# Faraday cage as light as possible to protect from lightning

1. Jun 10, 2014

### stevan

if I build a faraday cage just to protect device from lightning or other electrostatic source (not electromagnetic pulse), and I need that as light as possible...
I will build it using a mesh to make it light..

now, how large the mesh' holes is allowed ?
is there any calculation for this purpose ?

what in my mind is: I can use mesh with holes as large as possible...as long as the distance from electrostatic source to the mesh' wire is shorter than the distance from electrostatic source to the device I want to protect...

is it right ? or there another thing I need to consider to decide the holes size ?

Last edited: Jun 10, 2014
2. Jun 11, 2014

### Staff: Mentor

Passengers in planes seem to be protected, given that planes are frequently struck by lightning. And they do say that people sitting in cars are safe, and those windows are relatively large areas of non-metal. So from this you could probably draw some conclusions.

I do not know how much current your mesh should be capable of carrying, though.

Good luck!

3. Jun 11, 2014

### Delta²

Something tells me the larger the holes are the less effective the cage will be in neutralizing the external electrostatic field. Human body may be robust to small to medium electrostatic field, but this might not be true for the various devices.

An idea that crossed my mind which maybe naive afterall but, why dont you make a box covered entirely by aluminum foil (which i believe is quite light) and put the device inside? Or you need big holes anyway for some other reason related to the device that is gonna be shielded?

4. Jun 11, 2014

### stevan

maybe at normal condition, plane and car can protect from lightning, I think because the car/plane body have shorter distance to the lightning source than the passenger inside....so, what if the passenger stick their head to the window when the lightning struck ? also, I think because the window covered with rain water (good enough as conductor), so more difficult for the lightning to enter ?

yes, I also need the holes so the air can flow through the cage..
As I know, if the faraday cage is used for electromagnet pulse protection, the hole is depend on the frequency of the electromagnetic...higher frequency need finer hole mesh to protect from.....but in this case just to protect from static electricity...
maybe some one know how calculate the maximum hole size that is still safe enough for a faraday cage....

If I only make a simple frame like this one for the faraday cage, I don't think it will be effective..

Last edited: Jun 11, 2014
5. Jun 11, 2014

### davenn

No nor do I.

Have a look at some of the Faraday cages used by guys experimenting with the EHT Tesla Coil generators. They use a mesh where the holes are generally not more than a few inches square

cheers
Dave

6. Jun 11, 2014

### stevan

yeah right...I saw them use chain mail...that have holes very small..and the tesla coil always far enough from the cage

7. Jun 11, 2014

### Staff: Mentor

I think your biggest issue will be the thickness of the mesh, not the size of the holes. The current in a lighting strike is VERY high, and I'd bet you'd need very thick conductors to avoid destruction and breakdown of the cage. The lightning protection rods I've worked around typically have grounding cables about a quarter to a half an inch in diameter at least.

8. Jun 11, 2014

### stevan

yeah right, I will need thick wire for this..and I think, if I know the largest hole allowed, I also can reduce the requirement of thick wire