Protecting Electronics with Faraday Cages

I have done a lot of research on Faraday Cages and feel like I am finally beginning to understand them. A Faraday Cage is designed to protect electronics from EMP (electromagnetic pulse) that can be created by high altitude nuclear explosions or solar storms.  See  previous posts on EMP. Some simple examples of Faraday cages are shown below.

  • A booster bag (shopping bag lined with aluminum foil) acts as a Faraday cage. It is often used by shoplifters to steal RFID-tagged (radio-frequency identification) items.
  • The cooking chamber of a microwave oven is a Faraday cage, made to contain the RF (radio-frequency) signals of the cavity magnetron which cooks the food.

The other day I made a couple of small ones to protect a few small radios and other items.  I started out by removing all the batteries to protect the radios from corrosion caused be battery leakage.  Then I removed any antennas that were removable, without damaging the equipment.

Next the radios were placed individually in zip lock plastic bags which were then closed.  The radios were then wrapped in aluminum foil.  Be careful to completely cover the radios leaving no gaps in the foil.

Next I took two 50 cal ammo cans and lined them with styrofoam.  The foil packages were sealed in one gallon size zip lock bags and placed in the ammo cans.  A piece of styrofoam was then placed over the package so that the radios were completely insulated from the metal of the can.

Based on my research I do not feel that this needs to be grounded and will effectively protect the enclosed items.

See also  How Levees and Dam Failures would Affect Us

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18 thoughts on “Protecting Electronics with Faraday Cages”

  1. Concerning your post about Faraday cages made from ammo boxes, I was wondering what kind of research you did about the use of styrofoam as an insulator inside the can. I have no practical knowledge in this area but draw from past experiences with styrofoam. I have received several packages in the mail and by freight companies which have used styrofoam peanuts as shock absorbing packaging material. Every time I fish out the package from inside the peanuts, several of them cling to me and my package as it is withdrawn. Quite a bit of static electricity involved there. Is styrofoam the best medium for use as an insulator? I would imagine corrugated cardboard cut into the proper dimensions would be as, if not more, effective as a shielding from electricity when lining a metal box.

    1. Ammo cans have a rubber gasket under the lid so that theya re water tight … this keeps the lid from making metal-metal closure and allows EMP leakage … it is not a good faraday …
      maybe if the can were wrapped with tin foil … ?

  2. Good Article. What you have done will definitely provide a pretty good level of protection. Especially with the layered protection any induced current will be small enough not to matter. I am inspired actually, will have to do some of this myself.

    Small niggle, I would ground the ammo can if you can do it easily. If you are a geek and look up the physics of EMP you will see that the purpose of the ground is just to shed excess electrons (or pick up a few if needed). That way when you pick it up after an EMP, you will not get shocked. So, I would just note that if the worst happens, ground the can before touching it.

  3. This is most definitely inspiring. I’m somewhat young, and when I heard about EMP’s it scared me so I began to look more into them via the internet. I came across some great blogs that were informative, and I then became aware that there is a way to protect your things- with a Faraday Cage. This blog is very nice, thank you. I just wanted to share with you a Radio Blog that I have also come across. They have a Radio Show on the internet every Wednesday. Next week they are going to have Randy Tolman on their show as a guest. You may have heard of him. He’s going to be on there talking about different types of Faraday Cages. I really think you should check it out, I think it’s going to also be very informative.

    Thanks again for the great post on this!

  4. Michael MIller

    Ammo Can – I think I will use the ammo can for spare parts/chips/etc. Thanks! Those things are freaking useful! The mormons sell great silica gel packets. You can get like 8000? for like 125 bucks. 🙂 Great for ammo cans and just about anything else you can imagine. Vacuum sealed tools. Gotta love high humidity.

  5. Pretty nice post. I just stumbled upon your blog, I wanted to say that its really well written Ive enjoyed browsing it. In any case I’ll be subscribing to your feed and I hope you write again soon! But not on my iPhone as the layouts a bit off!

  6. every month I get meds through the mail and it comes in a really thick high quality tight sealed styrofoam box/cooler. Can I use JUST this cooler as a faraday cage or do I need ammo boxes and/or metal trash cans etc…? If I can JUST use the cooler or not can someone let me know. I’m in Los Feliz area(Hollywood Hills) Los Angeles CA, which is the best list or web site to go to to buy or print a list of and go to a reputable store(if you know of one thanks and good luck ,name address phone #)..********ALSO if anyone in the Los Feliz area(90027) would like to talk about teaming up in the JUST IN CASE future. I have a large house high on a hill(for the high ground asset until our team decides if we bug out). I’m a C.C.T/E.M.Ta,so I have medical training. Also take into account my armageddon partner has over 35 pistols to long guns and tons of ammo and tools.

    1. The cooler you talk about may work as a Faraday Cage if it is inside a tight metal container or wrapped in aluminum foil. The suppliers that are listed on the right side of this blog are ones I would recommend. I have no experience with stores in your area. As far as meeting with some one I strongly suggest that you and they consider all the aspect of operational secrecy and be careful with the information you share.

  7. We have a cat so I always have plenty of 35 lb litter tubs laying around. I take these, wrap them completely in foil and use aluminum foil tape to secure the foil and put my electronics in. If I need to open it and add something inside, I just need to slit the foil around the flap at the top, then seal it back up again with the foil tape. From everything I have read, this should be effective.

  8. Ammo cans have a rubber gasket which can let the emp inside. To the emp rubber gaskets are
    no different than air. Encapsulating with metal
    without a single pinhole or non metal gap filler is the only sure way.

  9. I’m hoping, as a Ham Radio Operator, that we might get some warning, if just a couple of minutes, that an EMP may occur. In this case I have planned to quickly unscrew antenna and power connectors from my transceiver, wrap a small couch blanket around it and set it inside athe washing machine, dryer, oven, microwave oven, even refrigerator. That way my radio would be insulated from the container and inside a grounded metal container. Maybe not the best Faraday shield, but a quick fix when seconds count. Replys welcome.

    1. I forgot to add another step to my plan above which I’d included in my original notes. I would suggest to keep a large roll of aluminum foil near the radio bench so to quickly wrap a couple of turns around and crinkle the edges for a complete seal. Then the blanket wrapped around that and into the major appliance of one’s choice.

  10. with this ammo can theory in mind, it would make sense that one could use one of the Stack On metal cabs as long as a person did a few alterations. Door gasket, tape the corners with military grade duct tape and the line it with styrofoam insulation. a long piece grounding rod from the local electric supply then finish it of with some….neoprene wrapped around the inside for both cushion and static electricity…..Maybe it’ll work…I’ve never been blown up before so I’m tossing an idea.

  11. Jeffery DeWeese

    I’m making some ammo can faraday boxes. I have a big roll of 3’ wide cork sheeting. It’s under 1/8” thick. I am wondering, as long as I cut it well to completely line the box, will one layer suffice or should I really go 2?? Or more?? Also, I’ve heard SO many times, people talking about the gasket. I really believe that instead of everything I’ve heard people doing, leave it as is. Once closed, use some good 2”-3” wide aluminum tape. Seal off the gap & the hinge & move on. Am I wrong??

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