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Re: need fast tesla help PLEASE
From: Esondrmn[SMTP:Esondrmn-at-aol-dot-com]
Sent: Monday, December 08, 1997 3:59 PM
To: tesla-at-pupman-dot-com
Subject: Re: need fast tesla help PLEASE
In a message dated 97-12-08 01:15:23 EST, you write:
<< From: Buckshot[SMTP:purplewax-at-juno-dot-com]
Reply To: potato-at-rose-dot-net
Sent: Sunday, December 07, 1997 4:40 PM
To: tesla-at-pupman-dot-com
Subject: need fast tesla help PLEASE
Hi,
I've just built a tesla coil powered by a 10kV transformer for a science
project and just for interest. Right now it is only producing sparks
of about 3 inches. I'm not sure if the
primary and seconday coils are quite right. My secondary coil is wound
around 2.5 inch pvc pipe with magnet wire and is 24 inches high. The
output terminal is a small, simple brass cap. Is that ok? My primary
coil is made out of #12 copper wire and I'm not sure at what radius and
height to wind it. Right now it is wrapped pretty much right next to
the secondary coil and goes most of the way up it. I don't think thats
right.
Could you PLEASE help me. I just can't figure out whats wrong.
Thanks a bunch,
Will Cross
potato-at-rose-dot-net
>>
Will,
A few comments. Tesla coils work best when the Height/Diameter ratio of the
secondary is kept at about 5:1 or less. Yours is 9.6:1. It would be better
to shorten the secondary to about half its present length. It sounds like
your coil is way over coupled and not in tune. I would suggest making a flat
spiral primary with an I.D. of 3.75" to 4.0". The #10 solid copper wire will
work fine. Get some acrylic plastic strips and cut notches in them every
.375" to .400" for the wire to fit in. You want about 12 to 14 turns. Mount
the secondary in the center spaced up one or two inches (between the lowest
secondary winding and the top of the primary). What are you using for a
capacitor? What are you using for a spark gap? Is the bottom of the
secondary connected to a good earth ground? You should have a safety spark
gap mounted close to the output of the HV transformer. It is made of three
electrodes, the outside two go to the HV leads on the transformer, the center
lead goes to the transformer case (if it is a center tapped transformer like a
neon sign transformer) and to the same RF ground as the bottom of the
secondary. Set the gaps to be just larger than the main spark gap in the tank
circuit. The safety gap should fire only intermittently (or not at all) when
the coil is running, unless there is a problem. You also need some other
means of protecting the transformer, like series resistors or inductors. For
minimum, use one 25 watt wire wound resistor of 1,000 to 3,000 ohms in series
with each HV lead from the transformer.
Good luck, Ed Sonderman