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supply electrode with the humidity of the soil

Discussion in 'General Electronics Discussion' started by hagi, Oct 17, 2015.

  1. hagi

    hagi

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    Oct 17, 2015
    I am working in my project to water plant with peristaltic pump , i am using 2 inox rails like electrodes and a LM311 to activate the threshold .

    To avoid electrolyse I don't want supply electrodes with dc, AC is better idea I think ,
    I was thinking to use NE555 to supply my electrodes , 10 minutes low level and 7 seconds high level , but in the output there is offset, but I don't know how resolve this issue .
     
    Last edited by a moderator: Oct 17, 2015
  2. Minder

    Minder

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    Apr 24, 2015
    Show the circuit, DC based switching or pulsing does not in and of itself, provide AC.
    M.
     
  3. hagi

    hagi

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    Oct 17, 2015
    this is the circuit .
     

    Attached Files:

  4. Minder

    Minder

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    Apr 24, 2015
    Does not appear to be any AC according to the circuit, pulsating DC maybe.
    M.
     
  5. hagi

    hagi

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    Oct 17, 2015
    there is pulsating dc with ne555 according electrod and résistor .
     
  6. Minder

    Minder

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    Apr 24, 2015
    But you said you needed AC?
    M.
     
  7. hagi

    hagi

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    Oct 17, 2015
    I want supply electrods with résistor in AC , because with the ne555 the is offset .
    I don't know how I use Ac to supply electrods with the résistor .
     
  8. Minder

    Minder

    2,871
    594
    Apr 24, 2015
    You need to set up a push pull circuit either + & - supply or a transformer driven output if using single supply .
    [​IMG]
    [​IMG]

    M.
     
  9. KMoffett

    KMoffett

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    66
    Jan 21, 2009
    I've used several versions of that 4093 circuit successfully in water lever detection. It might require a comparator
    at the output of the voltage doubler (or better quadrupler) instead of the gate for this application.

    Ken
     
  10. GPG

    GPG

    452
    66
    Sep 18, 2015
    Could use the 555 adjusted for 1:1 mark-space and pass through a capacitor to remove DC. This would also allow synchronous rectification on the receive side
     
    (*steve*) and duke37 like this.
  11. AnalogKid

    AnalogKid

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    Jun 10, 2015
    Given the timing data in post #1 and the schematic in post #9, maybe use 4093 pin 1 as an oscillator gate, and drive it with a separate timing circuit that produces 10 minutes off, 7 seconds on. This could be another oscillator with a 1.167% duty cycle (7 seconds / 600 seconds) or a higher freq oscillator, counter, and state decoder.

    ak
     
  12. hagi

    hagi

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    Oct 17, 2015
    thank you for your answers , but I'm not looking to make a dectection water , I just want to power the sensor with it résistor (divider resistor) drive of 10 minutes and 7 seconds off on, with the NE555 there is a DC voltage. I've heard of that could remove dc with another NE555
     
  13. hagi

    hagi

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    Oct 17, 2015
  14. KMoffett

    KMoffett

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    66
    Jan 21, 2009
    No. Slowly switching the output high (+5VDC) and low (0VDC) does not produce AC, just "pulsating" DC. You actually have to switch the polarity. You can do that by feeding the output of the 555 (or 4093 in my circuit) oscillator through a capacitor, into a resistive load. And to do that with a reasonable size capacitor, you would need a much higher frequency then your 10 Minutes and 7 Seconds.

    Ken
     
  15. KMoffett

    KMoffett

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    Jan 21, 2009
  16. GPG

    GPG

    452
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    Sep 18, 2015
    The way I read it the first 555 is capacitively coupled to the drive electrode.The receiver then operates a second 555 to produce the watering cycle presumably to let the water soak in and avoid runoff.
    Using the output of the first 555 to drive a couple of analog switches instead of using diodes will provide some noise immunity and improved sensitivity. Hagi What voltage supply?
     
    Last edited: Oct 20, 2015
  17. hagi

    hagi

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    0
    Oct 17, 2015
    My voltage is 12V .
     
  18. hagi

    hagi

    11
    0
    Oct 17, 2015
    I tkink I use first ne555 for temporisation 10 minutes and 7 secondes , and the second ne555 create 500hz signal .

    is it right ? signal elec.jpg
     
  19. GPG

    GPG

    452
    66
    Sep 18, 2015
    Regulated?
     
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