I am trying to create an arc generator and I have read about the marx generator but I am looking into more compact modules like the image below. All the ones I have found seem to be fake and actually supply less than 1/10th of what they are advertising.

Boost converter Is there any reliable way of generating a (non-continuous) super high voltage arc?

  • If say you wanted to get 1mA out at 800kV, that would require over 100A at 6V. I've got 30kV out of a flyback transformer from a 24V supply before pulling a more reasonable 6A. – Tom Carpenter Jan 15 '17 at 14:58
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    @TomCarpenter How do all the stun gun brands advertise bizarre voltages like 1MV? Are they just like 5A-6V to 30µA-1MV? – stenlan Jan 15 '17 at 15:05
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    They might be saying that the field strength is 1 mega volt when they mean 1 mega volt per metre. They may have conveniently forgotten to state the per metre part just like internet providers annoyingly leave off the per second part when quoting data rates. – Andy aka Jan 15 '17 at 17:55
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    That one in the photo- maybe 10-20kV. 800kV would initiate an arc over maybe 8" (200mm). It would also likely be a rather poor impedance match to human flesh (and thus ineffective) if it's a stun gun. A Taser open circuit is ~50kV perhaps but when delivering a shock the voltage drops to ~1.2kV. – Spehro Pefhany Jan 15 '17 at 20:38
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    In the flash camera, a very high voltage is needed for the flash itself. – quantum231 Jan 16 '17 at 22:56
up vote 33 down vote accepted
Is it really possible to “boost” 6 V DC to above 50kV? Or even 400kV?

Of course. One common example of something similar (although not as extreme as your specs) is using 12 V in a car to make several 10s of kV to fire the spark plugs.

The same concept can be scaled up to make higher output voltages. It won't be easy to build something with that stepup ratio and output voltage yourself, but the physics is certainly possible.

  • How is DC-DC booster made? What are its main components that makes it a booster? – Keno Jan 17 '17 at 19:47
  • @Keno: This is too long for a comment here. Look up boost converter, charge pump, and flyback converter. – Olin Lathrop Jan 17 '17 at 21:58

A battery powering a dc motor in a Van der Graaff generator can produce a million volts quite easily: -

enter image description here

  • A million volt is pretty optimistic. Assume 30 kV per centimeter of spark if you use nice big spheres and the air humidity is low. With spheres that are smaller than the gap, much less than 30 kV/cm. – Roland Jan 15 '17 at 17:48
  • One meter isolating distance would allow 3 million volt. – Uwe Jan 16 '17 at 10:59
  • I don't think using a motor to drive unrelated generator counts as "boost" – Agent_L Jan 16 '17 at 11:16
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    @Agent_L The title says this: "Is it really possible to “boost” 6 V DC to above 50 kV?" – Andy aka Jan 16 '17 at 11:39
  • @Uwe Exactly. Assuming a uniform field as, e.g. between conductive spheres with radius of several meters. Otherwise, the field strength will concentrate near the small conductors and create a spark at much lower voltage. You will need a hall of about 15 meters high or more to play with 3 MV. There are just a hand full of labs in the world that can do that. Fun though :-) – Roland Jan 16 '17 at 16:37
  1. Take your 6 volts and run it through DC-DC boost converter and then an inverter, you now have really rubbish AC at a slightly more respectable voltage.
  2. Feed rubbish AC in to a solid state boost circuit, say a Cockroft-Walton voltage multiplier
  3. Feed the high voltage through a current limiting resistor if you want any kind of continuous draw. Don't bother if you just want a spark.
  4. Do not lick the operational terminals.

The trick lies in how you manage to shove so many stages of a CW in a reasonably compact space. You're slightly saved on the issue of voltage isolation since the output terminals are at opposite sides of the ladder.

Can you get 800kV out of this? I highly doubt it. Let's say you get a boost converter to add an order of magnitude to your input voltage and the CW gets 60V... each stage of the ladder adds the input voltage to the output, so 10 stages is still only 600V output. As you increase your input voltage you also increase the boost per stage at the expense of needing all your components being able to handle the increased voltage.

I would imagine that with appropriately rated components (and a lot of them) you could step 6V to 800kV with this kind of approach but your output duty cycle would be ridiculous and the thing would be rather big. A lot of work for one spark. You'd probably also need a flyback to get the input to a level where the CW is practical, and at that point you're best off just getting wall AC and using a transformer to drive a CW or Marx up to that voltage.

As for that thing in the picture... some capacitor stack maybe? Weirdly wound transformer? Leiden jar?

