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RQ Schematics
Subject: RQ Schematics
Date: Fri, 18 Apr 1997 08:50:08 -0400
From: "Thomas McGahee" <tom_mcgahee-at-sigmais-dot-com>
To: "Tesla List" <tesla-at-pupman-dot-com>
CC: <bhofmann-at-ix-dot-netcom-dot-com>
> Hi Folks,
>
> Been browsing through messages on the list for a few weeks now. I'm
> a newbie to Tesla coils in a sense. I have played around with them
> in the past with very little success, but I think it was due to lack
> of, and poor information resources. This mailing list, as well as
> the FTP site has helped me to understand a lot.
>
Ben, welcome to the list!
> My question is:
> I have read before that when using a neon transformer to power a
> tesla coil, since the xfmr's secondary in grounded in the center, the
> CENTER of the primary for your coil also needs to be grounded, and
> tap the primary on either end with the HV lines. Is this correct, to
> ground the CENTER of the primary of your coil?
>
> I have read and browsed the information in rqdocs.zip on the FTP
> site, and could not find an answer to this.
>
Yeah, not all of the Richard Quick material is filed under Richard
Quick!
You sometimes have to rummage around in the general Tesla list archives
to
dig up the bits and pieces that are scattered all over the place. Lucky
for
you, I have been doing just that, and I am appending the stuff you need
to
this post.
> I also remember that the tank circuit should have two capacitors in
> series with the primary (one on either side), and the gap across the
> power supply end of the caps. Is this correct.
>
Yep, you are describing the modified equidrive circuit.
> I would appreciate any input. I have been itching to put together a
> coil, but my current status (college student living in the dorm) is a
> hindrance.
>
> Thanks.
>
> -Ben Hofmann
> bhofmann-at-ix-dot-netcom-dot-com
Randy:
I dug this out of the Tesla list archives. I am sure there are
other
newbies out there that are not aware of the existence of these materials
in
the archives, and as this material is of use to more than just yourself,
I
am adding the relevant post on Tesla Coil Schematics to this post
instead
of just telling you to go to the ftp site and dig them out yourself.
There
is much good material at the ftp site. In case you are not aware of it,
here is the relevant info:
try one of these :
ftp://ftp.funet.fi/pub/sci/electrical/tesla
ftp://nic.funet.fi/pub/sci/electrical/tesla
http://www.funet.fi/pub/sci/electrical/tesla
They point pretty much to the same site but because of routing in
tcp/ip some may work while others don't because of servers down
between nic and YOUR site.
As a final comment : Nic can sometimes be down but not for long. The
usual
reason may be that there are already so many users in the system that it
won't let any more - there are limits for the amount of foreign visitors
like in all anon-ftp sites.
The configuration you refer to in your post is a variation on the
equidrive
circuit. The specific variation is the connecting of the center taps of
the
transformer and the primary. I would comment here on the relative merits
of
each of the following circuits, but do not want to be the one to stir up
a
hornet's nest. Let us just say that next to religion and politics,
discussing what is the "best" way to wire up your Tesla coil is also
the
best way to start a lot of people off on lengthy discussions filled with
much personal passion.
<Pause...>
Oh, what the heck! My own personal favorite is any circuit that has the
main spark gap across the transformer. People who put the capacitor
directly across the transformer are unnecessarily jeapordizing their
neons.
There! I have set off the first round. You will now hear from people who
have their capacitors across the transformer, and have so far managed
not
to destroy their neons. You will also hear from people with pole pigs
who
can wire their transformers up any way they want with impunity, and who
look with disdain on the lowly neon. I warned you! Have fun!!!
Fr. Tom McGahee
Subject: Tesla Wiring Diagrams
From: richard.quick-at-slug-dot-org (Richard Quick)
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 here for simplicity, see additional circuits below)
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
Line in> ||O | | O O
--------O||O ------- |--->O O
O||O _______ C1 O O
--------O||O | O O
||O | O O
||O | O O
O------------------|-----------------------O___O
| |
| |
--- Gnd
Gnd
These are just a few of the many, many tank circuit configurations
explored by Tesla. In the circuit below there is 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.
Quoting gcerny-at-ix-dot-netcom-dot-com (Glenn Cerny):
> Richard,
> Your follow up to my earlier post has me wondering how to
> connect my bypass caps into my system. I have the 40000mmfd
> -at-30kv from HVPress. I was thinking that I would use one on
> each leg to rf ground somthing like below:
I added in my own ACSII artwork to show more detail:
X1
||O--------------------------------nnnnnnnn--TO-TANK-CIRCUIT->
||O | | RF1
||O ------- BC1 |
---O||O ------- |
O||O | *
O||O--GRND------|-----GRND----* SG
O||O | *
---O||O ------- |
||O ------- BC2 |
||O | | RF2
||O--------------------------------uuuuuuuu--TO-TANK-CIRCUIT->
Where:
X1 = Is the step up xfmr with grounded center tap
GRND = Dedicated RF Ground for the HV wiring and secondary coil
BC1 = Bypass Capacitance
BC2 = Bypass Capacitance
SG = Safety Gap w/grounded center post
RF1 = Radio Frequency Choke
RF2 = Radio Frequency Choke
This circuit should be set up such that the values of BC1 & BC2 are
matched or at least close in value. The same would also go for the
values of the inductance RF1 & RF2.
