Electrostatic machines for wintering chasers

Dan Robinson

A distant CG in the sandhills of Nebraska?
vdg13.jpg


Not distant at all - it's 4 inches tall and only 3 feet from the camera. This is a DA strike (dome-to-arm) from a Van De Graaff generator - arguably, for a lightning enthusiast, the greatest machine ever built!

A search on eBay last week found this generator and one of its relatives, the Wimshurst machine, available for less than $200 total. I quickly swiped both of them, and they arrived this week. I have to say that both of these machines, well, *rock*!

The Van De Graaff machine is an older model likely at least 40 years old, but it works like a champ. Only 17 inches tall and amazingly simple in construction (motor, rollers, a belt, 6.5" aluminum dome, braided wire charge sprayers and an inline lamp switch) this machine cranks out some serious discharges! I can't imagine having a large generator to mess around with after seeing what this small one can do.

When you first turn the unit on, it instantly comes to life with long, dim and extensively branched sparks jumping 8 inches from the dome to the base, *twice* every second.

vdg19.jpg


Mini anvil crawler.


This Van De Graaff machine will produce long, intense, bright and extensively branched 3" to 4" sparks to your hands and arms at rates as frequent as once per second. Dimmer and longer upward-branching sparks pop off the dome intermittently. Most of the VDG's sparks don't hurt, though you can definately feel them. A few of the brighter, longer ones will give you a good jolt. (click thumbnails to enlarge)





Here is a 5.8MB WMV video clip of the Van De Graaff generator in operation:
http://wvlightning.com/2006/vdg1.wmv
(WMV interlacing issues are hiding half of the sparks)

The second electrostatic machine I bought, the Wimshurst, is of a more complex (and much older) design. Its basic operating principle is separating charge by passing foil-plated discs spinning in opposing directions close together, then using wire pickups to transfer the charge to two leyden jars. This model uses a hand crank. Due to the increased capacitance from the leyden jars, the Wimshurst's sparks are very intense.

wimshurstp.jpg


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The sparks from this machine are only 3 inches maximum, but they are bright and sometimes branched. Spinning the discs very fast will yield vivid 3-inch sparks up to five times per second. Unlike the VDG, the Wimshurst machine's sparks are quite painful.





wimshurstb1.jpg


Here is a 2.6MB WMV video clip of the Wimshurst machine in operation:
http://wvlightning.com/2006/wimshurst1.wmv

SAFETY NOTE: Unlike these electrostatic machines, sparks from Tesla coils are NOT safe for a person come into direct contact with. The above machines produce short-duration sparks. The Tesla coil produces a continuous arc that can come into contact with live household power and electrocute the person in direct contact with the coil's arc.
 
Tesla Coil - Homemade Lightning!

Good day,

I have done some work with Tesla coils ... These are air-core resonant transformers which create high-frequency and continuous "lightning" effects. The key here is HIGH FREQUENCY (around 200 kHz) opposed to STATIC electricity (like a Wilmhurst / Van De Graaf machine). The arcing is continuous from a Tesla coil, unlike a static device where a charge has to "build up" and discharge intermittently.

tchpdme.jpg


Above is a picture of a large Tesla coil system I built with myself standing next to it. This unit is driven by a power supply that takes the 115 V from the wall outlet and steps it up to about 13,000 volts. The picture above is the Tesla coil itself, and NOT the power supply. The coil needs high voltage to operate, and works by a basic principle of and LC (inductor & capacitor) oscillating resonating circuit.

The unit above has both a spark-gap and capacitor bank in the base, the primary coil is a flat "pancake" coil of about 10 turns of 3/8" copper tubing (that's the inductor as well as the primary coil below the secondary form). The secondary coil, which is about 1000 turns of #22 magnet wire, is wound around a 6" diameter PVC pipe length of about 24". When the unit is energized, the capacitor charges to over 13,000 volts, then fires the spark-gap (arcs across it) which is in series with the primary coil. When the sudden surge of current flows through the spark gap and primary, it creates an L-C oscillating current at the resonant frequency of the system. This current creates an intense magnetic field about the secondary, and steps up the voltage from 13,000 to over 1.5 million volts. The large doughnut structure on top provides extra capacitance so that a "lightning bolt" will eminate from it from a small nail or bump on it.

