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Original question:

LDC1614EVM: How to use LDC1614EVM for lid open/close

LDC1614EVM: LDC1614

Amy Luo
Expert 6895 points
Part Number: LDC1614EVM
Other Parts Discussed in Thread: LDC1614

Hi team,

The customer has the following follow-up questions to the original question, please assist with the answer:

1.At a distance of 20 cm, how to sense the well cover switch, coil diameter need to be how large?

2, how to improve the sensitivity in the case of long distance?

3. The software shows the waveforms for channel 3 why this is so, very variable, how to determine the switch characteristics?

Best Regards,

Amy Luo

  • 0
    TI__Mastermind 18175 points

    Hello Amy, 

    The sensing distance for inductive sensing is related to the coil diameter. The farther the target is from sensor, the less change you will have in the sensor data. 

    20 cm is a very large distance for inductive sensing. Our normal largest sensor size recommendation is 50mm for a circular coil. Larger than this can start to cause issues with the device driving the coil. 

    Is the close position of the switch 20cm away from the sensor? Is there any way to make this distance shorter? 

    Additionally, do you just need to know if the lid is open/closed or do you need information on any of the in between states? 

    Best Regards, 

    Justin Beigel

  • 0 in reply to Justin Beigel
    TI__Expert 6895 points

    Hi Justin,

    Thank you for your assistance. The following is the customer feedback:

    Depending on the installation location, a distance of 20 cm is actually required. I only need the device to determine the switch status in seconds, the detection device needs low power control. 

    Best Regards,

    Amy

  • 0 in reply to Amy Luo
    TI__Mastermind 18175 points

    Hello Amy, 

    If there is no way to place the sensor coils closer to the target, then I don't think inductive is the right choice for this application. A 20cm switching distance will not be feasible with inductive sensing so another solution will need to be considered. With such a large distance, you could consider something like ultrasonic for the sensor. 

    Best Regards, 

    Justin Beigel

  • 0 in reply to Justin Beigel
    TI__Expert 6895 points

    Hi Justin,

    Thank you for your assistance.

    Below is the follow-up question for this customer, could you  please give your comments.

    If consider adjusting the structural distance, how to use it at a distance of 50mm?Is this by characterizing frequency variation? Is the reference coil mandatory?

    Best Regards,

    Amy

  • 0 in reply to Amy Luo
    TI__Mastermind 18175 points

    Hello Amy, 

    For 50mm, we would recommend using a 50mm coil to sense the target. With a target distance at 100% of the coil diameter, the coupling between the two will be minimal but you can still achieve an open/close detection at this range. For best coupling, the target should at least be the same size of the sensor coil. See the https://e2e.ti.com/blogs_/b/analogwire/posts/inductive-sensing-target-size-matters post for more information. 

    We have a 46mm coil in the LDCCOILEVM that can be used to help prototype this. 

    Best Regards, 

    Justin Beigel

  • 0 in reply to Justin Beigel
    TI__Expert 6895 points

    Hi Justin,

    Thank you for your assistance.

    May I ask you a few more questions so I can provide service to this customer.

    1. How does the different winding methods of inductance coil affect the detection distance, such as plane winding and laminated winding

    2. How does the size of inductance/capacitance value of LDC1614 resonator affect the detection distance?

    Best Regards,

    Amy

  • 0 in reply to Amy Luo
    TI__Mastermind 18175 points

    Hello Amy, 

    We typically recommend using planar coils over laminated with our LDC devices. We don't have any direct comparisons for for detection distance between similar planar and laminated coils. 

    The main thing that determines the sensing distance is the outer diameter of the sensor coil. Changing the inductance/capacitance can have a minor impact in some cases but not as much as changing the sensor diameter. 

    Best Regards, 

    Justin Beigel

  • 0 in reply to Justin Beigel
    TI__Expert 6895 points

    Hi Justin,

    Sorry to bother you again. Below is the follow-up question for this customer, could you please give your comments

    To shield against the impact of the metal around the coil, which effect would be better with a ferrite can-shaped magnetic core and a magnetic spacer for wireless charging of mobile phones? Which is better for the sensing distance?

    Best Regards,

    Amy

  • 0 in reply to Amy Luo
    TI__Mastermind 18175 points

    Hello Amy, 

    Can you share any diagram/drawing of the coil and the nearby metal that you are trying to shield from? 

    Thank you, 

    Justin Beigel