What is a Faraday Cage & How Does it Work?

A Faraday cage is a special built enclosure which can be used to shield and protect electronics from EMP and solar flares.  Faraday cages work by providing a conductive outer layer constant voltage, preventing excessive electric fields from damaging and frying electronic devices.    Faraday cages can be made in any shape or size, so long as it as it forms a complete enclosure. Michael Faraday is the inventor of this special electromagnetic discovery in 1836. Though almost 100 years earlier, Ben Franklin had already observed the effects. When used for defense (electromagnetic pulse defense, or to protect from solar storms), the cage can prevent the diodes of electrical devices from overloading. A Faraday cage works to thoroughly cancel the threatening field. For example, metal car will protect the occupants inside while being struck by lightning; and an airplane or elevator will do the same. Some suggest the best way to think of a Faraday cage is a hollow conductor, or a conductive container. Cellular phone dead zones are frequently Faraday cages.

It should be noted that traditional solar flares (or coronal mass ejections) usually will not be capable of overloading electronics, as long as a surge protector is in use; however, some experts have suggested the sun will be producing many more solar flares, perhaps even thousands more than ever before.  Some superflares will be extremely threatening to our electronic devices. In fact, the University of Warwick recently discussed on Eurekalert.org the Sun’s potential for flares 1000 times greater than ever recorded.

A compass will still work inside of a Faraday cage, as slow varying magnetic fields will still pass through.

Guide to Building your own Faraday Cage at Home

Faraday cages benefit from creativity, and can be constructed a number of ways.  Some quicker constructions involve wrapping a pre-existing non-conductive structure, such as a shed or a fallout shelter, with a conductive material.  For the quickest cage, aluminum foil is commonly used.  Only a few layers are required (technically only 2 layers of thick heavy duty foil) to cancel the damaging EMP fields and neutralize the threat; however, if aluminum foil is the only option due to an emergency, time-sensitive situation, it is wise to use a few extra layers to reduce leakages (having a few rolls of heavy duty aluminum foil is an excellent idea for an emergency).  It is okay to have holes or small gaps, as long as the holes or spaces are very small (millimeters) in size, they will not be large enough to leak any of the damaging field through.  Some people suggest using conductive tape to cover the gaps and holes.  A conductive metal mesh grid will work too, as long as the holes are only millimeters in dimension.

What Metal Should You Use for a Faraday Cage? 

Silver is the most conductive metal, however, it is not economically viable for a Faraday cage of any reasonable size (Even a shoebox size Faraday design would be unreasonably costly to wrap in silver).  This is why aluminum generally becomes a good, quick choice, and purchasing the right heavy duty aluminum foil, provides the conductivity and durability required, while still allowing the flexibility necessary to wrap nearly anything.  Remember, when using aluminum it is best to wrap the cage or device multiple times.  It can even be used to wrap the device itself directly for an extra layer of protection. Copper is also an acceptable metal frequently selected due to the fact it is drastically cheaper than silver (it is still far more expensive than aluminum, but still reasonable and a bit more durable). Copper provides much better conductivity.  Many commercial Faraday cages are made of copper or brass. The better material will better resist penetration.

Construction tip:  One of the most important things to remember when making a Faraday cage, box or container, is to ensure gaps and leaks are extremely small.


Pre-existing Faraday Containers in Everyday Life

It is true that there are a number of containers that are very common in a household or grocery store which can be turned into quick Faraday cages. A few examples of everyday Faraday cages include:

·         metal coffee cans

·         metal ammunition cans

·         metal computer tower cases

·         metal convectional and traditional ovens

·         metal refrigerators, dryers or washing machines

·         microwaves

·         grills

·         and metal garbage cans


The truth is, although many people will argue a Faraday cage must be grounded, a Faraday cage does not need to be grounded.  As long as the metal used is conductive enough with minimal leaks, it will work to prevent electromagnetic field radiation from affecting electronic devices inside.  For example, anti-static bags are not grounded.  Commercial anti-static bags employ Faraday cage technology, are available in a variety of convenient sizes, and provide excellent EMP protection. Some bags are better than others and will protect against more capable EMP threats, while some will not provide enough protection. The trick is to look for an anti-static bags which are thick (such as Mil PRF-81705, though a number of bags will work).


How to Use a Faraday Cage

Remember, the Faraday cage does not need to be grounded; it just needs to be an appropriate layer of conductive material.   However, if a cage is grounded, the ground will receive the charge instead of charging the container’s outer face.  A properly constructed cage with no leakage will work to keep unwanted charges out of the container, as well as it would work to keep charges inside of the container.  For example, USB, coaxial and other screened cables work to shield the cables internal conductive wires, preventing anything from leaking out, as well as external electronic noise from getting in.  In its most basic principle, a conductive container is capable of creating an opposing electric field that effectively cancels the external threatening field, the inside of the container retains a neutral charge.

Other Uses for a Faraday Cage

The Faraday technology has been used to solve a variety of needs throughout time since its conception.  They are frequently used in science to reduce electronic noise, especially in analytical sciences recording sensitive measurements.  And in modern times, in 2013 a Faraday cage was constructed in the Sistine Chapel to shield any electronic bugs from listening in during the Vatican’s papal conclave to elect the Pope.  Shoplifters commonly use Faraday cage technology by lining bags with thick foil to prevent RFID tags from signaling the alarm (by placing items with the anti-theft tags inside a “booster bag” before leaving the store).  Medical rooms containing any x-ray or radiation equipment (MRI rooms for example), are usually created as Faraday cages to prevent any surrounding radio frequencies (RF) from interfering with and compromising the scans.


Tags: Faraday cages protect against solar flares, Faraday cages protect against EMP, how to build your own Faraday cage, building a Faraday cage, how to make a Faraday cage, how does a Faraday cage work, homemade Faraday cages

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