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Re: Plastic soda bottles for bypass caps? (fwd)



---------- Forwarded message ----------
Date: Wed, 17 Dec 1997 20:08:11 +1100
From: Peter Electric <elekessy-at-macquarie.matra-dot-com.au>
To: Tesla List <tesla-at-pupman-dot-com>
Subject: Re: Plastic soda bottles for bypass caps?

I had the same problem also. Here in good old OZ, things such as
doorknob caps are not only hard to get hold of but damn expensive! I
then decided that making bigger chokes and not using any bypass caps is
a much cheaper solution. I have been using 30 mH Pi wound chokes and
safety gaps only and have not lost a Neon sign transformer since.

Cheers,

Peter E.

Tesla List wrote:

> From:   Adam[SMTP:absmith-at-tiac-dot-net]
> Sent:   Saturday, December 06, 1997 8:24 PM
> To:     tesla list
> Subject:        Plastic soda bottles for bypass caps?
>
> I know that plastic soda bottles make for poor tesla tank capacitors,
> but
> it seems to me that that you could make some decent bypass caps from
> the
> lossy material (PET).  I was flipping through surplus catalogs looking
>
> for doorknob caps for my bypass caps, and found that the size I am
> looking for (200-300pF -at- 20kV) would run my around $40 each, and I
> need
> 2!!! $80, I don't think so.  With kitchen Aluminum foil and a few
> pepsi
> bottles, I should be able to make 250pF caps that are quite small and
> practically free! Anything I am missing?
>
> I tested out some pepsi bottle material, and a single thickness
> (10-12mil
> I think) doesn't puncture with 25,000 VDC on it- good, since I will
> only
> have 4.5kVAC on it in use.  Plus, with a thickness of 10 mils, and
> k=3.0,
> I work out that the plates have to have only 4 square inches of
> overlap.
> Here is my calculation:
>
> e0 = 8.85418781762 * 10^-12 (dielectric constant of free space)
> k = 3.0 (for polyethylene terphthalate)
> 1 inch = 0.0254 meters
> Plates = two Al foil plates with 2" by 2" overlap area = 4.0 sq. in.
>
> (e0 * k * 4.0 * 0.0254) / 0.010" = 270 pF (approx)
>
> -Adam
>
> -----
> --------------------------------------------------------------------
> Adam Smith
> absmith-at-tiac-dot-net
> Epoch, Inc. Digital Music Project
>
> www.tiac-dot-net/users/absmith/                 MP3 Demo Tracks Now
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> ----------
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