The Perfect Pepper ! Arduino based Seed Growing Environment Monitoring Systems

6 May 2025

The project Inspiration:

I usually purchase pre grown seedlings for my deck garden, having tried growing plants from seed with minimal success.

This year I swung for the fence, built a project I've put off for a few years, a monitored growing system to germinate seeds and develop robust seedlings.

Hot peppers are often the focus of my garden because they are expensive at the store, if you can even find the varieties I look for. One favorite is Thai pepper.

This year's compulsion is to grow Aji Charapita and Aji lemon drop peppers. These are Peruvian varieties that can cost $17 a pound, if you can find them.

Once harvested, these peppers will be used in making unique recipes like venison chili, lamb chili, etc... frozen and pickled for fall and winter tailgating.

Great thanks to prior E14 shopping carts & webinar prizes for providing me a generous stash of controllers and sensors to have on hand. Some sensors that have been in my stash for years.

Research into growing the Perfect Pepper Seedings: https://peppergeek.com/germinate-peppers-seeds-fast/

Temperature is potentially the most important factor in successful seed germination,

Pepper seeds will germinate best when the soil is between 80-90°F (27-32°C).

Seed heating mat underneath propagation tray. Make sure to choose a mat that has a thermostat! otherwise, the mat will be on constantly, potentially over-heating the soil.

After your pepper seedlings are about 2-3 weeks old (after sprouting), they should be ready to move up to a larger pot.

https://www.outdoorapothecary.com/how-to-grow-pepper-plants-from-seeds/

Grow Lights – Peppers need 14-16 hours of bright light daily to grow strong and prevent legginess, use full-spectrum LED grow lights, positioning them 2-3 inches above the seedlings and adjusting the height as they grow. Keep the soil evenly damp but avoid overwatering.

Maintain Proper Temperature After germination, peppers grow best in daytime temperatures around 70-75°F and slightly cooler nights around 60-65°F.

Putting Plans to Action:

Keeping in line with the online advice to grow the Perfect Pepper from seed, my Grow System has 2 boxes:

one for seeds to germinate , and a second seedling box for development and hardening.

A heating mat isnt needed if the temperature at the plant pot base is kept to 70 degrees or so.

Material List (BOM) for both Germination Box and Development Box Arduino based monitoring systems

Qty 2 Arduino Nano , Also experimented using an Arduino Minima
Qty 2 49” OLED Display Module 64 X 32 Pixel SSD1315 I2C Mono Display as the HMI, one for each box
DHT11 & DHT22 humdity & temp sensors
Qty 15 MCP9700A-TO temperature sensors
Qty 2, 12V 1A wall wart power supplies
Parted out from an old server - 40x40x20mm Fan DF124020BH -Air Flow: 10.28 CFM. Speed: 9,000 RPM.Noise Level: <32 dBA.
5V Piezo buzzer
Flashing white LED + 1 K resistor

Getting right to the build,

This is the germination box in action video

https://youtu.be/0L-iM-O9sRQ

The Germination Box Monitoring System Schematics:

The is the Development Box Monioring System in action video.

https://youtu.be/oh0PZ_kW7sA

The is the Development Box Monioring System schematics:

Build history and lessons learned

Start with the Arduino Nano & MCP9700As -

1^st surprise – MCP9700A thermal sensor is the -40C to 125C model. So…….-40 is 0V and 125C=5V ?

NO !!! 0C is ~ 500mV and 125C =~ 1.7V

My desired measurement range is 5C to 45C or so……500mV to 1Vdc on the Arduino Analog input.

It is important to read the components datasheet first !

Accuracy:

Optimized for Analog-to-Digital Converters (ADCs):

- 10.0 mV/°C (typical) (MCP9700/9700A/

9700B)TA = -40°C to +125°C TACY -2.0 ±1 +2.0 °C MCP9700A

2^nd shocking surprise - with 5V = 1023 counts on the analog inputs , resolution is ~ 50 mV per count, 0C =~counts 50C ~ 200 counts a too touchy on the resolution , my spiderman senses tingle, this will not do. Lets make the resolution counts better.

3^rd surprise – increase analog input count resolution - setup the Arduino Nano to use the analog internal reference for 1 PU 1023 counts = ~ 1.5V. After a lot of measurements, offset measurements, and scale factor fudging discovered the real 1 PU volts is ~ 1.4V. Its a much better match for the range of MCP9700As useage.

