Greg's Garage Tesla Coil Site


Welcome to my home page devoted to Tesla coils and related apparatus. I've included information on Tesla coils that I have constructed as well as high voltage power supplies, Jacob's ladders, Tesla coil photography, and more. Enjoy!



This is the obligatory safety speech. I've been fooling around with Tesla coils since my teens, and I've been "bitten" a time or two. I survived my teenage experiments mostly due to luck, because I knew little about electricity or electrical safety. Now I have 21 years of experience behind me as an Air Force communication, navigation, and Doppler systems technician. I served for 10 years as an electronics instructor, 5 years as a shop and flightline avionics maintenance technician, 2 years as a radar repair shop supervisor, and 4 years as a depot-level avionics technician. I've also dabbled in amateur radio, including old vacuum tube HF radio gear. I've tinkered with every conceivable sort of transformer, power supply, PFN, modulator, thyratron, etc., etc. My point? I haven't been shocked in many years because I'm experienced and careful, and electrical safety has become a component of my personality. Car ignition coils can shock you silly. Neon sign transformers are very dangerous. Microwave oven transformers and pole transformers are positively lethal. If you don't have the maturity and experience to manage high voltage safely, then please take up another hobby. Don't try to build or emulate anything on this web page. It's all dangerous stuff. In fact, don't even read this web page. Just kidding on that last part, but please do be careful.

An Important Electrical Safety Video (MS Windows Media Player Format, turn up sound)


The Basics

A simple, illustrated explanation of what a Tesla coil is and how it works

Tesla talk--a glossary of commonly used jargon, acronyms, and abbreviations.


In the Beginning

I built my first Tesla coil when I was 13 years old. It was a small, crude affair, wound on a scrap of 2" PVC pipe and energized with an automobile ignition coil. However, it produced a nice lavender brush discharge and harmless 3 inch sparks to hand-held metal objects. I was hooked, and a lifelong interest in electricity was awakened. I tinkered with Tesla coils, ignition coils, electronics, and electrostatics for the remainder of my school years.

Not long after I married, I found a broken neon beer sign in a junk/antique shop. Of course, I didn't care a thing about the broken sign, but I was very much interested in the attached neon sign transformer!. I paid $5 for the "worthless" broken sign, and quickly removed the 8KV/40ma NST. It became the basis for a nice 3"x16" table top coil that produced lots of corona and very satisfying discharges up to 6" or so. I used window glass and foil to make the capacitor. I didn't know about toroids then, so I just had a machine bolt on top. Still, it worked pretty well until the NST mysteriously died one day (I didn't know about RF protection either).

My interest in Tesla coils was put aside for several years until I got my first home internet connection in 1995 while I was stationed at RAF Mildenhall in the United Kingdom. A casual search engine query on "Tesla coils" got scores of hits! I couldn't believe how many folks out there were building Tesla coils. Naturally I had to build a new one right away. I found an on-line dealer in the US who was willing to ship me a neon sign transformer, and the "Junk Box" coil was born.


The Junk Box Coil

If one is going to build a Tesla coil, one should have his/her goals in mind. Is the coil for a science fair project? Is it intended for classroom/educational use? Do you want to make great big sparks or do you want a small, safe coil for tabletop use? My goals were pretty straightforward. I wanted the simplest, cheapest coil possible, consistent with reasonable safety, appropriately sized for my 15KV/30ma NST, capable of producing interesting sparks. Also, I wanted to make maximum use of hardware, wire, plastic scraps, etc., already on-hand in my junk box, hence the name, "Junk Box Coil". Click on the hyperlinks to see captioned images of the original Junk Box Coil.

Junk Box Coil

Lower Deck Detail


The Improved Junk Box Coil

When I moved back to the US in 1999, I put hobbies aside for a year while I made improvements to my new home. I also constructed a very nice 24'x32' garage complete with a roomy work bench and 120/240V electrical service. Besides being a fine place to park my cars, it also serves as an excellent Tesla coil lab! No sooner had the paint dried when I began to rebuild the Junk Box coil. I made several improvements and modifications. In fact, the 4"x24" secondary and the wooden table are the only parts I recycled.

