You will need to be able to switch a capacitor equal to human body capacitance into the sense pad connection to self-test. How to you self-test the existing user button?

 

How to you self-test the existing user button?

We don't do self-test for the existing user button. This is a new requirement.

 

We don't do self-test for the existing user button. This is a new requirement.

It was a Validation (is the right system being built) question. It's just IMO that a PCB trace is just as reliable as a mechanical button after the final hardware design has been tested and verified to be reliable before production. It's much more likely that your software will be a input failure point. I might add a internal reference pad with a set value of fixed and stable capacitance for the touch software to monitor as a touch and to compare to the normal button pad.

 

It was a Validation (is the right system being built) question. It's just IMO that a PCB trace is just as reliable as a mechanical button after the final hardware design has been tested and verified to be reliable before production. It's much more likely that your software will be a input failure point. I might add a internal reference pad with a set value of fixed and stable capacitance for the touch software to monitor as a touch and to compare to the normal button pad.

Thanks for the suggestion, and I think adding an reference point is a good idea! And also the thanks for the file attached, it's very helpful!

 

@nsaspook any thought what I can use to switch say a cap equal to a C_touch to my actual touch pad? I am thinking solid state relay, I looked at a couple, but the capacitance is a bit high.

I guess what I need is a very low capacitance switch?