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Re: Concerned

Hi Ted,

A properly built and well thought out cage will do very well against
everything but magnetic fields which fall off quickly with distance.
However, a quickly strung up roll of wire or something could just act like
an antenna and actually make things much worse.

Bill Wysock's coil at the electronics store is certainly near electronic
devices:

http://www.ttr-dot-com/Fry-coil.htm

However, his cage is well thought out:

http://www.ttr-dot-com/its_model9.html

It is hard to explain to someone how to do all the tricks and good RF
things a great cage needs over E-mail...  Most important thing is to be
sure it has a good RF ground.  Galvanized chicken wire is not exactly the
greatest conductor of RF currents but probably better than nothing.
However, for electrical safety, it will stop arcs from getting to people.
electronic equipment may still need more protection...

Cheers,

	Terry



At 12:49 PM 02/15/2000 -0600, you wrote:
>Jim: Now I am really concerned.
>My 6x24 coil is destined to be used in a Frankenstein lab setting in a
>Haunted House this October. I had planned to line the entire room with
>grounded chicken wire. There will be a good iron pipe ground looking for the
>sparks a lot closer. But the chicken wire was going to prevent RFI to most
>electronic devices possessed by patrons walking by...perhaps 15 feet from
>the display.
>
>Are you now suggesting this is a waste of time/effort?
>
>Ted
>
>-----Original Message-----
>From: Tesla List [mailto:tesla-at-pupman-dot-com]
>Sent: Monday, February 14, 2000 9:35 PM
>To: tesla-at-pupman-dot-com
>Subject: Re: Pacmakers and Tesla coils = bad??
>
>
>Original Poster: "Jim Lux" <jimlux-at-jpl.nasa.gov> 
>
>However, building a GOOD Faraday cage is non trivial.  Any wire that
>penetrates the surface (including the twists in the chicken wire) can
>provide a pathway for RF energy.  The single best thing you can do is
>provide a good conductive counterpoise/ground underneath the coil so that
>the current induced by the RF field has somewhere "safe" to go (i.e. back
>into the other end of the coil).
>
>
>-----Original Message-----
>From: Tesla List <tesla-at-pupman-dot-com>
>To: tesla-at-pupman-dot-com <tesla-at-pupman-dot-com>
>Date: Monday, February 14, 2000 4:32 PM
>Subject: Re: Pacmakers and Tesla coils = bad??
>
>
>>Original Poster: rdgraaf-at-ocenl.nl
>>
>>There is a very simple solution: it's called a cage of Faraday...
>>Chicken wire will do the trick. Naturally this will cost some
>>performance, but hey what is more important? btw, will also protect
>>your own and your neighbours Hifi, TV, Computer, etc.!
>>
>>Ruud de Graaf
>>Holland
>>
>>
>>Date forwarded: Sun, 13 Feb 2000 20:14:02 -0700
>>Date sent:      Sun, 13 Feb 2000 20:14:43 -0700
>>To:             tesla-at-pupman-dot-com
>>Subject:        Re: Pacmakers and Tesla coils = bad??
>>Forwarded by:   tesla-at-pupman-dot-com
>>From:           Tesla List <tesla-at-pupman-dot-com>
>>
>>> Original Poster: Terry Fritz <twftesla-at-uswest-dot-net>
>>>
>>> Hi Stan,
>>>
>>> WOW!!!  When I was reading about pacemakers, it was implied that they
>>> could be accidently triggered by a number of things.  I was not really
>>> "sure" a TC could do it but the things they described seemed like it
>would
>>> be very possible.  However, this is proof that a 15/60 coil can trigger
>the
>>> defibrillator types at 25 feet.  The people that have these are warned by
>>> their doctors what the jolt they give is like so they will be somewhat
>>> prepared.  This is especially important if they are driving or something
>>> (Mark mentioned that they would normally be unconscious, but perhaps that
>>> can be programmed).  Pacemakers can also be stunned into safe and default
>>> modes if their logic detects something is wrong.  This may go unnoticed
>but
>>> they may not be able to operate as needed in such a fail safe state.  The
>>> equipment that "talks" to these pacemakers may be able to detect and
>count
>>> the number of times they are affected.
>>>
>>> There apparently are no official levels or standards of EM interference
>>> for these things.  Different brands appear to be affected more or less.
>>> They are somewhat "hardened" against normal EMI but a Tesla coil is
>>> obviously quite abnormal in most EMI respects.  CERN calls out 0.5mT but
>I
>>> am not sure that is well based.
>>>
>>> http://www.cern.ch/CERN/SafetyGuide/Part3/42.Magnetic.html#warning
>>>
>>> It would be nice if we could come up with a "safe" distance or some
>>> maximum EM level but there appears to be no such data that would apply to
>>> all manufacturers of pacemakers.  It looks like the only thing we can go
>by
>>> now is "Keep pacemakers FAR away from any TC!"
>>>
>>> Many thank for this very important post on this subject!
>>>
>>> Cheers,
>>>
>>> Terry
>>>
>>>
>>>
>>> At 09:15 PM 02/13/2000 -0500, you wrote:
>>> >I witnessed first-hand what a TC can do to a modern pacemaker.  A fellow
>>> >was about 20-25ft from a running 15/60 coil.  It ran for maybe 30
>>> >seconds then suddenly he shook violently and dropped down on to his
>>> >knees.  Apparently, the gap misfired or whatever and for a second the
>>> >frequency of the output was abnormal and triggered his pacemaker.  If I
>>> >remember right his delivered 5J.  Whatever it delivered, it scared the
>>> >holy heck out of me and was very painful for him.  Fortunately, the
>>> >shock had no ill effects on his rhythm.
>>> >
>>> >Obviously this situation could have been disastrous.  The TC could have
>>> >triggered his pacemaker and sent his heart into an irregular beat, or
>>> >perhaps worse could have quietly destroyed his pacemaker and would have
>>> >never been noticed until it failed to shock when it was really needed.
>>> >
>>> >IMHO it's just not worth it.  Keep pacemakers FAR away for any TC!
>>> >
>>> >-Stan
>>> >
>>> >Tesla List wrote:
>>> >>
>>> >> Original Poster: Terry Fritz <twftesla-at-uswest-dot-net>
>>> >>
>>> >> Hi Mark,
>>> >>
>>> >> I just want to thank you for adding this sort of expert addition to
>all
>>> >> this.  I got onto this pacemaker thing by accident, but the stuff I
>saw
>>> >> really worried me!!
>>> >>
>>> >> Having a pacemaker zap someone would be sort of unpleasant.  However,
>>> >> having it do ANYTHING it is not supposed to be doing is a real
>concern.
>>> >> Tesla coils would be almost a worst case situation to find these ultra
>>high
>>> >> tech gizmos dealing with.
>>> >>
>>> >> When they were just simply bipolar devices they were probably pretty
>>immune
>>> >> to a lot of things.  However, the are now really sophisticated and
>they
>>> >> could do a lot of harm if they were to get "confused".  I think we
>need to
>>> >> be extra careful of these things now!
>>> >>
>>> >> Cheers,
>>> >>
>>> >>         Terry
>>> >>
>>> >
>>>
>>
>>
>>
>>
>