Stormy (Nov 22 2010)


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Profile KWSN THE Holy Hand Grenade!
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Message 1051121 - Posted: 25 Nov 2010, 16:41:52 UTC - in response to Message 1050845.



If SETI@home comes up with a spare oh.. half million to a million, I am sure they could get the same hooked up. But they would definately need a bigger closet.



... more like storage basement, just for the batteries... I once saw the SF Opera House's Emergency lighting battery system, (12v, I think) the batteries were under the center Orchestra section and were about 2 feet tall - the room (estimated...) was about 150x250 feet. The batteries looked like they were original - 1932 (... and this was in 1981!...)
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Message 1051137 - Posted: 25 Nov 2010, 17:24:53 UTC - in response to Message 1051121.

They make the batteries different sizes. The ones you describe would keep the project running for many many days without a backup generator, and are usually supplemented with a backup generator. The point was, SETI will not be getting such a setup any time soon.
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Message 1052243 - Posted: 1 Dec 2010, 15:58:36 UTC
Last modified: 1 Dec 2010, 16:11:52 UTC

If the recent storm might have caused problems due to atmospheric effects rather than conductor channeled effects, has anyone considered putting up a light mesh screen around the closet? A simple Faraday cage can be really cheap.

If one were to acquire a few hundred square feet of household window screen (making sure to get metallic screen, not plastic) then put the servers on thin flooring of conductive metal, then get an old style shower curtain rod that hangs off the ceiling, and make a curtain out of wire mesh, then put more mesh on top over the hole in the middle.

Viola, Faraday cage on the cheap.

There are others here with much more practical experience than I have with electronics protection. Comments and suggestions on how to improve this idea on the cheap would be great.

**EDIT** If a cheap Faraday cage does not prevent computer issues after close lightning strikes, then the UPS's might need to be checked on again. It might also be a good idea to make sure that all of the server equipment grounds to a common ground. Having multiple grounds of different effectiveness can cause charge to move through your equipment rather than go to earth.

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Message 1052268 - Posted: 1 Dec 2010, 18:15:32 UTC - in response to Message 1052243.
Last modified: 1 Dec 2010, 18:17:07 UTC

Sorry, I knew I forgot something. If the system is grounded into the frame of the building housing it in more than one place, there might not actually be a common ground. A lot of people tend to think that all of the metal girders and whatnot in a building are all one conductor. For the most part, they will be, however not always. Especially in buildings that are very old, have had a lot of structural maintenance, or may have had expansions or additions built onto or into them.

Many years ago I was on a job where we had some low voltage door intercom system failures and ended up finding out that various bits and pieces were frying themselves because the equipment at the doors were grounded to the building frame, and one of the intercoms was in a section of the building which had been an addition. The addition was very poorly grounded - instead of going to ground nearby, the intercom at this door was going to ground through the control station elsewhere in the building frying various bits every now and then. The damaged ground cable in the addition was found and repaired, and heavy grounding cables were strung between the frame of the addition and frame of the older part of the building in several places, making the structure into a single conductor.

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Message 1052270 - Posted: 1 Dec 2010, 18:28:41 UTC - in response to Message 1052268.
Last modified: 1 Dec 2010, 18:29:19 UTC

Sorry, I knew I forgot something. If the system is grounded into the frame of the building housing it in more than one place, there might not actually be a common ground. A lot of people tend to think that all of the metal girders and whatnot in a building are all one conductor. For the most part, they will be, however not always. Especially in buildings that are very old, have had a lot of structural maintenance, or may have had expansions or additions built onto or into them.

Many years ago I was on a job where we had some low voltage door intercom system failures and ended up finding out that various bits and pieces were frying themselves because the equipment at the doors were grounded to the building frame, and one of the intercoms was in a section of the building which had been an addition. The addition was very poorly grounded - instead of going to ground nearby, the intercom at this door was going to ground through the control station elsewhere in the building frying various bits every now and then. The damaged ground cable in the addition was found and repaired, and heavy grounding cables were strung between the frame of the addition and frame of the older part of the building in several places, making the structure into a single conductor.


This particular event wouldn't happen to SETI, as the SSL building that the server closet is in is fairly new (1980's...) AND hasn't had any additions (yet, at least...)
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Message 1052381 - Posted: 2 Dec 2010, 3:00:46 UTC - in response to Message 1052243.

If the recent storm might have caused problems due to atmospheric effects rather than conductor channeled effects, has anyone considered putting up a light mesh screen around the closet? A simple Faraday cage can be really cheap.

If one were to acquire a few hundred square feet of household window screen (making sure to get metallic screen, not plastic) then put the servers on thin flooring of conductive metal, then get an old style shower curtain rod that hangs off the ceiling, and make a curtain out of wire mesh, then put more mesh on top over the hole in the middle.

Viola, Faraday cage on the cheap.

There are others here with much more practical experience than I have with electronics protection. Comments and suggestions on how to improve this idea on the cheap would be great.

**EDIT** If a cheap Faraday cage does not prevent computer issues after close lightning strikes, then the UPS's might need to be checked on again. It might also be a good idea to make sure that all of the server equipment grounds to a common ground. Having multiple grounds of different effectiveness can cause charge to move through your equipment rather than go to earth.

A Faraday cage is actually 3 layers. Two conductive layers and an insulation layer between. The two conductive layers are grounded together at exactly one point. All permanent openings are offset in the two layers.
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Message 1052439 - Posted: 2 Dec 2010, 10:03:02 UTC - in response to Message 1052381.
Last modified: 2 Dec 2010, 10:16:06 UTC

If the recent storm might have caused problems due to atmospheric effects rather than conductor channeled effects, has anyone considered putting up a light mesh screen around the closet? A simple Faraday cage can be really cheap.

If one were to acquire a few hundred square feet of household window screen (making sure to get metallic screen, not plastic) then put the servers on thin flooring of conductive metal, then get an old style shower curtain rod that hangs off the ceiling, and make a curtain out of wire mesh, then put more mesh on top over the hole in the middle.

Viola, Faraday cage on the cheap.

There are others here with much more practical experience than I have with electronics protection. Comments and suggestions on how to improve this idea on the cheap would be great.

**EDIT** If a cheap Faraday cage does not prevent computer issues after close lightning strikes, then the UPS's might need to be checked on again. It might also be a good idea to make sure that all of the server equipment grounds to a common ground. Having multiple grounds of different effectiveness can cause charge to move through your equipment rather than go to earth.

A Faraday cage is actually 3 layers. Two conductive layers and an insulation layer between. The two conductive layers are grounded together at exactly one point. All permanent openings are offset in the two layers.


Perhaps an ideal or extreme high voltage Faraday cage is three layers, but a single layer should work just fine for protecting a computer server system from errant EM from lightning. I dug around a bit and found a lab setup similar to what I described (single layer) though they have used larger mesh nonflexible sheet.

http://www.faraday-cage.com/wp-content/uploads/2010/11/faraday-cage.jpg

Oh - the cage itself must be well-grounded!


**********

This might be a little project that the SETI team could talk to the engineering department about - most engineering departments have project classes with materials budgets, and in today's world of electronics, Faraday cages are not as uncommon as many think. This would be a very good small scale project, and could be built more like the image above, rather than looking like a mosquito tent. A solid sheet Faraday cage would also be less likely to be damaged by accidents that don't involve a lot of force.

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