7 Replies Latest reply on Aug 14, 2018 6:45 PM by admic_2310931

    CapSense large intial sensor signal issue




      I have a CapSense slider project using the PSOC4000S that is giving me a bit of trouble at power up. I am getting a large sensor reading at startup that takes about 45 seconds to settle down. During this time the slider is unusable. The slider controls an LED light via PWM, it constantly flickers and is extremely annoying during this period. It is not something I could live with for a final product. Once settled it works well enough.


      Can I eliminate this issue?


      Some details:


      - 45 seconds for the signal to settle, and the rawcount/baseline to follow each other.

      - overlay 2mm wood

      - Slider adheres to design guidelines

           - 220mm length, 15mm height

           - 12 segment diplexed

           - 8mm wide chevrons

           - 0.5mm gap between sensors

           - 0.5mm gap between sense traces and gnd

           - 1.75mm gap between sensors and gnd

           - End segments attached to ground

           - Central sensor ground point at PSOC


      PCB stackup:

      - L1 Top (Components, signals, sense traces, gnd)

      - L2 (sense traces, gnd)

      - L3 (gnd)

      -L4 Bottom (sensor, gnd)


      - SNR of approx 19


      I will attach images of my PCB, main.c, CapSense settings and tuner graphs.


      I appreciate any input, Thank you.


      - Adam