Lego and other sensible things

Dave Halliday dave.halliday at
Fri Jun 27 03:59:46 CEST 1997

>>>What I'd REALLY like to have are some of those rising spark generators 
>>>that seemed to be in all the old Hammer horror flicks; Dr Frankenstein 
>>>would walk round his basement lab turning on all thse huge glass jars 
>>>containing a pair of filaments; big lazy sparks would climb the 
>>>filaments and make wicked arcing noises.
>     Yes, but you DON'T want one around your studio unless you want damage 
>     to your equipment.
>     The amount of high voltage radiation emitted from a tesla coil, van de 
>     graff generator or wimhurst static generator can do all kinds of 
>     damage to computer circuits and cause all kinds of RFI noise in a 
>     sound system. Trust me on this one.. I'm speaking from experience. :)

He was talking about a Jacobs Ladder which is pretty benign - have one 
in the studio and it makes no interference when I run it.

A Tesla Coil however is quite the different beast!  ( Have a small one 
of these in the garage )

If you run a single ended Tesla Coil that is not properly grounded, it 
will radiate prodigious quantities of RF and induce large voltages in 
pieces of metal for a surprisingly large area.  Keys and coins in your 
pocket will give off painful burns.  Any electronics with a power cord
will be fried as this works very well as an antenna.

You can safely run a Tesla Coil under two conditions.

A Double Ended coil will cancel out it's electromagnetic field
and cause very minimal interference beyond about three to five
radiuses  ( ie: maximum arc length = 2' - minimum safe distance
for electronics = 6' to 10' )  A double ended or balanced coil can
either be a single coil with the primary in the middle and two 
electrodes on ewach end fo the secondary or it can be two seperate but 
identical ( with large emphasis on _identical_ ) primary and secondary
circuits sharing a common exciter circuit and ground plane.
The tuning on this has to be spot on...

You can ground a single ended Tesla Coil and enjoy the same three to
five radius safe operating distance.  The grounding of the coils will 
also greatly improve their display.

This is a critical issue.
A small simple improvised ground WILL NOT WORK and it will
actually make things worse...

Tesla, in his Wardenclyffe NJ lab was running a coil 187' high.  The 
actual length of the secondary was less - guessing about 80' to 100'

His ground was a shaft 10'X12' extending 120' into the earth, lined 
with steel plate.  He also extended 16 lengths of iron pipe 300' ( yes 
300' ) into the surrounding earth.  This is a ground connection!!!

For my work, I am running an 18" tall coil powered by three neon sign 
transformers, my ground is three 10' lengths of copper water pipe 
driven into the front yard and on eather side of the driveway near the 
garage.  I can get up to 2' long arcs and have zero damage to any
of the computers or synthesizer equipment about 20' away.

I know that this is massivly off-topic but it is analog!!!  <grin>
--- Via Silver Xpress V4.4 [Reg]

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