Capacitive touch has become a popular technology for human-machine interface (HMI) design. In order to have a more sleek appearance, reduce manufacturing complexity and increase reliability, engineers have employed capacitive-touch technology to replace mechanical buttons in embedded designs such as building security panels, smart thermostats, home appliances and electronic door locks. These capacitive-touch button, slider, wheel and proximity designs are implemented on a printed circuit board (PCB) mounted behind a silkscreened cover lens. Many engineers also incorporate capacitive-touch technology in their HMI designs as touch sensors over liquid crystal displays (LCDs). Those applications require an optically transparent sensor.
While display touch sensors give engineers new ways to create innovative user interfaces, they also raise some challenges, including manufacturing cost, development time, environmental durability, system reliability and power consumption. This is especially true for those who want to transition from traditional mechanical buttons or resistive-touch sensors but are concerned about the price and difficulty of implementing a capacitive-touch sensor. If you’re unfamiliar with capacitive button, slider, wheel, proximity or capacitive-touch sensor design, these challenges can be difficult to understand and implement. In this paper, we will show one way to address these challenges, by combining a Texas Instruments (TI) MSP430™ microcontroller (MCU) with CapTIvate™ touch technology and a transparent touch sensor.