LDC0851: LDC0851evm

Janine Lin

Expert 2190 points

Part Number: LDC0851

Hello

By using LDC0851 EVM or using LDC0851 component, can we I use 3 set of stacked coil or side-by-side coil arrangement?

First figure is stacked coil and the second figure is side-by-side coil. Thank you for the answer.

over 5 years ago

0 Clancy Soehren over 5 years ago

TI__Mastermind 23810 points

So this application would have three LDC0851's? That shouldn't be a problem, but you will need to consider cross-coupling:

- You should make sure that the resonant frequencies of each set of coils has some separation.
- Physical distance between each set of coils will also help.
-Either stacked or side-by-side could work. For side by side coils, remember that only the sense coil should see the target. The ref coil should either have no target, or a target constantly at a fixed distance.

This stacked coil design app note is useful:
www.ti.com/.../snoa982

0 Janine Lin over 5 years ago in reply to Clancy Soehren

Expert 2190 points

Dear Clancy,

In the LDC0851 EVM user guide, the graph shows that the switching distance (ADJ 1) is about 7mm . We measure the sensing distance of ldc0851 evm that we purchased by using iron, aluminum, stainless and stainless as a conductive target and its individual switching distance is only 5.5 mm.

0 Clancy Soehren over 5 years ago in reply to Janine Lin

TI__Mastermind 23810 points

Janine,

Aluminum is probably the best material among those for that testing. Iron and stainless steel will have a slightly smaller response, which will impact the switching distance. Did you have anything situated behind the EVM during the tests? That could also impact the sensing distance.

0 Janine Lin over 5 years ago in reply to Clancy Soehren

Expert 2190 points

Dear Clancy,

During testing, there's nothing behind the evm. How to get 7mm or more sensing distance even with the presence of conductive material at the reference coil side?

0 Vaibhav Garg10 over 5 years ago in reply to Janine Lin

TI__Intellectual 1020 points

Janine

In account of the holidays, our responses will be delayed.

Regards,

Vaibhav Garg

0 Clancy Soehren over 5 years ago in reply to Janine Lin

TI__Mastermind 23810 points

The stacked coil article I linked to earlier explains how to adjust the switching distance:

www.ti.com/.../snoa982

7mm is close enough to 5.5mm that it is possible that a difference in measurement technique (eg. where you start measuring from) is impacting the results slightly.

0 Janine Lin over 5 years ago in reply to Clancy Soehren

Expert 2190 points

Thanks for the reply. I change the value of R4 to 0 Ω and switch the potentiometer to minimum ADJ 1. The result,sensing range reach to 8mm but the threshold is quite large. ON state at 8 mm, OFF state at 11 mm. Is there other way to minimize the threshold?

0 Clancy Soehren over 5 years ago in reply to Janine Lin

TI__Mastermind 23810 points

Janine,

There is no other way of adjusting the threshold without redesigning the sensor itself.

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LDC0851: LDC0851evm