Build a simple Marx Generator

Do you like the idea of tesla coils and other high voltage sparking stuff, but don't have the time, money or patience to build something that is elaborate?

Well, here's a fun 'n' simple project that can make big, fat, noisy sparks at least 2 inches long, and can be built very quickly and cheaply. It might be even more fun to use a marx generator than using a 'very complicated to build' tesla coil!

And to let you know, this "Quick & Dirty" Marx generator website helped me a lot to build this marx generator.

If you have no idea what is a marx generator, you might be saying this in your mind "What the hell is a marx generator!", read about it here on Wikipedia.

WARNING! This project generates very high pulse discharge voltages, which can seriously harm and could be potentially lethal to you and others that are careless to touch the output of the marx generator.

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Step 1: So, how does it work?

The Marx generator consists of an array of resistors, capacitors and spark gaps arranged as follows in the schematic...

The capacitors are charged up in parallel through the resistors, so they each become charged to the input voltage. When all of the spark gaps fires (sparks), the capacitors get effectively connected in series, therefor multiplying the input voltage by the number of capacitors and causing a long spark at the end of the marx generator.

Rb has a ballasting effect, it is used to prevent a continuous arc forming across the first gap - this prevents further firing of the marx generator. The value of the resistor will mainly depend on the type of power supply is used, in this case, we are going to use an 10M resistor for this marx generator on this instructable. However, you can reduce the Bb's value to try get more 'bangs per second' without causing an arc forming on the spark gap...

Now, you know how it works (I hope), so lets build it!
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arshiaIQ12 days ago

may i use full wave Cockroft-Walton generator for this...?

some body tell me perfect technique .......to make HV impulse generator of 100KV ...

mikeyfulton1231 month ago
I was thinking about using two aa batteries which feeds into a fly swatter circuit board creating an output of 3.5kv (from one source). Would I still be able to use the same capacitors and resistors as this example and would I get a fair arc out of it? Thanks
daniellong21 month ago

I didn't know the resistor value at the moment of buying, so I bought 33 ohm ones. what could go wrong if I put them?

Myrtonos1 month ago

Why do you need resistors? Wouldn't they just increase the time needed to charge the capacitors?

pavithran13133 months ago
pavithran13133 months ago
sarvesh75 months ago

can we use electrolytic caps??

3 months ago
you can, but you will need some diodes as well to prevent them form discharging into the power supply. I believe this is called a cockroft and watson cascade but please don't quote me
todybog3 months ago

Is it possible to use a flyback driver (with a lower mosfet, say 60 v) to power the main one, because i have 3 flyback transformers an 0 capacitor banks for the power supply.

maboy5 months ago

if the values of the capacitor (pf, voltage) are changed, would you also need different resistors? I can't seem to find 1000pf 4Kv capacitors, and 6kv caps seem much more common, so could I use those instead without changing the resistors?

maboy5 months ago

Hello. I plan on building your design, all the links are good except for the caps, which seem to have been discontinued. I found a few alternative capacitors so that's not too much of an issue. If I plan on using your power supply design and everything too, can I scale up the generator simply by adding more stages? Or would I also have to adjust the other component values? and how much would adding additional stages impact the spark length?

Ploopy5 months ago

Cool!

endolith4 years ago

Can this really harm you? The idea that a special number of voltage or amperage will automatically kill you is not accurate.

Scuffing your feet across a carpet and touching something metal also produces thousands of volts and large currents, but it obviously doesn't harm you, because the capacitance is small and the spark is very short-lived. Yes, it's high voltage and high current, but the duration is less than a microsecond.

I'm sure it hurts, but I'm skeptical that it would actually cause any harm. How long are the sparks in cm?

10x 1 nF capacitors charged to 7 kV store a total of 250 mJ. Scuffing your feet across the floor stores maybe 60 mJ max by comparison.

"The effects of electrical current passing through the human body are covered at length in the International Electro Technical Commission document IEC 479-2:1987. In this document it indicates that a transient or capacitive discharge, as is the case with static electricity, requires energy in excess of 5 Joules (5000mJ) to produce a direct serious risk to health."
Plasmana (author)  endolith4 years ago
Okay, you made a very good point, can my marx generator kill? Very good question, personally, I will NOT touch it even if its safe. I never really understand Joules as they are many other units of energy related to it. Each capacitor (1nF) holds approximately 4kV to 5kV, how do I convert that to joules to see if its safe(ish) or not?
7 months ago

the formula for joules is volts squared times capacitance

7 months ago

no, it's 1/2⋅C⋅V²

4 years ago
I already did that for you, but I was using 7 kV. :) The energy stored in a capacitor is given by 1/2 * C * V^2, so:

1/2 * 1 nF * (5 kV)^2 = 0.0125 J = 12.5 mJ

Wolfram Alpha can do a lot of work for you:

capacitor stored energy 5 kV 1 nF

Multiply by 10 and you have 125 mJ total, which is 1/40th of the energy that document says is the minimum that will hurt you.

