Electromagnetic Pulse: Protecting Your Components

Protecting your electrical appliances and sensitive electronic devices from EMP seems like a frightening and impossible challenge. But it’s not as difficult as you may imagine, and any protective action you take may guarantee functioning equipment after an EMP strike.

The damage that appliances and electronic devices receive from EMP depends of the conditions listed in Table 1.

Factors that Determine EMP Damage

• The strength of the incoming electromagnetic pulse.
• The distance from you to the source of the pulse.
• The angle of incidence from the source to your location on a rotating earth.
• The size and shape of the objects that receive and collect EMP energy.
• Isolation of appliances and devices from things that can collect and transfer EMP energy.
• Protection or shielding of appliances and devices.

Protecting Electrical and Electronic Equipment

You can protect your appliances and electronic devices by isolation and shielding.  You can disconnect them from electrical sockets. You can locate equipment away from long cables, wires, and antennas that can generate high current from an EMP. And you can put shielding over and around critical devices. The idea is to prevent an EMP pulse from getting inside appliances and devices to overload circuits, from changing electronic switch settings causing improper operation or temporary failures, or to prevent melting internal wires and components causing permanent failure.

In my research, I found a number of suggestions for minimizing the effect of EMP. Table 2 provides a shopping list of suggestions for protecting against EMP damage. Some have limited value depending on their use, but the ones involving isolation and shielding are the most helpful.

Suggested Protective Actions

• Unplug electronic devices when not in use.
• Unplug all electrical appliances when not in use.
• Avoid leaving components such as printers and scanners on “standby” power.
• Use short cable runs.
• Install induction shielding around components.
• Use components with self-contained battery packs.
• Use Loop antennas.
• Ground properly and where appropriate.
• Use a separate ground for each device or instrument.
• Connect all ground wires to one common ground point.
• Use smaller devices that are less sensitive to EMP.
• Install surge arrestors. Type 6 “snap-on” ferrite suppressors can attenuate a spike.
• Install MOV (metal-oxide-varistor) transient protectors on portable generators.
• Use UPS equipment to protect electronics from an EMP spike.
• Use blocking devices.
• Braid or twist wire runs so they cancel induced voltages.
• Use hybrid in-line protection devices (e.g., band-pass filter followed by lightning arrestor).
• Keep sensitive appliances and devices away from long runs of cable or electrical wiring, antennas, guy wires, metal towers, corrugated metal, steel fencing, railroad tracks, and aluminum vehicle or aircraft bodies. (There’s no need to attract a spark flashover.)
• Consider burying cable runs underground in shielded conduits.
• Construct one or more Faraday cages.
• Wrap solar panels with aluminum 20 mesh wire hardware cloth.
• Cover larger items with copper or bright aluminum screen.

A standby generator is not likely to be damaged by a solar storm but EMP can damage sensitive electronic controllers so shielding is appropriate. A portable generator probably won’t be affected by EMP but installing MOV transient protectors across one of the 120V outlets on the generator should provide added insurance protection. An uninterruptible power supply can be helpful.  If an EMP occurs, the sharp spike could destroy the UPS, but it would likely protect connected devices and components.

Constructing a Faraday Box/Cage

Shielding can be accomplished using a Faraday cage made from a metal trash can, metal filing cabinet, metal ammunition box, or an old microwave with the power cord removed—any metal container that has a continuous surface without gaps or large holes. Tight-fitting and locking-lid metal trash cans are excellent. Figure 1 and Figure 2 show containers that I actually use as my Faraday cages.

Fig. 1 – Faraday cage using a metal trash can.

Fig. 2 – Faraday cage using a metal storage box.

Place a non-conductive material (cardboard, wood, paper, foam sheets, or plastic) on the inner sides and inside top and bottom of the Faraday cage to keep the contents from touching the metal of the cage. In addition you could wrap each item to be protected in bubble wrap or plastic. Everything inside should be isolated from everything else and particularly from the metal container.

What to Place in Your Faraday Cage

Place anything you suspect of being sensitive to EMP inside your Faraday cage. Then place other items inside that you think are O.K. but want to provide added insurance that they, too, survive the pulse. As Table 3 shows, these items could include:

Items to Keep in Your Faraday Cage

• Extra batteries
• Battery-powered AM/FM radio
• Battery-powered short wave radio
• Portable CB transmitter-receiver
• Small portable television
• LED flashlights
• Solar battery charger
• Inverter
• Deep cycle 12V solar battery
• Computer (notebook or laptop)
• Cell phones / iPhones
• Electronic tablet –iPad, Surface Pro, etc.
• LED and CFL light bulbs
• Charging cords for cell phones and tablets
• Calculator
• Wind-up watch (no batteries needed)
• Wind-up clock (also no battery needed)
• Game box

Many things will survive an EMP strike, but you really can’t be sure which. A low-level EMP from a solar storm may have no effect, but it could take down the power grid. So be prepared. And consider backing up all your computer and business data on CDs and DVDs .The Cloud may be gone or not available for some time when power goes out.

Small objects with little or no antenna or a wiring harness are least susceptible to EMP damage. A battery-operated radio shouldn’t be damaged unless the radio is setting near an antenna, electrical line, tower guy wire, railroad track, or high voltage power line.

If an EMP warning is issued, immediately unplug all unused electrical appliances and lights. You could also open breakers and power switches to isolate your home wiring circuits from EMP on the power grid. Several reports stated that disconnecting electrical and electronic equipment from the power grid can significantly decrease the potential damage from an EMP strike. Finally, perform a mental inventory check to be comfortable that everything that needs to be shielded is properly protected.

If no warning is received, and all you see is a bright flash and power shuts off, you’re on your own. We never know when one will occur or how severe an EMP will be, but whatever preparation and preplanning you did before the strike will define how well you survive in a post-EMP world. Be prepared, and be safe.

Want to know more? Check out these related articles:

• EMP Incoming! | What to Expect from an EMP
• EMP Effects On People | Electromagnetic Pulse
• EMP-Proof Electronics | What You Need To Know

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Editor’s Note: This post was originally published on June 25, 2015, and has been updated for quality and relevancy.