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DRV5055: How does a circular magnet determine the optimal position of a linear Hall sensor

Cherry Zhou
Mastermind 22235 points
Part Number: DRV5055
Other Parts Discussed in Thread: TMAG5170

Hi team,

Using a magnetic ring with an inner diameter of 18, an outer diameter of 24, a thickness of 3 mm, a total of 6 linear hols are placed in a circle directly below the magnetic ring, with the hall print facing the bottom of the magnetic ring. The circle and the magnetic ring of the Hall distribution are concentric circles with two adjacent Hall spaced 60° apart.

Issue: In this case, the data is not read well and the maximum and minimum deviations are not significant. So the customer would like to know how to determine the position of the Hall relative magnetic ring when designing? And how to get the better data to the Hall?

Could you help check this case? Thanks.

Best Regards,

Cherry

  • 0
    TI__Mastermind 21120 points

    Cherry,

    The configuration you are describing sounds as if they are wanting to monitor the angle of the ring magnet as it rotates.  For this function, to use DRV5055 we would normally recommend two sensors placed 90 degrees apart at the same radius.  The observed result as the magnet spins is that a sine/cosine relationship should be observed.  To determine the angle, the arctangent can be calculated.  There is more detail in these application notes:

    https://www.ti.com/lit/an/sbaa503/sbaa503.pdf

    https://www.ti.com/lit/an/slya036b/slya036b.pdf

    Some calibration may be necessary depending on sensitivity and mechanical tolerances.

    This could also be accomplished by using a single TMAG5170 device placed below the magnet with the sensor aligned to the magnet center.  This presents a more ideal input which is less sensitive to mechanical errors.  TMAG5170 may be used anywhere near the magnet where sufficient field is present, but the system will likely require more calibration the further from center the sensor is placed.

    https://www.ti.com/lit/an/sbaa463/sbaa463.pdf

    If the function is different than angle sensing, let me know and I'll be happy to help work out ways to get the measurements needed.

    Thanks,

    Scott Bryson