Monday, March 9, 2009

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 1So, 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!
out:{ top: 0.49812734082397003, left: 0.238, width: 0.086, height: 0.12734082397003746, text:"Any value ceramic capacitor with voltage ratings of 4 - 8Kv." }

step 2The dangers you must know...

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.

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...
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step 3What you will need are...

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...

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

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step 4Also you need the tools!

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...
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step 5Power supply

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 350v inverter with a 18 stage voltage multiplier to get about 6.3Kv.

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.
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step 6The construction of the marx generator.

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.
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step 7Spark gaps

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...
out:{ top: 0.088, left: 0.174, width: 0.672, height: 0.6773333333333333, text:"Good. This is how you should do it." }

step 8Testing... Testing...

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.....






It works!!! Yay!


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step 9Troubleshooting

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...

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step 10SPARKS!!!

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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