LDC1314: Bezel Rotation Detection - Similar to Nest Thermostat 3rd Gen

Teja Chintalapati

Part Number: LDC1314
Other Parts Discussed in Thread: TMAG5273

Tool/software:

Hello,

I am working on a product which requires the code to detect the bezel rotation (by hand) at 1 Degree Accuracy. The device will have a similar edge like Nest Learning Thermostat 3rd Generation.

While going through magnetic solution seems straight forward, I am wondering if there is any cost effective option to achieve this purpose.

Can you please recommend a part/way forward for me to detect the rotation angle of the bezel?

Thanks

11 months ago

0 John Miller - Sensing 11 months ago

TI__Mastermind 40295 points

Teja,

Please take a look at the reference design TIDA-00508, 1º Dial Using the LDC1314 Inductance-to-Digital Converter.
Its a cost-effective design using the LDC1314, a four-channel, 12-bit inductive sensor.

Regards,
John

0 Teja Chintalapati 11 months ago in reply to John Miller - Sensing

Prodigy 50 points

Thanks, John, for the response.

I missed mentioning that the (user swappable) bezel is expected to be made out of different materials including Steel, Aluminum, Ceramic, Wood, etc.,

Given I need to capture user ratating the bezel and not sliding over it, do you think LDC1314 is the right part to go with? If so, can you help me understand how to achieve the (rotational) angular sensing mechanically?

Thanks

0 John Miller - Sensing 11 months ago in reply to Teja Chintalapati

TI__Mastermind 40295 points

Teja,

The reference design and supporting documents - user's guide, schematic, PCB layout - can give you some idea of the mechanical & electrical considerations for a rotating design. They show the underlying circuits and mechanics of a rotating dial, and the sensors to support the electrical measurements.

In many cases, its the mechanical requirements that will drive many of the decisions.
Spacings and materials are key considerations.

You mentioned the bezel can be made from different materials, some of them conductive.
This could be an issue because conductive materials can affect the behavior & performance of an inductive sensor.

Do you have any mechanicals about your application you can share?
Perhaps a mechanical drawing or diagram, with dimensions?

regards,
John

0 Teja Chintalapati 11 months ago in reply to John Miller - Sensing

Prodigy 50 points

Thanks, John.

The engineering (mechanical) drawings are under design. Here are more details:

Bezel Diameter: ~8cms

Spacing b/w IC & Coils: Design not yet ready. We have the flexibility to design to spec.

0 John Miller - Sensing 11 months ago in reply to Teja Chintalapati

TI__Mastermind 40295 points

Teja,

I will look into potential options and update this thread tomorrow.

regards,
John

0 John Miller - Sensing 11 months ago in reply to John Miller - Sensing

TI__Mastermind 40295 points

Teja,

The fact the bezel can be made of many different materials will complicate the sensor type selection.
A bezel of conductive materials - aluminum, steel, etc. - will interfere with the functioning of a capacitive or an inductive sensor.

If we can guarantee the bezel will be made of a non-conductive material - plastic, ceramic... - then we could probably make the LDC1314 work.

regards,
John

0 Teja Chintalapati 11 months ago in reply to John Miller - Sensing

Prodigy 50 points

Okay. Thanks for letting me know.

Do you believe a better approach would be to use a magnetic tape and do a (3D) magnetic sensing instead to detect angular rotation?

0 John Miller - Sensing 11 months ago in reply to Teja Chintalapati

TI__Mastermind 40295 points

Teja,

That approach might be more forgiving of the different bezel materials.
Do you have a conceptual model of how you would use the tape and sensor?

Regards,
John

0 Teja Chintalapati 11 months ago in reply to John Miller - Sensing

Prodigy 50 points

Thanks, Dr. John.

I thought of placing TMAG5273 at one of the edges of the PCB while the bezel shall have a grove for a magnetic tape, similar to the attached photo.

Feel free to suggest, if there's any better way to acheive the objective.

+1 John Miller - Sensing 11 months ago in reply to Teja Chintalapati

TI__Mastermind 40295 points

Teha,

The approach using magnetic tape with a magnetic sensing device should work fine.
If the tape is made of alternating north/south poles you should be able to track the rotational changes of the bezel with the TMAG and DRV series of Hall-based latches and switches.

I will be OOO for the remainder of the day, so please feel free to post any other questions you have on Monday, 10/14.

Regards,
John

Sensors

Sensors forum

LDC1314: Bezel Rotation Detection - Similar to Nest Thermostat 3rd Gen