Marx generator with homemade capacitors
Flatox, Thu Sept 08 2011, 11:09AMHi 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.
The power supply is a simple 555 and mosfet driving a monitor LOPT, with the quasi resonant mod posted by Dr. Kilovolt (thanks BTW
) 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 :
Thanks for reading, and feel free to comment
Re: Marx generator with homemade capacitors
magnet18, Thu Sept 08 2011, 11:14AM
Nice sparks, well done!
Are you open to critiques on your English? It's very good
magnet18, Thu Sept 08 2011, 11:14AM
Nice sparks, well done!
Are you open to critiques on your English? It's very good
Re: Marx generator with homemade capacitors
AleSeg, Thu Sept 08 2011, 12:46PM
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
AleSeg, Thu Sept 08 2011, 12:46PM
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
Re: Marx generator with homemade capacitors
Flatox, Thu Sept 08 2011, 06:01PM
Thanks for your comments
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 :
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).
Flatox, Thu Sept 08 2011, 06:01PM
Thanks for your comments
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 :
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).
Re: Marx generator with homemade capacitors
magnet18, Thu Sept 08 2011, 07:39PM
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
magnet18, Thu Sept 08 2011, 07:39PM
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
Re: Marx generator with homemade capacitors
Ash Small, Thu Sept 08 2011, 07:55PM
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.
Ash Small, Thu Sept 08 2011, 07:55PM
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
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
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.
Re: Marx generator with homemade capacitors
magnet18, Thu Sept 08 2011, 10:39PM
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"
magnet18, Thu Sept 08 2011, 10:39PM
Ash Small wrote ...
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.
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
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
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"
Re: Marx generator with homemade capacitors
Forty, Fri Sept 09 2011, 12:56AM
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.
Forty, Fri Sept 09 2011, 12:56AM
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.
Re: Marx generator with homemade capacitors
Ash Small, Fri Sept 09 2011, 01:51AM
On our side of the pond we refer to that kind of corruption of the English language as 'Americanisms'
Ash Small, Fri Sept 09 2011, 01:51AM
magnet18 wrote ...
.I know at my school we usually call them "those 3 ring divider things"
.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'
Re: Marx generator with homemade capacitors
Flatox, Tue Sept 13 2011, 05:42PM
Hi again,
I am having a minor problem with the marx, and thing that I do not understand, so I ask you guys
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
Flatox, Tue Sept 13 2011, 05:42PM
Hi again,
I am having a minor problem with the marx, and thing that I do not understand, so I ask you guys
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
Re: Marx generator with homemade capacitors
buxtronix, Tue Sept 13 2011, 11:57PM
When floating, the generator is going to hover around 1/2 the max voltage with respect to ground, both positive and negative. This will also reduce the tendency for corona discharge.
On the downside, it means the ground terminal of your flyback is also at high potential with respect to the low voltage side, so can arc over. Particularly when firing, as the ground terminal could be anywhere between 0 and the full output voltage from ground.
The arcing resistors are probably a side effect of the corona loss - current will constantly flow out the corona, which will create a voltage across the resistors (ohms law).
If you want to improve performance, you can do a couple of things:
1) Use some silicone sealant on exposed metal to reduce corona.
2) Run the generator in bipolar mode (and grounded). This will ensure no more than half the voltage will appear anywhere on the generator, both when charging and when firing. Bipolar mode is easy - just charge the generator from the middle rather than the bottom (and ensure the smallest gap is here too)
buxtronix, Tue Sept 13 2011, 11:57PM
When floating, the generator is going to hover around 1/2 the max voltage with respect to ground, both positive and negative. This will also reduce the tendency for corona discharge.
On the downside, it means the ground terminal of your flyback is also at high potential with respect to the low voltage side, so can arc over. Particularly when firing, as the ground terminal could be anywhere between 0 and the full output voltage from ground.
The arcing resistors are probably a side effect of the corona loss - current will constantly flow out the corona, which will create a voltage across the resistors (ohms law).
If you want to improve performance, you can do a couple of things:
1) Use some silicone sealant on exposed metal to reduce corona.
2) Run the generator in bipolar mode (and grounded). This will ensure no more than half the voltage will appear anywhere on the generator, both when charging and when firing. Bipolar mode is easy - just charge the generator from the middle rather than the bottom (and ensure the smallest gap is here too)
Re: Marx generator with homemade capacitors
Flatox, Thu Sept 15 2011, 04:12PM
Thank you for your answer, it really helps me to understand what is at stake.
In fact, to convert the marx to a bipolar, I just have to remove the fourth spark gap, and put the power supply there, whitout forgetting the ballast resistor
Flatox, Thu Sept 15 2011, 04:12PM
Thank you for your answer, it really helps me to understand what is at stake.
In fact, to convert the marx to a bipolar, I just have to remove the fourth spark gap, and put the power supply there, whitout forgetting the ballast resistor
Re: Marx generator with homemade capacitors
magnet18, Thu Sept 15 2011, 09:07PM
Lucas Electrical Co.
I need not say more
magnet18, Thu Sept 15 2011, 09:07PM
Ash Small wrote ...
On our side of the pond we refer to that kind of corruption of the English language as 'Americanisms'
magnet18 wrote ...
.I know at my school we usually call them "those 3 ring divider things"
.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'
Lucas Electrical Co.
I need not say more
Re: Marx generator with homemade capacitors
kiat, Wed Sept 28 2011, 01:01PM
But by connecting the HV supply half way, the end of the marx sitting on the floor will be at either + or - half Vout depending on how it was wired
kiat, Wed Sept 28 2011, 01:01PM
But by connecting the HV supply half way, the end of the marx sitting on the floor will be at either + or - half Vout depending on how it was wired
Re: Marx generator with homemade capacitors
Tetris, Sun Oct 02 2011, 03:33PM
Oh wow :) that is awesome! Hm... I have like a million page protectors lying around my house, and (though I am out of it I can esily obtain it) I can get aluminum foil and I am in a desperate need for capacitors, about 15nF worth. I still do not understand how you made the capacitors. Can you please explain again so I can make them so I can finally finish my SGTC? Also, do you need to dip them in oil? if so, what type of oil? I do not have access to cap oil... only cooking oil but I heard that works as well but won't it ignite?
:3 BTW epic marx generator, I was telling my dad just last night, "Who doesn't want a marx generator?" after he was talkin about travelling to Munich, a place I went before and saw one...
Tetris, Sun Oct 02 2011, 03:33PM
Oh wow :) that is awesome! Hm... I have like a million page protectors lying around my house, and (though I am out of it I can esily obtain it) I can get aluminum foil and I am in a desperate need for capacitors, about 15nF worth. I still do not understand how you made the capacitors. Can you please explain again so I can make them so I can finally finish my SGTC? Also, do you need to dip them in oil? if so, what type of oil? I do not have access to cap oil... only cooking oil but I heard that works as well but won't it ignite?
:3 BTW epic marx generator, I was telling my dad just last night, "Who doesn't want a marx generator?" after he was talkin about travelling to Munich, a place I went before and saw one...
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