Hello people,

     about two weeks ago I've sent a message to the groups PICLIST and
PICLISTBR about the above topic. Thank you to everyone that contributed
with this thread.

     The replies from both groups were very interesting and the solution
I've choose (for its simplicity) was to use an LDR with a 4k7 resistor:

      +5V
       |
      4k7
       |
       +----ADC(PIC)
       |
       LDR
       |
      GND

     That other solution with a transistor working as a current to
voltage converter for a phototransistor is also very interesting. I've
tried the circuit below and was amazed with the results:

           +5V
            |
           10k
            |
     ,------+----ADC(PIC)
     |      |
     E      C (BC547B)
     C------B
            E
            |
           GND

     I've lend my luxmeter to a collaborator but as soon as I get it
back I'll make some tests to compare linearity/noise/performance between
the two solutions. I could post the results here if anyone is interested.

     This application would be tested on the realworld in about 45 days,
but it's working very well on my lab.

     Best regards,

     Brusque
--
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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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