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4hv.org :: Forums :: High Voltage
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Marx generator with homemade capacitors

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Flatox
Thu Sept 08 2011, 11:09AM Print
Flatox Registered Member #4087 Joined: Thu Sept 08 2011, 09:54AM
Location:
Posts: 4
Hi there !

I am new to this great forum, and english is not my first language so please be indulgent.

I have made this post to present and share this project.

The marx gen itself is an 8 stages unipolar model with charging resistors. The capacitors are homemade type with rolled "plastic wallet" and aluminium foil. I measured their capcitance and they all have about 2.3nF. I don't know how many kV they can withstand but they were fine at 30-40kV. Charging resistors are made of three 330k 1W resistors put in series. Spark gaps are bent copper wire. The overall assembly is mounted vertically on a PVC pipe, drilled to hold the long capacitors.

P1040610

P1040611

P1040612

The power supply is a simple 555 and mosfet driving a monitor LOPT, with the quasi resonant mod posted by Dr. Kilovolt (thanks BTW shades ) I don't know the exact ouput voltage, but it should be arround 20-30kV.

Main spark gap of the marx generator is set to approx. 18cm, and the repetition rate is about 1/second, depending on the first spark gap sapcing. Sparks are loud and bright, but nos as bright and thick as the video and picture show.

Here is the link to the YT video :



Spark picture :

110

Thanks for reading, and feel free to comment smile
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magnet18
Thu Sept 08 2011, 11:14AM
magnet18 Registered Member #3766 Joined: Sun Mar 20 2011, 05:39AM
Location: 1307912312 3766 FT117575 Indiana State
Posts: 624
Nice sparks, well done!
Are you open to critiques on your English? It's very good
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AleSeg
Thu Sept 08 2011, 12:46PM
AleSeg Registered Member #2727 Joined: Tue Mar 09 2010, 02:39PM
Location: Montevideo - Uruguay
Posts: 33
Hey, Good work !!

Can you give us a better detailed description of your "plastic wallet" capacitors model?
What kind of plastic have you used ?

thanx
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Flatox
Thu Sept 08 2011, 06:01PM
Flatox Registered Member #4087 Joined: Thu Sept 08 2011, 09:54AM
Location:
Posts: 4
Thanks for your comments smile

I was sure the term "plastic wallet" would mean nothing in english, but at least i tried ! I don't how it is called in english, here is a picture of it :

Pp

This is the dielectric. I cut the holes and just keep the plastic sheet, in fact, there are two thin plastic sheet in each one. To make the capacitors, I put two "see the picture above", one aluminium foil sheet with a wire, three plastic sheet, one aluminium foil sheet with the other wire and then to finish, one plastic sheet. I roll this around a small PVC pipe, and secure the whole assembly with tape. So, anywhere in the capacitor, there are atleast 3 "plastic wallet" between each opposite polarity plate, that is to say 6 plastic foil. I also make sure that the aluminium plate have enough clearence to the edge of the plastic sheet to prevent arc over.

I am not sure of what plastic type the dielectric is made, as it is not labelled on the box, but I think it is PP.

So far, I haven't got any failure while running them at 30kV, and they do their job quite well for something that is home made.

The overall cost of this marx generator is about 8$ (I only count the parts that I bought especially to build it).
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magnet18
Thu Sept 08 2011, 07:39PM
magnet18 Registered Member #3766 Joined: Sun Mar 20 2011, 05:39AM
Location: 1307912312 3766 FT117575 Indiana State
Posts: 624
generally that's called a divider or separator or something along those lines
to be honest I'm not entirely sure of the name myself tongue
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Ash Small
Thu Sept 08 2011, 07:55PM
Ash Small Registered Member #3414 Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245
magnet18 wrote ...

generally that's called a divider or separator or something along those lines
to be honest I'm not entirely sure of the name myself tongue

I think you are confusing these with dividers. These are like an envelope that you put a sheet of paper inside, to protect it. I think I've seen them called wallets in the shops.
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magnet18
Thu Sept 08 2011, 10:39PM
magnet18 Registered Member #3766 Joined: Sun Mar 20 2011, 05:39AM
Location: 1307912312 3766 FT117575 Indiana State
Posts: 624
Ash Small wrote ...

magnet18 wrote ...

generally that's called a divider or separator or something along those lines
to be honest I'm not entirely sure of the name myself tongue

I think you are confusing these with dividers. These are like an envelope that you put a sheet of paper inside, to protect it. I think I've seen them called wallets in the shops.

We're also across the ocean from each other, so they might be called different things.
I know at my school we usually call them "those 3 ring divider things"
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Forty
Fri Sept 09 2011, 12:56AM
Forty Registered Member #3888 Joined: Sun May 15 2011, 09:50PM
Location: Erie, PA
Posts: 649
how about "page protectors"
if you could manage to slide a sheet of aluminum foil inside of them neatly, you could slap two together and roll them as a capacitor.
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Ash Small
Fri Sept 09 2011, 01:51AM
Ash Small Registered Member #3414 Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245
magnet18 wrote ...

.I know at my school we usually call them "those 3 ring divider things"

On our side of the pond we refer to that kind of corruption of the English language as 'Americanisms' smile
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Flatox
Tue Sept 13 2011, 05:42PM
Flatox Registered Member #4087 Joined: Thu Sept 08 2011, 09:54AM
Location:
Posts: 4
Hi again,

I am having a minor problem with the marx, and thing that I do not understand, so I ask you guys smile

My power supply is a 555 driving a flyback, but I am running the Hv side of the flyback ungrounded, I know this is bad, but I don't understand why.

The fact is that if i connect the HVGND of the flyback to the GND of the low voltage side, the marx does not work anymore. It fires erratically, the whole assembly is making a huge corona noise and most charging resistors are arcing over, which is bad. Once I unground the HV side of the flyback, the marx run perfectly well. How is it possible ?

Also, when I run the marx with the flyback ungrounded, each time the marx fires, I can see a small spark at the flyback's bottom, running from the HV GND to the core, even if the whole bottom of the flyback is "sealed" with hot glue. Is it happening because of a high potential running on the HV side ?

Thanks for enlighting me shades
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