hot, bright noisy sparks needed

[ScottM]

For an art project, I need to generate a bright, noisy arc about 1/2" long.In the past I've successfully done this with with this: https://www.sparkfun.com/products/11218 but that isn't working in the new installation; the devices get hot and fail after a few minutes of use. I'm looking for someonewith expertise in this area to suggest a design I can build.

The requirements are:

Able to be run off a small 12v lead acid battery. Extra points if it can run off 5v and 3A, which is what the sparkfun device uses.

Portable - I'll be carrying the circuit in a backpack. Large Marx generators need not apply. Neither do designs that require twenty pounds of copper tubing.

Stable and Safe - I'll be carrying the circuit in a backpack and long term stability is a concern. It will be heavily insulated but I am still very uninterested in sudden failures, magic smoke, fires, internal arcing, and other surprise effects. I need long-term reliability.

A bright, fat, noisy, snarling, visually continuous arcing spark - which probably means I need an output frequency somewhere between 40Hz and 200Hz. Idon't have specs on the sparkfun device, but it does "loud" and "bright" very well.

Capable of more or less any duty cycle; the design calls for about 10 seconds on and a few seconds off, repeating, but I want it to be able to run continuously.

Able to survive any sort of spark gap from "too big to actually arc" to "brief short circuit", but the typical gap is 3/8ths inch to 3/4ths inch.

Repeatability - I need to be able to build several and I want repeatability, so "scavenge a flyback from a CRT" is much less interesting than a mouseror digikey part number.

And - crucially - able to handle a capacitive load. The high voltage travels through two longish (several feet) parallel wires, though a small brass tube and into a chunk of aluminum that showcases the spark, but it all adds to the capacitance, and I think that's why the sparkfun devices are dying.

I'll say it now - yes, I know a spark that can bridge 3/4" and be "fat", bright and noisy requires tens of thousands of volts and several mA. I know that misuse of that kind of power leads to pain and possible death. Since I'll be carrying the device and the high voltage wires will be running down my arm I will be paying a lot of attention to insulation and safety concerns.. Extra points if the voltage and current can be minimized to limit risk, but no matter what I will consider any design as potentially fatal and treatit accordingly. I know about the one hand rule, and "heavily insulated" ismy favorite phrase.

I just built a Mazilli ZVS circuit (http://wiki.4hv.org/index.php/Flyback_transformer#High_Power_Drivers), and it works as advertised but it's not suitable here. Running the output through a twisted pair of insulated bell wire caused a very pretty purple corona glow along the length of the wires, and no spark at the end. When it does spark. it's much too high frequency - it hisses instead of snarls, and glows instead of being a fat bright spark. And it's too powerful - the voltage cracks the glass tubing I use as insulation. If it's possible to lower the frequency (greatly) without destroying the MOSFETs, it could be a candidate, but I don't know how to do this safely.

I'll accept any help, but I'm less interested in "well, you could try this"than "here is what is known to work." I've been researching things I couldtry for days, but mostly I've fried components and lost time. If you have expertise and don't mind drawing a schematic I will be very grateful. TIA!

 

[Oppie]

For an art project, I need to generate a bright, noisy arc about 1/2"
long. In the past I've successfully done this with with this:
https://www.sparkfun.com/products/11218 but that isn't working in the new
installation; the devices get hot and fail after a few minutes of use. I'm
looking for someone with expertise in this area to suggest a design I can
build.

The requirements are:

Able to be run off a small 12v lead acid battery. Extra points if it can
run off 5v and 3A, which is what the sparkfun device uses.

Portable - I'll be carrying the circuit in a backpack. Large Marx
generators need not apply. Neither do designs that require twenty pounds
of copper tubing.

Stable and Safe - I'll be carrying the circuit in a backpack and long term
stability is a concern. It will be heavily insulated but I am still very
uninterested in sudden failures, magic smoke, fires, internal arcing, and
other surprise effects. I need long-term reliability.

A bright, fat, noisy, snarling, visually continuous arcing spark - which
probably means I need an output frequency somewhere between 40Hz and
200Hz. I don't have specs on the sparkfun device, but it does "loud" and
"bright" very well.

