I am trying to detect light in a range from complete darkness to a tiny bit of light. Imagine my test set - a shoe box with a mobile phone, that way I can make it ring and get light. The room light is way more than present in the real situation. I could also use a water pipe and place a phone in the middle The light I want to detect is not natural, it will be LED and other light meant for humans (no IR or so). Also the space it will be used is very tiny. I cannot change the light provided in case some would suggest that.
The easy solution would be and LDR or photo transistor, some resistors and a comparator or ADC
I have tried with LDR's and found only a few that gives enough change on "a tiny change in light", however that work on my desk light on/off, but that is not the real case. I also found LDRs to react to light fast, but returning to dark is slow for some of them. This is ok, but I still found them too different to be reliable. I tried 5 of the same type and got 5 very different results. Once again, solvable in SW, ADC read min and max and react accordingly. But still....
I have tried one photo transistor which reads 860nm (~red), but it does not give any reading except 1-10mV (5V in series with 4K7), and a setup with an op-amp for amplifying it works with room light
Now, my transistor is at 860nm or red, and I am looking at present light, so I found another one that works around 550nm, which simulates the human eye: Datasheet:
What can the community here suggest? I need a rest and new thoughts now