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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?

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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!

Step 2: The dangers you must know...

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The marx generators are dangerous high voltage generating machines, they produce a pulse discharge of many thousands of volts at approximately 5 to 10 amps! If the spark from the marx generator bites you, your life is over...

There is one thing you must know, a healthy human heart can only withstand electric currents maximum 10mA. Currents over 10mA can results death, I am NOT joking here, this is serous stuff, a lot of people thinks your heart can handle currents up to 500mA, THIS IS NOT TRUE!!! THEY ARE WRONG!!! If you don't believe me, then test your self against a high voltage 500mA power supply, a small microwave transformer would do, put your hand on one lead, put your other hand on the other lead, turn on the power supply and you will be sorry...

The marx generator will also be dangerous after the power is turned off, because the capacitors will hold a lethal charge in them, so, MAKE ABSOLUTELY SURE YOU DRAIN ALL THE CAPACITORS BEFORE YOU TOUCH THE DEVICE!!! Otherwise you will get a 'surprise shock' form the capacitors which can seriously harm you or even death...

Also, every time a marx generator fires (make a spark), it kicks out a lot of UV radiation, and sometimes X-rays! Staring at the sparks form the marx generator can cause problems with your eyes, so wear UV sunglasses or briefly watch it every once a while. If you want to be safe, use laser protection glasses, it will take out nearly all of the UV emitted from the spark and you might not be able to see the spark well, but it much better for your eyes.


Okay, you might be a bit scared after reading this horrible step, so do you think you can build a marx generator? Or find it too dangerous to build it? The choice is yours...

Step 3: What you will need are...

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I based the components I had easily available.
The recommended components you should get are ceramic capacitors and 1M 1 watt resistors. The ceramic capacitors are best suited for this project, because they are cheap, readily available, and they are good for in pulse discharge circuits. Polypropylene pulse-rated capacitor would also work well, but are more expensive, and harder to find with high voltage ratings. The resistors should be about 1M and 1 watt type, the normal 1/4 watt resistors are very unsuitable, if used, it will cause arcing and the resistors will burn out and damage the marx generator, so use the 1 watt metal glazed or carbon film resistors is suitable.

If in doubt, try building just a couple of stages first to see how well the parts you use will work before you buy more...

But I will tell you what I used...

  • Ten 1nF, 4Kv ceramic capacitors
  • Twenty 1M, 2 watt, 500v carbon film resistors (I brought the 2 watt resistors because they are somewhat cheaper then the 1 watt resistors!)
  • Two 4.7M, 1 watt, 3.5Kv metal glazed resistor for the Rb.

Also you can use a base for your marx generator, the best suited base are glass (too fragile), ceramic (it's breakable) plastics (ideal, but some of them may be conductive), or whatever you think it is good! I use wood, a very baaad idea (because wood is conductive), but I have no choice, wooden base or no base.

You can use capacitors with larger values to get fatter, louder sparks, but take longer to recharge! You can often run capacitors in excess of their rated voltage, but obviously this increased the risk of failure!

And don't forget, the size of sparks at the output gap will depend on the input voltage and number of stages...

(UPDATE)
I got all my components from Farnell. Here is a list of things you will need to get if you are going to buy the components from Farnell.
1nF 4Kv ceramic capacitors
1M 2 watt 500v carbon film resistors
4.7M 1 watt 3.5Kv metal glazed resistor

Step 4: Also you need the tools!

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Also you need the tools!
What you will really need is a soldering iron! Or you will have a pain in the ass time to build the marx generator, and get very poor results because of the corona discharge...

You will need a helpers hands, they are very useful to have, they help you to get the job done quicker. If you don't have one, MAKE ONE! Salvaged Solder Helper

Hot glue gun is also very handy, it holds everything in place.

And you may need other common tools for this project...

Step 5: Power supply

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The marx generator requires a low-current, high voltage DC in the range 4-8KV power supply. Small, low-current HV power supplies are found in things like ionisers (air purifiers), photocopiers and laser printers, those should be suitable.

I made my own 6Kv power supply for my marx generator. My power supply is a small homemade 450v inverter with a 18 stage voltage multiplier to get about 7Kv.

OR, you can make your own power supply for your marx generator, go to this instructable: High Voltage Power Supply For Marx Generator

Also the marx generator has no polarity, you can connect it to the HV power supply in any way round.

Step 6: The construction of the marx generator.

Picture of The construction of the marx generator.
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Depending how you want your marx generator, I will tell you how I did mine...

I first hot glue the capacitors on the base.
Then I soldered the 1M resistors on the capacitors using my handy helper's hands, and cutting off the excess resistor's leads. But I did not cut the capacitor's lead down, you will see why on the next step...
Then I soldered the 4.7M resistors in.
And one more thing, make sure you have good solder joints, and make sure they are no pointy ends on the marx generator, except the capacitor's leads and the HV output of the marx generator. Otherwise having pointy ends all over the marx generator will cause corona discharge, and that will decrease the performance of the marx generator.

Step 7: Spark gaps

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Okay, once you had soldered the capacitors and resistors all together, you need to make the spark gaps.
This is what the capacitor's leads are for, making the spark gaps!
Okay, so bend the leads into a "V" shape and bring the ends of the "V" shaped leads about 2 mm (about 0.08 inch) close together.
But do not bring the pointy ends of the leads close together, that will cause a lot of corona discharge, and your marx generator will have very poor performance, or might not ever work...

