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Plant Monitor Tutorial

This tutorial includes a summary of the original article for the Plant Monitor Kit on Nuts and Volts - check out the original article for more info! Special thanks to John Gavlik for putting this kit together and documenting it well!

If you have got a green thumb and everything grows for you - this Kit may not be for you. But if you’re like most of us who see a plant at the store that’s growing like crazy (under the worst of conditions), buy it and then bring it home just to watch it die in a few days (under the best of conditions), then this kit may be for you!

The Plant Monitor Kit takes a lot of the guesswork out of growing and maintaining an indoor plant. Two important elements for good growth are moisture and light. This Kit monitors both and alerts you to when one, or the other, is less than optimal. In the end, we can’t guarantee a thriving plant with this Kit but, at least, you’ll have a better fighting chance for growing it successfully.

No soldering required!



Everything above is included in the Plant Monitor Kit!


Hardware Assembly

Plug in the Wirelings into the ports on the Wireling Adapter TinyShield indicated by the table below, then place the TinyScreen+ on top of the Wireling Adapter TinyShield.

Wireling Port Assignments
Port 0
Port 1
Port 2
Port 3

Upload Program

Download the project code: Plant Monitor Arduino Sketch

Open the program in the Arduino IDE and make the following Tools/ tab selections to upload the program to your TinyScreen+ (If this is your first time using the TinyScreen+, check out the TinyScreen+ Getting Started Tutorial):

  • Board: "TinyScreen+"
  • Build Option: "Default"
  • Port:
    • Mac: “/dev/cu.usbmodemXXXX (TinyScreen+)”
    • Windows: “COMXX (TinyScreen+)”.
    • (this number will be different for everyone, check the Port Trouble Learn Page if you are not sure which one it is)
//  Plant Monitor_v1.00
//  copyright LearnOnLine, inc
//  author:  John Gavlik
//           with contributions from (noted within)
//  Created  12/30/2019
//  Updated  02/09/2020

//--------------Program Description ---------
//  The Plant Monitor program is a graphical presentation of 2 soil monitor wirelings and 1 ambient light wireling
//  on the TinyScreen+ color OLED
//  It also uses a buzzer to alert the user to low moisture and low light levels
//  Hardware:
//            TinyScreen+ (1)
//            Wireling Adapter (1)
//              Soil Monitor Wireling (2)
//              Ambient Light Sensor Wireling (1)
//              Buzzer Wireling (1)
//                1 beep  - soil #1 sensor low
//                2 beeps - soil #2 sensor low
//                3 beeps - low light level
//            Custom plastic enclosure (1)
//            Assorted Wireling cables (4)
//            USB cable (micro to A) (1)


#include <Wire.h>
#include <SPI.h>
#include <TinyScreen.h>
#include <RTCZero.h>
#include <Wireling.h>

//Library must be passed the board type
//TinyScreenPlus for TinyScreen+
TinyScreen display = TinyScreen(TinyScreenPlus);

//--------------General variables---------------------
//--------------Global for Debugging------------------
byte    tempByte;

//--------------RTC variables---------------------
//--------------Global for Debugging------------------
/* Create an rtc object */
RTCZero rtc;

/* Change these values to set the current initial date */
byte  day                = 1;   //just some values that arn't displayed
byte  month              = 1;
byte  year               = 20;

/* Change these values to set the current initial time */
byte  seconds;                  //these time values are over written by user setting time
byte  minutes;                  //including 24hr or am/pm
byte  hours;                    //see set_time() for details

                                //For set_time()
byte  am_pm_24           = 0;   //0 = am, 1 = pm, 2 = 24hr

//These are the x/y coordinates for time on the OLED 96x x 64y screen
const byte  hours_x      = 18;  //OLED x for hours display
const byte  hours_y      = 0;   //OLED y for hours display

const byte  minutes_x    = 34;  //OLED x for minutes display
const byte  minutes_y    = 0;   //OLED y for minutes display

const byte  seconds_x    = 49;  //OLED x for seconds display
const byte  seconds_y    = 0;   //OLED y for seconds display

const byte  am_pm_24_x   = 64;  //OLED x for am/pm/24hr display
const byte  am_pm_24_y   = 0;   //OLED y for am/pm/2rhr display