4^th surprise – Tried using the Arduino Minima which can be configured for a 14 bit analog, 1 PU = 16383 counts. Much better accuracy, but doesn’t perform any better for this application. Using the analog reference , the count range for 500mV – 1V is much better, but doesn’t add any true value this project having +- 1 degree F is more than plenty accuracy.

5^th surprise – Added DHT22 humidity sensor to hardening box, expected it to mostly read ambient room humidity, which it did, unless the plants had just been watered. Adding DHT11 to the germination box, discovered the small stirring fan made a huge difference in humidity, it tended to dry out the internal air as this box was more sealed to hold in the lamp heat.

6^th surprise – Some MCP9700A leads weren’t completely covered with heat shrink tube or hot glue. Those sensors started to give bad readings and one failed. The combination of moisture and fertilized soil helped those leads corrode pretty quickly. Removing the corrosion brought the readings back on some, but one sensor had a lead totally eaten thru and broke off.

7th Gotcha - Temperature readings skyrocket when a thermistor lead opens. Some of the wiring had extra slack, wire loops dangled from the Germination Box and the table where the box sat. The temptation was too much for my furry friends. They had to snack on the yummy light gauge wire of the thermistors. I had to get more serious with the tyraps and not leave room on the table top lest they be tempted to play and chew on more thermistor wires.

8th Challenge - the temperatures displayed seemed noisy. The sensors have a relatively long time constant but were still subject to air breezes and drafts. To help stabilze the readings, 5 temperature reading samples, 600 msecs apart, were saved to an array then averaged to act as an averaging filter. That technique helped. The temperature variations in the Development box are OK for started seedlings, so the averaging was only done in the Germination Box Monitor System.

9th unexpected Event – the stirring fan mounting failed, the fan sat on the box floor, the lamps temperature reached 44C – enough concern to add a high temperature alarm for the system.

Added a flashing alarm LED and audible buzzer , and a silence pushbutton, to ensure a temperature alarm would be noticed. Adding alarm annunciation messages on the OLED screen caused the 10^th surprise.

10^th surprise – OLED SSD1315 screen limit. Had to remove a couple redundant print to OLED screens to alleviate this fault. It also crashed the Arduino.

Photos of the Germination Box Monitor Screens:

Photos of the Development Box Monitor Screens:

The Germination Box Monitor Code:

// this code is for the nano !!
// MCP9700AETO is an analog device whose output varies linear with temp -40C to 125C 
// -40C = ~ .2V    0 C ~ .5V   20C ~ .8V   50C ~ 1.4V   62.8 C per V    .628C per mV
// analogRead input natively has 5V = 1023 counts, 53.8 mV per count 
// using analogReference = internal, can change the 1PU on the analog to 1.1V !!!!so we shall

// MCP temperature transfer function Vout = Tcoefficient*Temperature + Vout@0C
// Vout@0C == 500mV   Tcoefficient = 10mV per degree C
// transfer function  (Vout-500mV)/10mV = Temperature C  

// https://randomnerdtutorials.com/guide-for-oled-display-with-arduino/
// A4 & A5 are reserved for the SSD1306 screen  A4(SDA), A5(SCL)

// this version takes 5 readings 1 sec apart, then averages
// Axcounts VAR becomes an array  remember the first element location is 0

// DHT11 was added in this version to allow the germination box to be used later a development-hardening box
// https://arduinogetstarted.com/tutorials/arduino-dht11
// 
 
int A0counts[]={0,0,0,0,0};
int A1counts[]={0,0,0,0,0};
int A2counts[]={0,0,0,0,0};
int A3counts[]={0,0,0,0,0};
int A6counts[]={0,0,0,0,0};

float A0countsAve=0; // calc the average of 5 readings
float A1countsAve=0; 
float A2countsAve=0; 
float A3countsAve=0; 
float A6countsAve=0; 


float A0millivolts =0;
float A1millivolts =0;
float A2millivolts =0;
float A3millivolts =0;
float A6millivolts =0;

int A0_TC; 
int A0_TF;
int A1_TC;
int A1_TF;
int A2_TF;
int A2_TC; 
int A3_TF;
int A3_TC; 
int A6_TC; 
int A6_TF;

int AnalogSampleInterval=600;

int ScreenOnTime=3000;
int ScreenClearDelay=250;
int TempAlarmThreshold=115; 

int HiTemperatureAlarm=LOW;
int ResetTempAlarmPB=HIGH;
int AlarmBuzzer=LOW;

int StirFanRelayOn = LOW; // preset Fan relay state
float StirFanOnTempThr = 96.0; // when stir fan turns on from A3 TC
float StirFanOffTempThr = 75.0; // when stir fan turns off from A2 TC

int A0_0C_offset = -5;// mV offset measured at 0C 
int A1_0C_offset = -10;// mV offset measured at 0C 
int A2_0C_offset = -5;// mV offset measured at 0C 
int A3_0C_offset = 0;// mV offset measured at 0C 
int A6_0C_offset = 0;// mV offset measured at 0C 

float DHT11_humidity=0; 


