ii. Illumination measurement application with multiple light sensors

Operation amplifier circuit for temperature measurement can also be used of illumination measurement. The only two things that have to be changed are the sensor and the second trimmer. The following example is based on fototransistor that has an open base which control the electron flow though collector and emitter. The fototransistor signal needs much less amplification, therefore 50k trimmer instead of 500k suffices.

It is possible to connect a much as 10 thermometer sensors circuits to one PIC18F2xJ50 microcontroller. The microcontroller on the photo below has just one such circuit connected to AN0 input. It is also possible to hookup temperature and illumination sensors to the same microcontroller using some analog input channels (ANx) for temperature measurement and some for illumination measurement.