Re: [TCML] pig Jacobs (don't totally blow off resistive ballasting)

["Tim Meehan" <btmeehan@xxxxxxxxx>]

I left the formula for concentration of copper sulfate vs. resistance in a
notebook I don't have with me, but if you need resistors to carry big
currents you could probably do something like that (as long as you don't do
it too long).  This is pretty similar to the garbage can with water and
baking soda idea, but these things can carry a lot of current as long as you
make sure that you aren't heating up your mass of water too much.  For home
experiments, I would probably do baking soda - copper sulfate is poisonous.

On Nov 27, 2007 12:39 PM, J. Aaron Holmes <jaholmes@xxxxxxxxxxxxxxxxxx>
wrote:

> If the element is immersed in water, even if it fails
> "open", it may not actually be completely "open"
> because of the water.
>
> ...which brings me to another suggestion for a
> ballast:  My first pig ballast was just two copper
> pipes held in parallel by nylon bolts and immersed in
> a plastic garbage can full of water.  I put a PVC
> sleeve over one of the pipes which could be raised or
> lowered to vary the resistance, then doped the water
> with baking soda until I'd achieve the desired
> resistance range.  It worked great and allowed for
> very smooth control, albiet farily lossy.  Since the
> PVC had to be raised to reduce the resistance, gravity
> would naturally turn the power down if I let go of the
> control handle (A PVC "T" joint with another small
> section of PVC sticking off the side).  Also, this
> meant that the heat production was always near the
> bottom of the garbage can, allowing for plenty of
> convection cooling.  It took quite a while for the
> water to get hot, even with many kVA's involved.
>
> So, despite the lossiness of resistive ballasting,
> it's still hard to beat for simplicity and smoothness
> of control.  And also (probably) cost.  Check the
> prices on 500ft rolls of #10 wire these days ... :-(((
>  Then compare to the prices of a few short sections of
> PVC, water pipe, and a plastic Rubbermaid (or similar)
> garbage can.  I think I spent about $20 total
> (although I already had the PVC).
>
> My ballast these days is a big variac which I lucked
> into at a great price.  If you want to build a big
> variable inductor for cheap, however, Goodle for
> "slide choke" and "tesla" and you'll get lots of good
> hits, I'm sure.
>
> Cheers,
> Aaron, N7OE
>
> --- david baehr <dfb25@xxxxxxxxxxx> wrote:
>
> >
> > Yea, 50+ amps is high for a JL , but, if ya wanna
> > see the big , thick plasma ( ? ) , ya gots too :-)
> >
> >           Oh, if the element fails , this would be
> > an 'open' circuit , woulnt it ?? it would just turn
> > off ?
> >
>
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