Capable of more or less any duty cycle; the design calls for about 10
seconds on and a few seconds off, repeating, but I want it to be able to
run continuously.

Able to survive any sort of spark gap from "too big to actually arc" to
"brief short circuit", but the typical gap is 3/8ths inch to 3/4ths inch.

Repeatability - I need to be able to build several and I want
repeatability, so "scavenge a flyback from a CRT" is much less interesting
than a mouser or digikey part number.

And - crucially - able to handle a capacitive load. The high voltage
travels through two longish (several feet) parallel wires, though a small
brass tube and into a chunk of aluminum that showcases the spark, but it
all adds to the capacitance, and I think that's why the sparkfun devices
are dying.

I'll say it now - yes, I know a spark that can bridge 3/4" and be "fat",
bright and noisy requires tens of thousands of volts and several mA. I
know that misuse of that kind of power leads to pain and possible death.
Since I'll be carrying the device and the high voltage wires will be
running down my arm I will be paying a lot of attention to insulation and
safety concerns. Extra points if the voltage and current can be minimized
to limit risk, but no matter what I will consider any design as
potentially fatal and treat it accordingly. I know about the one hand
rule, and "heavily insulated" is my favorite phrase.

I just built a Mazilli ZVS circuit
(http://wiki.4hv.org/index.php/Flyback_transformer#High_Power_Drivers),
and it works as advertised but it's not suitable here. Running the output
through a twisted pair of insulated bell wire caused a very pretty purple
corona glow along the length of the wires, and no spark at the end. When
it does spark. it's much too high frequency - it hisses instead of snarls,
and glows instead of being a fat bright spark. And it's too powerful - the
voltage cracks the glass tubing I use as insulation. If it's possible to
lower the frequency (greatly) without destroying the MOSFETs, it could be
a candidate, but I don't know how to do this safely.

I'll accept any help, but I'm less interested in "well, you could try
this" than "here is what is known to work." I've been researching things I
could try for days, but mostly I've fried components and lost time. If you
have expertise and don't mind drawing a schematic I will be very grateful.
TIA!

Oil burner ignition transformer is one way. A 12V to 120V inverter is
needed. Then again, here are several hits on google
https://www.google.com/search?q=oil...indow=1&q=oil+burner+ignition+transformer+12V

 

[Oppie]

Arrgh! https://www.google.com/search?q=oil+burner+ignition+transformer+12V

 

[George Herold]

For an art project, I need to generate a bright, noisy arc about 1/2" long. In the past I've successfully done this with with this: https://www.sparkfun.com/products/11218 but that isn't working in the new installation; thedevices get hot and fail after a few minutes of use. I'm looking for someone with expertise in this area to suggest a design I can build.

The requirements are:
Able to be run off a small 12v lead acid battery. Extra points if it can run off 5v and 3A, which is what the sparkfun device uses.

Portable - I'll be carrying the circuit in a backpack. Large Marx generators need not apply. Neither do designs that require twenty pounds of coppertubing.

Stable and Safe - I'll be carrying the circuit in a backpack and long term stability is a concern. It will be heavily insulated but I am still very uninterested in sudden failures, magic smoke, fires, internal arcing, and other surprise effects. I need long-term reliability.

A bright, fat, noisy, snarling, visually continuous arcing spark - which probably means I need an output frequency somewhere between 40Hz and 200Hz.I don't have specs on the sparkfun device, but it does "loud" and "bright"very well.

Capable of more or less any duty cycle; the design calls for about 10 seconds on and a few seconds off, repeating, but I want it to be able to run continuously.

Able to survive any sort of spark gap from "too big to actually arc" to "brief short circuit", but the typical gap is 3/8ths inch to 3/4ths inch.

Repeatability - I need to be able to build several and I want repeatability, so "scavenge a flyback from a CRT" is much less interesting than a mouser or digikey part number.

And - crucially - able to handle a capacitive load. The high voltage travels through two longish (several feet) parallel wires, though a small brasstube and into a chunk of aluminum that showcases the spark, but it all adds to the capacitance, and I think that's why the sparkfun devices are dying..

