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Switch motion sensor according to 1mm movement

Other Parts Discussed in Thread: DRV5032, TMAG5123-Q1

Sensor that switches from 0 to 1mm

I am developing automotive products.
I am looking for a product that switches on when the distance changes from 0mm to 1mm.
I'm thinking of proximity sensors, light sensors, and hall sensors.
I am looking for a product that switches off at 0mm and switches on at 1mm.

Magnets and sensors have a structure as shown in the figure below.
Look at the picture below.

As shown in the picture, the magnet moves about 1mm from the sensor.
When the magnet moves 1mm, I am looking for a product that turns the sensor from OFF to ON.
The magnet is 8mm in diameter, 20mm in length, about 1000 gauss, and Alnico magnet.

It doesn't have to be a magnet to move.
I'm looking for a sensor that turns ON from OFF when moving 1mm.
The switch must be activated when the magnet passes between 0.8mm and 1.2mm at least.

I look forward to your answer.

  • Thank you for reaching out with your question.  The right sensor here will wholly depend on the field strength of your magnet at the two ranges you are specifying.  1mm is a rather small motion to detect, so I do recommend some careful consideration of the field produce by your magnet.

    DRV5032 might be a good candidate to consider for this application.  For any Hall element, the device will be sensitive to the magnetic field component applied orthogonally.  We have two package variants available depending on how your sensor and PCB might be oriented with respect to the magnet.  The SOT-23 variant is a surface mount device which would detect the field component travelling into the PCB.  We also have a TO-92 package which would detect the component which is parallel to the surface of the PCB and directed through the face of the device.  A second option might be the TMAG5123-Q1, which is in a surface mount package, but is sensitive to the field component parallel to the surface of the PCB. and directed through the length of the device.

    Each device is also is available in a variety of sensitivities.  It will be important to determine the field at the sensor location for each switch position.  Particularly, you will want to ensure that the field exceeds Bop MAX and is below Brp MIN in your ON/OFF positions respectively.  The various sensitivities will impact the switching location for your device.

    To assist you with your efforts to determine the sensitivity you need we have a field calculator on the DRV5032 device product page.

    This calculator is only really helpful with your second condition.  You might find the calculator tools at these sources helpful as well

    K&J Magnetics – This calculator is for NdFeB cylinder magnets which are axially magnetized.  It will provide a 2D simulation of field components in plane with the polarization of the magnet.

    Magnetrechner – This calculator requires manual entry of magnet properites, but will calculate the field components at any point in space (3D) surrounding a specified magnet.  Many magnet options are available

    FEMM – This free simulation tool allows for 2D simulations.  As long as reasonable symmetry is maintained this can be used in many circumstances.