//--------------OLED Variables---------------------
//--------------Global for Debugging------------------
byte  pixel;                        //horizontal pixel from 0 to 95
byte  line;                         //vertical line from 0 to 63

//--------------Time Variables---------------------
//--------------Global for Debugging------------------
int   loop_time;                   //time around the main Loop set in Setup
int   loop_time_increment;         //number of milliseconds for each loop - set in Setup

//--------------Measurement Variables---------------------
//--------------Global for Debugging------------------

const byte  soil_1_start_x = 3;    //horizontal pixel starting point for soil 1 icon
const byte  soil_2_start_x = 78;   //horizontal pixel starting point for soil 2 icon

byte   soil_1_moisture_percent;    //soil 1 moisture percent (0-99)  
byte   soil_2_moisture_percent;    //soil 2 moisture percent (0-99) 

byte   soil_moisture_percent;      //used in draw_soil_icon()
byte   soil_moisture_percent_moving; //used in draw_soil_icon() to convert line # to soil moisture percent

byte   soil_1_temp;                //soil 1 temperature in degrees C
byte   soil_2_temp;                //soil 2 temperature in degrees C

int   lux;                         //immediate lux value (0-60K)
int   lux_ave_value;               //average lux value for storage to the lux_array @ lux_ptr

int   lux_ave_divisor;             //count of the number of times lux is averaged
int   lux_to_y_value;              //conversion from lux value to y-position on plot

const byte lux_x_plot_min = 25;    //min and max x/y for Lux line plots
const byte lux_x_plot_max = 72;   
const byte lux_y_plot_min = 62;    //this is no mistake 
const byte lux_y_plot_max = 24;    //this is no mistake 

//--------------Limit Variables---------------------
//--------------Global for Debugging------------------

byte   limit_index;                //used in set_limits()
                                   //0 = do nothing
                                   //1 = inc/dec soil_1 limit line    - reload limit_counter
                                   //2 = inc/dec soil_2 limit_line    - reload limit_counter
                                   //3 = inc/dec max lux for plotting - reload limit_counter

byte   limit_counter;             //used to time set_limit() aciivity
                                  //automatically gets out of set_limit() when limit_counter == 0
                                  //counted down each time thru and reloaded
                                  //for every button increment/decrement

const byte  limit_counter_reload = 10*4;  //10 second reload time based on 4 updates/second

const byte  soil_moisture_limit_min = 20; //min and max soil_moisture_limit values for limit_lines
const byte  soil_moisture_limit_max = 80;

byte   soil_1_moisture_limit;     //minimum to activate buzzer - set in setup() - can be changed in set_limits()
byte   soil_2_moisture_limit;     //minimum to activate buzzer - set in setup() - can be changed in set_limits()

int    soil_1_moisture_limit_counter; //counts all occurrances of soil_1_moisture_percent below soil_1_moisture_limit - buzzer()
int    soil_2_moisture_limit_counter; //counts all occurrances of soil_2_moisture_percent below soil_2_moisture_limit - buzzer()

byte   soil_moisture_limit;       //used in draw_soil_icon()
byte   limit_line;                //white line in soil icon to denote boundry between green and red

const int lux_top_plot_level_min = 10;    //min top lux
const int lux_top_plot_level_max = 1000;  //max top lux

int    lux_top_plot_level;        //level to use for top of lux plot - set in set_limits()
int    total_lux_this_day;        //lux_top_level_plot_level times the sum of all y_values in lux_array