#include <SPI.h>
#include <Wire.h>
#include <Adafruit_GFX.h>
#include <Adafruit_SSD1306.h>

#define SCREEN_WIDTH 128 // OLED display width, in pixels
#define SCREEN_HEIGHT 64 // OLED display height, in pixels

// Declaration for an SSD1306 display connected to I2C (SDA, SCL pins)
#define OLED_RESET     -1 // Reset pin # (or -1 if sharing Arduino reset pin)
Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, OLED_RESET);

#include "DHT.h"
#define DHT11_PIN 2
DHT dht11(DHT11_PIN, DHT11);


void setup() 
{
 analogReference(INTERNAL);
  pinMode(A0, INPUT); //thermocouple 1
  pinMode(A1, INPUT); //thermocouple 2
  pinMode(A2, INPUT); //thermocouple 3
  pinMode(A3, INPUT); //thermocouple 4 
  pinMode(A6, INPUT); //thermocouple 6
  pinMode(4,OUTPUT); // stir fan relay 
  pinMode(8,INPUT_PULLUP); // reset alarm PB
  pinMode(9,OUTPUT); // alarm buzzer
  pinMode (13,OUTPUT); // D13 LED is the alarm light

 dht11.begin(); // initialize the sensor

 
  Serial.begin(115200); // serial monitor for troubleshooting

if(!display.begin(SSD1306_SWITCHCAPVCC, 0x3C)) { // Address 0x3D for 128x64
    Serial.println(F("SSD1306 allocation failed"));
    for(;;);
    }
  delay(2000);
  display.clearDisplay();
  display.setTextSize(2);
  display.setTextColor(WHITE);
  display.setCursor(0, 10);
  // Display static text
  display.println("Boot Up");
  display.println("Screen");
  display.println();//blank the 3rd line
  display.display(); 
  delay(3000);
// remove screen for troubleshooting allocation
//  display.clearDisplay();
//  display.setTextSize(2);
//  display.setTextColor(WHITE);
 // display.setCursor(0, 10);
  // Display static text
//  display.println("  wait to");
//  display.println("stabilize");
//  display.println("   TCs");
//  display.println();//blank the 3rd line
//  display.display(); 
//  delay(3000);
   
}

    
void loop() {

/////////// DHT11 stuff ////////////////////
  float DHT11_humidity= dht11.readHumidity();
  // read temperature as Celsius
  float DHT11tempC = dht11.readTemperature();
  // read temperature as Fahrenheit
  float DHT11tempF = dht11.readTemperature(true);

// check if any reads failed
  if (isnan(DHT11_humidity) || isnan(DHT11tempC) || isnan(DHT11tempF)) {
    Serial.println("Failed to read from DHT11 sensor!");
  }
          display.clearDisplay();    
          delay(ScreenClearDelay);
          display.setCursor(0, 10);
        // Display static text
        display.println("Humidity");
        display.println("   %");
        display.println(DHT11_humidity);
        display.display(); 
       delay(ScreenOnTime);// for reading display


         display.clearDisplay();    
          delay(ScreenClearDelay);
          display.setCursor(0, 10);
        // Display static text
        display.println(" DHT11");
        display.println("temp F=");
        display.println(DHT11tempF);
        display.display(); 
       delay(ScreenOnTime);// for reading display




/// read input thermistors 
  
delay (100); // thermisters have a 500ms time constant, no rush
   
      ///  read A0 5 times
       for (int i = 0; i <= 4; i++) 
           {
             delay (10);
             A0counts[i]= (analogRead(A0)+ A0_0C_offset);  // read the input pin
            // Serial.println("A0 cnts value =");
            // Serial.println(i);
           //  Serial.println(A0counts[i]);
            delay(AnalogSampleInterval);
            }
       // calculate the average A0readings
       A0countsAve = ((A0counts[0]+A0counts[1]+A0counts[2]+A0counts[3]+A0counts[4])/5.0);
      
