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DRV5055: Need an expert to confirm the hall effect sensor would work in my application.

Shengwen Liu
Prodigy 25 points
Part Number: DRV5055
Other Parts Discussed in Thread: DRV5056

Hi there, I am looking for a Hall effect sensor to detect the magnetic field difference in my exoskeleton. I have attached a demonstrative picture below. The dot is where I intended to put the Hall Effect sensor and the distance between the two magnets are 14 and 20mm respectively. During my application, there is a magnet inside the frame that would rotate and attract and reject the two outside magnets shown in the picture respectively. Therefore I presume the magnetic field during the application would be constantly changing. I am wondering if the DRV5055Z2QDBZR linear Hall Effect sensor can achieve my requirements, My goal is to identify when the magnets attract/reject each other which means it should be able to detect very minimum magnetic field change. I have a 90% confidence level that this would work but I need an expert that has experience with this type of sensor to confirm that. I hope my explanation makes sense, let me know if you have any additional questions.

Here is a follow-up illustration of this issue. My goal is to differentiate these two instances shown here using the hall effect sensor. The product number I chose is DRV5055Z2QDBZR (package SOT-23 DBZ). I need an expert to confirm that the hall effect sensor would be able to sense the change in a magnetic field, I anticipate going with the highest sensitivity option(A4/Z4). Also, is there a preferred distance between the sensor and the magnet? Thank you so much, I am aware that there are a lot of questions, it would be ideal if I can have an engineer who reviewed the info below communicate with me on the phone. Thanks again!

 

  • 0
    TI__Genius 17390 points

    Shengwen,

    This is a very interesting setup.  The multiple magnets will certainly create a variable magnetic field.  For instance 1, the two aligned magnets will produce a field similar to one large magnet.  I would expect a larger magnitude input to DRV5055 in position 1. 

    While much of this is dependent upon the spacing and sizes of the magnets, I tried to roughly sketch what I would expect the behavior of the B-Field to look like.

    Since DRV5055 is only sensitive to the component of the vector in the direction of the red arrow you would only be able to monitor the change in the field in this direction.  If the sensor is roughly the same vertical displacement as the magnet in instance 2, then almost all of the field will be in the correct direction.  For Instance 1 I would expect there to be a little more curvature at this location, but still primarily in the correct direction.  I do expect you could make this work, though you would want to ensure that you do not saturate the input of the device.

    In both cases, I expect that we would always see a field in the same direction (never changing polarity). You might be interested to consider DRV5056 which operates similarly to DRV5055 but is a unipolar device. We would need to flip the polarity of all the magnets to ensure a positive field at the sensor.

    The magnetic flux density from any magnet will vary with the size and material of the magnet.  I cannot suggest the correct spacing or sensitivity without complete information.  If you had a prototype you could use the EVM at the link below to test it out and adjust spacing.

    https://www.ti.com/tool/HALL-ADAPTER-EVM

    I have send a friend request within E2E which I believe should send you my email for direct contact if you need to discuss further.

    Thanks,

    Scott

  • 0 in reply to Scott Bryson
    Prodigy 25 points

    Thanks a lot, Scott!!! You are very helpful, I will spend more time reading your response and get back to you if I have further question. 

    Thanks again!!