//---------------Array Variables-----------------------
//--------------Global for Debugging------------------

int    lux_array[48];             //light array to store 12 hours of light levels @ 15 min/sample
byte   lux_array_ptr;             //pointer to lux_array[]

byte   lux_array_ptr_last;        //last pointer value for computing average lux 
const byte lux_plot_offset = 24;  //add this to the lux_array_ptr for plotting update_plot_area()

const byte   lux_array_ptr_min = 0;  //min and max array pointers
const byte   lux_array_ptr_max = 47;

byte   mp_lux_array_ptr;          //mp is for MakerPlot - see output_serial_data() 

//--------------Button Variables---------------------
//--------------Global for Debugging------------------
                              //see Button_Actions for details

byte  buttons_get;            //value for this sample of buttons
byte  buttons_last;           //last button_get value
const byte  buttons_none = 0; //no buttons pushed value

const byte  button_set   = TSButtonUpperRight;  //set time
const byte  button_clr   = TSButtonLowerRight;  //set soil moisture / lux limits and clear buzzzer 
const byte  button_plus  = TSButtonUpperLeft;   //increment time/limit value
const byte  button_minus = TSButtonLowerLeft;   //decrement time/limit value

byte  button_set_counter;      //single button counters
byte  button_clr_counter;         
byte  button_plus_counter;       
byte  button_minus_counter;

const byte  push_action = 0;  //counter value to trigger push action
const byte  hold_action = 3;  //counter value to trigger hold action
                              //based on loop_time = 250 milliseconds

bool  hold_action_flag;       //0 = cleared, 1 when hold_action value from above is exceeded
                              //used to clear button counters when all buttons are released
                              //so that inadvertant "push" does not occur

byte  date_time_index;        //0 = display date and time
                              //1 = set month
                              //2 = set day
                              //3 = set year
                              //4 = set am/pm/24hr
                              //5 = set hours
                              //6 = set minutes
                              //7 = set seconds
                              //8 = set rtc to above and set date_time_index = 0

bool  button_set_flag;        //set in button_set_action()    cleared in set_time()
bool  button_clr_flag;        //set in button_clr_action()    cleared in update_buzzer()
bool  button_plus_flag;       //set in button_plus_action()   cleared in set_time()
bool  button_minus_flag;      //set in button_minus_action()  cleared in set_time()

//---------------Wireling Port and A2D pins-----------------
//               from
//                                                        relative to  display.setFlip(false);                              
#define LUX_PORT      3       //light sensor                                        (far-right)
                              //the soil ports are swapped to make up for where
                              //they are physically 
#define SOIL_1_PORT   1       //soil 1 moisture/temp monitor                        (top-left
#define SOIL_2_PORT   2       //soil 2 moisture/temp monitor                        (top- right)
#define pin (uint8_t) A0      //buzzer  - uses A0 - no port as it is not addressed  (far-left)

//---------------Light Sensor Variables-----------------
//               from
#define TSL2572_I2CADDR     0x39    //hex address of light sensor
#define GAIN_1X             0       //gain levels
#define GAIN_8X             1
#define GAIN_16X            2
#define GAIN_120X           3

#define GAIN_DIVIDE_6       true    //only use this with 1x and 8x gain settings
int gain_val              = 0;      //initial gain setting

float luxLevel;                     //lux as a float here

//---------------Moisture Sensor Variables-----------------
//               from
#define MINCAPREAD          710
#define MAXCAPREAD          975
#define ANALOGREADMAX       1023
#define BCOEFFICIENT        3380
#define SERIESRESISTOR      35000

int moistureLevel;
float tempLevel;

//---------------Buzzer Variables-----------------

byte  buzzer_flag;                  //0 = OFF, 1 = ON

const byte  buzzer_start_time = 16; //24hr start time for buzzer if below minimums - set_limits()
const byte  buzzer_stop_time  = 17; //24hr stop  time for buzzer if below minimums - set_limits()

int   lux_total;                   //total lux count for each element in lux_array 
const int lux_buzzer_min = 48*5;   //lux_total must be greater than this to avoid the buzzer beeping - see update_buzzer()     

