[sdiy] photo resistor as CV source

[daryl groetsch]

this one worked, thanks Ken. i've got it on a long
cord so i can stick it out the window and use the Sun
as a voltage source. got it taped to the TV screen
right now, it sounds really cool... 


--- Ken Stone <sasami at hotkey.net.au> wrote:

> 
> +15
> |
> R1 resistor
> |
> PR (photo resistor)
> |
> +----out
> |
> |
> R2 resistor = R1 + PR(dark)
> |
> |
> -15V
> 
> you may need a resistor across the photocell too,
> say 470k. R1 would be
> 100k, and R2 would be 560k-680k - perhaps a 1M
> trimmer to zero it out.
> 
> Ken
> 
> >hi all, 
> >i'm trying to use a photo resistor as a CV source
> for
> >my -/+15 Volt modular synth. the circuit i made is
> >just a >2 Meg photo resistor in series with 2 9
> Volt
> >batteries (18 Volts), with a jack coming off. it
> works
> >from about 8 Volts up to 18 Volts, but i can't get
> it
> >down to 0 Volts. I tried putting a potentiometer
> >inline and that lowered it, but not enough. i know
> i'm
> >missing something simple probably. can anyone give
> me
> >ideas or point me in the direction of a schematic?
> >thanks very much!
> >Daryl
> >
> >
> >
> >		
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>
_______________________________________________________________________
> Ken Stone   sasami at hotkey.net.au or
> sasami at cgs.synth.net
> Modular Synth PCBs for sale
> <http://www.blaze.net.au/~sasami/synth/>
> Australian Miniature Horses & Ponies
> <http://www.blaze.net.au/~sasami/>
> 
> 



		
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