LDC1614: Custom Inductive Sensing

Marko Jurisic

Part Number: LDC1614
Other Parts Discussed in Thread: LDCCOILEVM

Hi there,

My company and I are looking into building custom inductive sensing systems for humanoid robots. We are looking into using an IC like the LDC1614, along with a custom PCB with a planar Inductive coil. We found the evaluation kit to be promising, but we would like to speak with a TI engineer to evaluate options moving forward. Our main concern is how to build small sized (5 - 8mm by 5-8mm sizes) PCBs with planar inductors. It seems like the best solutions include active and passive coils, as opposed to one solid inductor.

Is there any way to speak to a TI engineer about our preliminary ideas, and to listen to their expertise about the best way to design these sensors? We require high accuracy, high repeatability and a small package size.

Ideally, we'd love to jump on a zoom call for half an hour with a TI engineer and gain their insights about how to work with TI to succeed in our designs.

Looking forward to hearing back from you.

Thanks,

Marko

over 3 years ago

0 Patrick Simmons over 3 years ago

TI__Mastermind 26335 points

Hello Marko,

Glad you have found the evaluation kit helpful. Presently both of our inductive sensing experts are out on leave. However, one of them will be returning next Tuesday. Would a discussion with him then be ok?

0 Marko Jurisic over 3 years ago in reply to Patrick Simmons

Prodigy 35 points

Hi Patrick, thanks for the response.

Yes, Tuesday should be tentatively be ok. What is the preferred method of online call?

Looking forward to it!

Thanks,

Marko

0 Patrick Simmons over 3 years ago in reply to Marko Jurisic

TI__Mastermind 26335 points

Hello Marko,

Our expert will reach out to you and tell you what medium to use for the call.

0 Marko Jurisic over 3 years ago in reply to Patrick Simmons

Prodigy 35 points

No worries, looking forward to it!

0 Justin Beigel over 3 years ago in reply to Marko Jurisic

TI__Mastermind 18545 points

Hello Marko,

For using small coils, this blog post talks about including a series inductor and the impacts it has to the sensor. Additionally, we have the LDCCOILEVM that has 4, 5, and 6mm coils for evaluation.

What is the resolution requirement you need out of your design?

Best Regards,
Justin Beigel

0 Marko Jurisic over 3 years ago in reply to Justin Beigel

Prodigy 35 points

Hi Justin,

We ideally need 0.1 degrees, but can survive with 0.5 degrees. We are doing arc sensing over 50 to 120 degree ranges (humanoid fingers). In tandem to the actual inductor, we will need to design a wiper that moves along the arc of the inductor.

Do you think this is do-able while simply measuring a pure change in inductance? Some more advanced designs use active and passive coils, and we are worried that without these active and passive coils we won't get the accuracy and resolution we need.

During our testing with the LDC1614 eval board, and some coils from the LDCCOILEVM we found the sensor to be susceptible to outside disturbances. We didn't control for the height of the wiper from the sensor, so that may have caused this issue. We used some of the medium sized coils from the LDCCOILEVM.

Thanks for the help,

Marko

0 Justin Beigel over 3 years ago in reply to Marko Jurisic

TI__Mastermind 18545 points

Hello Marko,

For the best resolution in this type of application, we recommend having multiple coils to determine the change in angular rotation. Using multiple coils and determining the change in inductance on each allows for a more robust solution as external impacts may effect both coils the same way. The 1º Dial Using the LDC1314 Inductance-to-Digital Converter Design Guide can be used as a reference for this. In that design, an angle accuracy of <0.1 degree was obtained.

If you only have one coil and are measuring just that change, the accuracy will be tough to obtain across multiple systems and temperature.

Best Regards,

Justin Beigel

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LDC1614: Custom Inductive Sensing