Capacitive touch can be hard to design since there are a lot of subtle constraints and potential problems or pitfalls that can creep into your board layout and ruin your electrodes or seriously limit their range or efficiency. You need a bit of GND beneath the electrode, but not too much, and it can vary from one chip manufacturer to another just what type of grid to place on the bottom layer, etc. You typically want a large GND reference and a smaller electrode on the top layer to amplify the signal strength a bit, yada yada yada. From experience, you can lose a day or three just reading app notes on layout considerations around cap touch! And while there’s definitely nothing wrong with digging in and doing the hard work yourself, if you use Cadsoft’s Eagle for your PCB layout PatternAgent’s Touch Widgets Library might save you some headache and trial and error. They’ve put together a set of footprints that should be easy to reuse in your next design, along with some suggestions on cap touch layout, etc. We haven’t tried it ourselves yet, but if you give it a go be sure to post up some feedback in the comments below!
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