Hall-Effect Sensor

A sensor that uses the Hall effect to turn changes in a magnetic field into an electrical signal.

A Hall-effect sensor works on the Hall effect: when current flows through a semiconductor strip, a magnetic field perpendicular to it produces a voltage across the strip's sides, with a stronger field producing a larger voltage. It's cheap, contactless, and small, making it one of the most common position sensors used in motors. In a brushless motor, three Hall-effect elements are typically mounted to sense the rotor magnets' approximate position, which the driver uses to decide which winding phase to energize (commutation); pairing a Hall chip with a radially magnetized ring magnet also makes a simple magnetic encoder for measuring a joint's angle. The Hall effect is also used for current sensing and proximity switches. Its resolution and noise immunity are lower than an optical encoder's, so in robot joints it's often used just for commutation or coarse position, paired with a more precise encoder.

ExampleIn sensored brushless motors common in RC models and self-balancing scooters, the thin bundle of wires coming out of the back of the motor is the signal lines from its three Hall-effect sensors.

Also called

Hall Sensor, Hall Switch

Related

Brushless DC Motor · Magnetic Encoder · Rotary Encoder · Field-Oriented Control · Servo Drive (Motor Driver)

Sources

Hall effect sensor - Wikipedia