[sdiy] photo resistor as CV source

[Cynthia Webster]

on 1/27/05 1:56 AM, daryl groetsch at synth_dg at yahoo.com wrote:

> 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...

There was a wonderful piece presented at Mills College in
the San Francisco Bay Area years ago simply called
"Cloud Music" it was a conceptual piece by David Behrman,
Robert Watts, and Bob Diamond in which there was an array
or grid of individual photo resistors taped to a television
set and the controller was a locked-off video camera
pointed at the sky...

It was an all day affair listening to speakers distributed
throughout the campus each playing a channel or group of
channels of circuitry controlled by the clouds in the sky
above.  

It could have been called "When Heaven Meets Earth" and
was one of the most blissful and meditative musical events
I can remember.

Cynthia





> 
> 
> --- 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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