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DRV5053 Vq and sensitivity

Other Parts Discussed in Thread: DRV5053

Dear all,

I have started testing DRV5053 for position sensing application, where I'm hoping it (or a pair of them) could help me understand where I am on a 20mm scale with at least +/-1mm precision and 5mm away from the magnet. While this the first thing I'm doing with analog hall sensors (have used digital on many projects) and I'm only in the very beginning in understanding if this is a solution to the problem at all, I'm encountering the first issues I do not quite understand and would be glad about some help.

First and foremost is Vq. It looked suspicious on the ADC result of MCU, but a simple multimeter confirms I have about 1.50V Vq on the device with no magnets around. I have tried to move it, to change the power supply to a different voltage, to hang it in a cable away from the desk and three different versions of DRV5053 (different sensitivity) and I get the same result. The temperature is not some 150C either - it is normal 'room temperature' or about 21C. How come if the data sheet says Vq should be 1.00V +/- a little bit?

Second, I'm using all sorts of magnets for testing, but even the largest of them might seem small to many - 10mm neodymium button magnet. Is it possible that I cannot sense a change in magnetic field from N to S even a few mV large with this sort of magnet? I mean, one on each side of my index finger are sort of painful :).

Thank you for your input,

Edmunds

  • Hi Edmunds,

    Our experts have been notified and should reply soon.
  • Hi Edmunds,

    You're right that the device output should be close to 1V when no magnet is nearby.  Have you seen this on multiple units?  Can you verify the pin connection schematic?  Is Vcc set to somewhere between 2.5V to 38V?

    I've found this calculator to be useful for determine the flux density that magnets produce at some distance: www.kjmagnetics.com/calculator.asp

    And of course, the Hall sensor should output a voltage equal to VQ plus the flux density present times Sensitivity.  Which Sensitivity version are you using?  And is the magnet oriented with North or South perpendicular to the face of the package? (that's the direction of sensitivity)

    Best regards,
    RE

  • Dear RE,

    Things are looking better now, since I do have the output close to 1V when no magnet is present.

    Thank you for the link to the calculator - seems a useful tool for the project :).

    Now, my latest problem is, I cannot achieve +/- picture on the output. I have a peak in the middle of the magnet and then falling voltages either side I go. This does not suit my application, as I need to know which direction is the deviation to correct it. I believe this is due to some misunderstanding with magnet pole/hall sensor relation so I have ordered a school blue/red U shaped magnet to see what is what.

    I'm starting to believe I will need two hall sensors or two magnets to achieve certainty/precision I need. Any linear position reference designs or case studies, where solutions can be at least visually appreciated would help.

    Thank you for your time,

    Edmunds

  • Are you using this type of configuration?

    In the middle position, the sensor will see no field.

    Best regards,
    RE

  • I would hope I'm using the configuration as in above picture, but I haven't found a compass around the house to be sure :).

    Anyway - no field in the middle is fine and understandable, but I would expect the voltage would go one way if the magnet in the picture moves to the right and the other way if the magnet moves to the left. What I have is same way (down) whatever direction the magnet goes.

    I'm testing the THT package, but actual application will be SOT, so I need to understand the required orientations for both.

    Edmunds

  • Your expectation is correct; moving left versus right should produce an opposite polarity of flux density.  One direction should bring the device output >1V, and the other should be <1V.

    If your magnet is in question, can you verify that a head-on approach from either side of the magnet produces different polarities?

    I recommend just buying a new magnet with trustworthy poles and magnetization.  One option is this.

    Best regards,
    RE

  • It is quite likely by now my magnet is just not polarised towards the ends but towards the sides. I looked at the website you suggested and it is by far the most comprehensive 'magnets house' I have seen online, so thank you for the link. However, I got a shipping proposal to Europe of 160USD for a ~5USD order and I think that is a bit steep :). Do you know of a similar supplier in EU or China for that matter?

    Thank you,

    Edmunds

  • I have sorted the magnet purchasing problem - aliexpress with free shipping the only problem being the delivery is now 4-6 weeks away. On hold until then.

    Thank you for all the assistance so far,

    Edmunds

  • Edmunds, here's a site sort of like K&J that's based in Europe:

    https://www.supermagnete.de/eng/

    Best regards,
    RE