        //A0counts= (analogRead(A0)+ A0_0C_offset);  // read the input pin
          //delay(500);
         // Serial.println("A0 cnts value =");
         // Serial.println(A0countsAve);
          // calculate inputs volts 
      
      A0millivolts=((A0countsAve*1060.0)/1023.0);//  
           // Serial.println("A0 millivolts =");
           // Serial.println(A0millivolts);
            //delay(1000); //for reading
            // transfer function  (Vout-500mV)/10mV = Temperature C  
      A0_TC=((A0millivolts-500)/(10));
            //Serial.println("A0 temperature C =");
             //Serial.println(A0_TC);
            //delay(1000); //for reading
      A0_TF=(((A0_TC*9)/(5))+32 );
            //      Serial.println("A0 temperature F =");
            //    Serial.println(A0_TF);
          // delay(100); //for reading monitor
          display.clearDisplay();    
          delay(ScreenClearDelay);
          display.setCursor(0, 10);
        // Display static text
        display.println("A0 Bottom");
        display.println("Temp F =");
        display.println(A0_TF);
        display.display(); 
       delay(ScreenOnTime);// for reading display
      

 /////////  read A1 5 times ****************************
       for (int i = 0; i <= 4; i++) 
           {
             delay (10);
             A1counts[i]= (analogRead(A1)+ A1_0C_offset);  // read the input pin
            // Serial.println("A1 cnts value =");
            // Serial.println(i);
            // Serial.println(A1counts[i]);
            delay(AnalogSampleInterval);
            }
       // calculate the average A0readings
       A1countsAve = ((A1counts[0]+A1counts[1]+A1counts[2]+A1counts[3]+A1counts[4])/5.0);
        
      //A1counts= (analogRead(A1)+A1_0C_offset);  // read the input pin
      delay(200);
      //Serial.println("A1 value =");
      //Serial.println(A1countsAve);
      A1millivolts=((A1countsAve*1060.0)/1023.0);//  
      A1_TC=((A1millivolts-500)/(10));
      A1_TF=(((A1_TC*9)/(5))+32 );
 //     Serial.println("A1 temperature F =");
  //    Serial.println(A1_TF);
      display.clearDisplay();    
      delay(ScreenClearDelay);
    display.setCursor(0, 10);
  // Display static text
  display.println("A1 Surface");
  display.println("Temp F =");
  display.println(A1_TF);
  display.display(); 
      delay(ScreenOnTime); //for reading display


       ///  read A2 5 times
       for (int i = 0; i <= 4; i++) 
           {
             delay (10);
             A2counts[i]= (analogRead(A2)+ A2_0C_offset);  // read the input pin
             //Serial.println("A2 cnts value =");
            // Serial.println(i);
            // Serial.println(A2counts[i]);
            delay(AnalogSampleInterval);
            }
       // calculate the average A0readings
       A2countsAve = ((A2counts[0]+A2counts[1]+A2counts[2]+A2counts[3]+A2counts[4])/5.0);
               
              //A2counts= (analogRead(A2)+ A2_0C_offset);  // read the input pin
      delay(ScreenClearDelay);
            //Serial.println("A2 value =");
            //Serial.println(A2counts);
      A2millivolts=((A2countsAve*1050.0)/1023.0);// 1050 is measured from PS
      A2_TC=((A2millivolts-500)/(10));
      A2_TF=(((A2_TC*9)/(5))+32 );
      //Serial.println("A2 temperature F =");
      //Serial.println(A2_TF);
      // delay(100); //for 
    display.clearDisplay();    
    delay(500);
    display.setCursor(0, 10);
  // Display static text
  display.println("A2 Ambient");
  display.println("Temp F =");
  display.println(A2_TF);
  display.display(); 
        delay(ScreenOnTime); //for reading display

  if ((A2_TF < StirFanOffTempThr )&&(StirFanRelayOn==HIGH))
                    { digitalWrite(4,LOW);
                    StirFanRelayOn=LOW; 
                        display.clearDisplay();    
                  delay(ScreenClearDelay);
                  display.setCursor(0, 10);
                // Display static text
                display.println("STIR FAN");
                display.println("OFF");
               // display.println(A3_TF);
                display.display(); 
                delay(ScreenOnTime); //for reading display
                 }

