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Old 21-10-2019, 12:46   #1
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Making a Faraday cage- anyone done it?

Morning 😊
We’ve been advised that simply bunging our electronic devices in the oven during storms won’t cut the mustard. It’s the glass door that is the issue allegedly.
Given that we are about to sail through both the SPCZ and the ITCZ we are keen to make a Faraday Cage.
Has anyone here done this?
Was it easy ?
Ta
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Old 21-10-2019, 12:55   #2
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Re: Making a Faraday cage- anyone done it?

Advised on theoretical grounds, anecdote, or data? I have built Faraday cages before and investigated how to do one on my boat but haven’t put it at the top of the priority list which I wouldn’t do without more than theoretical support for the value.
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Old 21-10-2019, 13:04   #3
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Re: Making a Faraday cage- anyone done it?

If I built one, it would be a bag of conductive fine mesh ( copper likely) in the bin just above my bronze dynaplate grounded to that plate. Anything that I wanted protected would be enclosed in a nonconductive waterproof plastic case easily found at Walmart. But the risk of death due to lack of a working gps or radio hasn’t made the anxiety radar yet to make the effort. In the event of an actual direct lightening strike I don’t think it would help. The mesh would vaporize I would think.
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Old 21-10-2019, 13:09   #4
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Re: Making a Faraday cage- anyone done it?

We have just used our SS oven. One reason we did not order one with a glass door
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Old 21-10-2019, 13:13   #5
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Re: Making a Faraday cage- anyone done it?

The microwave oven is a Faraday cage. How do you think it keeps the microwave energy inside so you dont cook?

The cage does not need to be grounded. The purpose is to allow the current to flow around the objects. Take an airplane as an example. They get hit by lightning all the time. The electricity just flows around the fuselage and they are not connected to any ground.

I would guess that even a metal mesh fruit holder that keeps bugs out would work.

So long as there is a path for some very high voltage and somewhat low current electricity to flow around the items you want to protect.

That being said. Lightning is a funny animal. Even a 'close' strike can set up a large voltage difference across a chip. This causes some erosion on the tiny wires in the chips and may contribute to a failure a week later. That happened to a TV. I saw the strike about 75 feet away and like 5 days later I went to turn on the TV and it did not turn on anymore.
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Old 21-10-2019, 18:18   #6
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Re: Making a Faraday cage- anyone done it?

Anyone just put a conductive wire mesh over oven glass door?
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Old 21-10-2019, 18:22   #7
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Re: Making a Faraday cage- anyone done it?

Hi all

Ok, what am I missing here please?

What’s this dust storm problem?


Are we talking about some sort of static electrical risk??


If so, why not just static protection bags?
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Old 21-10-2019, 18:25   #8
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Re: Making a Faraday cage- anyone done it?

Don't let perfect be the enemy of good. Using an oven as a faraday cage is easy and reasonable. Likewise using a microwave. Lightning is such a fickle beast when it hits near or on a boat that there is no telling what will and won't survive. I use the oven for backup gps and OpenCpn laptop. I also use heavy foil wrapping for backup autopilot controls.
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Old 21-10-2019, 18:32   #9
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Re: Making a Faraday cage- anyone done it?

Metal ammo cans like the us army uses make great Faraday cages and Come in various sizes. They are also water proof but will rust in asaltwater. Thx-Ace
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Old 21-10-2019, 18:52   #10
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Re: Making a Faraday cage- anyone done it?

http://en.blitzortung.org/live_lightning_maps.php
Try to avoid these areas
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Old 21-10-2019, 19:59   #11
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Re: Making a Faraday cage- anyone done it?

Making a Faraday Cage is dead simple. You need a conductive box (metal) with no openings. Very small openings are OK but the emphasis is on very small. The opening on the box (lid) must be electrically connected to the box. As posted earlier the box does not need to be grounded. All of this is basic science, is fully developed and is not conjecture.

Your oven with the glass is worthless, because the glass is not a shield.

Make a sheet metal box. Have the lid screw down with a few screws. It's not rocket science, and it is well worth having.
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Old 21-10-2019, 20:16   #12
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Re: Making a Faraday cage- anyone done it?

Quote:
Originally Posted by Pauls View Post
Making a Faraday Cage is dead simple. You need a conductive box (metal) with no openings. Very small openings are OK but the emphasis is on very small. The opening on the box (lid) must be electrically connected to the box. As posted earlier the box does not need to be grounded. All of this is basic science, is fully developed and is not conjecture.

Your oven with the glass is worthless, because the glass is not a shield.

Make a sheet metal box. Have the lid screw down with a few screws. It's not rocket science, and it is well worth having.
Yea the oven window fails just like the windows in a jet causes the lightning to jump inside and kill all the passengers.

A full metal box would be better, an oven is generally pretty effective. The paths of lightning and the damage done is unpreductable.
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Old 22-10-2019, 04:02   #13
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Re: Making a Faraday cage- anyone done it?

You can test your oven (conventional or microwave) by placing a radio or cell phone inside of it (don't turn oven on!), and checking for signal.
Can you call the phone in the oven? How is your radio reception once inside?
If you unable to make a call or get a signal, that would indicate that it’s blocking a pulse, in (at least) that* frequency range.

* Remember, microwave ovens (for instance) are not required to prevent ALL emissions, just the (2.45 Ghz) wavelength that they radiate on. Hence, a microwave oven does offer some protection against incoming radio waves, but it is most effective near 2.45 Ghz, less effective at other frequencies, and not absolute (even at 2.45Ghz).
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Old 22-10-2019, 07:16   #14
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Re: Making a Faraday cage- anyone done it?

Quote:
Originally Posted by Pauls View Post
Making a Faraday Cage is dead simple. You need a conductive box (metal) with no openings. Very small openings are OK but the emphasis is on very small. The opening on the box (lid) must be electrically connected to the box. As posted earlier the box does not need to be grounded. All of this is basic science, is fully developed and is not conjecture.

Your oven with the glass is worthless, because the glass is not a shield.

Make a sheet metal box. Have the lid screw down with a few screws. It's not rocket science, and it is well worth having.
Of course microwave glass doors have an embedded conducting mesh electricly connected to the rest of the metal shielding. But you're right, any metal box will do the job just fine, no need to get fancy.
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Old 22-10-2019, 07:24   #15
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Re: Making a Faraday cage- anyone done it?

Lightning has so much voltage that it might just blow through any cage. I would call any cage lightning resistant but not lightning proof. Remember that lightning has enough voltage to arc across miles of sky.
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