I'm working on a project, it's basically a hand-drawn paper keyboard based on capacitance.

I was thinking I can multiplex the different lines with shift register (74HC595) and switch (4066), and as I've got a lot of these here I gave them a try. But apparently not...

So I'm looking for a solution.

I've already found that : Multiplexer for Capacitive Sensors (MUXC01)

Can you confirm that this component could work or do you have any better idea about how to multiplex these keys ?

  • \$\begingroup\$ Erm, that looks pretty much exactly like a '595... \$\endgroup\$ – Ignacio Vazquez-Abrams Jan 17 '14 at 8:21
  • \$\begingroup\$ From what I understand in the doc it's not exactly that. They say it can switch one input (Signal IN, pin 10) to one or multiple output. So it's a kind of 2 * 4066 controlled by a shift register like a do but in a single. But they also mention "Very well suited for multiple-capacitance measurement". They also talk about using it both way. So in that case I would be able to measure up to 9 different capacitance on a single output. But as I say in my question, I'm not sure I understand correctly the datasheet :/ \$\endgroup\$ – Emmanuel Istace Jan 17 '14 at 8:29
  • \$\begingroup\$ Ah, I see. It allows faster signal switching that a '595 (since you don't need to wait for the serial propagation to flip the bit), but doesn't really offer much beyond that. Even that could be accommodated for with judicious use of the output enable. \$\endgroup\$ – Ignacio Vazquez-Abrams Jan 17 '14 at 8:37

I get the problem. It's not related to the 4066 or anything. It's that good ol breadboard.

I'm working with little capacitance difference and the breadboard itself have a capacitance. One or two connection, well that's ok, But I was having a long bus with at least 30 wires (so times 2 for pins connection) in series to connect the input of the AtMega328 with the 1M\$\Omega\$ to all the output of the 4066. The result was a big disturbance in the force ;)

I've done a test on a board with the chip soldered, barely not problems. Will just have to split in two groups, but not a big deal as I've got plenty of inputs remaining.


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