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Registered Member #2099
Joined: Wed Apr 29 2009, 12:22AM
Location: Los Altos, California
Posts: 1716
Patrick wrote ... ...@ProudMary where is your source for this BOPET claim, everywhere i look i see them quoted as polyester! ... wiki "pet film or bopet film" if this link doesnt work. ...
I think a result similar to Biaxial Orientation in flat film products is obtained when PET bottles are made by blow molding. An injection-molded preform like is softened by heat, then blown up inside a much larger mold or die. Resulting container has molecular chains oriented in the axial and circumferential plane. Many years ago I was into popping soda bottles. The ultimate strength, calculated from wall thickness and cylinder radius and burst pressure of 2 liter Coke bottles, was comparable to yield strength of mild steel!
Registered Member #2422
Joined: Tue Oct 06 2009, 02:41AM
Location:
Posts: 85
Patrick wrote ...
i think you have a slight or intermittent short, that would explain why it works now, but not before. maybe that hot-plate is not a very good method.
That's what the problem was, but I ended up not using the hot-plate method.
Cap is done now, here are some pics:
In progress:
Finished
Edge
Corner (the seal looks crappy, but works well)
Bottom
So it's 95nF, 20 to 28 kV (at least) 9 inches by 6 inches by 1 inch Total cost about $30
...of course as soon as I'm done I find caps with similar ratings on ebay for $12. D'oh. Well, building capacitors is an important life skill I suppose. And now I know where to get a replacement if the one I built blows up....
Registered Member #2431
Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639
i bet your capacitor is better then those 12$ ones. your cap looks like it is made out of real metal foil, most caps are the metalyized plastic type very thin metal (vapor deposit) that has high ESR, your cap may be able to put out more charge in shorter time without the foil melting at high freq. better Q, i think
Registered Member #834
Joined: Tue Jun 12 2007, 10:57PM
Location: Brazil
Posts: 644
Be careful with this. It will fail soon due to the air trapped between the metal plates and the dielectric getting ionized, but before this can store far more energy than the required to kill you.
Registered Member #1667
Joined: Sat Aug 30 2008, 09:57PM
Location:
Posts: 374
Antonio wrote ...
Be careful with this. It will fail soon due to the air trapped between the metal plates and the dielectric getting ionized, but before this can store far more energy than the required to kill you.
yeah, that's some beefy 30J at 25kV. I recommend vacuum potting with warm epoxy and preheated capacitor
Registered Member #2422
Joined: Tue Oct 06 2009, 02:41AM
Location:
Posts: 85
Patrick wrote ...
vacuum draw vegtable or corn oil into those and theyll last a long time
I poured corn oil in between each layer as I was assembling it. You can sort of see it in the corner picture. (I probably should have mentioned this earlier.)
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Overhead transparencies are conductive? (RESOLVED)
