Comments: AT42QT101X Capacitive Touch Breakout Hookup Guide

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  • In order to decrease noise, is it necessary to use a pull-down resistor in series with this digital out from this sensor into the digital input of an Arduino-Uno?

  • I’m newish to electronics and I’m very curious, why is there a cross-hatch ground copper pattern opposite the touch pad on the AT42QT101X Capacitive Touch Breakout - I mean, why is any copper there at all?

    I notice the adafruit version of this breakout also has the same ground copper cross-hatch pattern opposing the touch pad.

    I’ve made my own version of this board for my project - and I didn’t include the cross-hatch ground copper under the touch electrode pad; because the only guidance (copied below) I could find in the AT42QT1010 spec sheet said to keep any ground copper away from the touch electrode

    My board works mostly ok - but I’ve seen touch detection misses in the ballpark of 1 in 30 - which feels too high, so I’m wondering what I’m missing here?

    “Ground planes around and under the electrode and its SNSK trace will cause high Cx loading and destroy gain. The possible signal-to-noise ratio benefits of ground area are more than negated by the decreased gain from the circuit so ground areas around electrodes are discouraged. Metal areas near the electrode will reduce the field strength and increase Cx loading and should be avoided, if possible. Keep ground away from the electrodes and traces.”

    thanks, Kevin.

  • Is the touch limited to detecting human contact or would a steel ball rolling across the copper pad in your example trigger the detection?

    • Shawn and I just tested it out. Unfortunately, the steel ball basically extended the copper pad so it did not trigger the sensor. If you were holding the metal ball, the sensor would react.

    • Hmm, it depends on how much capacitance the steel ball has. I currently have a project set up with the AT42QT1011 and copper tape. Unfortunately, I do not have a steel ball. However, the sensor was able to detect a small bottle of water but not a rubber ball rolling over it.


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