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Thursday, November 29, 2012

Faraday Cage, How to Build and Use One

Original Article


First, what is a Faraday Cage?
A Faraday Cage is a simple container that by its design, shelters sensitive electronic devices from EMP Pulses (Electromagnetic Pulse) and Solar CME (Coronal Mass Ejection) pulses or emissions that can damage electronic circuitry.

At least that’s what it’s supposed to do! I’ve researched this topic for a while now and there are a lot of theories about the Faraday Cage but no tests using an actual nuke since the 1960’s but we were not electronic back then. So, there is much speculation and no hard and tested fact about what would happen with today’s electronic gizmo’s, electronic auto ignitions and our power grid using a real EMP nuke. However, the basic science is there and I’ll go with that rather than stick my head in the sand and hope for the best, so building a cage is worth the effort!

Inside the ‘Cage’ is where you will store your electronic devices like extra computers, cell phones, two-way hand held radios, ham radio, CB or regular am/fm shortwave radios, small flat panel TV, battery chargers, sensitive auto ignition parts or virtually any device the uses delicate electronic circuitry to operate.

The ‘Cage’ is simply a container sometimes made of metal wire mesh covering on all sides from the size of a shoe box to a 55 gallon metal barrel with metal lid.

Interior Insulating:
The inside of the cage must be electrically insulated so the electronic devices stored inside can not touch any of the inside metal surfaces otherwise an arc can jump to that device. Also the outside of the ‘Cage’ itself must be insulated from touching any surface that will ground it to earth. This includes, direct contact with earth, gravel, concrete floors or wire shelving that touches a concrete floor.


Building My Faraday Cage:
I used a 5 gallon steel bucket with a removable lid and a rim clamp and a 5 gallon plastic bucket that will line the metal bucket to act as an insulator.
  

I also used a lawn mower battery grounding strap to be sure there is electrical continuity between the lid and bucket.

  
As you can see here the plastic bucket almost perfectly fits inside the metal bucket.

  
I cut the upper rims off the plastic bucket

  
The plastic bucket without the rims almost fits all the way to the bottom of the metal bucket but not quite. The outside diameter was just a touch to large to fit perfectly.

  
I needed to reduce the plastic buckets diameter by a very small amount. The way I did that was to make a single cut down one side of the plastic bucket.


Now with the cut down the side of the plastic bucket I can overlap the excess plastic to fit all the way to the bottom of the metal bucket and have the electrical insulation needed to keep the electronics stored inside from touching the metal bucket walls. Simple and quick!

  
I ground off the paint where I will attach the battery grounding strap.
  

The attached grounding strap.

  
A quick coat of spray paint to prevent corroding of the connections.

   
Some of the electronics I store in the Faraday cage. Hand held radios, a “AA” NiCad battery charger and a portable CB radio.

  
Some more electronics, another NiCad battery charger and my 12 volt auto battery charger.

  
And the total of the electronics, 2 hand held radios, a hand held CB radio, 2 “AA” battery chargers, a 12 volt car battery charger and all my “AA” NiCad rechargeable batteries.


All I have to do now is put the lid on and my communications and electronics should be protected from EMP and CME pulses, I hope!


Summary:
The 5 gallon bucket has the advantage of fitting in the bucket storage shelving units so it takes no special storage requirements, just insulate it from the wire shelving.

Insulate the bucket or barrel from touching the ground including concrete.

A 55 gallon drum, if you have room for it, can easily hold all your sensitive electronics.