Dyah Setyaningsih

Project idea: https://miro.com/app/board/uXjVLBm7F8w=/?share_link_id=117991010729

Motivation

Are my plants breathing? They seem fine, their leaves are green... but are they really okay? To observe my houseplants' respiration, a prototype of soap bubble maker machine is being developed. The quantity of soap bubbles will be in accordance to the CO₂ level of the plants' (closed) environment, divided into three categories: Low, Medium and High CO2 level.

Materials

ESP32
CO₂ sensor MH-Z19C
Stepper motor 28BYJ-48
Stepper motor driver module ULN2003
PWM fan AMD Ryzen 7 1700
10kΩ resistor
Power supply 12 volts
Switch
Lots of cables...

To-Do List

Implement stepper motor speed (based on category (CO₂ value)) (s. Pseudocode below)
Solve technical problems (failed to connect with ESP32? Stepper motor not working after extending wires? Unstable wires?)
Stabilize bubble rings holder to the stepper motor (done)
For better and more directed air flow: add nozzle/funnel? (done, but is air flow strong enough?)
Make wiring diagram
Documentation

Pseudocode

Idea: assign CO₂ value into 3 categories; Low, Medium, High and adjust the stepper motor speed based on the category.

  DEFINE constants for CO2 thresholds:
    LOW_MEDIUM_THRESHOLD = 500 //to be determined via trials
    MEDIUM_HIGH_THRESHOLD = 700 //to be determined via trials
  
  DEFINE speed settings for each category:
    LOW_SPEED = 400      // Steps per second
    MEDIUM_SPEED = 800   // Steps per second
    HIGH_SPEED = 1200    // Steps per second
  
  INITIALIZE variable currentCategory to -1
  INITIALIZE variable lastCategory to -1
  
  FUNCTION setup():
    BEGIN
      SET maximum speed for stepper motor (e.g., 1200 steps/sec)
      SET acceleration for smoother operation (e.g., 500 steps/sec^2)
      START serial communication for debugging
    END

  FUNCTION loop():
    BEGIN
      READ CO2 value from the sensor (variable CO2)
      
      DETERMINE currentCategory:
        IF CO2 < LOW_MEDIUM_THRESHOLD:
          SET currentCategory to LOW
        ELSE IF CO2 < MEDIUM_HIGH_THRESHOLD:
          SET currentCategory to MEDIUM
        ELSE:
          SET currentCategory to HIGH
      
      IF currentCategory is different from lastCategory:
        BEGIN
          SWITCH currentCategory:
            CASE LOW:
              SET stepper motor speed to LOW_SPEED
            CASE MEDIUM:
              SET stepper motor speed to MEDIUM_SPEED
            CASE HIGH:
              SET stepper motor speed to HIGH_SPEED

          UPDATE lastCategory to currentCategory
        END
      
      RUN stepper motor at the current speed (use AccelStepper's runSpeed() function)
    END

Idea to determine thresholds: run trials on plants enclosed environment.

  DEFINE variables:
    minCO2 = Infinity     // Initialize to a very high value
    maxCO2 = -Infinity    // Initialize to a very low value
    startTime = CURRENT_TIME
    trialDuration = 30 minutes (in milliseconds, e.g., 30 * 60 * 1000)
  
  FUNCTION setup():
    BEGIN
      INITIALIZE serial communication for debugging
      INITIALIZE CO2 sensor
      PRINT "Starting 30-minute CO2 trial..."
    END
  
  FUNCTION loop():
    BEGIN
      WHILE (CURRENT_TIME - startTime) < trialDuration:
        BEGIN
          READ current CO2 value from sensor (variable currentCO2)
          
          IF currentCO2 < minCO2:
            UPDATE minCO2 to currentCO2
          
          IF currentCO2 > maxCO2:
            UPDATE maxCO2 to currentCO2
          
          PRINT currentCO2, minCO2, and maxCO2 to serial monitor
          WAIT for 1 second //reduce sampling frequency
        END
      
      PRINT "Trial Complete."
      PRINT minCO2 and maxCO2 to serial monitor
      
      CALCULATE range = maxCO2 - minCO2
      CALCULATE lowMediumThreshold = minCO2 + (range / 3)
      CALCULATE mediumHighThreshold = minCO2 + (2 * range / 3)
      
      PRINT "Thresholds:"
      PRINT "Low-Medium Threshold: " + lowMediumThreshold
      PRINT "Medium-High Threshold: " + mediumHighThreshold
    END

Gallery

The Plant Plant Gallery (Nextcloud Bauhaus Uni), Password: theplantplant (CO₂ sensor first trial pictures are inside)

References

Motivation

Materials

To-Do List

Pseudocode

Gallery

References

CO2 sensor MH-Z19C

PWM fan AMD Ryzen 7 1700

Stepper motor 28BYJ-48 and stepper motor driver module ULN2003

CO₂ sensor MH-Z19C