Here’s some cool quick notes on touch sensors QT113/118 for those of you trying to invent
touch enabled systems.
I need a touch sensor for a couple of projects, and the Qprox QT113 seems to be the way to go, particularly for interfacing with an Atmel processor. It’s easy to work with, and hooks-up with only a bare minimum of extra stuff. All you need is a resistor and capacitor and a bit of wire or trace to compose the sensor.
Tom Igoe documents most of the details here.
There’s one wrinkle in my project, and that’s figuring out what value I should use for the capacitor — which is basically what controls the sensor’s, you know..sensitivity. So, I tried to values, .01uF and .1uF, to find out what the thing means by “touch.” (I’m looking at something that is more ambient than a full-on, bone-jarring style touch — something closer to “nearby”.)