[sdiy] replacing resistor with vactrol??

[harry]

You get the data sheet for the Vactrol you wish to use... and the
resistance range will be specified in light and dark conditions.
There is a problem... the dark resistance is not reached (all the way)
for seconds / minutes / hours after the cell is exposed to light.  Cells
with higher resistance are usually slower .

Cells decrease in resistance much faster than they increase (you can
have a flashLIGHT (add photons) but not a flashDARK  ;^)

You can play some games by using more than one vactrol in series / shunt
to get different resistance response...

In general... what you want to try will work no problem... try it !!!

H^) harry

media at mail1.nai.net wrote:

> Let's say I'm designing a circuit that uses a resistor to control a timing
> function (eg. the resistor determines the charging rate of a cap)  Are
> there any rules of thumb to replace the resistor with a vactrol or LDR/LED
> combo in order to control the resistor's value with a control voltage??
> I'm unfamiliar with the specifications of such components, and looking how
> I would choose the right part.
>
> THANX!!