Reading bipolar signal from plants with Arduino

Discussion in 'The Projects Forum' started by chiara, Jul 31, 2013.

  1. chiara

    Thread Starter New Member

    Jul 31, 2013
    Dear all,
    I'm an art student, beginner with electronics, I'm building a circuit that monitors electrical signals in plants, and I'm trying to read it with an Arduino.

    The circuit I found is this:

    Description: "The signal from the electrode was transmitted into a CA3140 impedance converter,which is an integrated circuit operational amplifier that provides very high input impedance, very low input current, and high speed performance (Intersil Corporation), and is then connected to an AD620 amplifier. After amplification, the amplitude range of the electrical signals was 4000mV. In the greenhouse, the distance from the detection site to the computer is 30m, so a voltage to current converter (V/I ) is used so that the signal could be transferred reliably. After the long distance transfer, the current signal is converted back into a voltage signal by an I/V converter."

    In my case, I have an Arduino instead of a computer, and it is near to the plant, so I assume that
    - I don't need the V/I I/V
    - I have to use an Op Amp Summing Amplifier for arduino, like here:

    Do you have any advice on what would be the best way to adapt the circuit? How to choose the right OPAMP? I tried AD820 with no success.

    Thanks a lot in advance!
  2. MrChips


    Oct 2, 2009
    In a recent thread someone suggested an AD8220 instrumentation amplifier.
  3. wayneh


    Sep 9, 2010
    The CA3140 are wired now as high-impedance voltage followers. Fine. Once that step is complete, you just need to amplify the voltage and I think almost any op-amp would work for that. Show us what you did that did not work. It should have.

    I agree you do not need to worry about converting your signal to current and back to voltage. That's used in noisy industrial environments but I think you'll be fine, especially if you use shielded cable for signals and take care to minimize interference.
  4. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
    geesh.. now plants are bi-polar too.. Time to get it on the meds..
    #12 likes this.
  5. BobTPH

    Senior Member

    Jun 5, 2013
    Feed them some lithium!

  6. GohanViki

    New Member

    Aug 7, 2015
    I cant understand your logic. that where the positive and negative terminal actually in plants.. I mean where i have to fix the electrodes in plants.. Please guide me...