Many brushless motors (fans, electric scooters) have digital output (i.e. on/off) hall sensors triggered by motor magnets to read a coarse motor's shaft (to kno

Many brushless motors (fans, electric scooters) have digital output (i.e. on/off) hall sensors triggered by motor magnets to read a coarse motor's shaft (to know which coil should be energized). There is even a higher resolution approach of using two or three analog output hall sensors sensing motor magnets to read fine stator position (for example, gimbal motors for DJI drones use this technique). Then there are ICs that contain several hall sensors that are arranged to measure absolute angle of diametrically magnetized target (these are the one's used in hall effect potentiometers, and I've seen them used for position feedback in brushless motor control). So, most likely your project had an issue with sensor placement, or the sensor wasn't correctly selected for the application They are no more finicky than IR sensors reacting to sunlight, or just about every type of sensor *also* being a temperature sensor: you have to be aware of what exactly is the sensor measuring and how the environment may affect it's measurements.