Testing a Capacitive Button Panel


We wanted to see if it was possible to eliminate the physical buttons on the front of the phone by using a capacitive button panel.

It has a few advantages:

  • At this point in time, it's what people expect (it looks good)
  • If we do it right, it could be easy to let people swap out a PCB with a different button layout, opening up the ability to adapt the hardware to different purposes.
  • Potentially longer design life, due to no moving parts

Disadvantages:

  • Somewhat risky. Physical button panel examples are everywhere, but you don't generally see capacitive button panels as dense as we need. There's probably a reason for that, so we expect to have issues with crosstalk/inadvertent triggering of neighboring buttons.

We made a test panel, shown above, that has buttons of approximately the size and pitch we need for the phone. Overall, the test panel works OK. It is, in fact, easy to accidentally trigger neighboring buttons. But it was interesting enough we'll go ahead and make another panel using our current button layout and see how it performs in the phone.

1 comment

  • caleb

    Oh Lordy! Please no. I prefer buttons to work ;-)

    I used to work at Logitech, and they had a horrible fubar with cap touch buttons on the Z-10 loudspeakers. They all worked great when they left the factory. But as the paint cured over the first months of life, something about the paint in front of the buttons caused them to fail. So, imagine that - you manufacture 10,000 units and send them out, then after several months they all start failing. Ugh. There was a big recall and they replaced the front panels with panels that had real buttons IIRC. Beware… at best cap touch buttons are terrible buttons. :)

    But… really neat project. Looks like fun.

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