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So, this might seem rather basic, but I'm going to pose it in the hope that I can save some work. So, I have a series of electrodes that are sensitive to voltage fluctuations, but, before I pass the data into the Arduino and then into the computer, I wanted to create a circuit that acts as a bandpass filter in order to reduce 60hz noise from appliances as well as to limit the read frequencies.

Though, I plan on using a good number of electrodes (either 16 or 32 as of right now) so, rather than running each individual electrode through a separate bandpass filter, is it possible to apply these filters by passing multiple electrode signals through a single or a smaller number of filters rather than having to build one filter for every input? Thanks in advance for any insight you guys can provide.

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migrated from arduino.stackexchange.com Mar 24 '16 at 22:01

This question came from our site for developers of open-source hardware and software that is compatible with Arduino.

  • \$\begingroup\$ Can you pour 16 different fluids through a Britta water filter and have them all separate at the end of it? No. \$\endgroup\$ – Majenko Mar 24 '16 at 15:30
  • \$\begingroup\$ What frequencies do you WANT to sample? DC or frequencies up to? Down to? \$\endgroup\$ – Hans Neve Mar 24 '16 at 15:53
  • \$\begingroup\$ This question is how to create a bandpass filter before passing data to the Arduino, so I think the Electronics Stack Exchange is better suited to answering this. I'll migrate it for you. :) \$\endgroup\$ – Nick Gammon Mar 24 '16 at 22:01
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The only possible way you could to that is through a technique called Time Division Multiplexing.

This involves you having a set of analog switches to select one of your incoming signals at a time for filtering. You can only read one signal at a time, and each one for a period longer than you need for the filtering to have any effect.

Also this would probably increase your noise in your signal in the first place.

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    \$\begingroup\$ “Only possible way” ? I doubt it. Perhaps the easiest, however. \$\endgroup\$ – James Waldby - jwpat7 Mar 24 '16 at 17:29
  • \$\begingroup\$ Come up with another way then. Go on, I challenge you. \$\endgroup\$ – Majenko Mar 24 '16 at 17:30
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    \$\begingroup\$ 16qam can do it – but 16 separate filters would be a lot easier, and I suggest that explaining why separate filters will involve less messing around is what your answer should have, rather than suggesting TDM \$\endgroup\$ – James Waldby - jwpat7 Mar 24 '16 at 18:37
  • \$\begingroup\$ @jwpat7 I don't see what that has to do with anything... \$\endgroup\$ – Majenko Mar 24 '16 at 18:39
  • \$\begingroup\$ @jwpat7 I rather think that QAM is a little beyond the average Arduino user. If they have to ask this question then QAM is not going to be a feasible option for them. \$\endgroup\$ – Majenko Mar 25 '16 at 10:46

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