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LDC0851: LDC0851 sensor used to count forward and reverse rotation!

Ivano Cunha
Prodigy 10 points
Part Number: LDC0851
Other Parts Discussed in Thread: LDC1612, LDC1312

Hello guys,

I am evaluating the use of the LDC0851 sensor to count the number of turns of a hydrometer pointer to measure water. Each turn corresponds to one liter.

The problem I need to solve is that I need to detect whether the pointer is rotating in the forward direction (CW), or in the reverse direction (CCW). Could anyone tell me how I would do this using the LDC0851?

Or if I can't use it, what would be the appropriate device for this application?

Thanks.

  • 0
    TI__Mastermind 43440 points

    Hello Ivano,

    In order to determine direction, you would need to add a 2nd LDC0851 and sensor.  You can then determine direction based on which sensor switches first. 

    Another option would be to use something like the LDC1312(12 bit) or LDC1612(28 bit).  These are dual channel inductive sensor devices, so you could get both sensors with just one device.  They are a bit more complex than the LDC0851 as they are not a simple switch output, but rather use I2C interface that would connect to an MCU.  

  • 0 in reply to Eddie LaCost
    Prodigy 10 points

    Hi Eddie,
    Thanks for the quick response!
    Due to the application (Hydrometer) I must make the project as simple and cheap as possible, so the solution of two LDC0851 devices may be more suitable than more complex circuits with I2C, for example.
    Well, I have no idea how I should arrange the antennas on the PCB to capture the pulses and determine the direction. Do you know if there is any paper that describes this solution? Do you imagine what that would be like?
    Regards,

  • 0 in reply to Ivano Cunha
    TI__Mastermind 43440 points

    Ivano,

    That makes sense for simplicity.  

    To determine direction, you would place the two sensors next to each other so that the rotating target goes over both sensors individually.  With this setup, in clockwise direction, you would see one sensor 1 switch first followed by switch 2 and in counter clockwise, you would see sensor 2 switch first followed by sensor 1.  Take a look at the reference design below.  

    https://www.ti.com/tool/TIDA-00851-LDC0851