I'm looking for a photosensor/photo IC part (combination of photodiode, linear amplifier, Schmitt trigger and output transistor) that can be powered with 3.3V. Fairchild QSE256/257/258/259 is almost exactly what I need, except that it requires 4-16 volts supply voltage and not working very stable at 3.3. I know that there is a number of parts usually used in the infrared receivers, but they contain demodulator (from 38KHz) which I don't need. Anyone here knows a good alternative to Fairchild part?
Low Voltage Photosensor
lightphotodiodephototransistorsensor
Related Solutions
If you want to dinamically adapt the position of the panel with the position fo the sun, one good sensor is the panel itself :)
Doing MPPT (Maximum Power Point Tracking), you can also measure the output power and do small movements of the panel to detect the changes in power, and move it accordingly. It will be a bit tricky (and probably not worth) to tilt and rotate it, probably it's more convenient just to rotate.
You may also find this DIY light direction sensor interesting.
In your original circuit any current flowing through the photo transistor will go into the base of the NPN transistor and turn it ON.
Answer - change the position of the resistor in the photo transistor circuit and increase its value.
To turn the NPN transistor ON we need to raise its base-emitter voltage to 0.6V. With a 22k resistor this require a current of about 27 microamps (about half your measured value). To increase sensitivity increase the value of this resistor but remember there is ambient light which may cause the opto transistor to turn on so there will be a limit on how large you can make this value.
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Best Answer
In this thread is explained that a photodiode doesn't need a voltage across it to generate a photocurrent:
Do you need all the functions integrated into one IC? You have plenty of options if you would pick a common photodiode plus a comparator. Comparators exist for DLV (Damn Low Voltages™) these days; Digikey lists more than a thousand which will happily run at 3.3 V or less. The MCP6546 is the cheapest I found:
If the 30 mA current sink is not sufficient you can use the MCP6541, which has a push-pull output, from which you can drive an external transistor. This would also allow you to switch much higher voltages, as well as set your own hysteresis levels. In this answer I explain how to calculate the required resistances.