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I'm facing a quite hard task for my knowledge. I need to design a matrix for capacitive touch sensors with a LED at center. The touch controller is a AT42QT2640-AU that has the following limits:

limits

I'm requested to (try to...) reach those limits. Here my current approach:

touch

Some explanations:

  • the spacing between adjacent touch pads are 6 mm center to center
  • the external size of each touch pad is 5 x 5 mm
  • the inner slots (the white boxes) are 3.3 x 2.9 mm wide to accommodate an RGB LED mounted on bottom side
  • the tracks of the touch pads are 12 mil wide

Our application does not have to detect a single touch, on the contrary, it is expected that an entire hand is placed on the matrix. Hence, it's ok if you put a finger and all the surrounding touch pads detect something.

On the PCB will be placed a thin panel of glass (< 3 mm). My concern is about if those couple of traces can provide enough coupling to detect the touch.

Is there a way to find out is my design is faulty? Is there a better approach to design such a touch pad?

Of course I can order and make a real PCB to test, but if I can detect a wrong approach at design stage it will save some money and time.

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  • \$\begingroup\$ Did you end up ordering this? Did it work? \$\endgroup\$ Commented Apr 8 at 23:57
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    \$\begingroup\$ @JimJ.Jewett, I wasn't able to make a proper routing \$\endgroup\$ Commented Apr 9 at 10:07
  • \$\begingroup\$ I think "alas" is more appropriate than an upvote, but I do appreciate the followup. \$\endgroup\$ Commented Apr 9 at 17:27

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