, I transmitted with 100mW and the receiver inside the metal can had no issues getting a clear signal.
I did not bother to put a camera inside to catch the signal level as it was just on the edge of getting a clear signal, so now I just have to do the math to figure out how much attenuation that is.

knowing this much I would be unplugging the antennas and power cords on any radios inside the galvanized cans.

so i ran the test again with out the antenna on my receiving radio,
outside the metal can the 100mW transmitter maxed out the signal meeter
inside the metal can, 5W of transmitting power sometimes broke the squelch

so if you disconnect the power cables and antennas and put your radios in the metal can,
they should be ok,

I may just go back to using a cardboard box wrapped in aluminum foil,
I know that works very well.

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 Post subject: Re: My Faraday Cage
PostPosted: Sat Nov 27, 2010 5:07 pm 
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Here are the pictures I promised, sorry it took so long.

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The can before the ground is added

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The ground cable I built

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The tester, showing a properly grounded outlet

Image
The end that connects to the can

Image
The plug. Only the ground is connected, the others are blank.

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The toothed washer on the bottom lip of the can, washed with acetone and sanded to make it rough.

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The order of assembly when drilling into the can

Image
Showing the lip of the can from the bottom

Image
After assembly

Image
The finished product

The only thing inside right now is 2 handheld ham radios and a few packs of AA batteries, encased in a cardboard box for insulation. I plan on adding more batteries and more radios soon, as well as my holographic weapon sight. I'm working on a generator as well, which I plan on adding to the pile. I can't decide which energy source I want to go with yet.

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