Advanced features for motor control

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DocID022500 Rev 4

Hall sensor

The Hall sensor is a type of sensor based on Hall effect: when a conductor is placed in a

magnetic field, a voltage will be generated perpendicular to both the current and the

magnetic field.

There are four types of Hall sensor IC devices that provide a digital output: unipolar

switches, bipolar switches, omni polar switches, and latches. The main difference between

them is the output waveforms (pulse duration).

The digital Hall sensor provides a digital output in relation to the magnetic field to which it is

exposed. When the magnetic field increases and is greater than the BRP (magnetic field

release point value), the output will be ON. When the magnetic field decreases and is lower

than the BOP (magnetic field operate point value) the output will be OFF.

Figure 9 presents the output waveform of a typical Hall sensor.

Figure 9. Output waveform of a typical Hall sensor

Generally, the Hall sensor is used in the three-phase motor control. Figure 10: Commutation

sequence presents the commutation sequence.

Figure 10. Commutation sequence

How to use the Hall sensor interface

The STM32 timers can interfaces with the Hall effect sensors via the standard inputs (CH1,

CH2 and CH3). Setting TI1S bit in the CR2 register, allows the input filter of channel 1 to be

connected to the output of a XOR gate, combining the three input pins TIMx_CH1,

TIMx_CH2 and TIMx_CH3.