tcnewps1.jpg


Here is the power supply I built for it. Like a person suffering from SDS has nothing better else to do, right? Anyway, inside this unit is four 12,000 volt @60 mA neon-sign transformers in parallel. A large variac allows the voltage from the wall to go into the unit at 115v, but drive the transformers at 0-130 V. Finally, output of this unit is variable from 0 to over 13,000 volts at about 240 mA (over 3,000 watts) ... A 30 amp breaker is a must for this puppy!

tchpjl2.jpg


Here is a picture of some sparks right off the 3,000+ watt high voltage power supply. I built this 9-foot tall jacobs ladder to test it. Sparks start at the bottom and climb up the two electrodes until it reaches the top. Frankenstien need not apply.

tchpsp8.jpg


Finally, above, the whole Tesla coil system is driven together with the high-voltage power supply. Huge lightning "arcs" dance around, the one here is over 6-feet long, and dissapears into the ceiling!

tchpsp4.jpg


Here is another 5-foot lightning bolt hitting the far left wall at a grounded point to the left of the Tesla coil.

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Another really cool thing ... RF energy (about 150 to 200 kHz) is RADIATED away from the Tesla coil. This will not hurt you, however, it will light a fluorescent tube in my hand since I am within the reactive near-field of the Tesla coil (it is a low-performance "antenna" in this case)!

tcbigsp7.jpg


Here is a time-exposure of some of the "lightning" generated by the Tesla coil system above.

tctthold.jpg


On a much "lighter" note, I also constructed a small Tesla coil system. This is a "table-top" and self-contained design. The capacitors, power-supply, and spark gap are all in the base of the unit, with the primary inductor-coil an inverted cone with about 12 turns of 1/4" copper tubing and a secondary of about 500 turns of #22 magnet wire about a 24" section of 2" diameter PVC. Opposed to the larger coil, this unit runs on only 230 watts, and has a power supply of 10,000 volts at 23 mA. The output is about 400,000 volts at a 500 kHz frequency (sparks are 10 - 12 inches).

tcttparc.jpg


Here is a picture of the sparks from the table-top coil. The "lightning" here is continuous and about 10" to 12" long. Note the "blue glow" (St Elmos fire)!

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Here is a nice "brush discharge" of many small 6" bolts of lightning from the same table-top tesla system.

Finally, any electical-engineering fans out there? I provided a schematic for the large coil from my site below!

tcbigscm.gif


For more information about these Tesla coils, please visit the section on my site about them ... Many, many details on safety, how to construct one, schematics, step-by-step construction puctures, even an experimental "air cannon" to test debris impacts!

http://www.sky-chaser.com/tesla.htm

Enjoy - Chris Collura - KG4PJN
 
Here's something I've always wondered: I always see people standing near Tesla coils with flourecent bulbs. If one of the bolts arcs out and hits you on the head or something, isn't that dangerous? And yet people stand so close! Or are the bolt discharges harmless?
 
Originally posted by Ryan McGinnis
Here's something I've always wondered: I always see people standing near Tesla coils with flourecent bulbs. If one of the bolts arcs out and hits you on the head or something, isn't that dangerous? And yet people stand so close! Or are the bolt discharges harmless?

This page is certainly getting alot of hits, hmm I wonder why....
 
Ahhhh - I see! I wondered why my server access log today is already 6 times bigger than it normally is.

Chris can probably do a better job explaining this than I can, but the main threat from a Tesla coil is not from the output arcs themselves, but the danger of the arcs (basically conducting paths) connecting to 60hz household current at the same time the operator is in contact with an arc. According to some of the safety information on the subject, this can happen either externally (arc hitting a 110V wall outlet and ground) or internally in the coil unit (particularly poorly constructed ones) from arcs from the primary to the secondary coil, which allows 60hz houshold current to flow through the arc coming out of the primary. There have been three documented deaths from this happening and many more 'close calls'.

The sparks from electrostatic machines like the VDG and Wimshurst aren't continuous arcs like the ones from a Tesla coil, so they can't transfer sustained household current to the person in contact with the spark.