//#define pin (uint8_t) A0         //buzzer  - uses A0 - no port as it is not addressed  (far-right)
const unsigned int soil_1_frequency      = 2700;     
const unsigned int soil_2_frequency      = 3000;
const unsigned int lux_level_frequency   = 3300;
unsigned int   frequency;          //frequency choice from above
const unsigned long duration = 200;//tone duration

//  ------------------------------------------------------------
//  Simple templated averaging class based on Running Average 
//  by Rob Tillaart:
//  ------------------------------------------------------------

template <const unsigned int N>
class RunningAverageFloat
    void addValue(float val) 
      _ar[_index] = val;
      if (_index == N) _index = 0;
    void fillValue(float val) 
      for (unsigned int i = 0; i < N; i++)_ar[i] = val;
    float getAverage() 
      float sum = 0.0;
      for (unsigned int i = 0; i < N; i++)sum += _ar[i];
      return sum / (float)N;
    int _index = 0;
    float _ar[N];

RunningAverageFloat<35> moistureAverage;
RunningAverageFloat<35> temperatureAverage;
RunningAverageFloat<35> luxAverage;


void setup() 
  display.begin();                //OLED settings
  display.setFlip(false);        //flip the OLED display                          
//  display.setFont(liberationSans_10ptFontInfo);
//  display.setFont(liberationSans_14ptFontInfo);
//  display.setFont(liberationSans_16ptFontInfo);
//  display.setFont(liberationSansNarrow_8ptFontInfo);
//  display.setFont(liberationSansNarrow_10ptFontInfo);
//  display.setFont(liberationSansNarrow_12ptFontInfo);
//  display.setFont(liberationSansNarrow_14ptFontInfo);
//  display.setFont(liberationSansNarrow_16ptFontInfo);
//  display.setFont(liberationSansNarrow_22ptFontInfo);

  Wireling.begin();               // Enable power & select port
  delay(200);                     // boot sensor

                                  //fillValue on light and moisture sensors



  SerialUSB.begin(9600);          //set the serial USB port to 9600 baud
  rtc.begin();                    //initialize RTC

  hours   = rtc.getHours();       // Get the time
  minutes = rtc.getMinutes();
  seconds = rtc.getSeconds();

  display.clearScreen();          //clear the entire screen
  clear_lux_plot_area();          //and the lux plot area
                                  //plus draw a white rectangle around it
  clear_lux_array();              //and clear the lux array that contains data for it

  lux_top_plot_level  = lux_top_plot_level_min; //can be adjusted in set_lux_limit() 

  button_set_flag     = 0;        //clear the button flags
  button_clr_flag     = 0;
  button_plus_flag    = 0;
  button_minus_flag   = 0;

  soil_1_moisture_limit = 35;     //buzzer below this value - can be changed in set_limits()
  soil_2_moisture_limit = 35;     //buzzer below this value - can be changed in set_limits()

  limit_index         = 0;        //initial state of set_limits() switch case
  buzzer_flag         = 1;        //buzzer is initially ON

  date_time_index     = 0;        //show the time
  lux_array_ptr_last  = 99;       //so lux plot will reset immediately

  mp_lux_array_ptr    = lux_array_ptr_max; //mp stands for "MakerPlot"
                                  //this ensures that mp_lux_array_ptr will start at lux_array_ptr_min
                                  //see output_serial_data() for details

  initialize_lux_plot_area();     //initialize the lux plot area
  update_lux_plot_area();         //update the lux plot area

  loop_time_increment = 250;      //250 milliseconds per loop
  loop_time           = millis(); //initial loop_time before we begin the loop (next)  


void loop() 
    while (millis() < loop_time + loop_time_increment)
      //   //wait until loop_time_increment has elapsed before going on
     loop_time = millis();       //re-initialize loop_time  
//  IMPORTANT!.................................................
//    Keep functions below in the order as they are now
//  IMPORTANT!.................................................

