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Splitting & Tank Circuit
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To: tesla-at-grendel.objinc-dot-com
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Subject: Splitting & Tank Circuit
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From: richard.quick-at-slug-dot-org (Richard Quick)
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Date: Wed, 11 Oct 1995 23:53:00 GMT
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* Original msg to: usa-tesla-at-usa-dot-net
Quoting "McKee David" <McKee.David-at-mail.ndhm.gtegsc-dot-com>:
> Richard,
> You say that you use the floating tank circuit method, do you
> then have two movable connectors to the primary inductor in
> addition to the fixed end, one for the high voltage and one for
> rf ground that is used during the charging phase?
> Does it really matter where this "middle connection" on the
> primary is, ie: must it be in the center of the primary"
> --Dave McKee.
Whoa! You lost me completely. I said I let the tank circuit float
ungrounded, and I used a grounded center post on the safety gap so
that the tank circuit has a ground reference when required (during
HV incidents such as kickbacks, flashovers, etc.). The diagram
below is typical of what I am referring to:
TESLA COIL SCHEMATIC ---------
| | T1
---------
O
X1 C1 O
| | O L2
O-----------------------------| |----- O
||O | | | | | L1 O
||O | | | O O
-----O||O * SG * |--->O O
O||O----*---|Gnd G1 O O
-----O||O * * O O
120 ||O | | O O
Volts ||O | | O O
O-----------------------------------------O O
|
|
Gnd
X1 = Neon Sign Transformer, grounded center tap
SG = Safety Gap.
G1 = Main system (tank circuit) Spark Gap.
C1 = Tank circuit capacitor
L1 = Primary Coil.
L2 = Secondary Coil.
T1 = Toroid discharge terminal
Gnd = RF Ground.
I have deliberately left out bypass capacitors and RF chokes to show
the correct circuit in the simplest form. Reading from the left to
the right, we start with the line in to the neon transformer. I am
showing three leads leaving the transformer towards the coil. The
center lead is the internal ground on the transformer and case.
The transformer case is grounded to the RF ground. A safety gap
with center post is placed between the two high voltage bushings.
The safety gap center post is connected to the RF ground and forms
the ground reference for the high voltage circuit.
G1 is placed directly across the two high voltage bushings.
C1 is placed in series with the primary coil.
Bypass capacitance is placed across the HV line, and RF chokes are
placed in series with the HV line, between SG and G1 in this diagram.
(not shown for simplicity)
The actual oscillator or "tank circuit" is the loop between L1, G1,
and C1. This circuit, patented by N. Tesla, is the most fundamental
RF oscillator known. Since the inductance is commonly referred to
as "L" in circuit diagrams, and capacitance is commonly referred to
as "C", this is known as an "LC oscillator". The loop between the
inductance "L", capacitance "C", and the switch (in this case a spark
gap) forms a "tank" where heavy currents can oscillate with low
impedance. This circuit is properly called the Tesla tank circuit.
There is no need to "ring" or oscillate the tank circuit off of a
ground reference. The tank circuit will actually ring better in most
cases if it is allowed to "float" ungrounded. Any imbalance or kick-
backs will seek the center post at the safety gap for a ground
reference, so the circuit is as safe as any.
A variation on this circuit (one of many) is shown below, where
the location of C1 and G1 are reversed:
TESLA COIL SCHEMATIC ---------
| | T1
---------
O
X1 O
G1 O L2
O----------------------------* *----- O
||O | | | L1 O
||O | | | O O
-----O||O * SG ------- |--->O O
O||O----*---|Gnd _______ C1 O O
-----O||O * | O O
120 ||O | | O O
Volts ||O | | O O
O-----------------------------------------O O
|
|
Gnd
Another variation, showing one end of the primary coil grounded
to the base of the secondary coil is shown below. The safety gap
should be placed across the HV bushings on the capacitor C1.
NOTE: THE CIRCUIT BELOW CANNOT BE USED WITH NEON SIGN TRANSFORMERS!
TESLA COIL SCHEMATIC ---------
| | T1
---------
O
X1 O
G1 O L2
O----------------------------* *----- O
||O | | L1 O
||O | | O O
-----O||O ------- |--->O O
O||O _______ C1 O O
-----O||O | O O
120 ||O | O O
Volts ||O | O O
O------------------|-----------------------O___O
| |
| |
--- Gnd
Gnd
These are just a few of the many, many tank circuit configurations
explored by Tesla. The circuit you are probably referring to has
a grounded center tap in the middle of the primary coil. The value
of C1 is divided into two equal parts (C1 & C2) which are then
placed in series with the primary coil. The gap is across the line:
TESLA COIL SCHEMATIC ---------
| | T1
---------
O
O
O
O
X1 C1 O
| | L1 O L2
O-----------------------------| |-------->O O
||O | | | O O
||O | O O
-----O||O * O O
O||O-------Grnd-------------*--------------->O O
-----O||O G1 * O O
Line > ||O | O O
||O | | | O O
O-----------------------------| |---------O O
| | |
C2 |
Gnd
Tesla experimented at length with the circuit diagrammed directly
above in the latter half of August, 1899. This is a variation of
the "balanced" or "equidrive" Tesla tank circuit. Tesla's diagrams
and performance notes may be found in the COLORADO SPRINGS NOTES.
Richard Quick
... If all else fails... Throw another megavolt across it!
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