"Thin Magnetic Sensor for Angle Measurement in Folding Structures"

"Magnetic sensors are popular for rotation sensing in hinges and knobs because they do not require a mechanical or electrical connection between moving parts. However, the straightforward solution of spinning a permanent magnet about the rotation axis puts components directly on the hinge line, preventing its use in thin folded structures. Toward thin folding shells that can sense their own internal angles, this letter investigates a 1.5 mm thick flexible printed circuit board (PCB) design using a small permanent magnet and a magnetic vector sensor, with no components or PCB traces on the hinge line, covering an angular range of 10 to 360 degrees. Our method for calculating the hinge angle runs on a microcontroller and is insensitive to magnet strength, parametrized only by the PCB layout dimensions. The angle uncertainty is 5 degrees, limited chiefly by background from the Earth's magnetic field."