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FDC2114: high proximity range with telescopic antenna possible?

Ralf Altmann78
Prodigy 50 points
Other Parts Discussed in Thread: FDC2214EVM, FDC2214, FDC2114EVM

Hello,

I want to use a telescopic antenna as proximity sensor with FDC2x14.

My requirements:

  • detection of human hand at up to 50-100cm distance
  • the digital value read from the sensor should reflect the distance from the antenna, so it's rather a distance measurement than a presence detection

To check if it's possible, maybe someone can help me with the following questions:

  • I've a FDC2114EVM, so the sensor resolution is 12 bit. The FDC2214 has 24 bit resolution. Should I use the FDC2214 instead for those requirements? If yes, can I simply replace the device on the EVM and the EVM microcontroller and the GUI software will work correctly or do I have to buy the FDC2214EVM instead? On a first look, the firmware of the microcontroller is the same for both devices.
  • According to application notes, the LC tank capacitor should be as small as possible. If I reduce the capacitor value on EVM and increase the inductor value, would this help to increase the range and the sensitivity?
  • If I understand the sensor types correctly, I should use the single ended configuration. So, the antenna reference is earth. This means, the circuit GND must be connected to earth, right?
  • Which register settings have most effect on range and sensitivity? It seems that there's no software tool which goes through the different combinations automatically to figure out the best results.

Thanks a lot for comments and suggestions.

Regards,

Ralf

  • 0
    TI__Expert 6480 points
    Hi Ralf,

    Unfortunately, it will be difficult to achieve accurate distance measurements with our FDC devices - especially at such a large range and even with the FDC2214. However, I have answered your questions below in case it helps with your analysis:

    - I would suggest buying the FDC2214EVM because with the FDC2114EVM software, you will not be able to activate CH2 and CH3
    - Reducing the cap value on the EVM will help with increasing range and sensitivity. A higher L will only affect the sensor tank frequency but not so much sensitivity.
    - Correct.
    - The RCOUNT register values will most likely have the greatest effect on range and sensitivity. The higher the RCOUNT value, the longer the conversion time, the more accurate the result.

    Thanks,
    Rachel
  • 0 in reply to Rachel Liao
    Prodigy 50 points
    Hello Rachel,

    thank you for your reply.

    Regarding the accuracy of the distance measurement, I don't need an absolute value. It would be enough to have relative values, and it doesn't matter if the values will change between power cycles of the circuit. However, it would be nice if small movements of the hand will result in detectable change of the value.

    Is the software for the two EVM different? I'm not sure which software I've downloaded, but if remember correctly, I was able to configure/enable four channel, and the EVM itself also has four sensor connections.

    Regards,

    Ralf
  • 0 in reply to Ralf Altmann78
    TI__Expert 6480 points
    Hi Ralf,

    Sorry, I misread your question - yes, the GUI/firmware should still work. I was thinking about our 2CH part vs. this 4CH part.

    Thanks,
    Rachel
  • 0 in reply to Rachel Liao
    Prodigy 50 points
    Hi Rachel,

    okay, then I'll try with modified capacitor value and different register settings to see if it would work.

    Thank you for your help.

    Regards,

    Ralf