Rain on this touch panel parade won’t matter

Capacitive touch panels can be touchy, especially in the rain when a drop of water can look a lot like a fingertip and the swipe of a drying towel can drive lesser microcontrollers (MCUs) crazy.

The problem can be particularly troublesome for applications like electronic locks (e-locks) or an outdoor security panel that might, for example, open and close gates around an apartment complex. In addition to rain, such applications are subject to other harsh conditions like high temperatures and humidity. In some regions, insects and animals like geckos can trigger false touches. And certain installations are sometimes plagued by electrical noise from close by motors.

About a year ago, a new capacitive touch front end was integrated into the MSP430™ FRAM MCUs, creating a one-chip solution for a wide range of capacitive touch applications. These new MCUs integrate CapTIvate™ touch technology which is ultra-discriminating, so much so that it can sense through a driving rain storm to eliminate false readings. After all, no one wants to stand outside in the rain while the security lock malfunctions.

The heightened sensitivity of CapTIvate touch technology means that system designers can seal the touch panel, electrode sensors and other electronics behind thick glass, translucent plastic or even metal to keep the moisture out and yet still distinguish the difference between a drop of water and an actual finger touch. CapTIvate technology is so sensitive it can measure changes in capacitance as small as 10 femto-Farads while sensing a wide dynamic range of capacitance of up to 300 pico-Farads. Touches can be sensed through glass overlays of 60 mm and plastic up to 25 mm thick. It also features a special guard channel that is able to detect and adjust for changing environmental conditions like rain. A library of touch software modules makes it easy for developers to fine tune their systems to the expected environmental conditions of an application and its locale.