[Prev][Next][Index][Thread]

Re: First spark !

<< Subscriber: Hans.Grimstad-at-maxware.no Sun Jan 12 22:09:25 1997
>Date: Sun, 12 Jan 1997 15:40:52 +0100
 >From: Hans.Grimstad-at-maxware.no
>To: tesla-at-pupman-dot-com
> Subject: First spark !
 
 >Hello everyone !
 
> I just finished my first coil. The secondary is 1400 turns of 1/2 mm
diameter 
 >enameled copper wire on a 7 1/2 cm diameter PVC form. The primary is 20
turns of 
> flat strap rising in a 45 degree angle. The static spark gap is made from a
couple 
> of heavy bolts. The capacitor is made of six wine-bottles. These are
approx.  700 
 >pF each.  The coil is powered by two 3000Kv/50mA neons where the
secondaries 
>are connected in series (Thanks to Kristian for the neons!). The neons are 
 >connected across the spark gap. This is in series with the salt-water caps
and the 
>primary. The top turns on the secondary emits a heavy corona, and I get
aprox. 15  
> cm streamers out in free air (still some tuning to do...). 
 
 >This may be a small coil compared to what the people on this list are 
>experimenting with, but it sure got my adrenaline pumping ! The sound from
spark 
 >gap, the streamers, the smell of ozone and NOX, the UV (and the mad
girlfriend 
 >complaining about the noise...). This is sooooo *FUN* !!!
 
 >Some questions to the gurus on the list:
 
>1) How long streamers can I hope to get with 300W in an optimal system ?
 
> 2) How can I get a good RF-ground in an apartment building (second floor).
I don't 
 want to fry any computers, TVs (or neighbours...)
 
> 3) Do I need RF chokes to protect my neons with only 300 W ?
 
> 4) Is there such a thing as an optimal frequency for a Tesla Coil ? I
 estimated the 
 resonance frequency om my secondary to be 400kHz. This is perhaps a bit high
? 
 
>5) Have anyone tried to excite a laser with the RF from a Tesla coil ? My
coil 
>already looks like something from a Flash Gordon movie, so why not stick a 
>nitrogen laser in there ? ;))
 
 > Hans J|rgen
>Still some tuning to do...
  >>

Hans,

Great news!!  It's always great to get that first coil working!  My first
spark-gap TC was a 1/2 wave type, that gave about 2" spark from each end.
 Second coil gave 1' spark that was so dim, it could be seen only in a dark
room, used glass plate caps and pointed gaps---ugh!   Third SG coil was
actually a "converted" tube coil.  Used 30 turn # 12 gauge stranded wire in
the pri., cap was .009 uF rolled polyethylene, sec was 7" dia. by 19" high
wound with # 28 formvar (magnet) wire.  Toroid was 17" dia. by 4" cross
section aluminum dryer ducting.  Spark gap was 4 series gaps made from
contactors from a giant car-crushing machine, these contactors had silver
arcing surfaces.  Power was supplied by a 360 watt, 12 kV, 30 ma neon
transformer with power factor correction.  Current draw was about 500 watts.
 This system gave a maximum 40" spark but easily gave 32 -- 36" sparks.
 After about 10 seconds, the gaps would overheat and the spark would shrink.
 I tried a newer neon transformer (same specs), but it gave only 27" of
spark.  So it seems that all neons "ain't the same"!    Also, since I ran
with the tightest possible coupling, and with my relatively poor quenching
and thin wire, I got occasional racing sparks on the secondary which
eventually destroyed it!  Definitely a fun project!   I also built a smaller
coil powered by a 23 ma, 10 kV, 230 watt oil burner transformer, this gave
nice 13" sparks.

I don't think there is an optimal frequency, but losses will be lower at
lower frequencies, but I don't think this makes a whole lot of difference.  A
small coil will tend to have a high freq. and a large coil will tend to have
a low freq.  Toroids will lower the freq. and increase the spark, but if the
toroid is too large for the power level, the spark won't be able to "get
out".

Safety gaps are a must for protecting the transformer.  Also wide gap
settings will tend to destroy the transformer.  There are many differing
opinions on the use of chokes and choke types.  You can use series resistors
in the HV supply leads instead of or in addition to the chokes.  I'm sure
you'll get plenty of viewpoints and comments from others.  

"Keep the arcs blaring!!"

John Freau