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FDC2212: Rain sensor using FDC2212

Sarang Anjal82
Prodigy 230 points
Part Number: FDC2212

How to use FDC2212 for rain sensor application and how to design the sensor for sensing rain droplets on

the windshield how to decide the LC tank circuit for best possible counts in CHANNEL0 LSB and MSB 28 bits

please suggest some Application note to use FDC2212 for rain sensor application.

  • 0
    TI__Genius 14270 points
    Hello Sarang,
    You may want to refer to the Ice & Frost detection app-note: www.ti.com/.../snoa973.pdf for some information.

    Regards,

    ChrisO
  • 0 in reply to Chris Oberhauser66
    Prodigy 230 points

    Hello Chris

    I want to sense water droplets on the windshield of the car so the sensor should be placed inside the car beneath the

    windshield there is no direct contact with water and what should be the best possible values of L and C.

    How should i design the sensor, for placing under the windshield and sensing water drops above the windshield.

    thanks

    Sarang 

  • 0 in reply to Sarang Anjal82
    TI__Genius 14270 points
    Hello Sarang,

    You can refer to Direct vs Remote Level sensing app-note (www.ti.com/.../snoa935a.pdf ) for information. The appropriate value for the setting of C is based on the sensor change in capacitance; if your sensor changes a small amount in capacitance, then you should use a smaller valued sensor cap. Keep in mind that you also need to include the variation in the parasitic capacitance - which includes the fixed inductor.

    You should use a shielded fixed inductor which is sufficient to produce a sensor frequency that is within the device's specified range (up to 10MHz for the FDC2xxx). For larger sensors (10cm+) you should use sensor frequencies <4MHz to minimize transmission line effects across the sensor.

    Use of a reference sensor is strongly recommended.

    Regards,

    ChrisO
  • 0 in reply to Chris Oberhauser66
    Prodigy 230 points

    Hello chris,

    I have tried a sensor with two copper plates and shielding between them with ground by connecting the plates to IN0A and IN0B(single channel) the variation in count is not much the L and C values are 18uH and 33pF respectively.

    The variation in count is not accurate how to fine tune this reading.

    thanks

    sarang

  • 0 in reply to Sarang Anjal82
    TI__Genius 14270 points

    Hello Sarang,

    The distance between the sensor plate and the ground should be larger to reduce the fixed sensor capacitance; the sensor capacitive shift will still be about the same magnitude, and so with a smaller fixed capacitance the sensor signal will be larger.

    Also, consider adding a cap on the opposite input channel to improve the sensor drive characteristics:

    Make sure that the IDRIVE setting is large enough so that the sensor signal is ~1.5V.