Step 8: Testing... Testing...

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All right, you had built a marx generator, and it is now time to test it! Wire up your marx generator to the HV power supply and flip the switch!

3... 2... 1... *Flips switch* And.....

SNAP

Wow!

SNAP

Cool!

SNAP


It works!!! Yay!

SNAP

Step 9: Troubleshooting

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If you have problems with your mark generator, read here...

Q. - My marx generator is not making any sparks, but I hear faint hissing and/or faint snap noise, and sometimes see a purple glow.
A. - This is a good thing, your marx generator is working, but one or more gaps are probably too far apart, push them closer together. If gaps are too close, especially near the supply end, you may see a continuous arc forming, preventing further operation. Increasing the gap on the first (and possibly second) stage may reduce the tendency to arc. Increasing the ballast resistor Rb also helps, at the expense of slower recharge time.

Q. - My marx generator is not doing anything what so ever.
A. - Is there something wrong with the inverter? Check it to see if it working or not.
A. - Did you make sure you built the marx generator properly?
A. - Did you miss out any connections?

Q. - My marx generator is working, but after a few seconds, it made a "POP" noise, and it did not work again...
A. - That is a bad sign, a capacitor may have been destroyed from excess voltage OR your HV power supply has been killed from the extremely high voltage spikes from the marx generator. Replace the capacitor/inverter and don't make that same mistake again...

Step 10: SPARKS!!!

My marx generator works very well, it generates loud, bright, sparks that are up to 2 inches long (5 cm)! That is about 50Kv (50,000v) coming out of that thing!

Well I hope yours works when you build one! :)
And can you post a picture of your marx generator if you build one?

To let you know, all of the photos that has a few sparks in a single picture are 4 second long exposures.

I hope you enjoyed this instructable, and enjoy the photos down below! And the video I just uploaded!

Comment if you need help, have question, or anything! I like comments!

(UPDATE) I just uploaded a video of my marx generator working, sorry for the poor quality with no sounds, I had used my crappy camera. :(


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zapper4502 days ago

all of the spark gaps on mine are firing, but there is nothing on the big spark end. what is the problem?

smartermonkey3 months ago

in electricity / electronics world..my teacher ..an old guy..once showed us how in the old days he would apply the one hand rule in all high voltage situations..(120 volts and higher AC)..he said he always put one hand in his picket while he wet the tips of his fingers and touched the outlet he was checking..the theory is that electrical current always flows to the shortest path. He demonstrated it and yes go a minor shock through his hand as the current travelled in one finger and out the other of the same hand..while his other hand remained in his pocket..i dont advise doing this with alternating currents..since even a minor voltage can upset your hearts biorythyms and cause it to become irregular..which is bad..you then have to go to the hospital so they can refibulate your heart..always apply common sense when using electricity and stand on a rubber mat..wear insulated electrical rated gloves and test circuits to see if they are "live" ..with a volt meter. Remember..volts do the work when current flows and resistance is present ..high amperage is bad for the body..but pulsed current even at low levels can stop your heart..play safe my friends!

eerambach4 months ago

If you are using a 7kV power supply how can you use 4 kV capacitors? Or are you just taking the risk of blowing them out?

Myrtonos9 months ago

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

They do increase the time, but if they weren't there the circuit would short itself out when it discharges. One possible way to overcome that though would be to use high-power diodes instead of resistors, but they are a lot more expensive than resistors.

NaeemG7 months ago

Could someone please tell me, what are the red and black wires connected to?

arshiaIQ7 months ago

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

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

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
daniellong28 months 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?

pavithran131310 months ago
pavithran131310 months ago
sarvesh71 year ago

can we use electrolytic caps??

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
todybog11 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.

maboy1 year 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?

maboy1 year 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?

Ploopy1 year ago

Cool!

endolith5 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)  endolith5 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?

the formula for joules is volts squared times capacitance

no, it's 1/2⋅C⋅V²

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
Its not all about just the Amp or voltage its how it travels through your body if it goes in through your hand and out your elbow (just saying this way you'll see why in a min) all it will do is is give you some bad burns no matter how high either the Amp or Voltage is but if the same current goes in one hand up your arm across your chest and down your other arm it will travel through your heart which will stop it resulting in death. It also doesn't have to affect your heart to kill you it can go through your diafram(sorry cant spell) and your lungs stop working which will cause you to suffocate, if your an electrical engineer you should have learned that in first year I know in my first year we weren't allowed to touch any of the equipment until we did a report on the dangers of electricity and the rick of burns in the lab to show that we didn't just know about the dangers but fully understood them.
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.
The total voltage could be 70 kV, which means the arcs should be able to jump about 1 inch. Does that seem right?

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.

"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.

I saw on mythbusters that only a few milliamps across the heart will kill you.
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.
chakra endolith5 years ago
WOW!! U sure R a expert on electricity!! where u got all those facts from??
endolith chakra5 years ago
I'm an electrical engineer. :)
dillonxti1 year ago

where is the schematic for the inverter you used

twotower2 years 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!

Rb = Ballasting Resistor

jeanrenaud1 year 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_Henrik1 year ago

SNAP... YAY sparks! :D

DrZoiberg1 year ago

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

eerambach1 year 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.

Magnetron1 year ago
I love this very cool and simple to build
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