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Original question:

LDC1612EVM: The sensor frequency shown in the UI

LDC1612EVM : Identifying Sensing Objects

jung yong hoon
Prodigy 30 points
Part Number: LDC1612EVM
Other Parts Discussed in Thread: LDC1612

Can the LDC1612EVM be used to distinguish steel balls (1mm, 3mm, 5mm, 7mm...)?
If possible, which part of the EVM GUI can you edit or enter?

  • 0
    TI__Genius 17440 points

    Hello,

    Depending on the size of your sensor, you might be able to use the LDC1612 to distinguish between steel balls of various sizes. The larger the target, the stronger the inductive response (though once the target is the same diameter as the sensor coil, the increases in inductive response are minimal). You would probably want to use a sensor coil that is the diameter of the largest steel ball.

    There would be two significant challenges here:

    1. Inductive sensing is extremely sensitive to movement closer to and farther from the coil (axial sensing). The steel balls would need to be in the same position every time, otherwise a farther target could be misinterpreted as a smaller target.

    2. You would need to make sure that the smallest diameter ball is still detectable by the coil. 

    It's not possible to edit the EVM GUI, but if you would like to control the MSP430 on the EVM using your computer we have some sample code in the FAQ (see the link in my signature below).

    Best Regards,

  • 0 in reply to Kristin Jones93
    Prodigy 30 points

    thanks for the information.

    Please review the test results below.

    Waveform when iron powder, steel ball(Ø3, Ø5, Ø7) are attached

    The red shadow areas show the waveform changes when iron and steel ball are attached and removed.

    In case of iron powder and Ø3 steel ball, inductance is increase and Ø5, Ø7 steel ball makes inductance decrease.

    　 iron powder Ø3 steel ball Ø5 steel ball Ø7 steel ball
    inductance 2.003 μH 0.3849 μH -0.2819 μH -0.5023 μH
    frequency -0.2953 MHz -0.0652 MHz 0.0499 MHz 0.0907 MHz

    Can we change the threshold at which the output value is converted?

    For example) The output direction is converted between Ø3 steel ball and Ø5 steel ball.

                          Can we make the converted point at between iron powder and Ø3 steel ball value?

  • 0 in reply to jung yong hoon
    TI__Genius 17440 points

    Hello,

    Thank you for your patience waiting for a reply; I was on vacation last week.

    It's not expected behavior for the metal target to make the sensor inductance increase (so it's not possible to change the threshold where the response inverts). Metal targets should always make the inductance decrease as long as eddy currents are able to form. I suspect that for the smaller steel balls and the iron powder the eddy currents do not form well, so you are seeing more of a capacitive response than an inductive response. You can see a similar response by touching the coil with your finger.

    Best Regards,