AT42QT1012 or AT42QT101x - Recalibration (self-calibration) OFF!?

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Hello,

 

I decided to use the AT42QT1012 for use behind a plastic board to control light and so one (the output is connected to the input of a microcontroller).

It is working, however sometimes it does not respond (the sensor) and I need to turn it off and on again.

I supose that it happens due to the Recalibration (self-calibration). From What I have read I can not turn off the recalibration. My question is, there is any way to eliminate this behaviour?

Should I use antoher IC? Do you recomend somenthing?

 

Hope to get any suggestion from you.

Attached follows my electronic design.

 

Thank you.

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If it's recalibrating on its down, it's probably related to drift compensation. If that's the case, the only way to eliminate the behavior is through Cs or Cx where Cx is the capactive load of your touchy parts.  Are you certain that what's happening isn't related to the 1012 being toggle output on detect? If the output is changing as soon as you break contact with the sense surface, you may need to revisit your Cs or Rs values or the interconnect between the sensor and the IC.

 

I'd start with removing your C22, it shouldn't be there. Your R6 is below what the datasheet recommends and your Cs shouldn't need to be that high for touch detection. It depends on the size of your sense surface and the dielectric properties of your plastic board but larger Cs will generally aid with near touch proximity evaluating as a detection so you're probably fine leaving it as-is. You don't have a label on OUT indicating where your connecting to your uC so make sure to reference the datasheet to make sure you're connected to the correct side of your active-high configuration resistor. Looks like your R8 is also setting the device in 15 minute auto off and probably doesn't need to be 1M R. Since you're using a uC with it, you might consider ditching the bypass cap and powering it from a GPIO as well. Section 4 of the datasheet mentions your Cs and Rs ranges but somewhere in there it also does suggest running it as a resistive load load from a gpio.