noise Re: [Beowulf] Re: Setting up a new Beowulf cluster

Prentice Bisbal prentice at ias.edu
Thu Feb 14 08:20:03 EST 2008


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This thread has gone horribly off topic. There's more noise about noise
than there is about the original question.

Prentice Bisbal
Linux Software Support Specialist/System Administrator
School of Natural Sciences
Institute for Advanced Study
Princeton, NJ


Robert G. Brown wrote:
> On Wed, 13 Feb 2008, Jim Lux wrote:
> 
>> That's what the big Tesla Coil or quarter shrinker is for.
> 
> Mad science.
> 
> Oh, yeah.  Let's put a great big tesla coil right in with all those
> computers!  Wait, I hear it now...
> 
>   Fzzzzssszzzssszzzssst.
> 
> (...that's the sound of all those itty bitty gaps on a circuit board or
> NIC arcing at the same time...;-)
> 
> OK, funny story time, sort of.  Stop me if you've heard this one.
> 
> My kids in E&M get to do an extra credit project for a 1/3 of a letter
> grade promotion at semester's end, and maybe a decade ago I had a
> student who wanted to build a tesla coil for his project and I said,
> sure, cool, go for it.  So off he went and with whatever web browsers
> were around and pre-google alta vista found some howto sites for
> building coils, and a few weeks later ran down a neon sign transformer,
> built a saltwater-aquarium-wine-bottle capacitor array, assembled a
> fan-quenched spark gap, and hand-wound the coils and added a toroid on
> top.
> 
> We still had our "old" lab rooms for the intro courses -- no computers,
> stained lab benches and tables a big lead sink and gas and air nozzles
> in the central bench(es) up front.  Imagine old wooden (oak) chassis lab
> equipment in glassed cabinets around the walls, a huge beam balance with
> brass weights that was probably worth a kilobuck as an antique on top of
> a tall cabinet in the back, that sort of thing.  So my student rolls his
> creation on a big cart into this, and I and the class all gather to
> watch.
> 
> Naturally, we turn off all the lights and darken the shades the better
> to see the lightning.  Student hooks it all up, flicks the switch on the
> neon sign transformer to power it all up, and bzzzzaaappppppp -- the
> spark gap starts going off like a machine gun and footlong purple
> lightning starts zapping off the top toroid, impressive as all hell.
> 
> And every fluorescent light in the room goes on.
> 
> And they were turned OFF, remember.  They were "on" being driven by the
> radiated RF power coming off of the thing with no other source, just
> like Tesla dreamed.
> 
> In addition, as I walked around the room, I noted that pretty much every
> metal gap a millimeter or less was arcing.  Little arcs zapping across
> the fixtures in the sink, the bolts on the tables, no doubt across the
> wires holding up the drop ceiling.  I could imagine arcing occurring
> across my teeth if I grinned just right.
> 
> After a few minutes of harmless fun and demos (which involved yours
> truly taking a 100+ kV "hit" straight in through the >>glass<< of a
> fluorescent tube that I inadvertently waved too near the toroid and
> drawing down the fire to pass through me to ground through my rubber
> soled shoes, which amused the heck out of the kids but which was NOT fun
> for me) we powered it off and it went into class history as one of the
> coolest projects ever.
> 
> Three years ago, a second round of students wanted to build one, and did
> so using 1F caps that you can apparently now buy over the counter --
> back when the first one was built I used to tell students that a 1F
> capacitor would end up being the size of a bench or good sized filing
> cabinet, but this is no longer true.  In the meantime, all the lab rooms
> were gutted and rebuilt, and each workstation has its own computer.  The
> entire building is now filled with computers.  The computers are now all
> unshielded twisted pair networked, not thinwire ethernet.  If I were to
> turn on a tesla coil inside the building ANYWHERE (unless it were inside
> a faraday cage, of course), I'd probably blow $10,000 worth of
> equipment, as a tesla coil is sort of a steady state EMP bomb or solar
> flare on a table.
> 
> We demo'd this one OUTDOORS in the parking lot, figuring that the
> building steel would act as enough of a cage to protect the interior,
> with a surge protector inline to help keep the primary power cable from
> carrying back too much of an RF harmonic onto the building wiring.  I
> was a bit worried about the cars nearby -- if you drive an arc at e.g.
> the cap on a gasoline supply it can be a bad thing -- but cars tend to
> have metal on the outside and again cage off their guts.  No worries --
> or at any rate none of the cars exploded or blew their starter coils.
> 
> But putting one in a server room, with all of those wires strung around
> in loops and connected to electronics that really hates high voltage
> even at very low current -- that's just plain funny...:-)
> 
>     rgb
> 
> (P.S. -- every few years I have to explain to one student or another
> that no, they are NOT permitted to build an EMP bomb for their project.
> They are driven by high explosive and -- however much fun it would be --
> where and how would we test it?  Without, of course, bringing out the
> mob with pitchforks and torches afterwards...)
> 
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