20150223

Angry Electric Pickle

Years ago, my dad pulled off a memorable trick for a Halloween party.  He cut an extension cord in half and stripped the wires back a bit.  After connecting the hot and neutral wires to dinner forks ("What's he doing?" I thought), he set up an electrically isolated jig to hold a pickle which is now impaled on either end of said forks. Plugging the extension cord into the wall gave us a 120 volt pickle-colored light show, something like this one. 



Okay, maybe our light show that evening was not quite that scale, but you get the idea.  The yellow-green glow is actually the spectral emission of sodium, through a pickle filter.  (Would this be called an Organic Light-Emitting Diode?)  Think of the color of the Sodium lights we all know from streetlights.

One of the perks of hackerspace patronage is that you get access to things like bigger and better power supplies, and you can use those tools to facilitate thinking "out of the box".  

There is a 15KV neon sign transformer sitting on the back bench, but after some consideration, I worried about the pickle lasing onto my bare retinas, or emitting energetic x-rays if I used the wrong thoriated tungsten electrodes.  I wondered if I was thinking in the wrong direction. 

"Hey, that big TIG/Arc welder in the back is essentially a big low-voltage transformer that can handle a lot of abuse..." 

A few months ago, me and Harald were trying to solve a problem.  We had a hundred or so lengths of 3/4" mild steel bar that needed to have 90* bends in them.  There were too many bars for the amount of acetylene that remained squirreled away in the tanks, so we had to consider a heat source other than oxyfuel.  In his stereotypically overbuilt fashion, Harald remarked, "Maybe we could use carbon gouging rods" 

Carbon's melting point is roughly 6500F, it can surely handle the amount of heat from the torrent of electrons flowing through an arc.  Using a single electrode attached to a welding stinger, you can generate a powerful enough stream of electrons and photons to cut through thick chunks of steel.    Carbon electrodes are also used in electric arc furnaces, the heart of most modern foundries.  Giant electrodes flow tens of thousands of amps to melt large cauldrons of steel and aluminum.  Serious heat generating capability, for sure. 


So what happens, we thought, when we connect two of these electrodes together?  Better yet, who remembers the inanimate carbon rod that saved Homer Simpson and all those astronauts many years ago?  The inanimate carbon rod was also given the "Worker of the Week Award" in recognition of his long overlooked "tireless efforts" which the plant could not function without, earning a managerial position above Homer.  Heh heh heh. 
Have you ever seen a carbon arc lamp attached to a searchlight?  That's the type of brilliant photonic emission we're talking about.  Pure bright white light from a large electric arc between two carbon electrodes.  For a second, consider the vast amount of visible light emitting from this beam.  There's also a healthy amount of infrared photons, which is far easier to detect when you're up close and personal.


Harald and I put on our P.P.E. (safety third), connect the electrodes, flip the welder into AC mode, and strike an arc between the carbon rods. It took a moment to get the hang of scratch starting them together, and getting the arc gap set just right between my hands.  Playing around with the gap and the orientation of the electrodes allowed us to controlthe shape and the brilliance of the arc. 

We could only do this for about 30 seconds at a time before the residual oil on the backs of the welding gloves started to vaporize from the sheer intensity of infrared radiation of the arc.  Even after wrapping our gloves in aluminum tape, the heat was still too intense to bear for more than a brief moment.

I'll never forget the neighbor's surprise.  He saw our silhouettes outlined on the opposing building's wall and came over to find out WTF we were up to.  "I was wondering what you guys were doing" he remarked with a chuckle.

Harald and I wound up cold-working the steel bars.  Give me a lever long enough and a fulcrum on which to place it, and I shall move the world.

Problem solved, but now we have a bunch of useless carbon gouging rods. 

Or are they....

The arc welder and accoutrements are rolled out into the parking lot, along with the beefiest extension cord known to man.  A makeshift pickle jig is hastily cobbled together from a milk crate, duct tape, and pvc pipes.  We get the pickle and electrodes assembled on the rig, excitedly twisting knobs and flipping switches on the welder to get the AC settings just right.  After some fussing, gloriously brilliant results burst out as jets of plasma along the pickle's major axis. 



Unlike the parlor trick from Halloween from many years ago, this monstrosity is a significantly different energy source for the pickle light, causing a distinct "dual mode" effect.  ar the Halloween trick, at 120 volts coming out of the wall (15 amps at most), you're looking at 1800 watts of electric power.  Max.  With dinner forks, operating in low-energy mode, there's not so much of an electric arc as a dull glow reminiscent of a nightlight.  When attached to the welder, pushing 48 volts at 200 amps max, that's nearly 10 kw of pickle-colored goodness running full blast.


Here's another vantage point, from a previous event...

https://www.youtube.com/watch?v=Qdba67KyR-s

(for some reason, blogger isn't letting me embed this video).  Note in this one the jet of fire shooting out the sides of the pickle before it takes off with super-bright mode. 

Here's Trent from MAG Lab running the pickle rig.  Note the brilliant white light projected on a wall from the hole that the arc has burned through the pickle, directly emitting arc light. 


A diagram of our electric pickle jig -


The trick was in setting the arc gap just right.  Sometimes, the pickle would only steam, without generating any light at all, this usually happened due to misaligned electrodes.  Other times, it would only fizzle a little bit of light and give up; a dud.  After some experimentation, we found the more coaxially aligned the electrodes were to one another, the better the results.  It also helped to get the electrodes located correctly the first time, as subsequent stabs would turn the pickle's innards into mush.  When set just right, for the first 30 seconds the pickle emitted a nice gentle sizzling glow.  Once warmed up and excited, it would suddenly take off into arc lamp mode, and emit what must be at least a million times more photons.  Once in this excited state, raising the amperage makes the pickle go into overdrive. 

A gap between the electrodes of about 1/4" seemed to be optimal, but sometimes I'd have to tease the electrode ever so gently to scratch-start the arc.  Use caution, as this is a deadly amount of energy should the arc cross certain parts of your body.  Handling the pickle left me soaked in brine, which gave me a temporary but much-needed OCD hand washing complex.  Also, don't adjust the electrodes with both hands while the machine is running, only use one hand at a time, that will prevent stray current from crossing your heart. 

One mistake I should share, we initially made a pickle holder out of stainless steel, trying to get the weight off of the electrodes.  After ignition, a stray arc made quick work of the holder, quickly slicing off a support arm. You can see remnants of it in the second video on this page. 

The Angry Electric Pickle is a neat parlor trick, and was a definite draw for the Sparklecon crowd.  Try it at your next party to win friends and influence people.  If you don't electrocute yourself, let us know how it goes.  If you DO electrocute yourself (and survive), let us know how it goes.  Whatever you do, make sure that you have a buddy standing by with a wooden baseball bat to slug you to safety, should any electrical mishaps occur. 

Happy scienceing!

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