Matthias Wandel built a sensitive capacitive displacement sensor using a Raspberry Pi Pico by exploiting the GPIO pins' inherent capacitance and built-in pull-down resistors to form an RC circuit. By timing how long a pin takes to fall from high to low, the system measures picofarad-level capacitance changes. The sensor was sensitive enough to detect hand proximity through a thick wooden floor and measure dielectric constant changes from waving an ABS pipe between two metal plates. The project explores the same capacitive principles used in digital calipers, though achieving precise positional measurements proved challenging due to capacitance varying with both X- and Z-axis plate shifts.
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