I'm trying to do a pressure sensitive keyboard (2 layers of perpendicular conductive bands separate by a compressible layer like foam)



If I do a 5x5 mm overlap and a 0.1 (compressed) to 0.5 mm (uncompressed) height, it's like a 5pF difference. I only need to measure the relative change between compressed and uncompressed not the absolute capacitance value. Do you think it's measurable? I'm thinking to generate some frequencies to an end (red for example) an measure the relative amplitude to the other end ( blue). Do you have better idea if achievable?

 

Some of the newer PIC’s have a charge time measuring unit (CTMU) for capacitive touch sensing. They even do the multiplexing in hardware, if I recall correctly.

 

That is a very small distance for the compression change. Many foam materials take a permanently in a fairly short time. So that may be an issue relative to product life.

 

Many of the newer MCU include (sometimes quite a few) touch inputs. For example, the ESP32-S3 has 14 touch inputs with a hardware peripheral handling the sensing.

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