• State TI Thinks Resolved
  • Locked Locked
  • Replies 10 replies
  • Answers 1 answer
  • Subscribers 79 subscribers
  • Views 315 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

MSP430FR2675: Slider Sensitivity Issue

Pallavi Y
Prodigy 80 points
Part Number: MSP430FR2675


Tool/software:

Hi Team,

We are working on 4 element sliders. While testing on bare PCB the slider works effectively. But when add an overlay of 2mm acrylic is attached on top of it, the minimum value i am getting is 14 and maximum value is 85.

i tried changing threshold value but that didnot help.

Can you guide me to solve this problem   

                         

Thanks and Regards

Pallavi Y

  • 0
    TI__Genius 17412 points

    Hi Pallavi,
    My recommendation is to increase the sensitivity (change the conversion count to a maximum of 800). Also, are there any grounds near the sliders? What kind of ground are you using (solid vs. hatched)? Depending on which one it is, it could lead to some parasitic capacitance affecting your PCB. If you could share a picture of the ground plane or the PCB layout, that would be great.
    Best Regards,
    Diego Abad

  • 0 in reply to Diego Abad Sajamin
    Prodigy 80 points

    Hi Abad,
    Thank you for the response
    i have tried increasing conversion count to 800 but the issue remains the same

    Below i have attached the PCB layout. 
    It is not ground plane. But we are using hatched fill connected to 45 degree plane is CAP1.2 and configured as TX Pin in captivate.

    However in bottom layer we have full ground plane.

  • 0 in reply to Pallavi Y
    TI__Genius 17412 points

    Hi Pallavi,
    Thanks for letting me know. The bottom layer could be causing some parasitic capacitance. I'll need more data to make more recommendations. You should be able to share the values you get when using the slider. Can you share that with me?
    Best Regards,
    Diego Abad

  • 0 in reply to Diego Abad Sajamin
    Prodigy 80 points

    Hi Abad,
    i have attached the required file

         

    Thanks and Regards
    Pallavi

  • 0 in reply to Pallavi Y
    TI__Genius 17412 points

    Hi Pallavi,
    Thanks for sharing this information. I'll analyze it, and give you some feedback by tomorrow afternoon.

    Best Regards,

    Diego Abad

  • 0 in reply to Diego Abad Sajamin
    TI__Genius 17412 points

    Hi Pallavi,

    After talking with my team, I think that the problem relies on the full ground plane underneath the sensor, which is affecting its sensitivity. For more information about this, please refer to the Ground Planes sections in the CapTIvate Technology Guide. I will recommend removing the full ground plane from the sensor and only keeping the hashed ground plane.

    Best Regards,

    Diego Abad

  • 0 in reply to Diego Abad Sajamin
    Prodigy 80 points

    Hi Abad,
    Thank you for the response. We will update the PCB design and test it.

    However we have been using buttons with the same design but never observed any sensitivity loss. Infact in the same board. we have buttons which are working fine with or without the overlay.

    So what do you think can be the exact problem related to the slider alone?

    Thanks and Regards,
    Pallavi Y

  • 0 in reply to Pallavi Y
    TI__Genius 17412 points

    Hi Pallavi,
    From what I understand, buttons and sliders have different electrical behaviors. Assuming you are referring to Self Capacitive Buttons, they have greater sensitivity than sliders due to their size, which could be the reason why they are not as affected as the slider. For more information, I would recommend looking into the Buttons and Sliders chapter in the CapTIvate Technology Guide. 

    Best Regards,

    Diego Abad

  • 0 in reply to Diego Abad Sajamin
    Prodigy 80 points

    Hi Abad,
    Ok i will go through the document .We will make the necessary changes in the hardware and get back to you

  • 0 in reply to Pallavi Y
    TI__Genius 17412 points

    Hi Pallavi,
    Sounds good. Let me know if you need further help in this thread.

    Best Regards,

    Diego Abad

**Attention** This is a public forum