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for a science-project I need to create 4-5 capacitive touch buttons through thick glass or macrolon. I think we talk about 15cm atleast, if not 20. I wonder if a big coil or big sheet of tinfoil would work through the glass? The ESP32 comes with capacitive pins, can I use these or do I need to build some amp-stage to boost it? Each touchbutton should be somewhat big, like 15x15cm. Unfortunately radar and sonar can't be used for this.

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closed as unclear what you're asking by Marcus Müller, Leon Heller, Olin Lathrop, Transistor, brhans Apr 1 '18 at 15:26

Please clarify your specific problem or add additional details to highlight exactly what you need. As it's currently written, it’s hard to tell exactly what you're asking. See the How to Ask page for help clarifying this question. If this question can be reworded to fit the rules in the help center, please edit the question.

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    \$\begingroup\$ Now you're mixing up things: if you use a coil, it's almost certainly not capacitive sensing anymore. \$\endgroup\$ – Marcus Müller Apr 1 '18 at 10:23
  • \$\begingroup\$ Also; even if I've posted an answer, voting to close as unclear, because your science experiment seems to be very important to what kind of answer you'll need, and therefore, should be described in the question. Happy to take back that vote if you add such information! \$\endgroup\$ – Marcus Müller Apr 1 '18 at 10:31
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    \$\begingroup\$ Optical as Marcus suggests. Photosensors on the inside, directional LEDs operated by touch switches outside. Modulate the LED with different signals (frequencies or digital codes) and you can get away with one photosensor. \$\endgroup\$ – Brian Drummond Apr 1 '18 at 10:58
  • \$\begingroup\$ Did you mean 15mm thick? Do you have 15cm glass to test with? \$\endgroup\$ – AlmostDone Apr 1 '18 at 13:06
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    \$\begingroup\$ Another big problem is where you're going to get glass 150 mm (6 inches) thick. Even if you do source some, that's going to be really heavy. This smells strongly of a X-Y problem. Pop up two levels and explain what you are trying to accomplish overall. \$\endgroup\$ – Olin Lathrop Apr 1 '18 at 13:23
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15cm means that whatever capacitance your potential finger-dielectric-conductor plane plate capacitor has will be extremely small, and so will be the difference between there being a finger or not.

Since all systems on this earth expose noise, I'd be hesitant to say this might theoretically work, and I'm certain to say that no, it won't work with an Arduino.

Trying to help by adding an amplifier betrays a bit of misunderstanding what capacitive sensing is.

All in all: no, won't work. People tend to go optical in that case (it's often easy to see a finger pressed against a flat transparent surface with even minimally cognitive vision). Or, really, use radar technologies, as you've suggested yourself.

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