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Tuesday, October 27, 2009

Sheilding Your Electronics from EM Radiation Using the Faraday Cage

As I discussed in many other posts, Gamma Rays emitted from radioactive fallout particles and the initial blast itself produces intense electromagnetic radiation. Electromagnetic radiation as the name says it, produces electricity. This electrical current will follow all conductive material with its extremely high voltage. To large electronics such as large electrical motors and power plants, the damage is minimal. However, to electronics that use small motors (such as hard disks) and microprocessors (such as computers, phones, and cars) this can be lethal. The high voltage fries the processor and circuits which not only disables the electronic device but also permanently destroys it. A car that was subject to a electromagnetic radiation will results in a fried Engine Control Unit (ECU) and Ignition. On modern cars the damage is much worst since it uses more electronics. A rule of thumb is that any thing containing a circuit board will most probably be fried. The real annoyance is that even if the electronic device is turned off or disconnected, it will still fry. This post will address the issue of shielding your electronics against electromagnetic radiation using a Faraday Cage.

A Little History Before We Start:
Michael Faraday Cage BoxThe principle of using a conductive material to shield the interior from current was first observed by Benjamin Franklin in 1755. He conducted the first experiments using a metal can and a cork ball. However, Franklin did not popularize his discovery as it had little use back in the 1700s. It was not until 1836 that Michael Faraday realized full sized experiments with an electrostatic generator. He discovered that the metal cage distributed the current on its surface and effectively shielded the inside contents. The discovery was thus named after him.

The Faraday Cage:
As outlined in the precedent section, the Faraday cage consists of wrapping the sensitive object in a conductive material leaving no gaps. Getting a little scientific, there may be holes in the shielding material as long as they are smaller than the radiation's wavelength. The general rule is to try and not have any holes, all windows and ventilation openings may be covered in a tight metal screen.

Sheilding Your Electronics From Electromagnetic Radiation:
Faraday Cage BoxThe real annoying fact with EM radiation is that it follows all conductive materials including wires. This means that even if you would make a metal box around your computer, it would still fry. The first path the EM radiation would follow is the utilities electrical wires. The only real solution to shielding objects from EM radiation is to make sure everything is contained withing the box and no wires exit it. Such a a setup can be seen if for example you put your laptop in a metal box, the complete setup is enclosed, therefore protected. Shielding a desktop computer will still be effective up to some point even if it is connected to the utility. The best bet is to keep a spare computer, backup hard disk, cellphone, etc. Put these spare objects in a Faraday box disconnected, and take them out if something happens to your main computer. It should be noted that there is no limit to the size of a Faraday box, whole server rooms are normally shielded. My personal favorite to make a full size Faraday cage is a boat. A steel boat already has metal hull and if the deck is shielded then you have a complete Faraday cage. Windows and ventilation shafts can be shielded using a metal mesh, the more layers, the better the shielding.

Remember that the biggest Faraday cage is the earth's magnetic field which protects us from EM radiation in space. Keep reading for future posts!

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