Tesla Coil, Electrostatic, Artistic Stuff
First coil of any power
Second coil of even more real power
My pre-neon sign transformer coils, including my very first (unbelievably primitive) coil
A newer, and smaller coil.
Pictures of my coils, mostly of the babycoil
Construction Information, Connection Details of The Whole shebang
Types of Spark Gaps
The Allmighty terminal
The High-Power Capacitor
Our beginnings of a Vacuum-Tube tesla coil
Tesla Coil Gallery
Read About the Man Himself!
Easy HV generators. Flyback transformer Drivers!
More About Me
Other High Voltage More Stuff
My electrostatic projects, namely a sectorless Wimshurst generator and 3 Van de Graaf's
A collection of some of the various HV projects I and the Voltage Obsessives have worked on
How to get EXPENSIVE stuff CHEAP
Exploding Wires!

Our Baby Coil.

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Power: 9000vac @ 30ma Neon Sign Transformer. 270 VA
Capacitors: 4 wine bottle salt water caps
Spark Gap: This uses a neat, 3-stage adjustable gap. Each gap is formed between the flat head of a 1.25" steel bolt and a flat plate of steel. Each bolt cab be threaded closer or further away, making the gap good for any voltage under 12KV. It perfromed as well as the RQ gap in the BBC. Orinally 5 gaps, accross the heads of a series of roofing nails in a piece of wood. Later it was a series of 3 gaps made from steel L-braces.

Primary: Originally was 10 turns of insulated, stranded speaker cable. A pin was pushed through the insulation to make the tap. Then was steel wire wrapped around a cardboard form (Quaker Oats can) 13 turns total, tapped at 6th turn. Now is Bare copper 12 gauge wire, wrapped around a 5" form, 12 turns total
Secondary:2.25"X11" PVC. Winding length is 10" 24 gauge magnet wire

Our BigBaby coil

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This coil is forever approaching its final form, so pictures will come eventually (once I finish off the roll, and get them developed, and scan them, and write the html for them, and upload them;-)
sneak peek, these are some of the oldest photos I have for it!

Specs
Power: Is, and for ever shall be, 12000Vac @ 60ma, 1 NST
Unless, of course, I up that through modification to 12000Vac at 90ma.
Input voltage controlled by a either a 10A 140V 60Hz variac, or the pictured 10A 220V 50Hz variac

Arc Length: Now it's well over three feet. Not sure of the exact length, but adding a 120bps AC synchronous rotary spark gap was wondrous. When the second toroid was added, the arcs were nearly three feet. I hadn't had the chance to actually measure the max distance, seeing how the arcs were striking the ceiling of the basement.

With each previous modification, the arc length did this: 18",25", 28", ~35". This will improve, very much so, -I hope-, when I eventually complete the rolled poly cap for it. 50" would be nice.

RF Protection: Two 2.5" by 6" hand-wound air-core chokes, using 24 gauge wire on PVC, and a center-grounded saftey gap on the HV side. A 20 amp line filter is used on the 120Vac side. May eventually get rid of chokes, add bypass caps, ~800pf each, and power resistors to spoil any nasty 60Hz resonance.

Spark Gap: An AC-syncronous rotary spark gap!! Most recently before that an RQ-style gap, complete with a muffin fan for cooling, ionized air removal, and ozone dispersion. Before that it was a nice gap with three adjustable sections, each gap being between a oversized (1.15") bolt head and a flat steel plate. The heads are very parallel to the arc plates, and this thing works nearly as well as the RQ-style gap. Before that it was 4 gaps made with steel 90-degree angle braces, but the fourth gap was slotted on it's support so as to be adjustable.

Primary: Now is a large, 17 and 5/6 turn flat spiral using 1/4" coper tube on six 1/2" thick plexiglass supports, 2" high.
This replaced a crappy 15-turn flat-spiral coil using stranded 14 gauge wire, stripped of its insulation, supported on 4 slotted wooden supports.

