TMAG5173-Q1: HALL Sensor Recommendation

Hi Egemen,

To help determine if the joystick has been tilted up/down/left/right, one option would be to look at the magnetic results of the X and Y-axis, namely the zero-crossings. See the quick TIMSS simulations that I made to demonstrate this below:

• When pointing upwards(rotation angle 0º/360º) with a 45º tilt, the X-axis observes a magnetic field of about 0mT whereas the Y-axis sees a larger negative magnetic field. 

• When pointing to the left (rotation angle 90º) with a 45º tilt, the X-axis observes a larger negative magnetic field whereas the Y-axis sees a magnetic field of about 0mT.

• When pointing downwards(rotation angle 180º) with a 45º tilt, the X-axis observes a magnetic field of about 0mT whereas the Y-axis sees a larger positive magnetic field. 

• When pointing to the right (rotation angle 270º) with a 45º tilt, the X-axis observes a larger positive magnetic field whereas the Y-axis sees a magnetic field of about 0mT

For more specific joystick positioning, you can use the XY angle calculation, shown in the Device Output 2 plots above.

I have attached the JSON file below for the joystick example that I made so that you can play around with some of the parameters to see how different inputs affect the results. For the below simulation, I have the sensor lined up so that the center of the magnet is centered with the sensing element.

{
  "version": "3.4.0",
  "design_name": "Joystick Example",
  "magnet_id": 5,
  "poles": 2,
  "material_id": 1,
  "grade_id": 1,
  "select_remanence": "br_average",
  "remanence": 1200,
  "temperature": 20,
  "temperature_coefficient": -0.12,
  "coercivity": 10.9,
  "function_id": 4,
  "magnet_geometry": {
    "outer_diameter": 5,
    "inner_diameter": 3,
    "height": 6
  },
  "magnet_position": {
    "x_position": 0,
    "y_position": 0,
    "z_position": 5
  },
  "magnet_angle": {
    "x_angle": -45,
    "y_angle": 0,
    "z_angle": 0
  },
  "magnet_movement": {
    "arc_length": 360
  },
  "sim_setting": {
    "angular_step_size": 0.1
  },
  "sensor": [
    {
      "sensor_id": "TMAG5173-Q1",
      "sensor_position": {
        "x_position": 0.12,
        "y_position": 0.4,
        "z_position": -5
      },
      "sensor_angle": {
        "x_angle": 0,
        "y_angle": 0,
        "z_angle": 0
      },
      "custom_inputs": {
        "variant": "TMAG5173D2QDBVRQ1",
        "applied_vcc": 3.3,
        "temperature_compensation": 0,
        "averaging": 32,
        "maximum_input": 133
      },
      "id": 28681,
      "user_design": 41221
    }
  ],
  "parametric_sweep": [
    {
      "sweep_values": {
        "values": "-45,-35,-25,-15,-5,5,15,25,35,45",
        "from": -45,
        "to": 45,
        "step_size": 10
      },
      "is_combination": false,
      "parameter": "magnet_angle:y_angle",
      "sweep_type": "Range",
      "user_design": 41221,
      "id": 12501
    }
  ]
}

To determine whether a button press has occurred, I would recommend using the device's calculated magnitude results and checking to see if the magnitude exceeds some set value which would equal a button press.

Best,

~Alicia

Egemen,

Since an axially polarized magnet has radial symmetry, the field will not change when twisted 0-360° at any joystick position, so there will not be a measurable change in the magnetic field.

Typically for rotation a diametric magnet is used.

However, this magnet type is less ideal for joystick functionality.  If you are able to track the 0-360° rotation, it might be possible to derive a calculation to determine the joystick tilt, but this will be more computationally difficult than the original alignment with an axially polarized magnet.  The observed joystick tilt will be directly dependent on the rotation angle applied.

It may be possible to add a second magnet on the shaft that could be used to track the rotation, but you would likely need a second sensor placed to measure the field from this magnet. The two magnets may interact with each other depending on how you intended to place them.  The tilt this magnet experiences may also impact the linearity of the angle measurement performed by the second sensor.

Thanks,

Scott