Variable Load Resistance by Using CdS Analog Linear Optical Coupler for Automated Measurement of Capacitive Energy Harvester

Abstract In this work, we demonstrate a load resistance measurement system aimed at automating a vibration type capacitive energy harvester using a CdS analog linear optical coupler as a variable resistor. The CdS variable resistor exhibits non-polar, very low parasitic capacitance below picofarad and high allowable voltage over a wide range of variable resistance. By controlling a LED driving current of the CdS analog coupler, variable resistance range of 10 MΩ to 100 kΩ was obtained by 0.4 µA to 6 µA driving current. The results show that the resistance is reproducible at full scale with a low error rate of less than +3%. The detailed characteristics of the CdS coupler and the automated measurement results of the piezoelectric MEMS vibration energy harvester by using Arduino microcontroller are also described.