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FDC1004EVM: Capacitive Sensing

Brant Beck
Prodigy 40 points
Part Number: FDC1004EVM
Other Parts Discussed in Thread: FDC1004

I am working on a design where I believe I would like to use a Mutual Capacitance matrix (maybe 8x8). The dielectric between our X (horizontal) and Y (Vertical) grids is compressible and I would like to measure the increase in capacitance as areas of the grid become compressed while being isolated from any external signals. I ordered the FDC1004EVM just to get some values to prove the concept. I do not think this is the best device for my needs and it also does not have enough channels. I have read through your design guide at https://software-dl.ti.com/msp430/msp430_public_sw/mcu/msp430/CapTIvate_Design_Center/1_83_00_08/exports/docs/users_guide/html/CapTIvate_Technology_Guide_html/markdown/ch_basics.html and found it to be very helpful. 

I should not need to measure above 16pF though the ability to have an offset is helpful. I need to detect multiple points of contact. I would like at least an 8x8 Matrix. Picking up signals from any distance is actually a hinderance so an isolated signal with higher resolution would be great. 

Any help selecting the best device for this application would be greatly appreciated. 

  • 0
    TI__Mastermind 40295 points

    Brant,

    Thank you for your interest in TI products.

    Can you say a little more about your goals for the design?

    For example, what measurement range & resolution does your application need?

    Will this be more like a push-button or switch-like application - perhaps with some hysteresis  - or will it be position-sensing where it will be used to detect over a continuous range of values?

    With respect to managing interfering signals, the FDC1004 does have on-chip active shield drivers that can help manage the effects of EMI.
    Just so you know, more detailed info is available at FDC1004 Capacitive Sensing FAQs , including app notes, blog posts, reference designs and so on.

    Regards,
    John

  • 0 in reply to John Miller - Sensing
    Prodigy 40 points

    Hi John,

    This will be in the 0 - 20 pF range. A resolution in the 10s of femto farads is fine. We will be monitoring a continuous range of values across the Mutual Capacitance Matrix.

  • +1 in reply to Brant Beck
    TI__Mastermind 40295 points

    Brant,

    The FDC1004 is the best position-sensing device we have to offer. It can be made to support your measurement range and it has built-in active shield drivers to help manage EMI. Having said that, your channel count will demand multiple devices.

    If you are interested in our CapTIvate product line you can visit our E2E MSP low-power microcontroller forum to post any questions you may have. 
    A list of reference designs and other collateral may be found here.

    Regards,
    John