attention EE's ( stugray)

[A.T.T.R]

can you guys double check me on this :]

trying to build a capacitor ( bored leave me alone lol and its cheep to do)


using PVC as the seperator at .007 mm thick it will breakdown at 28 volts

correct?

if i increase that to 1.25 mm of pvc i should get 5000 volts? but at a GREAT sacrifice to capacity ( due to less surface area due to greater thickness in the rolls ( meanin i can fit less plates in the same area) and also since it will have a greater difference)


know of anything that will let me get a stronger voltage at fractions of a MM? ( but still as cheep as pvc )


yes this is what i do when its 100 degrees outside and im all video gamed out !

 

[stugray]

A.T.T.R

Before I even get out my textbooks to check your numbers:

1 - Why are you trying to build one of the cheapest electrical components around? I have a ton that I could send you free.

2 - What is the application? The only application that I can imagine where you try to build your own is where you are looking for huge capacitances ( greater than 1 Farad ).

3 - There are new hybrid caps on the market that can squeeze 1 Farad into something the size of 8 quarters ( google ultra capacitor ).

Are you trying to build a high voltage power supply? An old CRT will provide you with enough capacitance to kill a person ;-)

Once we get over that, the easiest way to make a giant cap is to roll aluminum foil with plastic sheet in a long roll. I have watched a capacitor bank that takes hours to charge over the grid, but releases a 10 foot long bolt of lightning when discharged.

Stu

 

[A.T.T.R]

lol yeah that is what im doing foil and pvc sheet rolled into a 6 inch diam tube lol


i saw those super and ultra caps but couldent find pricing but am really impressed by the numbers


and there is no real reason im building one rather then buying excpet that its all in the DIY spirit

anyways fromw what i found PVC breaks down at 40MV/m so im jsut not sure if i converted it right to 4KV/mm

 

[A.T.T.R]

LOL wow



ok i also just calculated that at 32 sqmeters of plate area seperated by .007mm pvc i get
k=3.4 area = 32 distance = .007
so
3.4*32/.007 = 15542 PICOFARADS! LMAO wow

 

[stugray]

A.T.T.R

the breakdown ( assuming your 40MV/m # is correct ) is 40,000V/mm or 40V/um.

Your .007mm PVC ( dont think you can buy that..... ) is 7um so its breakdown would be 7*40=280V

the 1.25 mm would breakdown at 50000V

And your final # is tiny "15542 PICOFARADS" is 15 microfarads. I have a 330uF one in my hand that is smaller than a pencil eraser.

Stu

 

[buck50bmg]

Building it for a Tesla Coil? Ive built many. If you really want a cool cap and really DIY it, try a beer bottle cap. Look for it on the net.

 

[pdelcast]

<a href=showthread.php?s=&postid=12533063#post12533063 target=_blank>Originally posted</a> by stugray
A.T.T.R

the breakdown ( assuming your 40MV/m # is correct ) is 40,000V/mm or 40V/um.

Your .007mm PVC ( dont think you can buy that..... ) is 7um so its breakdown would be 7*40=280V

the 1.25 mm would breakdown at 50000V

And your final # is tiny "15542 PICOFARADS" is 15 microfarads. I have a 330uF one in my hand that is smaller than a pencil eraser.

Stu

Ooops, nope. 15542 Picofarads is only 15 NANOfarads (.015 microfarads.) There is a million picofarads in a microfarad.

Patrick

 

[A.T.T.R]

yeah i know thats why i was laughing the number is almost non existant

 

[pdelcast]

<a href=showthread.php?s=&postid=12534311#post12534311 target=_blank>Originally posted</a> by A.T.T.R
yeah i know thats why i was laughing the number is almost non existant

Yeah, high value capacitors use dielectrics that are only a few ATOMS thick -- that's how they get a lot of capacitance in a small package.

 

[stugray]

pdelcast,

Yup - got me there - "15542 Picofarads is only 15 NANOfarads"

I just grabbed the nearest cap by me ( 330uF ) and was comparing to that.
Sorry ... "whats a few orders of magnitude between friends" ;-)

Stu

 

[MJDiP]

You guys are blowing my mind!! ... I'm a "power" guy and am going to take the PE next year - Looks like I should start studying now because I don't remember any of this stuff!

 

[pdelcast]

<a href=showthread.php?s=&postid=12534654#post12534654 target=_blank>Originally posted</a> by stugray
pdelcast,

Yup - got me there - "15542 Picofarads is only 15 NANOfarads"

I just grabbed the nearest cap by me ( 330uF ) and was comparing to that.
Sorry ... "whats a few orders of magnitude between friends" ;-)

Stu

ROFL!

It's interesting to note that a 330uf polypropylene or paper capacitor would have to be about the size of a coffee can. It's that horribly thick .007mm dielectric.

Aluminum capacitors are made with foil that is allowed to oxidize to a controlled thickness -- the oxide is used as the dielectric. The electrolyte becomes the other plate. SO, if you got a nice big piece of aluminum foil, allowed it to oxidize, rolled it up in a can, put in some saltwater (from your tank would be fine!) you might get a decent (low current, high capacitance) capacitor.

Or, you could just go to Radio shack and buy one for $.25

Patrick

 

[A.T.T.R]

new ideaconsist of pvc piping.
the dielectric is pvc pipe at 2mm think giving me 80kv with a surface are aof about 18 sq ft

any one know if

k*sqmeters / distance give results in picofarads or uf

 

[A.T.T.R]

ok im getting 23906.692913385826771653543307087 pico farads

 

[A.T.T.R]

Charge: 0.0191248 Couls
Energy: 7649.92 Joules