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Need help : sunlight detector and flash detector circuits

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yaya_sensei

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sunlight detector

Hi,
Im a final year degree student in electrical and electronics. Im doing a project that has to do with detection of sunlight illumination and flash. Can you recommend sunlight detector and flash detector circuits that can easily be integrated with PIC16F877A?

Thank you
 

sunlight detector

You would need photodiode for flash rather than photocell as it is much faster responding. Flash durations may be too short for any meaningful processing, you may need some sort of sample and hold circuit. Sunlight should not be a problem at all.
 

photodiode flash sensing diode

I did buy a PIN photodiode but I could not get the output. Probably the circuit Im using is not suitable for photodiode. Can you recommend any circuits that are using photodiode which can really produce outputs? I would really appreciate if you can give me schematics of the circuits.
 

detector flashcan

The current of back biased diode depends on light energy coming to its sensing side. Also diode dark current will depend on temperature and varies a lot .
Trying to use same sensor for flash and sun illumination detection means at some extend the amplifier should support wide input current range from diode and be not excited at same time.

The flash can be detected by differentiating the photodiode amplifier output (simple rc circuit).
I would go with transimpedance amplifier (that depends on your strict requirements which you dont know yet) with low gain first and then additional amplifier for sun illumination level detection. Differentiate the output from first amplifier and detect it with threshold tune comparator.

Low gain transimpedance is needed to prevent amplifier from excitation when diode is maximum radiated under the sun , dark current (when exposed to highest possible temperature) is maximum and there will still be room for flash detection.

Pay attention to opamp offset vs temperature and photodiode current vs temperature .

What is the pin diode id you own? BPW34 is nice one for such things.
 

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