Help with Capacitive touch sensitivity

Using Arduino Project Guidance
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Hey guys,

I have a project where we need to trigger an touch display through an 3-4mm wooden plate.
We are using the Sparkfun capacitive touch based on the AT42QT1010. Instead of using the breakout touch we are using an cable connected to the "Pad". It all works great once we have short cables but the set up requires about 1meter cable. If we only connect a a cable to the "pad" we will trigger the touch sensor by touching the cable or even getting close to the cable. This thing is super sensitive.
I have not been able to get this thing working with such long cable. We did try to use an shielded cable and connect the "shield" to GND but this did not work, I guess the capacitive in the long cable is too high..

Has anyone successfully done something similar? Is there anything we can do except move the breakout board closer to the touch area?

Setup:

Btw. We have also tried to work with the wonderful Capacitive touch library ( Arduino Playground - CapacitiveSensor ) but this require direct contact i.e 3-4mm wooden plate will not work.

/ Erik

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What's so difficult with moving the breakout board closer to the touch area?

As you already found out, a long cable to the touch area will add a capacity, much higher than the sensor capacity, and also will turn the cable into kind of an antenna, sensitive to whatever electric noise in its neighbourhood.

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If we only connect a a cable to the "pad" we will trigger the touch sensor by touching the cable or even getting close to the cable. This thing is super sensitive.

Yes it is. You can alter that sensitivity by using the AT42QT1010 in the I2C mode and not the stand alone mode that the sparkFun board configures the chip in. That way you may be able to turn things down, but the cable will always be part of the sensor circuit and will always be prone to triggering the sensor. Think about it, how could it be otherwise.

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Grumpy_Mike:
Yes it is. You can alter that sensitivity by using the AT42QT1010 in the I2C mode and not the stand alone mode that the sparkFun board configures the chip in. That way you may be able to turn things down, but the cable will always be part of the sensor circuit and will always be prone to triggering the sensor. Think about it, how could it be otherwise.

Interesting. I will have a look at this.
Thanks,

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