Excellent! I was going to ask why the spark fun thingie wouldn't work. Youmay not like this answer, but it might be easier to try and reduce the cable and stray capacitance rather than design a beefier HV supply. So perhaps you can separate the wires that carry the HV... and maybe move the generator closer to where you want the arc.

I'll say it now - yes, I know a spark that can bridge 3/4" and be "fat", bright and noisy requires tens of thousands of volts and several mA. I knowthat misuse of that kind of power leads to pain and possible death. Since I'll be carrying the device and the high voltage wires will be running downmy arm I will be paying a lot of attention to insulation and safety concerns.

Oh! (don't kill yourself) OK some thin HV wire with big *thick* insulation.. (Personally I wouldn't touch this project with the proverbial ten foot pole.)

Extra points if the voltage and current can be minimized to limit risk, butno matter what I will consider any design as potentially fatal and treat it accordingly. I know about the one hand rule, and "heavily insulated" is my favorite phrase.

I just built a Mazilli ZVS circuit (http://wiki.4hv.org/index.php/Flyback_transformer#High_Power_Drivers), and it works as advertised but it's not suitable here. Running the output through a twisted pair of insulated bell wire caused a very pretty purple corona glow along the length of the wires, and no spark at the end. When it does spark. it's much too high frequency -it hisses instead of snarls, and glows instead of being a fat bright spark.. And it's too powerful - the voltage cracks the glass tubing I use as insulation. If it's possible to lower the frequency (greatly) without destroying the MOSFETs, it could be a candidate, but I don't know how to do this safely.

OK again I think you need wires with better insulation.. You can adjust thefrequency of the flyback. (I think)

George H.

 

[RobertMacy]

For an art project, I need to generate a bright, noisy arc about 1/2"
long. In the past I've successfully done this with with this:
https://www.sparkfun.com/products/11218 but that isn't working in the
new installation; the devices get hot and fail after a few minutes of
use. I'm looking for someone with expertise in this area to suggest a
design I can build.

...snip...excellent description

For insulated wiring, you should be able to use spark plug cabling. Don't
use the resistive kind, use the racing kind with wires, not carbon. From
memory it should be good out to around 10-20kV

I used to work in 150kV to 200kV power supplies. I cannot stress enough,
Just keep THINKING: at high voltage EVERYTHING CONDUCTS! And probably not
like you expect. There is 'through' conductivity and 'surface'
conductivity. Even AIR conducts, not much, but enough to quickly build up
charge somewhere else that may wish to arc over as the voltage gets too
big.

Watch out for sharp edges. of anything. make stuff rounded with clean
radii. Even inside an insulating blob a sharp point can ionize and set up
disastrous failure mechanisms later.

 

[Adrian Jansen]

For an art project, I need to generate a bright, noisy arc about 1/2" long. In the past I've successfully done this with with this: https://www.sparkfun.com/products/11218 but that isn't working in the new installation; the devices get hot and fail after a few minutes of use. I'm looking for someone with expertise in this area to suggest a design I can build.

You mean, like one of these:

http://shaddack.twibright.com/projects/reveng_type800stungun/

 

[LM]

Could a metal jacket help. I don't know what they are called, or how do youget them. But I have seen cloths woven of/with? metal wires. At least larger sparks do not penetrate them. But I am not going to try my self, of course. So it is your skin not mine.

 

[Scott M]

The oil burner transformer looks like a possibility, but I can't tell from the description how to drive it. Does it spark continuously when power is applied? Can I pump 12v into it as a 40Hz square wave at, say, a 50% duty cycle and get a 40Hz spark out the other end?

