8 Replies Latest reply on Aug 8, 2018 9:12 PM by brvi

    Sensitivity Guard Sensor

    assiswillys_2927726

      Hello everyone, in my project I use cy8cmbr3110. I'm having problems with the sensitivity of the guard, I need to decrease the sensitivity of the guard. My settings for the guard are:

       

      Hardware:

      Guard sensor thickness: 2mm.

      Overlay = 4mm glass.

       

       

      EZ-Click:

      Sensitivity (fF) = 400.

      Automatic threshold = Enabled.

      IIR filter = Enabled.

      Median Filter = Enabled.

      Debounce: 3.

      Enable EMC noise immunity: Disabled.

       

       

      With these settings it is still possible to decrease the sensitivity of the guard without changing the hardware?

        • 1. Re: Sensitivity Guard Sensor
          brvi

          Hello,

           

          Can you lease tell me what is the Cp value of your guard sensor? Sensitivity will be high if the Cp value is very less.

           

          Disable automatic threshold and increase the threshold of the guard sensor by writing the threshold value directly into the registers.

           

          If your environment is too noisy, you can turn on the EMC noise immunity feature. But this feature works only if automatic threshold feature is disabled.

           

          What is the dielectric material you are using( mention dielectric constant)? . Materials with high dielectric constant results in higher sensitivity of sensors.

           

          Also please clarify if hatch pattern was implemented as per recommendations.

           

          Regards,

          Bragadeesh

          1 of 1 people found this helpful
          • 2. Re: Sensitivity Guard Sensor
            assiswillys_2927726

            Hello,

             

            Can you lease tell me what is the Cp value of your guard sensor? Sensitivity will be high if the Cp value is very less.

             

            Cp value guard sensor: 30

             

             

             

            Disable automatic threshold and increase the threshold of the guard sensor by writing the threshold value directly into the registers.

             

            I used the maximum value (200) for the threshold of the guard sensor, but it still remains very sensitive.

             

             

             

             

            If your environment is too noisy, you can turn on the EMC noise immunity feature. But this feature works only if automatic threshold feature is disabled.

             

            I activated EMC noise immunity, but the sensitivity did not decrease.

             

             

             

             

            What is the dielectric material you are using( mention dielectric constant)? . Materials with high dielectric constant results in higher sensitivity of sensors.

             

            Overlay Material : Glass (Standard).

            Dielectric constant : 8.

             

             

             

             

            Also please clarify if hatch pattern was implemented as per recommendations.

             

            I followed all recommendations for hatch pattern.

            • 3. Re: Sensitivity Guard Sensor
              brvi

              Hi,

               

              Can you share your layout files in Gerber format?

               

              Regards,

              Bragadeesh

              • 4. Re: Sensitivity Guard Sensor
                nsha

                Hello,

                 

                You could use the following firmware technique, instead of guard sensor.

                You can configure the host in such a way that the sensor status would be rejected, if two or more sensors are triggered at the same time. (Two or more sensors would be activated when there is liquid pool on the board)

                I assume that your application does not require two sensors to be detected simultaneously.

                I hope this helps.

                 

                Thanks,

                Shanmathi

                • 5. Re: Sensitivity Guard Sensor
                  assiswillys_2927726

                  Hello,

                   

                  Attached is the gerber file.

                  • 6. Re: Sensitivity Guard Sensor
                    assiswillys_2927726

                    Nsh ,

                     

                    I'll try this. But this way, I have to disable Auto Reset to continue detecting the liquid in the panel. In my project, auto reset must be enabled.

                    • 7. Re: Sensitivity Guard Sensor
                      assiswillys_2927726

                      I increased the value of the resistor in series with the guard sensor, with that it decreased the sensitivity. Is this advisable? Can I have problems with this change?

                      • 8. Re: Sensitivity Guard Sensor
                        brvi

                        Hello,

                         

                        Increasing the resistor value can affect the signal level. Since your Cp value is within limits, increasing the resistor value wouldn't affect your signal much. But make sure the guard sensor capacitor is charging and discharging completely. Also in your EZ- Click, make sure that your SNR is greater than equal to 5:1. If the SNR is greater than this ratio, then there wouldn't be any problem.

                         

                        Also mention the series resistor value you have used. Do the SNR test and post your results so that it will be helpful for the community users.

                         

                        Regards,

                        Bragadeesh.