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Author Topic: 16 electrodes with only one QT300 sensor  (Read 569 times)
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melbourne, AU
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hi all...

i'm making a touch-sensitive surface: i want to use arduino + a qt300 chip to sense the capacitance on 16 different electrodes in sequence, using only the one qt300.  (for now i'd prefer to use the qt300 rather than a Qslide etc because it's simple and cheap and easy and flexible)

anyone got any ideas how to do this, using as few arduino pins as possible?  my thought is that i could use a 1:16 demux chip to route the acquisition bursts from the QT300 through each sense electrode in turn, but i've never used de/multiplexers before... would that work?

the eventual aim is to make a large touch-sensitive field using about 60-100 conductive traces etched onto PCB, or something.  hence trying to conserve arduino pins... space is also extremely limited, so as little QT300s as possible, too, hence some kind of 16:1 routing chip.  any suggestins more than welcome, as i don't really know what i'm doing... as usual.

love,
jon.
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I'm not familiar with the QT300, but I wouldn't think the 74xxx series digital muxes would work for this application.  There is such a thing as an analog mux, but I don't recall any part numbers.  There's also a "quad bilateral switch" CD4066, that is similar to a mux.

-j
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melbourne, AU
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thanks for the suggestion -  i've done some searching around and found this 16:1 analog cmos multiplexer from maxim:
http://datasheets.maxim-ic.com/en/ds/MAX396-MAX397.pdf

do you think this might be suitable?  it says it's suitable for routing audio signals, so i suppose it would also do for routing aquisition bursts from a capacitance sensor...? but i have no idea how these things work....
cheers,
jon
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