The Improved Junk Box Coil

Primary Coil

MMC Capacitor

Single Static Vacuum Spark Gap

Spherical Top Load


The New & Improved Junk Box Coil

The New & Improved Junk Box Coil

Saltwater Capacitor

The Reconstituted New & Improved Junk Box Coil

Perpendicular Flow Air Blast Gap

Inside-Out Sucker Gap

Cactus Cap MMC

Flex Duct Toroid


The 6-Inch Tesla Coil

First Light

Primary Deck

Flat Spiral Primary

Secondary Coil

Experimental Large Toroid with Spark Images

Asynchronous Rotary Spark Gap

Really Big Bottle Capacitor

New Pool Toy Toroid

Arc Welder Ballast

35mm Spark Photos of 6-inch coil


Power Supplies

Neon sign transformers (NSTs) are popular and a good choice for beginners. In many areas, used NSTs are difficult to find and new ones are very expensive. Microwave oven transformers (MOTs) offer a cheap alternative to the elusive NST. A single MOT has too little voltage and too much current for Tesla coil use. However, by combining two or more MOTs in various ways, the hobbyist can create a very potent and useful Tesla coil power supply. The ultimate power supply is the single phase distribution transformer, also called the "pole pig" by some coilers. These are the bulky, barrel-shaped transformers which feed power to our homes from utility poles. I was able to obtain an old, rusty, surplus 5KVA/11KV pole transformer for free from my power company in the UK. It looks rough on the outside, but the transformer inside looks great and functions perfectly. At the other extreme, one or two automobile ignition coils can provide a few watts of high voltage current for very small table top coils.

Car Ignition Coils

Neon Sign Transformers (NSTs)

Microwave Oven Transformers (MOTs)

Distribution Transformer (Pole Pig)


Spark Images

The new & improved junk box coil energized by the dual MOT power supply with voltage doublers. 1 second time exposure, Yashica Electro 35 range finder camera, f4, 200ASA color print film, ambient light plus artificial light from small, fluorescent camping lamp. Want to see more spark photos of this coil?


Click on the hyperlinks below to view spark images. The low-resolution shots are captured video. The higher resolution shots are scanned 35mm prints. Most of the spark images are of the improved junk box coil running at 1080VA with the twin 9KV/60ma NST supply. One of the hyperlinks will show you some captured video of the new & improved junk box coil being driven by a 2KVA MOT power supply. Some of the images are captioned, others are just plain JPG files.

Streamers (35mm time exposure. 1080VA NST power)

vspark6.JPG (Captured video. A hot single spark! 1080VA NST power)

Light Bulb Experiment (Looks Cool! 1080VA NST power)

vbulb3.JPG (Another light bulb experiment. 1080VA NST power)

Tube Light (A florescent tube experiment. 1080VA NST power)

New & Improved Junk Box Coil captured video images (New secondary, cap, toroid, and power supply)

New & Improved Junk Box Coil, 35mm spark images (Insane sparks)

Low budget MOT experiment (Just 2 MOTs for power--no doublers, no ballast--totally nuts!)

First Light for 6-Inch Coil (Captured video frames)

35mm Spark Photos of 6-inch coil

The Reconstituted New & Improved Junk Box Coil

Jacob's Ladder (Effortless entertainment)

Streaming Video (Maybe!)

Digital Spark Photo (Kodak DX3900)

More Digital Spark Photos (6" coil this time)

Photography Notes (Spark Photography and General Photography)



Stuff I Don't know how to classify.

Triggered Spark Gap Driver Schematic

Triggered Spark Gap Pulse Generator Schematic

Synchronous TSG Pulse Generator Schematic

Marc Metlicka's Party Cup Cap, a neat new design

Exotic Marx / Tesla coil schematic

Sue Gaeta's Tesla Coils, including the "Radical Radio"

Black Widow Living in Greg's Garage (Uninvited)

Water Balloon Canon

Electric Coil Winder Jig


 An Invitation

Want to see my Tesla stuff? If you're ever on the Mississippi Gulf Coast, feel free to drop by for a guided tour of the garage. This invitation goes double for any of you UK Tesla coil lunatics who cross the pond. Y'all come.

Want to show me your Tesla stuff? I live in Long Beach, Mississippi, not far from Biloxi, and only a short drive from New Orleans. If you live anywhere near my neck of the woods, drop me an e-mail and we can schedule a tour of your Tesla lab.



Special thanks to:

Gary Lau, from whom I borrowed the idea for my single static spark gap. I also like his ideas about NST protection.

Marco Denicolai, from whom I borrowed the idea for the MOT power supply. I also helped myself to his asynchronous rotary spark gap design based on an angle grinder. If you are a shameless copycat like I am, then I recommend Marco's web site. He builds good stuff.

Terry Fritz, for information about MMC design and NST protection circuits. He's also hosting this site on his hot-streamer domain. Thanks for the new home Terry.

J. H. Couture, whose excellent book: Tesla Coil Construction Guide, provided a ton of practical information as well as inspiration. I devoured every single page of it. If you can only afford one Tesla coil book, make it this one.

Aric Rothman, for obtaining the Seacor capacitors for me from which I fabricated my first MMC.

Michael Tucknott, for shipping me a big batch of polypropylene pulse caps from the UK at a bargain price. They are the basis for my second MMC.

Michael Vincent, for his generous donation of professional-looking computer generated schematics to replace my crude-looking hand drawn sketches.

Steve Young, for contributing his excellent schematics to this web page, including a MOT voltage tripler, a triggered spark gap driver, and a triggered spark gap pulse generator. Good artwork & good science Steve, thanks.


Best Regards,


Note: Remove the "MURDER_A_SPAMMER_TODAY" notation in order to contact me. The e-mail link isn't clickable. You'll have to copy & paste it. Sorry about that--too much SPAM lately