> Using one cap per side with a common rf ground in centerpoint
> to each leg. I think you get the picture. Can you recommend
> if this is good, or perhaps a better design available. I did
> buy 4 of the caps. If more are needed, I'll get them.
The diagram above shows how I wire the HV filter/safety gap into
the HV buss that supplies the Tesla tank circuit. This is assuming
that I am using a grounded center tap power supply with neons or other
center tap ground transformers. You will need more than one .004 MFD
capacitor in series between each HV buss and the ground. You have
four of these already, I would purchase at least two more, preferably
four more.
I have used these exact same caps in several filter boards. I have
found that you need at least three of these caps in series between
each HV buss and ground when using 9kv or 12kv neons. You need four
of these caps in series between the HV buss and ground when using 15
kv neons. Check the caps and ground conductor for warming as an
indication that too much bypass capacitance is in the circuit. Too
much bypass capacitance allows parasitic oscillations between the
power supply and the ground, a condition which must be avoided to
prevent fires and power supply failures. Generally I don't like
using much more than .001 MFD of bypass capacitance between any
HV buss and ground, or directly across the HV buss. This is one
instance where a little less capacitance is really better than a
little more.
Word on the Net has it that Nick Andree, 305 Wisconsin Ave.,
Oceanside, CA 92054 has these same capacitors priced under $5.00
each. It does not hurt to have a dozen or so of these on hand.
> If you have a favorite circuit design showing placement of various
> components, please send that along too. I am really undecided how
> to approach the design for cap, gap, choke, safety gap placement.
> I have seen a lot of designs to choose from and the "classic" is what
> I am leaning to.
TESLA COIL SCHEMATIC ---------
| | T1
---------
O
X1 C1 O
RF1 | | O L2
||O---------------nnnnn---------| |----- O
||O |BC1 | | | | | L1 O
Line in> ||O ----- | | | O O
--------O||O ----- * SG * |--->O O
O||O----|------*--|grnd G1 O O
--------O||O ----- * * O O
||O ----- | | O O
||O |BC2 | | O O
||O---------------uuuuu---------------------O O
RF2 |
|
Gnd
X1 = Neon Sign or other xfmr with grounded center tap
SG = Safety Gap.
BC1 = Bypass Capacitor
BC2 = Bypass Capacitor
RF1 = Radio Frequency Choke
RF2 = Radio Frequency Choke
G1 = Main system (tank circuit) Spark Gap.
C1 = Tank circuit capacitor
L1 = Primary Coil.
L2 = Secondary Coil.
T1 = Toroid discharge terminal
Grnd, Gnd = RF Ground.
Now for those of you who are using power supplies that do not
have a center tap ground (two bushing pole pigs for instance)
the correct bypass/filter schematic appears below:
X1 RF1
||O------------------------------------nnnnnnnnnn--TANK-CIRCUIT->
||O | |
||O | |
---O||O | BC |
O||O ------- * SG
O||O ------- *----|grnd
O||O | *
---O||O | |
||O | |
||O | |
||O------------------------------------uuuuuuuuuu--TANK-CIRCUIT->
RF2
Where:
X1 = is the step up transformer WITHOUT grounded center tap
GRND = Dedicated RF Ground for the HV wiring and secondary coil
BC = Bypass Capacitance
SG = Safety Gap w/grounded center post
RF1 = Radio Frequency Choke
RF2 = Radio Frequency Choke
When using a transformer without a grounded center tap it is best
to place the bypass caps directly across the HV line without a ground
reference. I put four of the Sprague .004 MFD 30kvdc barium titanates
(ceramic) in series and place the series stack directly across the HV
buss for the bypass capacitance. This method has worked extremely well
for me in conjuction with a moderate RF choke inductance. I always
place a grounded center post between the two hot electrodes of the
safety gap to provide a ground reference for the power supply/tank
circuit in the event of a flashover.
The coil schematic could look something like this:
TESLA COIL SCHEMATIC ---------
| | T1
---------
O
C1 O
X1 RF1 | | O L2
O---------------nnnnn---------| |----- O
||O | | | | | | L1 O
||O | BC | | | O O
--------O||O ----- *SG * |--->O O
Line> O||O _____ *--|grnd G1 O O
--------O||O | * * O O
||O | | | O O
||O | | | O O
O---------------uuuuu---------------------O O
RF2 |
|
Grnd
Richard Quick
..... If all else fails... Throw another megavolt across it!
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