On changing the wire length - I probably cannot. The spark gap is a piece of machined aluminum held (via appropriate insulators) in my hand. The circuit is in a backpack. And since I'd prefer the high voltage wires not be tight against my arm, I need at least 3-4' of wire between the driver and the spark gap. For the last 8" or so the wire goes through a narrow brass tube;if that's a significant source of capacitance I could perhaps replace thatwith plastic. The aluminum part itself probably adds some as well, but forwhat I spent getting them machined I'm not going to discard them. I designed this whole thing around the sparkfun devices, because they worked ok in previous and vaguely similar designs, but the rash of rapid failures has left me with a large investment in a design that I can't modify very much, given the costs. If there are ways to reduce the capacitance between two wires (other than "make them shorter and further apart") I'm interested.

The 3v spark circuit looks like a more fragile cousin to the sparkfun device. For the price I could try it, but I'm skeptical. The stun gun circuit worries me because it's overtly designed to hurt people and that's something I need to avoid the suggestion of. I want the spark to look scary, but if possible not BE scary. I'll look at the ignition circuit.

Right now I'm wondering if the ZVS circuit I built could be modified. It puts out high frequency (~70kHz?) AC, which I assume is why everything I connect to it acts like a capacitor and drains the power away in a corona before it reaches the spark gap, but what if I rectified and smoothed it into DC? And then turned the ZVS circuit on and off at 40Hz or so?

 

[Lasse Langwadt Christensen]

Den fredag den 1. november 2013 00.07.18 UTC+1 skrev Scott M:

The oil burner transformer looks like a possibility, but I can't tell from the description how to drive it. Does it spark continuously when power isapplied? Can I pump 12v into it as a 40Hz square wave at, say, a 50% duty cycle and get a 40Hz spark out the other end?



On changing the wire length - I probably cannot. The spark gap is a pieceof machined aluminum held (via appropriate insulators) in my hand. The circuit is in a backpack. And since I'd prefer the high voltage wires not be tight against my arm, I need at least 3-4' of wire between the driver and the spark gap. For the last 8" or so the wire goes through a narrow brass tube; if that's a significant source of capacitance I could perhaps replace that with plastic. The aluminum part itself probably adds some as well, but for what I spent getting them machined I'm not going to discard them. I designed this whole thing around the sparkfun devices, because they worked ok in previous and vaguely similar designs, but the rash of rapid failures has left me with a large investment in a design that I can't modify very much, given the costs. If there are ways to reduce the capacitance between two wires (other than "make them shorter and further apart") I'm interested.



The 3v spark circuit looks like a more fragile cousin to the sparkfun device. For the price I could try it, but I'm skeptical. The stun gun circuit worries me because it's overtly designed to hurt people and that's something I need to avoid the suggestion of. I want the spark to look scary, but ifpossible not BE scary. I'll look at the ignition circuit.

it doesn't matter if you write stun gun or spark generator on the schematic
it is basically the same thing, and anything that makes a 1/2 spark is scary


-Lasse

 

[Greegor]

I'm intrigued that what you had "broke glass".
Got a photo of that?

 

[Scott M]

I'm intrigued that what you had "broke glass".

Got a photo of that?

There's now a hairline crack in a 6mm bit of glass tubing (the sort used inchemistry). Inside the tube is one wire of the output; just outside the tube and all around it is the aluminum that forms the other leg of the output.. In one test the arc decided that cracking through the 1mm or so of glass tube wall was a better option than the 3/4" of air I'd planned for it.

From videos I've seen on the web this kind of behaviour isn't too uncommon for this oscillator. Someone running one at 36v decided to put the output across (not through) a glass lightbulb and had something similar happen: http://www.instructables.com/file/FJQ6WBSG9NH8XA4

I don't know if my phone camera can do a good job of photographing a hairline crack in a small glass tube but if I can get it to show up I'll send it along.

 

[Scott M]

<http://www.analog-innovations.com/SED/CD-Ignition-Basic.pdf>

Can you explain the workings? If I'm reading that right - no guarantees there - it looks like all the spark comes from the discharge of the 1uf cap, and I'm surprised there's enough power available from one. It also looks like the transistor gets to sink not just the power from the cap, but all the amps from the battery, when it goes on. Does it need a massive heatsink? I'm using IRFP260 for this kind of thing.

I'd expect to drive it with a 555 - what kind of timing would it want? Fromthe notes it looks like the "on" time is critical...

