ChallengesBringOpportunitesI’m pleased to say I was able to turn on/off the CO2 gas.  This gave me a better feel for how long to turn the valve on/off.  Summary:

 Roughly, I’ll start with something simple like (assumes LED light is on – or no point in adding CO2!)  if CO2 < 800ppm, turn CO2 valve on for 5 seconds.  If > 800ppm but < 1,200ppm, turn CO2 valve on for 2 seconds.

WhyCat

Hold Up…Do I REALLY Need to use the UART?

 Well looky what it says on the WH-Z16 data sheet …Output method:UART,analog voltage signal,PWM wave…I shouldn’t have to rely on UART.  FrustratedBut sadly, on further investigation, the Grove CO2 connector only connects RX, TX, VIN, GND and does not connect the other pins:

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I could modify the connector.  Since I do have UART working with the Arduino, for now I’ll go back to using the UART :-).  Good to know though.

Adjusting CO2

I left off yesterday with an Arduino test script to help me determine what initial settings I should have for turning on/off the CO2 solenoid valve.

Steps:

  • upload script to Arduino with Grove Shield containing the WH-Z16 CO2 sensor.  Validate that we are getting a reasonable reading.
    • The readings from the WH-Z15 CO2 sensor has come down from about a week ago.  I’m thinking there must be a burn-in time for the sensor.

CO2 level: 436
CO2 level: 436
CO2 level: 436
CO2 level: 436
CO2 level: 436
CO2 level: 436

  • The reading from the Extech CO2 meter:
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  • calibrate the Grove CO2 sensor with the Extech CO2 sensor by matching the readings from the Arduino sketch to the Extech CO2 sensor readings.  I’ve seen ~ 100 ppm difference between the two.  Let me rant again about the difficulties in calibration.  What I ultimately have for now is not scientifically accurate however as I understand – certainly within range of “good enough” for the Leaf Spa needs – which is to maintain a CO2 level of ~ 1200ppm when the LEDs are on.
    • The readings are “close enough.”  I don’t feel I need to adjust the MH-Z16 to the Extech.
  • turn the CO2 regulator’s flow adjustment knob such that the ball inside the flow scale tube shows a flow rate of 1
  • I turned the CO2 regulator on “just a smidgeon.”  When the CO2 regulator went on, it was on ~1.
  • run script with various amounts of seconds the CO2 regulator pumps CO2.  Measure the CO2 values.  Keep doing this until I have a comfortable feel for the length of time needed to adjust the CO2 to 1200ppm and how long between readings before more is needed.  This will provide insight into initial variables for auto adjusting.
    • CO2 goes up quickly.  Roughly, I’ll start with something simple like (assumes LED light is on – or no point in adding CO2!)  if CO2 < 800ppm, turn CO2 valve on for 5 seconds.  If > 800ppm but < 1,200ppm, turn CO2 valve on for 2 seconds.
  • Also measure the CO2 values outside of the Grow Chamber.  Is the leakage significant?
    • I was concerned with poisoning my family.  Leakage does not appear significant.  

WhyCatSomething I don’t understand…the valve turned ON when I set the digital pin to LOW.  I expected the opposite.  I will debug this tomorrow?

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