Here is an interesting site on the subject:

http://www.pupman.com/safety.htm

The streamer can still, and sometimes does strike a point downstairs that is part of the LETHAL high voltage 60 Hz circuitry. When such a contact is made, any person also connected to a corona/streamer link to the secondary at the same time will, via the ionized air path, become connected to lethal 60 Hz mains current. You could try the trick you described standing on the cement floor in your tennis shoes half a dozen times and live, or be killed the very next time you try it. The fact that the bottom of your secondary is tied to ground will not save you!
 
Try going out on a moonless night under high tension lines (the big ones). It will partially light a flourescent tube. A British guy actually did an art project involving hundreds of them...

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Some times if you jump while holding it, you'll get a small shock ;)

Aaron
 
You should read some of their comments....like

"I bet these dorks really fark up their neighbors television reception..."

I know, I am...I added the link to them.



BTW, to keep my post somewhat related, I will say I would love to have one of those to play with. I would take my dorkhood even further and build or buy some miniature homes/trailers and zap them.
 
Expect the wife to not understand!

Good day,

I read the pupman list alot on Tesla coil stuff, and yes, there is a well written page on safety for it there too...

http://www.pupman.com/safety.htm

And I mean in every DETAIL too, such as an I-Rate wife / husband (see quote below)...

The Spouse

Another potential hazard is if the spouse thinks one is spending too much time on his or her hobby. ANY HOBBY!!!!

Expect the wife to not understand!

I laughed the first time I read that one!

Chris C - KG4PJN
 
I've got to say, you guys really do have some cool toys! I can imagine what the sparks sound like. The only thing missing would be the requisite "It's ALIIVE!

8,000 hits on this page already? That's Farkin' impressive :D
 
After some further experimenting, I figured out a way to consistently get long discharges that are nearly exact replicas of cloud-to-ground strikes (a long main channel with downward branching). Some of the main channels are splitting in two close to the 'ground'.







I have only been able to produce these with the Wimshurst machine, sending a spark from one of the terminals to my forearm. They are very bright and I am sure they would show up easily on slide film or a digital camera. They are very painful and leave red, hive-like raised welts on your skin that last for a few hours (as if someone slapped you hard with a ruler!). I'm trying to figure out a 'stage' where I can get these with some other discharge surface other than my skin (IE, without the pain factor).
 
A few interesting links, them I'm going to put away the spark machines until next winter. Natural lightning is coming soon, and it's going to get too humid for these machines anyway. Well, check these links out for now - there is some cool stuff here.

A Marx impulse generator - easy and cheap to build. This guy built a homemade million-volt model that produces sparks 4 feet long:

http://www.electricstuff.co.uk/marxthree.html

Some interesting stuff at the rest of that site. Take a look at the spark-o-phone:

http://www.electricstuff.co.uk/

Here is a great site by a guy who has built just about every type of generator ever invented:

http://www.coe.ufrj.br/~acmq/electrostatic.html

Check out this huge 4' diameter Wimshurst that somebody built that runs off of a *treadmill motor*. Its sparks are huge:

http://research.microsoft.com/~swinder/spa.../wimshurst.aspx

And the ultimate Van De Graaff is this monster at the Museum of Science in Boston, MA. I'll let these photos speak for themselves. The first shot is the machine inside of a large airplane hangar, with sparks that have to be at least 10 to 20 feet long!

http://www.mos.org/sln/toe/historical/famous.jpeg
http://www.mos.org/sln/toe/historical/moresparks.jpeg
http://www.mos.org/sln/toe/gallery1.html

Coke Can Van De Graaff Generator: Very simple generator made out of PVC pipe, rubber band and a can of Diet Coke!
http://www.scitoys.com/scitoys/scitoys/ele...o/electro6.html

The Electrophorus, the simplest generator of them all:
http://www.alaska.net/~natnkell/electrophorus.htm

More Electrostatic Machines:

Sparks from fur and a rotating drum:
http://www.alaska.net/~natnkell/staticgen.htm

Bonetti Machine built on plastic shelving:
http://www.geocities.com/teslinasite/electrostaticB

Lorente´s Generator, Four rollers (2 metal, 2 dialectrically opposed material):
http://www.uned.es/electrostatic-generator/

Kelvin Generators, charged by drops of falling water:
http://web.mit.edu/Edgerton/www/Kelvin.html

Carré Generator, an interesting machine:
http://www.thebakken.org/artifacts/Carre.htm
 
Everything about this thread is completely and totally cool. Just wanted to get that out of the way :)

You'll love this too - this guy uses voltage as a paintbrush to create his artwork.

http://www.davearcher.com/

If I don't get some lightning soon, I'm going to have to make some too.
 
