6-Button Keypad with Capacitive Touch Sensing

The project is based on the QProx QT160 charge transfer proximity sensor chip which aims to develop a simple 6-button keypad.

All the work is done by the chip which functions as the brain of the operation. It will work properly with the implementation of special mylar capacitors with 10MHz resonator. During the construction, the buttons are printed out on a plain paper using the silkscreen layer from the PCB layout program. A multilayer capacitor known as capacitive dielectric is provided by the FR4 PCB material, the paper, and a 1/8th inch thick layer of plexiglass.

For the chip to sense proximity, it uses the electrostatic field that is being radiated by the simple copper rings that comprise the sensors. The cross-talk between sensor channels is minimized by a ground plane poured around the IC. It also prevents stray fields from detecting proximity around the chip. The capacitors near the chip need to be shielded with aluminum foil since it also sense proximity. The amount of capacitance can be increased by a different capacitor. A 2×8 header is also made to accept a ribbon style connection for easy connection.

Rest of the project