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FDC2214EVM: Hand on/off detection on the steering wheel

Simon Schnider
Prodigy 85 points
Part Number: FDC2214EVM
Other Parts Discussed in Thread: FDC2214, FDC2214PROXSEN-EVM

Hi,

I will use the FDC2214 EVM (to start, I will use the Eval-Board) to get a hand on/off detection on the steering wheel for a research project (autonomous driving). As “sensor(s)” I will u a self-stick copper tape (under the synthetic leather coating). I will place 2, 3, or 4 segments of copper tape circle. Is this a good solution for my application? Can someone give me some hints in terms of: sensor material, sensor layout and set up for the FDC2214?

What can I do against the temperature drift? Is it recommended to do differential measurements?

 

Best regards

Simon

  • 0
    TI__Genius 13335 points

    Hello Simon,

    We typically use self-stick copper tape or a single layer PCB (flex or FR4) to prototype cap sensors for the FDC2214.  I would refer to the following application notes for how to use the FDC2214 for proximity detection:

    Also refer to the following TI designs which are all proximity based event detection using FDC2214:

    If you want to compensate for temperature drift, your thinking is correct, you can use a 2nd channel as a reference sensor to make a differential measurement.

    Regards,

    Luke LaPointe

  • 0 in reply to Luke LaPointe
    Prodigy 85 points

    Hi Luke,

    Thank you for your fast answer and for the linked documents. I will have a look at it, before I will do the design.

    Best regards

    Simon

  • 0 in reply to Luke LaPointe
    Prodigy 85 points
    Hi Luke

    I’m working now with the FDC2214 and did a first few measurements. In the datasheet of the FDC2214 I saw the very helpful chapter 8.2.4 Recommended Initial Register Configuration Values. But for me it’s not clear, how to calculate the value of CHx_SETTLECOUNT (Page 44, Point 3 (a)). The formula includes the following variable:
    Vpk -> set to 1.68V
    fREFx -> set to 40MHz
    C -> means this the capacitive of the sensor (copper plate) or the additional capacitive?
    IDRIVEx -> set to 15 (from Point 2, Page 43)
    So my question is, which value I do have to set for C and did I set the other variables correct. I don’t understand how you get the result of 7.5.

    Best Regards
    Simon