I have chosen a power harvester to power a few things as part of a wireless system.
This one is the one I have and it seems to be operational:
http://www.powercastco.com/PDF/P2110-datasheet.pdf
http://www.powercastco.com/PDF/P2110-EVB.pdf
It provides the proper voltage set around 3V, and otherwise fits the RF frequencies required including the range of dbms .
However, I want to characterize the rfid system further than the nominal values given on the data sheet. i.e. get experimental values as well as relevant information relating to my use case.
I have standard laboratory tools such as a signal generator, oscilloscope, etc.
I have already gotten charge/discharge time of a capacitor at a given frequency and dbm. Further, I want to measure the charge times with different loads.
For my prototype, I will use the evaluation board with capacitors on it. My issue lies in that the power harvester only outputs one DC voltage at the threshold of 1V at the capacitor. This means that as I discharge it, and my reading goes to 0V for the output, the capacitor still has energy stored at that 1V threshold, and my Vout reading remains 'useless' with a 0v. As such when Vout is 0V and thus not providing power or discharging the capacitor.
I am using the Vout and GND pins as well as the capacitor pins for readings.
How can I characterize this threshold, and the discharge past the threshold? What other things should I measure about the power harvester? Perhaps I am missing some information to do with the capacitors.
Best Answer
I'm not sure I understand, but is there a problem to measure directly on Vcap (adding a resistor to load it there, or using the Dset pin and measuring the analog 'Dout' (less accurate resistor, but no boost converter, cap added to Dout))?
If you have the capacitor value Q=CV tells you how much charge is there. E=QV tells you the total energy in Joules. Q=C(Vcap-Vmin) gives a pretty close value for how much charge will be available at Vout if the boost converter is efficient, and E=C(Vcap-Vmin)*Vcap is the energy available for the boost converter.
Other than that, you can probably set the voltage at Vcap externally and measure how efficient the boost converter is.
And it seems a little bit silly here if the harvester cuts power practically at the same time as it tells you there is no power available anymore. Allthough that function might not be necessary in all applications though ...