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DRV5032: Reed switch replacement in door/window sensor

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Replies: 4

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Part Number: DRV5032

Hello Team,

We offered DRV5032 as replacement for Reed switch in our customer's devices - door/window lock sensors.
Currently the customer have setup of magnet which DRV5032 doesn't support(due to the 15-19 page of datasheet).
Do you have any sollution to replace reed switch with following setup?(pictrure):
Magnet located at the far corner of the door. Can DR5032(or another sensor) detect field in this case?

BR,
Ilya

  • Ilya,

    Great question. There's a few potential ways to solve this.

    First, there is a spin of this device planned in TO-92 package some time in the future that would potentially work here. I can't comment on timeline here on the forum, but if you can follow up with me via email, we can discuss your customer's timeline and see if this would be a potential option.

    Next, as you can see in the datasheet snippet, having a DRV5032 sensor below a magnet oriented this way is not necessarily a death sentence.

    Do we have the ability to place the sensor slightly offset from the magnet? If so, placing the location of the Hall element directly under the surface of the magnet should provide enough field in the sense direction to trigger the sensor. Can you share details of magnet used here (dimensions and grade). I can run a few brief simulations to show you the field strength at an optimum point and ensure that the device will trip. 

    Best Regards,

    Carolus Andrews, Analog Applications, Current and Hall Effect Sensors

    Getting Started with Current Sensing Video Training Series

    TI makes no warranties and assumes no liability for applications assistance or customer product design. You are fully responsible for all design decisions and engineering with regard to your products, including decisions relating to application of TI products. By providing technical information, TI does not intend to offer or provide engineering services or advice concerning your designs.

  • In reply to Carolus Andrews:

    Carolus,

    Thank you for the detailed answer!

    Magnet's datasheet in attachment.
    The customer have ability to place the sensor very slightly offset from the magnet (move the sensor's layout inside the device).
    They doubt that the sensor will work stably under these conditions. 

    If you can provide brief simulations - it would be great!

    Also I should add - why are they asking for configuration of sensor simmilar to reed switch:
    The customer already produce large volume of various door sensors based on reed switch and their End customers are used to installing this sensors in a certain way.

    The customer’s doubts are based on the fact that even if this would work fine on the table, in real conditions new sensor may not work correctly.
    For example - The door sagged, the door arched from the temperature difference, moved away, etc.

    3250.8X16_data_sheet.pdf

  • In reply to Carolus Andrews:

    Carolus,

    Thank you for the detailed answer!

    Magnet's datasheet in attachment.
    The customer have ability to place the sensor very slightly offset from the magnet (move the sensor's layout inside the device).
    They doubt that the sensor will work stably under these conditions. 

    If you can provide brief simulations - it would be great!

    Also I should add - why are they asking for configuration of sensor simmilar to reed switch:
    The customer already produce large volume of various door sensors based on reed switch and their End customers are used to installing this sensors in a certain way.

    The customer’s doubts are based on the fact that even if this would work fine on the table, in real conditions new sensor may not work correctly.
    For example - The door sagged, the door arched from the temperature difference, moved away, etc.

  • In reply to Ilya Mazurenko:

    Ilya,

    Thanks for the information. The viability of Hall as a solution will come down to that offset. For the purposes of these simulations, I am looking at DRV5032DU, which has a sensitivity of 3.9mT, or 39 Gauss. With the type of magnet your customer is using, have a look at the below field strengths:

    What this means is that, provided the sensor element is aligned with the edge of the magnet, the sensor could be placed up to ~19mm away from the edge of the magnet (23mm-4mm to account for the diameter of the magnet)! However, when we move the sensor to the middle of the magnet:

    You can see that all of the field in the x-direction is now gone. In short, as long as the customer provides some offset to the magnet, they should be able to use the DRV5032 as a suitable replacement, they will just need to work out how far apart they plan to placed the magnet and sensor, and identify a suitable range for placement. 

    Best Regards,

    Carolus Andrews, Analog Applications, Current and Hall Effect Sensors

    Getting Started with Current Sensing Video Training Series

    TI makes no warranties and assumes no liability for applications assistance or customer product design. You are fully responsible for all design decisions and engineering with regard to your products, including decisions relating to application of TI products. By providing technical information, TI does not intend to offer or provide engineering services or advice concerning your designs.