I'm not claiming that this thing definitively can't hurt you. I'm just skeptical that it's dangerous. Even if it's not harmful to health, the shock might still hurt like hell. :D
1 year ago
4 years ago
For another example, I'm looking at a safety test certification document for EN 60065, and they limit the maximum energy of a discharge to 350 mJ.
4 years ago
The total voltage could be 70 kV, which means the arcs should be able to jump about 1 inch. Does that seem right?
7 months ago

who says this procedure u jus mentioned (Scuffing your feet across a carpet

and ...) produces high currents???
currents than around mA value will shock u and more than 50 mA will kill u jus before u feel it !!!

and the tolerated amperage of ur body during the time is obtained from some equations expressed like the form: (i^2 * t) = cte (around 0.156 i think) so this fact that u mentioned doesn't hurt u cuz the values are lower than this equation. and ti is not related to the capacitance. there is a kind of a surge formation when u touch the metal with ur charged body. and the amount of current depends on the discharge resistance before and after its formation. which varies during the discharge time. so it doesnt hurt u cuz the values of volts and amperes are too low. and the idea that "a special number of voltage or amperage will automatically kill you" IS definitely ACCURATE.

7 months ago

"who says ... Scuffing your feet across a carpet ... produces high currents???"

People who have measured it. See http://www.wolfsonelectrostatics.com/04_news/index.html#current-and-time

"so it doesnt hurt u cuz the values of volts and amperes are too low."

No, the reason it doesn't hurt you is because the *energy* is too low.

'the idea that "a special number of voltage or amperage will automatically kill you" IS definitely ACCURATE.'

No it's not.

1 year ago
I saw on mythbusters that only a few milliamps across the heart will kill you.
1 year ago
But how much voltage do you have to apply to your body to get milliamps across the heart? And how long of a duration does the current need to last to kill you? if it's 10 milliamps for 1 nanosecond I doubt it will do anything.
4 years ago
WOW!! U sure R a expert on electricity!! where u got all those facts from??
4 years ago
I'm an electrical engineer. :)
dillonxti7 months ago

where is the schematic for the inverter you used

twotower1 year ago
Thanks for your instructable! Since I'm still learning, I'm not up on all of the abbreviations. Can you please tell me what 'RB' stands for? Certainly not Rhythm & Blues...."humor"
Thanks!
7 months ago

Rb = Ballasting Resistor

jeanrenaud7 months ago

Hi, i've made a 5 stage Marx Generator, with initial voltage ±10 kV (hard to tell i can't measure it reliably, but it's a CRT monitor flyback).

After some experiments, all the resistors between stages blew out (my ohmmeter shows "OL"). In your instructable, you used 1M 500V 2W carbon resistors. I've choosen 1.8M 1W 3.5 kV metal film resistors. I'm not sure how this happened ;)

My ballast resistors (rated 10kV) are still ok.

Any idea, guys ? I don't blame anybody but myself ;) but some opinions are welcome.

Jan_Henrik7 months ago

SNAP... YAY sparks! :D

DrZoiberg8 months ago

I made it,but i have only 2cm long spark why????

eerambach9 months ago

What sort of amperage and voltage do you put into it? I was hoping maybe an electric flyswatter would be enough for a really small one.

Magnetron10 months ago
I love this very cool and simple to build
W I N G M A N10 months ago

Could this be connected to a inductor coil and be used as an EMP generator?

Fayez slim11 months ago

can i use a ceramic capacitor rated with 2000v inside 4000v because i cant find 4000v ceramic capacitor

Eternal661 year ago
cool man!
pacina1 year ago
Hey I just built this and the power supply but I have a question before I put any power to it how do I fully discharge it after words so it is safe to touch again, I know with a normal capacitor you just short out the ends is it the same with this??? and is there any way I can add a dummy resistor into it somewhere that will just drain the power away itself when the power is turned off.