Background: I currently have an ATmega AVR microcontroller development board and hope to use it to measure the moment a screen changes from black to white to determine the time when a screen refresh occurred. This is in the hopes to accurately determine when someone sees something for EEG research. My ideal is to attach the dev board and breadboard to the back of a computer monitor and just have a photodiode attached to the corner of the display via cables. I purchased a bunch of OP950 side-view flat photodiodes (http://optekinc.com/datasheets/OP950.PDF) to lay flat against the screen.
Question: My question is how do I properly use this photodiode? I read the spec sheet forward and back and researched how to use these, but I feel like I'm missing some crucial aspect to make sense of it all.
From what I've read so far:
- I want it reversed biased for speed.
- I need to determine the resistance based on it's reverse light current.
- I might need an OP AMP to boost the signal (although I only really want a binary response of no light vs. light)
I know this is a pretty general question, but after looking through books, learning about semiconductors and photodiodes at a micro level I still don't know what exactly I'm looking at with the spec sheet.
In my attempt to solve this alone, I've come up with this:
- The spec sheet lists 60V as the reverse breakdown voltage, which I want to stay away from since it would result in damaging the diode.
- The spec sheet lists Reverse Dark current as 60nA Max, which is the current it always has when connected due to leakage.
- The spec sheet lists Reverse Light current as 8μA-18μA, which is the range of current that is created by shining light on the photodiode when provided a 5V reverse voltage.
- The resistor needs to come between the 5V pin on the arduino and the negative pin on the photodiode.
- The resistor needs to account for the reverse light current and the 5V power supply.
I assume many of my assumptions are incorrect, and researching others' similar questions were too divergent to make sense of my component's spec sheet. Also, I would include a diagram, but I feel very uncertain how it would look and would prefer to think this out with better information from anyone who can help.
Thanks in advance for anyone's support!