Converting A Microwave Oven Into An EMP Resistant Enclosure

Electromagnetic Pulse, or EMP as it is more commonly called, is a natural or manmade event causing over voltage conditions due to high power microwave electromagnetic radiation exposure in electrical and electronic equipment. This over voltage most commonly burns open semiconductor junctions and coils of wire. It happens in the smallest electronic watch all the way up to the power grid. Severity can be mild, such as a close lightning strike, or severe enough to destroy every motor, transformer, computer, and for all practical purposes anything else electrical or electronic in a wide area. If you are at ground zero for an EMP pulse the following may, or may not, save what you have stored in it. High level microwave energy, directly radiated over a small area (ground zero), means you cannot predict effects with any degree of certainty. What survives, survives, and what doesn’t, doesn’t. Only extreme measures with sophisticated engineering will protect devices at ground zero to any degree of certainty. The farther you are away from ground zero, the less these effects will be. This article is for the home DIY’er who wants to protect communications and other necessary post event electronic items from the effects of EMP in an economically repeatable way.

This is a common microwave oven “liberated” from my place of employment. It started burning holes in the cavity and replacement was cheaper than repair. It is perfect for our project. As it sits it is useless, but with a bit of work and aluminum duct tape it will make a good, inexpensive, EMP resistant enclosure.

First UNPLUG the power cord. Now cut the cord off and save it for another project. You will next take the cover off of the oven by removing the necessary screws. I found two Torx security screws on mine. You can purchase an inexpensive set of ¼” security screwdriver bits from places like Harbor Freight. I feel they are well worth the price. One thing I have to caution you about is the sheet metal used in ovens. I found that the edges on this one were VERY sharp. Be extremely careful as most ovens have old food debris in them and getting that in a cut is not a good thing.

This shows the bulk of the internal workings of the oven. It also shows most of the tools I used in the process. Leatherman tool, Phillips screwdriver, ¼” drive screwdriver, and ¼” bit set. The only other tool I used was a pair of scissors for the aluminum duct tape. Now the hard work starts. First, look in the bottom right hand corner. There is a silver component that looks like a can with two red and one white wire coming out of it. With the POWER REMOVED AND POWER CORD CUT OFF short all of the terminals on top together using an insulated wire, screwdriver, or alligator clip lead. This is a capacitor and can hold a substantial electrical charge. It may pop and spark when you do this, but that is good! This means that IF there was a charge, it is now discharged. Do it a few times to be sure. IF, and I mean IF, something in the circuit was broken, it MAY have a charge. In a normally working circuit, it should discharge itself in a minute or so, but always make sure by shorting first.

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