Capacitors: I've broached the MMC barrier! While I may be the only person to ever use polyester, POLARIZED caps, it works! Only Salt-water for now, A Varied collection of 15 caps, the value being arrived at after I had someone be so nice to as to let me borow a capacitance/inductance meter!(thanks, Mr. M.) Nearly each one uses a different type of bottle... Originally set in one (for up to 8) or two (for up to 16) foil-lined plastic bases made to hold 8 plastic 2-liter soft drink containers. Now they all rest on a single piece of 1/16" aluminum, which in turn lays on a sheet of 1/2" plexiglass, which is usually supported off the floor by a plexiglass box.

I'm in the process of gathering materials for a polyethylene dialectric oil-filled capacitor, which will probably be of the rolled type for my first attempt. I have a good deal of 4 mil polyethylene sheeting, which I plan on using in sections of ten layers, for 40 mills of dialectric. I also have a roll of aluminum flashing, but no insulating oil as of yet.

Secondary: Wound on a 4.5"X18" section of PVC pipe, winding length = 16". This uses 24 gauge magnet wire, though when I first wound it I thought I was using 22 gauge.. ;) hey- the wire was free!
Sealed with multiple coats of polyurethane.
I want to replace it with a 20" bifiliar winding on thinwall 4" PVC.

The Early Coils

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Before I created the Voltage Obsessives, I built a series of small tesla coils, all but the last being powered by flyback transformers. These coils included a range of components that existed as part of each system at one time. All the coils were make-shift, low-tech, I-really-have-no-idea-how-to-make-a-tesla-coil-type coils. I remember the first one clearly...

The Proto-Morphic Coil. I call my first coil ever this as it changed and grew, with its components eventually integrating themselves into other, later coils. The secondary is still existant, though I'd never use it for anything, and can hardly believe that it worked in the first place. Wrapped on a 2.25" cardboard form, wound with multiple sections of 22 gauge plastic-coated wire, with each section connected to the next through bared ends, twisted together. winding length, ~13"(this changed several times:)So, the secondary is this multi-colored cylinder with about ten sharp projections along its sides, and no discharge terminal, just the top turn ending with a bared wire pointed outwards.

The original primary was simply about 4-5 turns of insulated solid-conductor 12 gauge wire stapled to the table in a plat spral pattern. I DIDN'T EVEN KNOW WHAT "TUNING" A PRIMARY MEANT when I set this thing up. It used a single salt water capacitor, and a SPST copper ceramic-based knife switch for a spark gap. The cap is still in use, paralelled with seven others, in the baby and big baby coils, and has made appearances in pretty much all coils I've ever wound and tested. Even with all that, the coil still ran, and produced an arc about 1.5" long. And ALSO with that I was grounded for several weeks. My mother seemed to recall telling me specifically to NEVER EVER build a tesla coil :(

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The Post-Proto-Morphic to Pre-Alpha-NST Coils These were a series of fly-back transformer powered coils, made up of a variety of simple spark gaps, primaries, and three(later five-one was split in half)secondaries. I became creative with these things, and began to use them more like induction coils than tesla coils. The most interesting of all my experiments during this phase produced some sort of tree-shaped discharge 7" long.

BUT, mind you, this was not the classic bright-purple tendril of a tc. I increased the capacitance as much as I could, and then opened out the spark gap to the point where I was getting perhaps 4 firings per second. The secondary was wound on a 3" cardboard form, with ~17" of 22gauge magnet wire and perhaps 3" of 24 gauge magnet wire at one end of that(both pulled of of the windings in the back of TV's), and a 1.25" steel ball-bearing on a plastic insulator was being used as a discharge terminal. When the coil was operated in this fashion in complete darkness(meaning the spark gap was heavily shielded), a set of pale-white, tree-shaped discharges would appear, leaping off the top surface of the ball bearing. I could draw them to my outstretched palm with absolutely no sensation... ...it really was beutiful and earie.

