Friday, September 19, 2014

Making Your Own Faraday Cage

Not actually Erin.
Picture by KJ Photography
& is used with permission.
Last week, I reported that a coronal mass ejection (CME) hit the Earth. Fortunately for us, the resulting geomagnetic storm never went above G3 intensity, and the only effect I noticed was increased interference when talking to friends who used wi-fi to connect to a Google Hangout.

On this week's Gun Blog Variety Cast, I talk about the many uses a 5-gallon food-grade bucket has, and how you can get one for little to no money.

Today's post is an intersection of these two ideas, as I will be teaching you how to make a Faraday Cage -- something that will shield your delicate electronics from stronger EMP sources (like a G5 intensity storm) -- using the aforementioned bucket and common household items.

Special thanks to Chaplain Tim, Lokidude, and Scott Bascomb for helping me with this.

Items you will need
  1. 5-gallon plastic bucket. It doesn't need to be food grade -- save those for other uses! 
  2. A new roll of aluminum foil. In this case, the larger the roll the better. 
  3. Spray adhesive. 
  4. Rubbermaid or Tupperware boxes. Alternately, newspaper and spray-on Plasti-dip
  5. An extension cord you don't mind cutting up. 
  6. A hose clamp (or, in a pinch, electrical tape). 
  7. A copper rod several feet long and a soft patch of earth, OR a cold water pipe made from copper or iron. 
  8. Various tools

  1. Ensure that your bucket is clean. 
  2. Measure the distance along the interior of the bucket from the bottom to the lip, and write it down. (We will call this measurement A). 
  3. Measure the distance across the interior bottom of the bucket, and write it down. (We will call this measurement B). 
  4. Create the following formula: L=(2A+B)+2. This will give you a length, L, that goes down the inside of the bucket, across the bottom, and up the other side, with an additional inch sticking out on either end. 
  5. Measure and cut at least 5 sheets of aluminum foil to length L. 
  6. Apply spray adhesive to sheets (sparingly, and in stripes) and then glue them together. 
  7. Iron out any air pockets you find! The layers of foil MUST be as flat as possible. 
  8. When the last layer has been laid and glue sprayed onto it, place the foil inside the bucket and smooth it out. 
  9. REMEMBER: No air gaps within the foil. 
  10. REMEMBER: Leave an inch of foil on either side of the lip. 
  11. Repeat steps 5-10 to that all sides of the bucket's interior are lined. 
  12. IMPORTANT: No plastic should be visible on the inside!

Why are we doing it this way? The idea is to make an easily portable and durable shelter for electronics. If the foil is on the outside, it will be vulnerable to tearing. This method takes more time to set up but leaves you with a more rugged Faraday cage.

Why not use a galvanized steel trash can?Because steel doesn't conduct electricity as well as aluminum, and the idea is to create a path for the EMP around the electronics.

  1. Measure the diameter (distance across) the bucket lid. 
  2. Cut at least 5 sheets of foil to this length. (It's okay for the sheets to remain square.. we'll use that bit in a moment.) 
  3. Glue the sheets together as described above. 
  4. Glue the sheets to the inside of the lid, making sure that the foil covers any gasket the lid may have. 
  5. IMPORTANT: No plastic should be visible on the inside!

Items Inside
  1. Place any items you want protected inside sealable plastic containers, like those made by Tupperware or Rubbermaid. 
  2. Items which cannot fit inside plastic containers may instead be wrapped in newspaper and then sealed with the spray-on Plasti-dip. Make Sure all bits of newspaper are covered in a plastic shell. 
  3. If your electronic device will not fit inside the bucket, you will need to acquire a larger one. (Chaplain Tim suggests going to your local Army surplus store and seeing if you can find shipping containers for radios and other forms of electrical gear.)
  4. IMPORTANT: At no point should any electronics be in contact with the foil! Always make sure there is a thick layer of insulating plastic between the foil and the electronic device. 

  1. Carefully place the lid on the bucket and seal it without damaging the layers of foil. The extra inch of foil extending past the bucket's lips needs to make firm contact with the foil along the inside of the lid. 
  2. Take your extension cord and cut the plug off each end. Strip the plastic off to expose at least one inch of wiring. NOTE: extension cords have between 2 and 3 wires per cord -- strip and expose ALL of them. 
  3. Take one end of the cord and glue or duct tape the stripped leads to the foil. An ideal location for this is one of the surplus corners from the lid. 
  4. Wrap this end up tight. You do not want it to come loose! 
    • If you intend to ground your cage outside, take your length of copper outside and hammer it into the ground as deep as possible. 
    • If you intend to ground your cage to a cold water pipe, take your bucket over to the pipe. You may need to scrape the pipe to remove any rust, paint, or corrosion. at the place where you want the grounding to take place. 
  5. Secure the other stripped leads to the pipe or rod with a hose clamp or more duct tape.

If you want a more portable option:
  1. Buy a second extension cord. 
  2. Plug first cord into second. 
  3. Cut ends off as per above. 
  4. When storm has passed, unplug extension cords from each other. 
  5. Take bucket inside (or wherever you keep it). 

Your home-made Faraday cage is now complete!

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