I have a question about adding more capacitive touch sensors through a multiplexer. I'd like to add a bunch more sensors providing continuous data (i.e. not digital on-off buttons). The tests I've made make me concerned that I won't be able to get smooth, consistent data when reading this through a multiplexer (MC14067). I understand that with wires dangling and a breadboard one can pick up stray capacitance so it's not the best test but my tests have led me to be concerned anyway and I thought I'd ask if anyone can confirm the possibility (or impossibility) of this technique before I go through all the effort of getting a PCB made.
Here's the situation:
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Connecting a sensor and the resistor directly to the Arduino pins produces smooth, continuous data as my finger moves across the sensor (as long as there's some insulation over the copper - scotch tape has worked fine for my prototypes).
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Connecting the sensor and resistor into a breadboard and then on to the Arduino also produces smooth, continuous values (though slightly different than number 1).
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Connecting the pins through a multiplexer to read multiple sensors produces approximately accurate results but the values jump around a bit. That is, it won't be completely random but with a constant finger position it will jump back and forth within a small range. Too much change to use smoothing in the code I think.
The fact that both 1 and 2 work well leads me to believe that it's the multiplexer, not the breadboard/dangling wires that is causing the problem.
Anyone have any thought on how/if this setup could work?
Thanks.