I am in need for a low cost light detector that has a use settable
trigger point for the light/dark threshold. My first thought has been to
just set up a voltage divider in the following way.

        +5V
          |
         | |
         | | 500K
         | |
          |
          |
          |--------- PIC ADC
          |
          |
         | |
         | | LDR
         | |
          |
          |
         ---

The LDR has >500K resistance in darkness and 3K-20K at 10 Lux.

One could use a PIC output pin to feed the divider instead of the +5V
and just activate this when a measurement is needed.

Is there any drawbacks with such a scenario? Is there a better way to do
this in a low cost way?

/Ake

 ---
Ake Hedman (YAP - Yet Another Programmer)
eurosource, Brattbergav=E4gen 17, 820 50 LOS, Sweden
Phone: 46 657 413430 Cellular: 46 730 533146
Company home: http://www.eurosource.se      Kryddor/Te/Kaffe:
http://www.brattberg.com
Personal homepage: http://www.eurosource.se/akhe

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