Houseplant Soil Moisture Project

[last updated: 2022-04-24]
go to: soil moisture monitor methods
go to: resistive monitoring investigations
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• General software procedure:
  Make one probe high, the other low
  pause (stabilize)
  take a reading
  turn off high probe
  pause (recovery)
  make second probe high
  pause (stabilize)
  take a reading
  turn off high probe
  pause (recovery)
  this completes one "pair" of readings
  repeat for desired number of pairs, then average all

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  basic test circuit
  
  

  equivalent circuit with software "flip"

• Rev 1 - basic flip-flop test circuit with serial monitor readout:
  • Using basic test circuit (schematic above), starting from the GardenBot.org circuit, eliminated the 100-ohm resistor used in that circuit (see: ... methods), since "current limiting" is not needed on the high-input-impedance analog inputs, and the 56k R_D gives plenty of limiting for the current between the two drive pins.
  • Discovered there is a lot of variability in readings, even successive readings with no probe movement in between. (see: ... investigations)
  • However I managed to get stable readouts by taking 3 pairs of readings and averaging them, and adding some pauses
    Code: ...
  • OTOH, there was little consistency between readings taken at different points - that is, removing the probes, and reinserting them a slight distance away.

• Rev 2 - OLED readout:

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