////////////// A3 section /////////////////////
       ///  read A3 5 times
       for (int i = 0; i <= 4; i++) 
           {
             delay (10);
             A3counts[i]= (analogRead(A3)+ A3_0C_offset);  // read the input pin
             //Serial.println("A3 cnts value =");
            // Serial.println(i);
             //Serial.println(A3counts[i]);
            delay(AnalogSampleInterval);
            }
       // calculate the average A0readings
       A3countsAve = ((A3counts[0]+A3counts[1]+A3counts[2]+A3counts[3]+A3counts[4])/5.0);
                   ///A3counts= (analogRead(A3)+ A0_0C_offset);  // read the input pin
      delay(200);
      //Serial.println("A3 value =");
      //Serial.println(A3counts);
      A3millivolts=((A3countsAve*1050.0)/1023.0);// 1.05V==1023 counts 
      A3_TC=((A3millivolts-500)/(10));
      A3_TF=(((A3_TC*9)/(5))+32 );
      //Serial.println("A3 temperature F =");
      //serial.println(A3_TF);
      // delay(100); //for 
    display.clearDisplay();    
    delay(ScreenClearDelay);
    display.setCursor(0, 10);
  // Display static text
  display.println("A3 Lamp");
  display.println("Temp F =");
  display.println(A3_TF);
  display.display(); 
  delay(ScreenOnTime); //for reading display

  if ((A3_TF > StirFanOnTempThr )&& (StirFanRelayOn==LOW))
      { digitalWrite(4,HIGH); 
       StirFanRelayOn=HIGH; 
       display.clearDisplay();    
    delay(ScreenClearDelay);
    display.setCursor(0, 10);  // Display static text
  display.println("Stir Fan");
  display.println("RUNNING");
 // display.println(A3_TF);
  display.display(); 
  delay(ScreenOnTime); //for reading display
      }

  //////////////// A6 counts //////////////

             ///  read A6 5 times
       for (int i = 0; i <= 4; i++) 
           {
             delay (10);
             A6counts[i]= (analogRead(A6)+ A1_0C_offset);  // read the input pin
             //Serial.println("A6 cnts value =");
             //Serial.println(i);
             //Serial.println(A6counts[i]);
            delay(AnalogSampleInterval);
            }
       // calculate the average A6readings
       A6countsAve = ((A6counts[0]+A6counts[1]+A6counts[2]+A6counts[3]+A6counts[4])/5.0);
            
          ///A6counts= (analogRead(A6)+A6_0C_offset);  // read the input pin
      delay(50);
      //Serial.print("A6 value =");
      //Serial.println(A6counts);
      A6millivolts=((A6countsAve*1050)/1023);//  
      A6_TC=((A6millivolts-500)/(10));
      A6_TF=(((A6_TC*9)/(5))+32 );
      //Serial.println("A6 temperature F =");
      //Serial.println(A6_TF);
      delay(50); //for 

     
            display.clearDisplay();    
          delay(ScreenClearDelay);
          display.setCursor(0, 10);
        // Display static text
        display.println("A6 Lamp");
        display.println("Temp F =");
        display.println(A6_TF);
        display.display(); 
              delay(ScreenOnTime); //for reading display


        if (StirFanRelayOn==HIGH)
            {
              display.clearDisplay();    
              delay(ScreenClearDelay);
              display.setCursor(0, 10);
            // Display static text
            display.println("Stir");
            display.println("Fan is");
            display.println("Running");
            display.display(); 
            delay(ScreenOnTime); //for reading display
            }
            else 
            {
              display.clearDisplay();    
              delay(ScreenClearDelay);
              display.setCursor(0, 10);
            // Display static text
            display.println("Stir Fan");
            display.println("  is   ");
            display.println(" OFF  ");
            display.display(); 
            delay(ScreenOnTime); //for reading display
            }

 ///////////// temp alarm /////////////////////

            if ((A3_TF>TempAlarmThreshold)||(A6_TF>TempAlarmThreshold))
              {
                HiTemperatureAlarm=HIGH;
                ///// annunciate on screen  
               // tone(9,1000); 
              display.clearDisplay();    
              delay(ScreenClearDelay);
             display.setCursor(0, 10);
            // Display static text
 //           display.println("WARNING");
 //           display.println("hi temp");
 //           display.println(" alarm   ");
//            display.display(); 
//            delay(ScreenOnTime); //for reading display
            }
            else 
              {
                HiTemperatureAlarm=LOW;
                AlarmBuzzer=LOW;
              }
            digitalWrite(13,HiTemperatureAlarm);
            ResetTempAlarmPB=digitalRead(8);
            if ((HiTemperatureAlarm==HIGH)&&(ResetTempAlarmPB==HIGH)&&(AlarmBuzzer==LOW))
                { 
                  tone(9,950); 
                  AlarmBuzzer=HIGH;
                }
            else
              { noTone(9);
              }
         //    Serial.println("HiTemperatureAlarm =");
         //    Serial.println(HiTemperatureAlarm);
                                       
