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FDC 1004 vs FDC 2x1x for Capacitive Sensing

Clinton Burns
Prodigy 135 points
Other Parts Discussed in Thread: FDC1004

Hello,

I am trying to create a circuit that will measure shear in a shoe sole based off of a change in capacitance. I have been looking between the FDC 1004 and FDC 2x1x capacitive sensing chips and I am not sure which one to use. I read that the FDC 1004 has shielding against interference such as human hands and since this is going near a human foot, I figured that the FDC 1004 would be the best option here. Is this a valid though process or would the FDC 2x1x family be better for this?

Thank you

  • 0
    TI__Expert 8050 points
    Hello Clinton,

    You are right that FDC1004 has a built-in shield driver. However, FDC221x has better resolution and noise immunity. So the optimal choice would depend on your system implementation. For example, when you measure shear, is it only when the shoe is being worn? If that's the case, the foot basically introduces a constant offset which can be ignored.

    Regards,
    Yibo
  • 0 in reply to Yibo Yu
    Prodigy 135 points
    Thank you for the reply. In out case, we would only be measuring shear when the shoe is being worn. Sine this is the case, would the FDC221x be the chip to go with?
  • 0 in reply to Clinton Burns
    TI__Expert 8050 points
    Hi Clinton,

    On second thought, there are a few more things to consider for this application, so the answer is not immediately obvious.

    For example, depending on whether a person is walking or running, the foot signal is likely to change and may not always be a constant. In this case, shielding would be necessary.

    The capacitance to ground will also vary significantly depending on the surface of contact, e.g. wet vs dry, height of building, etc.

    Regards,
    Yibo