MPR21 Adafruit capacitive sensor

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papadonik
 
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MPR21 Adafruit capacitive sensor

Post by papadonik »

I was wondering if there is a non polarized or any other type of capacitor device that I can use to simulate the human touch that triggers the MPR21 Adafruit capacitive sensor. I am reading that the capacitance of a human body is approximately 100 pF. Thank you

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adafruit_support_mike
 
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Re: MPR21 Adafruit capacitive sensor

Post by adafruit_support_mike »

A non-polarized 1nF capacitor should work as long as its other side is connected to the MPR121's GND.

The connection on the far side is the part that matters. The capacitance added to the pad has to act in parallel with the reference capacitor inside the MPR121.

The 100pF-ish contribution of a human finger touching the pad is more complex than a simple capacitor. It represents the energy necessary to polarize the water in the finger relative to all the rest of the water in the body.

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