  
}

The Seedling Development Box Arduino Code:

//
//
// this code is for the nano !! The Seedling Development/Hardening Box
// MCP9700AETO is an analog device whose output varies linear with temp -40C to 125C 
// -40C = ~ .2V    0 C ~ .5V   20C ~ .8V   50C ~ 1.4V   
// analogRead input natively has 5V = 1023 counts, 53.8 mV per count 
// using analogReference = internal, can change the 1PU on the analog to ~1.1V  we shall

// MCP temperature transfer function Vout = Tcoefficient*Temperature + Vout@0C
// Vout@0C == 500mV   Tcoefficient = 10mV per degree C
// transfer function  (Vout-500mV)/10mV = Temperature C  

// https://randomnerdtutorials.com/guide-for-oled-display-with-arduino/
// A4 & A5 are reserved for the SSD1306 screen  A4(SDA), A5(SCL)
//
// https://www.electroschematics.com/arduino-dht22-am2302-tutorial-library/

#include "DHT.h"

#define DHTPIN 2     // what pin we're connected to
#define DHTTYPE DHT22   // DHT 22  (AM2302)
DHT dht(DHTPIN, DHTTYPE);
 
int A0counts=0;
int A1counts=0;
int A2counts=0;
int A3counts=0;
int A6counts=0;

float A0millivolts =0;
float A1millivolts =0;
float A2millivolts =0;
float A3millivolts =0;
float A6millivolts =0;

int A0_TC; 
int A0_TF;
int A1_TC;
int A1_TF;
int A2_TF;
int A2_TC; 
int A3_TF;
int A3_TC; 
int A6_TC; 
int A6_TF;
int DHTtempF; 

int ScreenOnTime=3000;
int ScreenClearDelay=250;

//int StirFanRelayOn = LOW; // preset Fan relay state
//int StirFanRelayOff = HIGH;//preset Fan Relay State
//int StirFanOnTempThr = 90; // when stir fan turns on from A3
//int StirFanOffTempThr = 75; // when stir fan turns off from A2

int A0_0C_offset = -10;// mV offset measured at 0C 
int A1_0C_offset = -1;// mV offset measured at 0C 
int A2_0C_offset = -3;// mV offset measured at 0C 
int A3_0C_offset = -1;// mV offset measured at 0C 
int A6_0C_offset = 0;// mV offset measured at 0C 


#include <SPI.h>
#include <Wire.h>
#include <Adafruit_GFX.h>
#include <Adafruit_SSD1306.h>

#define SCREEN_WIDTH 128 // OLED display width, in pixels
#define SCREEN_HEIGHT 64 // OLED display height, in pixels

// Declaration for an SSD1306 display connected to I2C (SDA, SCL pins)
#define OLED_RESET     -1 // Reset pin # (or -1 if sharing Arduino reset pin)
Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, OLED_RESET);


void setup() 
{
 analogReference(INTERNAL);
  pinMode(A0, INPUT); //thermocouple 1
  pinMode(A1, INPUT); //thermocouple 2
  pinMode(A2, INPUT); //thermocouple 3
  pinMode(A3, INPUT); //thermocouple 4 
  pinMode(A6, INPUT); //thermocouple 6

 dht.begin();
 
  Serial.begin(115200); // serial monitor for troubleshooting

if(!display.begin(SSD1306_SWITCHCAPVCC, 0x3C)) { // Address 0x3D for 128x64
    Serial.println(F("SSD1306 allocation failed"));
    for(;;);
    }
  delay(2000);
  display.clearDisplay();
  display.setTextSize(2);
  display.setTextColor(WHITE);
  display.setCursor(0, 10);
  // Display static text
  display.println("Hardening");
  display.println("  Box ");
    display.println("Monitor");
  display.display(); 
   