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    A search for photos of Cockroft-Walton generators produces satisfying results. – Malvolio Jan 15 '17 at 18:37
  • ROFL/upvoted for do not lick... :-) – Bob Jarvis Jan 15 '17 at 20:08
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    @BobJarvis Indeed. I'm picturing a DIYer, tongue poised, suddenly noticing Step 4. – Sneftel Jan 16 '17 at 1:41
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    (GLaDOS voice) Do not lick the operational end of the device. Do not submerge the device in saliva, fully or partially. And most importantly, under no circumstances should you -- – immibis Jan 16 '17 at 22:48
  • "The trick lies in not licking the terminals" – algiogia Jan 18 '17 at 8:57

Yes, quite easily. The 1990s had hand-held TVs that actually had Cathode-Ray Tubes like "proper" living room TVs; those were powered using a couple AA batteries (ie. 6V or the like).

CRTs need a couple of kV to accelerate electrons towards the screen. So, building a device that does only that is actually not that hard – these TVs were (presumably) simply based on commodity flyback transformers.

Here's a video showing the use of hand-held Electrostatic Discharge generators; these are available in battery-operated versions.

ESD gun in the hands of a very diligent EE

Now, from 10–25 kV it's still quite a way to 0.8 MV, but the transformer principle used in such devices does allow for higher voltages, too. See Tesla Coils for a classical way of building such high voltage generators.

EDIT: If I'm already promoting that guy above, here's a tesla coil driver circuit from his website:

tesla coil driver

Circuit is omitting the flyback diodes integrated in the MOSFETs.

As you can see, it's operating from 12 V - but there's no particular reason this couldn't work with 6V from a battery, either (though you might need to use different transistors); the 12 V might also be generated by a separate step-up converter from any lower voltage source. V_SUP is typically higher - that's where you'd use a step-up converter to convert e.g. 6 V to 32 V first, in order to be able to drive the coil with high power. Roughly guessing from the spark's length, this is around 100 kV.

  • You cannot measure the voltage from the spark's length if the field is not homogeneous. If one or both conductors are pointed, all the field will concentrate around the point, the field may locally reach 30 kV/cm, the arc may start there, and then jump over great distances. – Roland Jan 16 '17 at 0:50
  • That's why I said "roughly guessing" :) – Marcus Müller Jan 16 '17 at 9:59
  • That movie is really funny! But note the pointed device. It has a sharp point, instead of a big sphere, to make nice sparks at a relatively low voltage. The spark is created by the sharp point, without that the spark would be much much smaller. That's why you can really not measure the voltage from that spark's length. Not even "roughly guessing". Unless you mean that you might overestimate with a factor of ten or more. – Roland Jan 16 '17 at 11:38
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    Forgot the flyback diode across Q1-4? Or want to blow up those at the end of the first pulse? – Roland Jan 16 '17 at 11:47
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    @Roland well, considering this is not my circuit and that it works in real world (although I'd have my concerns on the simultaneity of the switching of four opamp-driven gates...), I'd simply assume those MOSFETs integrate these - and in fact, the used SCT2450KEC do exactly that. – Marcus Müller Jan 16 '17 at 13:17

I'd recommend that you buy Prutchis' book: "Exploring Quantum Physics through Hands-on Projects" and then go to their web links:

  1. d.i.y. 250 kV High Voltage DC Power Supply with Neat Trick for Switching Polarity
  2. d.i.y. 15 kV @ 30 mA Floating-Output AC or DC High-Voltage Power Supply
  3. Original Source for Flyback Driver Hack?
  4. Adding Your Own Primary to High-Voltage Flyback Transformer for Resonant Driving
  5. diy Low-Cost, Regulated, Variable, Low-Ripple High-Voltage (2kV) Photomultiplier Tube Power Supply
  6. Assembly View of diy Variable-Output, High-Performance PMT High-Voltage Power Supply

The book is worth it. I picked it up for less than $59 new, back when it wasn't so well known or the value of the US dollar was different. Amazon wants more, now. But you can search around and see what you can find. The book is definitely worth getting, though. Very good stuff reading through it.

And you will be able to then make up some defensible reasons for wanting something like this.

From my high-voltage class I remember that the maximum field strength is about 30 kV per centimeter. And this is for a homogenous electrical field, e.g. between large spherical conductors, where the conductor diameter is large compared to the gap distance.

Hence, for 800 kV you need an air gap of at least 25 cm, between spherical conductors with a radius of, say, over 1 meter. Just google at "high voltage lab" and you will see such spheres. The Vandergraaf Generator, sketched in another answer, has such a sphere, and its diameter and distance to Earth limits its top voltage.

