I try to measure light indoor with solar sensor (DS2438 & SFH203P). With the 390 Ohm sense resistor there is no sensitivity for low light, so I replace it with bigger values like 200k. If I verify with a digital meter the voltage over the sense resistor I now get the 0-250 mV scale all right, but the readings through Ha7Net and owfs are something different. The vis reading through owfs varies between a little below the real value shown by digital meter to about the real value doubled. So, for example, if the meter says 100 mv, then vis in owfs varies all the time between something like 95 and 200.
Is this normal or am I doing something wrong here? I tried this with a couple of different temp/solar/humidity boards and components, and always get the same behaviour. I power the board with external power, no parasite, so that shouldn't cause the problem either.
Is this normal or am I doing something wrong here? I tried this with a couple of different temp/solar/humidity boards and components, and always get the same behaviour. I power the board with external power, no parasite, so that shouldn't cause the problem either.