 

[Adrian Tuddenham]

For an art project, I need to generate a bright, noisy arc about 1/2"
long. I [...]
A bright, fat, noisy, snarling, visually continuous arcing spark - which
probably means I need an output frequency somewhere between 40Hz and
200Hz. I don't have specs on the sparkfun device, but it does "loud" and
"bright" very well.

Don't do it. Find another project.

 

[Martin Brown]

The oil burner transformer looks like a possibility, but I can't tell from the description how to drive it. Does it spark continuously when power is applied? Can I pump 12v into it as a 40Hz square wave at, say, a 50% duty cycle and get a 40Hz spark out the other end?

On changing the wire length - I probably cannot. The spark gap is a piece of machined aluminum held (via appropriate insulators) in my hand. The circuit is in a backpack. And since I'd prefer the high voltage wires not be tight against my arm, I need at least 3-4' of wire between the driver and the spark gap. For the last 8" or so the wire goes through a narrow brass tube; if that's a significant source of capacitance I could perhaps replace that with plastic. The aluminum part itself probably adds some as well, but for what I spent getting them machined I'm not going to discard them. I designed this whole thing around the sparkfun devices, because they worked ok in previous and vaguely similar designs, but the rash of rapid failures has left me with a large investment in a design that I can't modify very much, given the costs. If there are ways to reduce the capacitance between two wires (other than "make them shorter and further apart") I'm interested.

The 3v spark circuit looks like a more fragile cousin to the sparkfun device. For the price I could try it, but I'm skeptical. The stun gun circuit worries me because it's overtly designed to hurt people and that's something I need to avoid the suggestion of. I want the spark to look scary, but if possible not BE scary. I'll look at the ignition circuit.

it doesn't matter if you write stun gun or spark generator on the schematic
it is basically the same thing, and anything that makes a 1/2 spark is scary[/QUOTE]

More to the point anything producing hot bright electrical sparks 1/2"
long is going to be dangerous or even deadly if you make a mistake.

Your best bet is something along the lines of a Jacobs ladder device
where the rising plasma allows a lower voltage that strikes across the
narrow lower arc gap to rise and carry a noisy spark with it.

It probably contravenes lots of RF emissions regulations too.

I expect to read about this exploit in the Darwin Awards.

 

[Scott M]

I expect to read about this exploit in the Darwin Awards.

I appreciate the concern, but I've built devices like this several times and used them successfully for days at a time, based around the sparkfun device. I understand the risks and I understand how to manage the risks.

That said, I'm always interested in lower voltage approaches. Jacob ladder drivers would generate more voltage than I need, since they are trying to sustain an arc larger than 1/2" at many points. There are designs on the webfor circuits that generate several inches of arc, but they aren't anythingI want to carry in a backpack. The ZVS oscillator is not a favored candidate for the same reason - there is more power there than I need.

 

[Greegor]

This doesn't strike me as very creative.

 

[Ecnerwal]

Jacob ladder
drivers would generate more voltage than I need, since they are trying to
sustain an arc larger than 1/2" at many points.

You appear to miss a fundamental point of what you are playing with. (I
spent about a decade working in a plasma lab...)

The voltage required to START an arc is much, much higher than the
voltage required to SUSTAIN an arc. Once started, an arc (plasma) is a
pretty darn good conductor.

Martin Brown (quoted below) explained it, but you skipped right past
that. By striking an arc on a small gap, a much larger gap can be
_spanned_ without needing a voltage that will _start_ an arc on the
large gap.

Your best bet is something along the lines of a Jacobs ladder device
where the rising plasma allows a lower voltage that strikes across the
narrow lower arc gap to rise and carry a noisy spark with it.

Sharp, pointy electrodes also lower the voltage needed for arc
initiation. You could probably follow the lead of most sustained arc
circuits and have a pulse generator of a high voltage and short duration
to start the arc, and a lower voltage sustained supply to maintain it.
Every florescent light does this, for instance.

I'm a bit concerned about your proclivities from this snippet from your
OP, as well:

Running the output through a twisted pair of insulated bell wire caused a
very pretty purple corona glow along the length of the wires, and no spark at
the end.

