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A simple six button keypad based on the QProx QT160 charge transfer proximity sensor chip.
The chip QT160 does all the work. The "buttons" are printed out on plain paper, using the silkscreen layer from the pcb layout program. The capacitive dielectric is provided by the FR4 pcb material, the paper and a 1/8th inch thick layer of plexiglas.
The sensors are simple copper rings, which radiate the electrostatic field this chip uses to sense proximity. A ground plane pour around the IC helps to minimize cross-talk between sensor channels and prevent stray fields from detecting proximity around the chip itself. The capacitors near the chip also sense proximity and will need to be shielded with aluminum foil or something.
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