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Re: Capacitor construction
Brad
I just spent a month building, shorting, tearingdown and rebuilding a flat
cap and here is my take on it. 1st, a one inch margin of dielectric aroun the
edges of the plate is sufficient *except* where the foil "lead" is taken off.
Here, (on that side) the distance from the edge of the dielectric to the
edge of the next foil plate should be at least two inches to duplicate the
dielectric properties of the rest of the system. Explanation: For a plate to
short form one plate to the next, the current path would have to travel "up"
one inch to the top of the dielectric, then over the thickness of the
dielectric, then down another inch to the edge of the next plate (greater
than two inch toal travel), Current only has to travel halfo of that
distance if it arcs from the the foil lead of the next plate over to the
previous plate. I realise that this may sound confusing but make a dummy of
a few plates and dielectric and perhaps you will see what I'm saying.
no2. Don't try using heat ot attach the foil to Low density Polyethelene
because at a temperature that begins to have a chance of attaching the two
materials together, the poly and the alluminum will begin to deform and warp.
Even if you succeeded in getting them to adhere to one another, they would
no longer be anything close to flat which would be a great disadvantage. (I
tried it)
no3. If you spray or apply with a small piece of cloth, a small amount of a
fairly thick oil to the surface of the dielectric (the oil you intend to use
to fill the cap will ususally work but heavier works better) and then apply
the foil using a small cloth wad to smooth the aluminum foil, and then an
artists rubber roller to remove the remaining bubbles, you will find a strong
level of adhesion developes. If you fruther design your case so that the
plates are firmly clamped, little movement of the plates whould result.