The basic idea is that it’s possible to measure a capacitor’s capacitance using two microcontroller ... used as a hidden touch sensor that works through an enclosure’s wall by using similar ...

After packing a 2N3904 transistor, an LM386 amplifier, and every Hackaday reader’s favorite chip the 555 timer into an enclosure along ... Look ma, no MCU! The sensor coil was made by salvaging ...