Capacitive Pressure Sensing Based Key in PCB Technology for Industrial Applications

This paper reports the design and manufacturing of a device suitable for use in command panels of industrial equipment in the place of mechanical buttons and switches. The device consists of a capacitive pressure sensor, low-cost microcontroller, current driver, and state indication LEDs. All components are embedded into multilayer printed circuit board using standard manufacturing steps. The device has user-programmable properties and it can behave either as a key or as a switch. An interconnection feature is provided in a sense that multiple devices can be organized into an array thus forming a keyboard. A simple two-wire communication interface for controlling the keyboard is described.