Gene,
A HID floodlight or neon sign ballast could produce voltages in that range. I saw the Thunderwood demonstration video Steve Good posted and was quite impressed. He has contact info on his website if you would like to ask him for more details.

I'm curious to know if it is just water he's using, or if he has added any electrolytes to it to make it conduct better. I don't know how much current he is pushing through there, or if it's AC or DC. With the one clip showing the marks coming from both direction leads me to think in may be AC

The random pattern it produces are beautiful.


http://store.everything-neon.com/powersupplies.html

 

Thanks Doug.
I assumed it was DC because he was painting the water(?) on while it was working. I wouldn't do that if it were AC.

 

I assumed it was DC because he was painting the water(?) on while it was working. I wouldn't do that if it were AC.

The last part of your comment suggests to me, Gene, the belief that DC is inherently safer than AC. Be careful, that is not true, current of either type is dangerous. We can be lulled because most DC we experience is from a small battery.

 

It's certainly possible he was using that much DC to pyro-craft. If the 'equipment' was 'home crafted', it is far more likely he was using AC. Neon sign transformers were fun to play with in school to make 'Tesla Toys'....

The fundamental distinction between AC and DC is whether the voltage measured across the same two points fluctuates (Alternates) or remains constant (direct). Voltage coming 'directly' out of a transformer is AC by it's very nature. The induction process relies on the fluctuation of pulses flowing through the input winding (usually called a primary) in order to transfer them to the output winding (usually called a secondary). The frequency or pulses per second is transparently transferred across.

That being said, in a purest sense, DC isn't really 'pure' DC unless it comes out of a battery.

The DC in your car battery is really DC. The DC coming out of the alternator that keeps it charged and powers the vehicle when it is running is more along the lines of 'close enough to true DC', or what is often called 'ripple DC'.

I was taught that anything with a measured frequency greater than 2800 cps can be regarded as DC, especially for power purposes.

When there is a need to convert it to DC, devices classified as 'rectifiers' are used to accomplish the conversion. A basic rectifier is called a diode, and only allows current to flow in one direction. 4 diodes, connected to form a circle create what is called a 'full wave bridge rectifer' and is a very common way to convert AC to DC. The modern semiconductor of choice in power conversion is what they call an SCR, or silicon control rectifier.

 

Yi! where to begin? Electrical current is DC(direct current) if it always flows the same direction. AC(alternating current) reverses direction/polarity.

A properly designed DC power supply provides pure dc as long as operated within its ratings. Even the output voltage of a battery will vary as the load changes. Measure the voltage of your car battery when the starter is running for instance!

Raising the frequency of AC does NOT make it DC for ANY application.

Fluctuating or rippling dc is still dc unless the polarity reverses. It has an AC component but is still DC!

SCRs are usually used for either regulation or switching, not USUALLY for rectifying per se.

Just trying to clear a few misconceptions. Too big a subject to cover in depth in 1 post!

 

Obviously not very many amps if he is using automotive wire and small alligator clips. Depending on the tapwater, there might be enough mineral in it to carry a charge at that voltage.

 

The only safe way to produce 12Kv DC is with a switch mode power supply where a high frequency oscillator is stepped up to the required voltage in a Ferrite cored transformer, because of the high frequency, the transformer is a fraction of the physical size of one designed for 50 or 60Hz. The output is rectified and filtered. Whilst such power supplies can be designed for high currents, for 12Kv the current available would be milliamps, plenty for the purpose described.
Cathode Ray tube TV used a somewhat similar system by using the high voltage produced by the flyback pulse, that is at the end of each line, the spot had to "flyback"to the start of the next line and this back EMF was stepped up in the line output transformer which operated at 15,625Hz on our system and 15,750 on the American NTSC system.
These days we find small switch mode power supplies in all manner of everyday items from battery/mains shavers, to downlight and fluorescent fittings to flat screen TV's. They are far cheaper to produce than linear power supplies containing a wound transformer operating at mains frequency. Even though toroidal transformers are commonly used in linear supplies and they are wound on ingenious machines, they are far more costly than circuit boards that are produced and fully populated so fast that it makes one feel dizzy watching!

 

Thanks Harry. I knew you'd come through.
You've given me quite a lot to ponder.

