[volt-nuts] Bohnenberger electrometer DANGER

[Dr. David Kirkby]

On 8 March 2018 at 07:19, Andre <Andre at lanoe.net> wrote:

> Hi, re. capacitors it might be worth mentioning that the normal equation
> assumes charge and discharge through a constant current.
>

What 'normal equation' do you mean?


> Don't forget that the equation includes a non linear term so you'll need
> to take that into account (Q=CV2 iirc) where Q is Coulombs, C is
> capacitance.
>

I am puzzled by CV2.  The energy (joules) stored in a capacitor is 1/2 C
V^2, where C is the capacitance and V the voltage. I don't know if that's
what you mean.


> If this is done using something like an LM317T in CC mode or even a string
> of them (my idea) with anti-overload circuitry added externally then this
> may well work.
> Any series resistance will cause problems so you'd need quite a lot of
> regulators but there are ways to use JFETs selected by hand if you really
> wanted to
> make a test setup.
>

I am totally lost here!

If anyone has an explanation of whether any of the energy to move the leaf
comes from the battery/capacitor, or does it all come from the charge
applied to the unit, I would like to know.  If no energy (apart from
leakage) comes from the device applying the electric field, a small
capacitor is suitable, and very safe. If at least some of the energy
required to move the leaf comes from the voltage supplying the electric
field, then a small value capacitor will be no use.

This is a fairly low priority task for me at the minute, as I need to do
some real work until Friday evening. But over the weekend I will play with
this.

Dave