Wow, I really wanted to know that person's name!

I saw a special on him back in 1986 on "Ripley's Believe It Or Not" ... I am even more impressed on his Tesla Coil system.

Not much different than the one I fire-off in my garage!

I can imagine the heat and shock-waves from the arcs create the patterns, which are second-to-none (never the same, very chaotic, abstract, and surrealistic) - Way cool!
 
Not much different than the one I fire-off in my garage!

That stuff you made in your garage totally rocks. Truly.

Do you think that your Tesla coil could move paint or ink around? Wouldn't that be a cool experiment.
 
Well, I couldn't help myself. I just broke down and bought a large Van De Graaff generator from an online science catalog. It is almost 3 times larger than the one I bought last month.

More power!

8)
 
That's beautiful, man <sniff>

Yeah, the lengths and expense I will go to for this stuff :shock: I'm planning to rent it out and do demonstrations at schools to pay for it, that's the only way I could justify the cost.

...or I could just set it up on a street corner downtown with the case open for people to toss money into :)
 
The new Van de Graaff generator arrived this week. Its optimal operating days are numbered as the higher humidities of spring are on the way. Nonetheless, I did get a chance during the past couple of days of dry weather to give it a try.

The generator came with a mirror-finish spherical dome, an unconventional shape which looks really cool but is actually not the best type of VDG upper terminal. The conventional oblate (flat oval) shaped dome, the one the unit should have come with, is a better shape for larger sparks and less corona leakage around the support column opening. I wrote the company I ordered the generator from and they should be sending me the correct terminal sometime soon.

With some electrical tape, the corona leakage problem around the dome opening is mitigated to some extent, allowing the dome to charge up enough to produce some nice sparks. Actually, some of these in my opinion cross over the threshold enough to be called 'bolts'! Currently I'm able to get 5"-6" long 'solid' sparks to my arm and to the dome of the small generator. These sparks are very bright and ear-ringing loud! (see video clip below) Despite their size, these do not hurt much at all providing they strike my forearm, though they cause a pretty potent muscle contraction in my arm. The smaller Wimshurst sparks are much more painful (due to the 'complete circuit' current path and the capacitance from the leyden jars). Sparks to my fingertips are slightly painful, but due to the 'pointiness' of human fingers causing corona, sparks to fingers are cannot get nearly as big and long as these.

MPEG video clip, 1MB
http://wvlightning.com/2006/newvdg.mpg
(Indoor thunder - turn your volume up for the full effect of how loud these are)

armstrike3.jpg


Click the thumbnails below for larger versions:



This one even has a video 'ghost' channel like a full-size lightning bolt!



Dimmer 'gossamer thread' sparks up to 20 inches long jump from the dome to the base and from the dome to my shirt sleeves.

colspark1t.jpg


Here is a cool anvil crawler-like spark to the small VDG dome surrounded by 'gossamer thread' channels.



And of course, I had to try this.



Here are a couple of shots of the new generator along with the small one for a size comparison. (The small VDG (center) was the one I took to Denver):

 
Originally posted by Dan Robinson
Despite their size, these do not hurt much at all providing they strike my forearm, though they cause a pretty potent muscle contraction in my arm.

That is one awesome machine. Hours of fun :)

That must feel really weird though on your arm, it makes the muscle contract? What does it feel like? Squeezing a tennis ball?
 
It's really strange, depending on where the spark hits it will contract a different set of muscles in my arm, hand and fingers. It is painless, kind of like a doctor using the rubber hammer to check your reflexes.

Most sparks cause the muscles that rotate and flex the wrist to contract, causing my hand to turn and flex. Other sparks will cause one or more of my fingers to flex, particularly the ones that hit closer to my wrist. A spark that hits on the inside of my palm will usually make my fourth (pinky) finger flex outward (you can see this in this video clip)
 
OK, I know I've worn this thread out, but I had to post these.

Daylight 'CG's to the head and wrist.

headstrike1.jpg


wriststrike1.jpg


wriststrike4.jpg
 
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