 

Many thanks to Duane & Harry for helping me touch up my perceptions of the electron!

Their comments make sense to me, some of Harry's (as they typically do!) have a way of zooming over my head...

In the context of 'ocilliscope displays', AC = "Sine Wave" and DC = 'Flat Line".

Even when I was working in the field (1980-1990 or so) the equipment that I was working on and working with was designed in the mid 70's or before.

Yesterday while thinking about this, my brain ground to a screeching halt trying to remember the fundamental differences between a 'generator' and an 'alternator' within the scope of 'automotive' power systems.

 

Just to be pedantic Bill, AC doesn't have to be a sine wave, it can be square, triangular or any other irregular shape. You mention oscilloscope, if you view your voice on one that is alternating current...AC.
DC or direct current is as you say, a straight line, the current flow is in one direction only.

 

Very cool, that's neat!

I wonder if you could do this with a car battery, or two in series. I've read about people making ******* welders that way, if it's good enough to weld, it should be good enough to burn wood?

 

I'm sure that a car battery, ignition coil and probably a buzzer plus a high voltage rectifier stack would produce an interesting result.

 

My curiosity was aroused by not knowing exactly what you meant by 'high voltage rectifier stack.

This baited me into bouncing the phrase off of the "great google" just to see what came back at me. I found this on ebay! ($15.62 seems kind of inexpensive for anything with a 20kva output!)

High Voltage Silicon Stack Diode Rectifier 20 KV 1A 2DL

Oddly enough, the specifications didn't list an 'imput voltage', so that has me wondering if this is the kind of 'stack' you were talking about.

 

Bill, that one is overkill, not only because of physical size or price but, 20 thousand volts at 5 amps is a definite KILLER!
Basically, a rectifier is a one way way device, current can only pass in one direction. Various materials can be used to make a rectifier, Silicon, Copper oxide, Selenium, Germanium to mention the most common. In my younger days to achieve high voltage rectification, lots of physically small rectifiers were encased in a tube and known as a rectifier stack. How things have changed, take a look at this: http://www.rectifiers.com/pdf/download/Diodes.pdf
I haven't even mentioned the thermionic rectifier diode as used for so many years in tube radio and early monochrome TV's.

 

Thanks for the introduction to the technique of stacking them up to increase the output. As for regular 'simple' case diodes, I remember them from the hobby kit days as a teen when I would craft up stuff on home made circuit boards. It took four of them to craft up a full wave bridge, for those to cheap to buy it as a 'packaged component' (like I was!).

Considering that I haven't used one in more than 30 years, give or take a couple, I can't remember with clarity whether the silver band marked the anode or that cathode, or which of the two is positive.....hmmmm.....guess I am rusty at some of this stuff....

Most of those memories have a fond flavor, so thanks again for stirring them back to life!

 

I will try to get Mike Anderson, the Thunderwood person in the video, to join this forum, and post here. I am in a woodworking club with him.
Paul

 

Hi I'm the artist you saw.. I call the process Thunderwood .. I use a sign transformer for 12,000v. AC .. The liquid is salt water .. A friend in NEOS scroll saw group saw your post.. We hosted a scroll saw picknick this year and I put on 2 seminares on the basic's .. Enjoy, but don't touch while it's "Thunderizing"

 

Thank you for joining the forum to clear that up for us, Mike.

Really appreciated...:yes4:

http://youtu.be/Ksd3klpI2Jc

 

Thanks Mike for the explanation. This opens the possibility of a mobile display, hook up to a spark plug with the motor running, that should produce 20Kv+!

 

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http://1.bp.blogspot.com/-eT0FA5LJE7o/T-sgoe0SRyI/AAAAAAAAMqg/CM9WEtxvDbk/s1600/oso.jpg

 

Cute Dan but I expected all my apprentices to read the colour code like it was the written word. A bit like my objection on this forum to off-set charts, budding routologists should reach the stage where, with metric, the calculation should be done in one's head and with imperial I'll settle for a pencil and paper, or even a calculator! Mike is doing a great job convincing manufacturers to produce metric bits for the American market.

 

Thunderwood Man, My next experiment with high voltage and wood is going to be a testla coil .. 500,000 to 1,000,000 volts ... If 12,000 volts is good, more should to be better ???