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MK-6 18V Lightning Gun

Generation 6 handheld Tesla Gun

This hardware piece is dedicated to Paul O. Benigni - fatally injured on August 19, 1990 in a hit and run car accident.
Here's the LCD splash screen it shows while the micro loads the FPGAs:

Today we’re going to talk about my favorite social taboo: The Lightning Gun.   It’s common knowledge that such things don’t really exist - if they did, they’d likely need a power source so huge as to be incalculable in mass and complexity. You can’t imagine my disappointment as a small child when my daddy told me “that shit is fake - it’s all special effects” after we watched Ghostbusters on our honkin’ big Pop Top VHS player.  

Fastforward 20  years - It stuck with me...time and time again I wanted a proton pack...but WTF...Tesla coils are retarded huge and nowhere near as spectacular.  An internship with the Department of Energy, MDS Nordion Nuclear, and then some hard time with IBM - followed by a brief tenure at Plug Power - A government subsidized boondoggle run by a Texan that loved to shovel money into his consultant friends hands... I learned a lot.

Lightning guns are deceptively simple so I’ll break it down piece by piece:

The main resonator is the heart and soul of the lightning gun.  While it’s an entirely passive device...it’s 1400 turns of human hair thin copper wire wound in one continuous spiral.  If there is a single defect or kink or overlapped turn - it probably will not work well, if at all... If a turn is shorted to an adjacent  - turn -it will catch fire.  Recall that one of Maxwell’s equations tell us that a shorted turn of wire shall have no flux or something like that.

This is your typical resonator.  It’s just a coil of wire...nothing scary here.

The resonator has a few parts...most notably - the topload.  Owing to me being a slave to image - it’s brass , and resembles a 1950s Sci-fi piece.  Really, it’s shaped that way for a very specific set of reasons.  The staged plate stack with asharp point on top is largely decorative.  Staged plates like that are often used for insulators to create a very large creepage distance for high voltage in small volume.  That’s not what is going on here. It just looks cool.  Sharp point = Extremely high field density where the sparks break out.  It wants nothing to do with the plates below it.   

See - ain’t that pretty...Spun brass...Brass is the poor man’s gold. Angels have the blue box. NILBOG is GOBLIN spelled backwards...it’s all true.

The last piece of the resonator is the Primary coil, or the inducer.  It looks like a glommed coil of perhaps 10-11 turns, but this one is special.  It’s wound of special wire called “Litz”  The one large cable is made up of many thousands of micro-fine wires.  In this case, 2880 strands of wire about 1/20th the thickness of a human hair.  At radio frequencies, electricity crowds to the outer surface of conductors because it’s afraid of the dark.  At some frequency higher than DC, a piece of copper pipe is just as good a conductor as a piece of solid copper because of this.  Gut the copper, sell the copper at the scrap yard, and get your boss to give you a promotion for making it lighter!

The whole premise of the Tesla coil/Lightning Gun is that there are two coils and two capacitors.  When a coil and capacitor are placed in an electric circuit - they have a natural oscillation frequency - much as the different sized pipes in an organ make different tones.  We have one tiny capacitor (called the topload) - and a huuuuge coil of 1400 turns of fine copper.   We then have the smaller coil of only 10 turns - actually 2880 small coils all individually insulated from each other, of 10 turns each - all in parallel, so we need a capacitor to tune this coil to match the big long one.  Here it is:

This is called the primary resonant tank capacitor. It’s red.

So - now we have a set of tuned circuits.  They’re like a set of identical bells... There’s this phenomenon where if you have two musical bells side by side - and they’re identical - or at least very similar, you can ring one of them, and the other will ring nearly as loudly all by itself.  That’s because it has a resonant frequency where it naturally wants to oscillate.  The same principles apply to sound waves as electrical signals though they are different types of energy...grumbles something about transverse waves versus compressional....grumble grumble. CAPTAIN PLANET!

Now that we have these wonderful tuned circuits, we need a hammer to ring them up with.  This comes in the form of a Radio Frequency Inverter.   It takes direct current and converts it into alternating current at frequencies typically associated with AM radio waves.  Interesting side note - humans can’t detect alternating currents over 10,000 Hz as our nerves are relayed chemical systems and don’t conduct signals efficiently or quickly.  Sound travels faster than most nerve signals though this varies depending on the type of nerve tissue and everybody is different.  The energy from the lightning gun isn’t painful, but it can cause deep penetrated tissue burns.  They’ve been known to scar bones in ways that are visible on x-rays.  I know what my next body modification is going to be.

Here’s the RF inverter up close

And with the controls and safety board removed to show the energy storage and power semiconductors.  The transistors are of the IGBT type.  This is an acronym for “It’s a Great Big Transistor” or “Insulate Gate Bipolar Transistor” depending on how much of a heathen you are.  The transistors are mounted to a heatsink (the big finned black thing) to carry heat away from them.  They don’t really get hot.

A Typical RF inverter for a unit of this power is the size of a small shoe  box.  Google “Solid State Tesla Coil”, and you’ll see most people make them a bit too heavy to carry around.

Now we need a power source.  Any dummy can make a 300 Watt DC to DC converter to take 18V from a cordless tool battery and turn it to 400V or so to drive the inverter.  I decided to use a dynamo and spur belt transmission drive because spinning gizmos are sexy.   The core powerplant for this is a battery powered circular saw...Who bad? That's right, I am :D

Thanks for reading!  If you want to see a menacing video of this thing in action throwing 26” white hot scary loud arcs, check it out on my Youtube.

Here’s a link to the video: