- Mon Sep 23, 2013 8:13 am
#163806
Again ... if the output of the PV panel is not connected to anything, it will generate a voltage but not deliver any power. The voltage a PV panel will generate is dependent on how much light it is receiving and the load that it's connected to. If you want the voltage measured, and any power reading derived from it, to have any real world meaning, you need to attach a load resistor to the PV panel. That load resistor should be representative of what you want to use the PV panel for.
If the PV outputs a voltage larger than the Arduino can safely handle, then you can split that load resistor into 2 resistors, making a voltage divider so that the voltage going into the Arduino is now small enough (5V or 3.3V Max, depending on which Arduino you have). Since you know the resistance and measure the voltage across one resistor, you can compute the current being supplied by the PV panel. Knowing that current and both resistances you can compute the total power.
If your panel claims to output 12V while supplying 83 mA, then perhaps you want verify if this is true. If you attach a load of 150 ohms to the panel, then at 12V the PV should also deliver 80 mA. That's also (12V * 0.08A = ) 0.96W !!! Now split that 150 ohms into 2 resistors and measure the voltage across the smaller resistor. Be aware you can't use standard 1/10 or 1/8 W resistors as they will burn up.
