DIY Faraday Cage for important electronic devices.

[BaldrickCunningPlan]

Hi. I'm new to the forum. I'm ex army, been "Prepping" for years insomuch as I have always had reserves of water, food, fuel, medicines etc and solar / generator to get me by as and when it goes tits up. My mates take the p155 but they were queuing in the rain for dog food and toilet paper during the covid scam while I wasn't so I'll carry on being prepared in the hope that I can relax when the SHTF.

I'm an I.T. Engineer by trade and I have a a massive digital archive of important documents etc (Including a massive prepping ebook collection) so what I'm now looking at is a Faraday Cage. Something to store really important electronic devices like USB Hard Drives and laptops that would survive an EMP from something like a massive solar flare. Obviously if the EMP were to come from a nuclear bomb, that would be a different matter and I'm not building a bunker but solar flares happen and they're not predictable hence the question.

I understand the basics and it doesn't seem like rocket science but before i crack on and do it, I'd appreciate any comments or advice from anyone who has already been down this route.

TIA. Baldrick.

[pseudonym]

Plenty of small sized DIY videos on you tube:

https://www.youtube.com/watch?v=8-dEDCsYTKM

https://www.youtube.com/watch?v=2s8CpK6F7UM

https://www.youtube.com/watch?v=sBl552KdLbY

hth

[jennyjj01]

... so what I'm now looking at is a Faraday Cage. Something to store really important electronic devices like USB Hard Drives and laptops that would survive an EMP from something like a massive solar flare.

Hi and welcome.

No help from me

I don't believe that USB sticks or small disconnected electrical devices will suffer any harm from solar flares or even EMP bombs. They induce current into long conductors such as power and phone cables. They probably induce current down antenna cables. But self contained and disconnected devices???? I don't buy it.
Look at real world shtf situations such as Gaza and Ukraine and note how thousands of drones, rockets and bombs can impact on our devices Isn't that the greater threat.

Meanwhile, ChatGPT disagrees with me and does want to help you...

Are home made faraday cages really going to be useful in protecting my electrical and electronic devices?

ChatGPT said:
Homemade Faraday cages can be useful in protecting electronic devices from electromagnetic pulses (EMP), radio frequency interference (RFI), and electromagnetic interference (EMI)—but their effectiveness depends on construction quality.

When Can a Homemade Faraday Cage Work?
EMP Protection (e.g., solar flares, nuclear EMP):

Needs full enclosure with conductive material (e.g., aluminum foil, metal containers).
No gaps, as even small holes can let in electromagnetic waves.
Devices should be insulated inside (e.g., wrapped in a plastic bag or placed in a non-conductive box).
RF Shielding (e.g., blocking cell signals, Wi-Fi, Bluetooth):

Simpler constructions (e.g., metal mesh or foil-lined boxes) can be enough to block RF signals.
A quick test: Put a phone inside your DIY Faraday cage and try calling it. If it rings, the cage is ineffective.
Common DIY Faraday Cage Setups
Metal Ammo Cans or Toolboxes – Effective if sealed properly and lined with insulation inside.
Aluminum Foil Wrapped Boxes – Work well for small devices but require multiple layers.
Metal Trash Cans with Lids – Good for larger storage if the lid is tightly sealed with conductive tape.
Wire Mesh Enclosures – Work for some frequencies but require fine mesh to block high-frequency waves.
What Won’t Work?
Thin or loosely wrapped foil with gaps.
Cages that are not grounded properly (if grounding is necessary).
Containers with poor seals or large openings.
Verdict:
Homemade Faraday cages can work if built correctly, but they are not foolproof against high-intensity EMPs unless carefully designed. If you’re serious about EMP protection, consider commercial-grade Faraday bags or enclosures designed for high-level shielding.

So..... Ammo boxes?

[hobo]

So..... Ammo boxes?

That’s what I use, just for small stuff like Anker power bricks, usb lights and radio. Whether I need to or it will work I don’t know!

[pseudonym]

So..... Ammo boxes?

That’s what I use, just for small stuff like Anker power bricks, usb lights and radio. Whether I need to or it will work I don’t know!

Put your mobile in, ring it from your landline if it rings there might be a gap in the seal, if not it works.

[PPrep]

With any kind of Faraday enclosure, the seal is all - important. The flap on envelope type Faraday bags needs to be well secured. Such bags can leak with a lot of use as the conductive material can wear.

I've used a couple of 5l paint tins (new and unused from eBay), but found I needed to remove the varnish from around the lid and its mating surface on the tin to ensure conductivity. These I lined with cardboard. A bit expensive at around £8.50 each, though.

Biscuit and similar tins can be used as well. Note that aluminium, and some copper, tape has non - conductive adhesive.

[hobo]

Thanks pseudonym, it works!

[GeraldTheBonzai]

Would recommend a faraday pouch, if you have keyless entry on your car. Less to protect against an EMP and more to stop your car getting pinched.

[pseudonym]

Thanks pseudonym, it works!

You're welcome, now to scale it up

Wonders if a microwave/oven/fridge would do the same thing (unplugged of course)

[jennyjj01]

Thanks pseudonym, it works!

You're welcome, now to scale it up

Wonders if a microwave/oven/fridge would do the same thing (unplugged of course)

The mesh on microwave doors is tuned to microwave frequency. Other frequencies would pass through.
Fridge door rubber seals would let radiation pour in