A Miniaturised Device with Programmable Excitation Signal for the Inductive Coupling with LC Circuits and Sensors

This paper presents an open-source miniaturised readout device designed for the wireless interrogation of passive LC sensors and wireless power transmission. The system is based on a Sparkfun RedBoard Artemis microcontroller with a custom printed circuit board as an extension, providing a compact, low-cost alternative to expensive laboratory-grade equipment. The reader coil is excited by a signal that can be tuned digitally in both frequency and amplitude. The resonance frequency of a wirelessly coupled LC tank is detected by monitoring the voltage minimum of a rectified signal envelope, which corresponds to the impedance change of the reader inductance at resonance. Experimental validation demonstrates that the device accurately tracks resonance frequency shifts resulting from variations of the LC tanks capacitance, performing comparably to laboratory-grade impedance analysers. Testing the influence of axial separation between the two coils from 10mm to 25mm showed stable and identifiable voltage dips. The programmable excitation signal peak-to-peak voltage ranges from 0.81V to 5.35V. The device supports fully stand-alone operation with a display and navigation switch, making it suitable for untethered LC wireless sensing and actuation applications.