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Increasing Range/Sensitivity of LDC1000

Puru Rastogi
Prodigy 70 points
Other Parts Discussed in Thread: LDC1612, LDC1614

I am building a trash-can, which can detect when a metal is thrown into it. (footprint :15X25 cm)

Now, trash could be of various size, from as small as a nut (M10 : 1 cm ), to as big as a wrench (15 cm). Moreover bigger objects would be placed diagonally, so their footprint could be small.

The PCB coil would be spread on the base. What would you advise to keep in mind while designing the coil on web-bench of TI.

>Should the coil be square/circle?

> How small should it be? (I guess I have to connect multiple of them to cover the area without affecting the sensitivity of the device)

> How Is inductance and capacitance  related to (varies with) sensitivity?  (by sensitivity I imply, that if it is high its proximity/Rp value will change even if the object is small)

Another Question:

another idea is to make a coil around the entrance of trash-can, so that every trash passes through it. So, its diameter/dimension would be same as that of trash-can (i.e. large).  Question: will it be able to detect small objects? > should I be going for any other LDC?


Last question (quick one):

Last time I used arduino to get data from my LDC. It ran for a while, then I connected my custom coil, it was fine (i didn't adjust Rp registers). Then to get the Rp values, I connected back to msp430 part og EVM and used GUI, but then it stopped detecting it. Later on, arduino also stopped showing the values. It has broken, but do you think it was because of arduino??? (my arduino was running on 5v)

  • 0
    TI__Genius 13650 points
    Hello Puru,
    please consider our high-resolution multi-channel LDCs (LDC1612, LDC1614); they should give you better performance than the LDC1000.

    If you want to detect objects that are much smaller than the coil (such as in your application), then I recommend a larger trace width/spacing, but drawing traces closer to the coil center. Here is more information on detecting small objects: e2e.ti.com/.../inductive-sensing-target-size-matters

    Circular coils are usually recommended, unless a coil needs to fit into a very small rectangular space, which is not the case in your application. Refer to this apps note for more tips on coil design: www.ti.com/.../snoa930.pdf

    Multiple coils in the base of the trash can or a wire wrapped around the trash should both work, but I recommend trying both approaches to find out which one works better for your system.

    Which GUI revision and firmware revision did you use when you experienced the detection failure? Are you sure that all traces (front and back of the PCB) have been connected in the same way as before you separated the EVM portions, using short cables?