This circuit uses a CA3140, an operational amplifier with FETs in the input stages. Equivalent can be used. The range is adjusted by a 220k ohm potentiometer. This potentiometer can be increased up to 4M7 according the measured range of light; Power comes from a 9-V battery and current drain is very low.

 

Photometer Using the CA3140
Photometer Using the CA3140

 

 

 

Datasheets


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