HV --> Bell wire? Seriously? Shee-zeus! Does the concept of a voltage
rating for insulation pass right over your head? HV wire with nice fat
silicone insulation is really easy to get. HV-Heat-shrink can add some
insurance (even regular heat-shrink adds quite a bit.) The more cautious
approach is to run the HV inside a grounded sleeve - either coax or
sleeved in hollow braid. Keep capacitance down by using small-center
conductor large insulator coax.

But...given the size that "taser" type circuits can be shrunk to (and
the truth that they are pretty much exactly what you are building, no
matter how uncomfortable that makes you), no real reason to run HV along
your arm - run 12V DC along your arm and limit the HV generation to
right where it's used. If you manage to zap yourself then, you'll
probably live (your hand will hurt like hell, but there's no reason for
the current to travel through your heart, as there is with a back-pack
generator and an arm terminal, should anything go wrong.)

Have fun.

 

[[email protected]]

it doesn't matter if you write stun gun or spark generator on the schematic
it is basically the same thing, and anything that makes a 1/2 spark is scary

More to the point anything producing hot bright electrical sparks 1/2"
long is going to be dangerous or even deadly if you make a mistake.[/QUOTE]

Tesla coil? Jacob's ladder? Whimhurst wheel?

Your best bet is something along the lines of a Jacobs ladder device
where the rising plasma allows a lower voltage that strikes across the
narrow lower arc gap to rise and carry a noisy spark with it.

It probably contravenes lots of RF emissions regulations too.

Bet on that.

 

[[email protected]]

This doesn't strike me as very creative.

Sometimes it's more important to try to avoid destruction, like the
Republicans in congress, lately.

 

[Adrian Tuddenham]

This doesn't strike me as very creative.

On the contrary, it offers the opportunity of even greater creativity to
the O.P. He can find another way to achieve his ultimate goal of
amazing/ entertaining/ people without doing anything with such a high
risk (almost a guarantee) of fatality.


If you want something to start you thinking about alternatives, here are
three examples:

1)
For theatrical 'short circuits' I used a trembler-bell type of apparatus
with a low-voltage carbon arc run from a small welder. A magnetic
pickup on the welder choke fed sound into the theatre's P.A. system.
The arc was inside a strong metal housing and was not directly visible,
the light was reflected off crumpled aluminium foil. The power never
exceeded 80v or 20A, but the crackling and buzzing noises were enough to
convince the audience that something really powerful and devastating
was taking place.

2)
On another occasion I arranged a 'magic' sword fight between two
marionettes. They stood on pieces of aluminium foil on a sheet of plate
glass, wires from the soles of their feet led to their sword arms. The
aluminium sheets were supplied with about 15kV from an old television
EHT generator, allowing spectacular sparks to be drawn whenver the
swords clashed. The current was limited to less than 1mA. and the
operators were insulated from the supply by the puppet strings.

The power supply was fitted with a Yale-key-operated switch and the only
key was held by a technically-qualified operator . In addition, a push
button with a strong spring had to be held down to energise the
generator; the operator had a good view of all the procedings. This was
in the 1960s, long before the draconian Health & Safety laws were
passed, but we took every precaution to ensure reasonable safety whilst
still giving a spectacular show.

3)
Quite recently I had to produce a portable 'spark transmitter' for a
play about the First World War. The electrode balls were joined by a
transparent tube which contained white and blue L.E.D.s. Each time the
Morse key was pressed, an old contactor wired as a trembler made a
raucous rattling buzz against a thin wooden panel. Simultanelusly a
capacitor discharged into the white leds and the blue leds were
illuminated in the usual way. By carfully scratching the inside of the
tube, the light was diffused and appeared, from a distance, to be an
electric arc. The whole thing was powered from a 9V battery.



I would strongly advise the O.P. against getting anywhere near high
voltages with a current capability (either continuous or instantaneous)
of more than 1mA. There are other way of achieving the required effects
which do not pose this near-certain risk of instantaneous death.