}

    
void loop() {

/// read input thermistors 
  
delay (500); // thermisters have a 500ms time constant
      ///// yea, I should make it a loop, easier this way to rework IO if needed
      
      ///  read 
      A0counts= (analogRead(A0)+ A0_0C_offset);  // read the input pin
      //delay(500);
         // Serial.println("A0 cnts value =");
         // Serial.println(A0counts);
          // calculate inputs volts 
      A0millivolts=((A0counts*1060.0)/1023.0);//  
           // Serial.println("A0 millivolts =");
           // Serial.println(A0millivolts);
            //delay(1000); //for reading
            // transfer function  (Vout-500mV)/10mV = Temperature C  
      A0_TC=((A0millivolts-500)/(10));
            //Serial.println("A0 temperature C =");
             //Serial.println(A0_TC);
            //delay(1000); //for reading
      A0_TF=(((A0_TC*9)/(5))+32 );
       //      Serial.println("A0 temperature F =");
       //    Serial.println(A0_TF);
      // delay(100); //for reading monitor
    display.clearDisplay();    
    delay(ScreenClearDelay);
    display.setCursor(0, 10);
  // Display static text
  display.println("A0 Bottom");
  display.println("Temp F =");
  display.println(A0_TF);
  display.display(); 
 delay(ScreenOnTime);// for reading display
      
        
      A1counts= (analogRead(A1)+A1_0C_offset);  // read the input pin
      delay(500);
      //Serial.println("A1 value =");
      //Serial.println(A1counts);
      A1millivolts=((A1counts*1060.0)/1023.0);// yes, introducing a 3.3% error by using 5000 mV/1000 cnts rather than 1023 cnts, so so much cleaner 
      A1_TC=((A1millivolts-500)/(10));
      A1_TF=(((A1_TC*9)/(5))+32 );
 //     Serial.println("A1 temperature F =");
  //    Serial.println(A1_TF);
      display.clearDisplay();    
      delay(ScreenClearDelay);
    display.setCursor(0, 10);
  // Display static text
  display.println("A1 Soil");
  display.println("Temp F =");
  display.println(A1_TF);
  display.display(); 
      delay(ScreenOnTime); //for reading display

       
      A2counts= (analogRead(A2)+ A2_0C_offset);  // read the input pin
      delay(ScreenClearDelay);
      //Serial.println("A2 value =");
      //Serial.println(A2counts);
      A2millivolts=((A2counts*1050.0)/1023.0);// yes, introducing a 3.3% error by using 5000 mV/1000 cnts rather than 1023 cnts, so so much cleaner 
      A2_TC=((A2millivolts-500)/(10));
      A2_TF=(((A2_TC*9)/(5))+32 );
      //Serial.println("A2 temperature F =");
      //Serial.println(A2_TF);
      // delay(100); //for 
    display.clearDisplay();    
    delay(500);
    display.setCursor(0, 10);
  // Display static text
  display.println("A2 Soil");
  display.println("Temp F =");
  display.println(A2_TF);
  display.display(); 
        delay(ScreenOnTime); //for reading display

 // if ((A2_TF < StirFanOffTempThr )&(StirFanRelayOn==HIGH))
 //     { digitalWrite(4,LOW);
 //     StirFanRelayOn=LOW; 
 //         display.clearDisplay();    
//    delay(ScreenClearDelay);
//    display.setCursor(0, 10);
  // Display static text
//  display.println("STIR FAN");
//  display.println("OFF");
 // display.println(A3_TF);
 // display.display(); 
//  delay(ScreenOnTime); //for reading display    
//      }

    
      A3counts= (analogRead(A3)+ A3_0C_offset);  // read the input pin
      delay(500);
      //Serial.println("A3 value =");
      //Serial.println(A3counts);
      A3millivolts=((A3counts*1050.0)/1023.0);// yes, introducing a 3.3% error by using 5000 mV/1000 cnts rather than 1023 cnts, so so much cleaner 
      A3_TC=((A3millivolts-500)/(10));
      A3_TF=(((A3_TC*9)/(5))+32 );
      //Serial.println("A3 temperature F =");
      //serial.println(A3_TF);
      // delay(100); //for 
    display.clearDisplay();    
    delay(ScreenClearDelay);
    display.setCursor(0, 10);
  // Display static text
  display.println("A3 Amb");
  display.println("Temp F =");
  display.println(A3_TF);
  display.display(); 
  delay(ScreenOnTime); //for reading display