  get_measurements();       //get soil moisture and light level values
  update_plot_area();       //update plot area     
  update_buttons();         //update button conditions
  set_time();               //set and display the time  
  set_limits();             //set soil moisture and light threshold limits
  update_buzzer();          //update buzzer                           
  output_serial_data();     //output serial data via USB port to MakerPlot software
///  debug();                  //-----------remove----------     

Post-Upload Setup

The four buttons on the sides of the TinyScreen+ can be used to adjust the time, soil moisture thresholds, lux range, and buzzer operation.

Setting the Time

The first thing you want to do after you turn your unit ON is to set the time. And for this you have two choices: AM/PM or 24-hour time. While the unit has a battery it’s not a dedicated battery backup for the clock, so you’ll need to do this every time you turn it ON. It’s simple so here’s what to do...

  • Setting starts with choosing AM, PM or 24hr format
  • Push the Top Right button and AM is seen blinking
  • If you want AM then push the Top Right Button again to advance to hours
  • Otherwise, push either the Top Left(+) or Bottom Left (-) button to select PM or 24 as below...
  • Push the Top Right button again. The AM/PM/24 are stored, and the hours blink once a second
  • Use the Top Left (+) or Bottom Left (-) buttons to adjust the hour if necessary
  • Push the Top Right button again. Hours are stored and the minutes blink once a second
  • Use the Top Left (+) or Bottom Left (-) buttons to adjust the minutes if necessary
  • Push the Top Right button again. Minutes are stored and seconds blink once a second
  • Use the Top Left (+) or Bottom Left (-) buttons to adjust the seconds if necessary
  • Push the Top Right button again. The seconds value is stored
  • Finally, push the Top Right button again and the time display will “flash” indicating that it’s set
  • If you made a mistake, then simply repeat the procedure

Changing Soil Moisture Threshold and Lux Range

  • Push the Bottom Right button anda red rectangle begins flashing in thesoil moisture #1icon
  • Use the Top Left (+) or Bottom Left (-) buttons to adjust the white line up to 80% or down to 20% or just leave it alone if you want it there.

  • Push the Bottom Right button again and a red rectangle begins flashing in the soil moisture #2 icon

  • Use the Top Left (+) or Bottom Left (-) buttons to adjust the white line up to 80% or down to 20% or just leave it alone if you want it there.

  • Push the Bottom Right button a third time and a red rectangle begins flashing around the LUX plot area–the rectangle in the middle.

  • Push the Top Left(+) or Bottom Left (-) buttons to adjust the lux plot range setting (the number in the upper-left corner) to match the level of LUX you desire. The plot will adjust with every push of the + or – buttons and the lux range will change by 10 each time -- up or down -- here we set it to 10.
  • Finally, push the Bottom Right button to escape this mode as shown here
  • In any of the above cases you can just wait 10 seconds and the flashing red rectangles will disappear. When this happens, the mode is canceled.

Turning the Buzzer Off

The buzzer sounds between 4 PM and 5 PM, once every 10 seconds, to alert you to the following: If either one of the soil moisture levels are below minimums, i.e., below the white line, the buzzer will sound. Also, if the total LUX value for the day is below what it should be the buzzer will also sound. * One beep at 2700 Hz for soil moisture #1 * Two beeps at 3000 Hz for soil moisture #2 * Three beeps at 3300 Hz for low LUX levels

To turn the buzzer off...

  • Push the Bottom Right button once

The buzzer will remain off until the following day between 4PM and 5PM and will remain permanently off if the soil or light conditions are fixed before then.


Contact Us

If you have any questions or feedback, feel free to email us or make a post on our forum. Show us what you make by tagging @TinyCircuits on Instagram, Twitter, or Facebook so we can feature it.

Thanks for making with us!