I want to use specifically the SFH 309 NPN phototransistor in order to create a pulse sensor that works as seen below:
The IR diode emits IR light to the fingertip from the one side and on the other side the phototransistor is picking up the light "converting" it to voltage values. When there is a pulse, the excess blood "blurs" further the fingertip and the transistor is picking a weaker light beam.
The problem statement here is: How do I find the right resistor to get the best result? (interested more in the procedure of what to look for in the data sheet and how to calculate it)
This is the kind of signal that I am looking for (here the diff is 50mV, and I am hoping for something better than this).
The VCC is 5V.