Looking at your picture with thin wires expecting to carry 800 kV, I do not see a homogeneous field, and the distance between the conductors is in the range of millimeters. If you charge up those wires, you will get sparking long before you reach 30 kV. Not only sparking at the end of the conductors, through air, but also through the plastic insulation.

For illustrations about the difference between conductor shapes, search for Rogowski Profile or Electrode, e.g. here

So the question is not how to transform a low voltage to a high voltage, but how to prevent sparking.

  • Potting is how you prevent such things :) – ThreePhaseEel Jan 15 '17 at 23:49

Andy's Van de Graaff generator definitely works. Tesla coils do as well. Google search homemade/designing Van de Graaff generators/Tesla coils. I'm not familiar enough with Van de Graaffs to speak on how easy or cost effective they are to make but Tesla coils definitely seem doable for someone with the time and desire to learn.

The only part you probably wouldn't want to make yourself is the initial step up transformer. That's a lot of windings to hand wind. Used microwaves go for 10-20 USD at thrift stores here. They're usually around 1500W and 2kV.

This was one of the first detailed description of building a large one that I came across: http://www.rmcybernetics.com/projects/DIY_Devices/tesla-coil-srsg.htm

He used a neon sign transformer. It is a higher voltage lower current transformer. It's probably possible to compensate for that in the design of the resonant transformer that it feeds. Otherwise you could get transformers with close current ratings and put the secondaries in series. I don't know where to reliably find neon sign transformers for cheap. I have only found one and it was by luck. It was 10kV like his but rated for 10% of the current.

How do all the stun gun brands advertise bizarre voltages like 1MV?

The stun guns and tasers that advertise 1MV may be able to reach 1MV. I believe they only reach the advertised voltage during open circuit conditions. Once you break down an insulator it becomes easier to keep current flowing than it was before you did. Due to internal resistance a voltage source's output voltage decreases under load. So when the terminals on a stun gun or taser arc through air or flesh the voltage drops due to the flow of current. Look up Jacob's ladder traveling arc to see a demonstration.

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    "Used microwaves go for 10-20 USD at thrift stores here." -- whenever I want one, I find wandering around the kind of areas where university students live on rubbish collection day you can usually find somebody throwing one out and pick it up for free. It may not work, but the transformer is rarely the failure point. – Periata Breatta Jan 15 '17 at 20:14

The principle on which the most common type device to do this works is identical to the way in which a hammer can drive in a nail or break a hard object: force is proportional to the rate of change of momentum. The hammer's momentum is built up by applying a modest force during the second or so that the swing lasts. When the hammer hits the nail its momentum is absorbed within around a millisecond, so the force applied to the nail is in the region of a thousand times the force used to swing the hammer.

The electrical analogue of force is voltage, of velocity, current, and of mass a quantity called inductance, in which energy is stored in the magnetic field that is generated by any electric current. This energy is analogous to the kinetic energy of the hammer.

Winding wire into a coil increases the inductance and giving the coil a ferromagnetic core increases it more. When a low voltage is applied across the coil the current will build up gradually, typically over tens of milliseconds, until it is limited by the resistance of the wire. If the circuit is now broken the current drops to zero in a very short time, producing a voltage proportional to the current just before the break divided by the time taken for it to drop to zero. If you could stop the current instantly then, theoretically, the voltage produced would be infinite.

This is exactly the way that conventional coil and contact breaker ignition systems work, as well as demonstration devices that used to be common in school physics labs which could generate sparks several centimetres long.

The same principle is used in the "boost" DC to DC converters that generate the 18V needed by by laptop computers from the 12V from a car battery.

  • This analogy is: distance is to mechanics as charge is to electromagnetism. Mechanical energy equals force times distance; electrical energy equals charge times voltage. Velocity equals distance divided by time; electrical current = net charge divided by time. – Jasper Jan 16 '17 at 1:03

Cockroft-Walton Circuits , also known as Voltage Multiplier Circuits , are conventionally used to step up 100 V AC or 230 V AC supply input to EHV /UHV DC , upto 20 MV DC , ac DC supply outputs for Particle Accelerators in High Energy Physics , also as inputs to Impulse Generators for testing HV/ EHV insulators used in HV AC/ DC Transmission lines.
The description of these circuits can be found in WIKIPEDIA or through GOOGLE SEARCH for Cockroft- Walton circuits.
If the input is 6V DC ,this has to be converted to AC by an Inverter or Oscillator Circuit and then amplified to 110 V or 230 V by a step up Transformer . Using a TESLA COIL to further step up this Voltage to Higher Voltages , for input to the Voltage Multiplier Circuit , is also a possible Alternative .
Designing a HARDWARE for this is a VERY RISKY job . So you must take the help of High Voltage Experts from a Technical University.

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