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The Alpha-Neon Sign Transformer Coil, or the A-1 TC This was the first tesla coil I built using a power source other than a flyback transformer. Using a cardboard form with a 2.25" dia wound with 22gauge magnet wire (pulled of of the windings in the back of TV's) and three salt water capacitors, I set up a coil with a 6000Vac 30ma NST I had borrowed from a friend. The discharge terminal was a 1.25" steel ball bearing, and it used a simple adjustable static gap, just two bolts between two steel L-braces. Even only at 180 watts and 3" of arc the thing roared loud enough to disturb everyone, but "strangely" I wasn't punished for building this one... `:)

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After I returned the transformer to the friend from whom I'd borrowed it, I was unable to do any coiling for a considerable length of time...
...this was my parents' decision, not mine...
...I then was forced to turn my HV persuits away from tesla coiling and towards electrostatics...
...though they tried, my parents couldn't stop me from learning about tesla coils, though...

Tesla Coil Details

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Here's the basics: how to connect all those wonderful HV parts together once you've scrounged, built, bought, borrowed or stole (8o!) them. (So what if I'm having a little fun with font colors?!)

This is the very basic circuit, showing only the neccesary components. The high voltage transformer is shown as "NST", meaning Neon Sign Transformer, since that is what most coiler use to power their systems. The case of the transformer is grounded, which also forms the ground for the center tap of the secondary. (center tap is connected to the core internally) The spark gap is shown connected parallel to the transformer output, but its location is interchangeable with the tank capacitor. The cap is shown simply connected between on leg of the gap and one side of the primary coil. The primary is shown as having an adjustable connection on the side opposite the capacitor, obviously, which side the adjustable tap is on doesn't matter.

The distance between the primary and secondary should be variable in your setup, so as to be able to change coupling. Just know that you need to fiddle with it to get optimal performance, it isn't neccesary to understand coupling. The secondary is shown with only a very small terminal, as no discharge terminal is neccesary to have a functional system. You may not want the arcs coming directly from the top turn of the secondary, and the streamer length will greatly improve with a large terminal, so It should really be used with any system. Also, be sure that the ground for the secondary coil is the one used to connect to the transformer case, and not the electrical ground. The special ground for the secondary coil is referred to as the "RF ground", and should be a separate connection to a ground rod driven into the ground somewhere. In a pinch, a house's cold water pipe can be used.

Ah, a more complete system. In order to prevent damage to various components, and reach a maximum performance with a coil, I'd recommend something at least as complex as shown. Now there is fuse protection on the 120V side, a center-grounded saftey gap, RF chokes, and a large discharge terminal. The saftey gap serves the purpose of shunting any really high voltage out of the primary system, hopefully before it can damage the transformer or capacitors. Each side is set so it will -just- not arc to ground when only the transformer is connected to them. This way, anything significanlt higher than the voltage the transfomer is rated at will arc harmlessly to ground, which should, BTW, be the RF ground, not the electrical ground.

The RF chokes should be somewheres about 1mH in inductance. I built two using 26 AWG, wound on 2" id PVC, each about 5" long, and one measures 2.18mH, the other, 2.17mH. Everything else is the same with this system as the first shown, accept for the discharge terminal, which should be electrically connected to the top turn of your secondary coil. One thing to watch out for is making any kind of connection that forms a shorted turn on the primary or secondary, or even just near them, as it will suck massive amounts of power out of the system.

I would definately approve of this configuration, which has all items for optimal, and safe, performance.The changes include the addition of a variac (variable autotransformer) to control line voltage, replacing the RF chokes with power resistors and RF bypass caps, and adding a strike ring to guard against arcs from the secondary to the primary. Now I am getting beyond myself, here. I have niether a strike ring, RF bypass caps, or power resistors in my system, though I surely wish I did. The RF bypass caps should be rated at the same voltage as the tank cap, and have a value of a few hundred pF. The power resistors should be about 25-50W, 500-1K ohms. Be very sure that any strike ring has a gap in it of at least 2", since completing it as a whole loop will drain energy away,as well as heat up the ring.