Photoresistor? Wide conductance range depending on light level...

Imre

On Fri, 2 Jan 2004, Edson Brusque wrote:

> Hello everyone,
>
>      I'm scratching my head for some days but still haven't found a
> simple and working solution to measure the light level on a given ambient.
>
>      I've been trying it with this circuit:
>
>      +5V
>       |
>       C
>       E(phototransistor)
>       |
>       +----ADC(PIC)
>       |
>      10k(resistor)
>       |
>      GND
>
>      But the results haven't been that good. Lots of noise and very poor
> linearity. Also, I've tried I->E (current->voltage) converters using
> opamps but still nothing have convinced me.
>
>      To easy the implementation simplicity is very desirable. I don't
> need a precision circuit and I don't need to convert the readings in lux
> or any other real-word value.
>
>      The circuit would be used for feedback on a system that will try to
> keep the lighting level constant on an ambient with natural and
> artificial lighting.
>
>      Someone been there and done that? Any ideas?
>
>      Thank you very much,
>
>      Brusque
> --
> ---------------------------------------------------------------------
> Edson Brusque                     C.I.Tronics Lighting Designers Ltda
> Research and Development                   Blumenau  -  SC  -  Brazil
> http://www.suporte.ind.br/ryan/netiqueta.htm     www.citronics.com.br
> ---------------------------------------------------------------------
>
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