//  if ((A3_TF > StirFanOnTempThr )& (StirFanRelayOn==LOW))
//      { digitalWrite(4,HIGH); 
//       StirFanRelayOn=HIGH; 
//       display.clearDisplay();    
//    delay(ScreenClearDelay);
//    display.setCursor(0, 10);
  // Display static text
//  display.println("Stir Fan");
 // display.println("RUNNING");
 // display.println(A3_TF);
 // display.display(); 
//  delay(ScreenOnTime); //for reading display
//      }

  
      
      A6counts= (analogRead(A6)+A6_0C_offset);  // read the input pin
      delay(500);
      //Serial.print("A6 cnts =");
      //Serial.println(A6counts);
      A6millivolts=((A6counts*1050.0)/1023.0);// 
      A6_TC=((A6millivolts-500)/(10));
      A6_TF=(((A6_TC*9)/(5))+32 );
      //Serial.println("A6 temperature F =");
      //Serial.println(A6_TF);
      delay(100); //for 
      display.clearDisplay();    
    delay(ScreenClearDelay);
    display.setCursor(0, 10);
  // Display static text
  display.println("A6 Lamp");
  display.println("Temp F =");
  display.println(A6_TF);
  display.display(); 
        delay(ScreenOnTime); //for reading display

///////////////////////////// DHT22 humidity sensor ////////

// Reading temperature or humidity takes about 250 milliseconds!
  // Sensor readings may also be up to 2 seconds 'old' (its a very slow sensor)
  float DHThumidity = dht.readHumidity();
  // Read temperature as Celsius
  float DHTtemperatureC = dht.readTemperature();//temp is in C 
             Serial.print("Humidity: "); 
            Serial.print(DHThumidity);
            Serial.print(" %\t");
            Serial.print("Temperature: "); 
            Serial.print(DHTtemperatureC);
            Serial.println(" *C ");
  DHTtempF=(((DHTtemperatureC*9)/(5))+32 );
  
  // Check if any reads failed and exit early (to try again).
  if (isnan(DHThumidity) || isnan(DHTtemperatureC)) {
    Serial.println("Failed to read from DHT sensor!");
    return;
  }

      display.clearDisplay();    
    delay(ScreenClearDelay);
    display.setCursor(0, 10);
  // Display static text
  display.println("Humidity");
  display.println("   % ");
  display.println(DHThumidity);
  display.display(); 
        delay(ScreenOnTime); //for reading display
        
      display.clearDisplay();    
    delay(ScreenClearDelay);
    display.setCursor(0, 10);
  // Display static text
  display.println("DHT22");
  display.println("Temp F= ");
  display.println(DHTtempF);
  display.display(); 
        delay(ScreenOnTime); //for reading display


        
}

At the end I had learned new lessons, had a tremendous germination yield of 80% , and have a beautiful pepper garden to look forward to.

Parents

DAB 9 days ago

Great project.

I have always had good luck growing hot peppers from seeds.

Yes Thai peppers are my favorite as well.

Loved to take them to the office and watch the idiots try them.

Unlimited entertainment value.

This year I am trying a hydroponics system to grow herbs.

I have also added cherry tomato and hot pepper seeds.

I had tomato and radish sprouts in 3-4 days.

Everyday I see new sprouts in the containers.

Lots of fun every day.
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DAB 9 days ago

Great project.

I have always had good luck growing hot peppers from seeds.

Yes Thai peppers are my favorite as well.

Loved to take them to the office and watch the idiots try them.

Unlimited entertainment value.

This year I am trying a hydroponics system to grow herbs.

I have also added cherry tomato and hot pepper seeds.

I had tomato and radish sprouts in 3-4 days.

Everyday I see new sprouts in the containers.

Lots of fun every day.
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Children

beacon_dave 9 days ago in reply to DAB

I used to always use 'bird eye' Thai peppers as I found that they tended to gave a consistent heat output and flavour when cooking. But I believe there are many varieties of Thai peppers with different heat ranges so I may have been at the milder end of the scale.

There are some crazy varieties now like 'Pepper X':
https://www.youtube.com/watch?v=hUYtDA7j19c

"Did you invent that pepper ?"
"Yeh"
"why?"

Which made a world record in 2023 at 2,693,000 Scoville Heat Units:
https://www.guinnessworldrecords.com/news/2023/10/pepper-x-dethrones-carolina-reaper-as-worlds-hottest-chilli-pepper-759706

(Thai are only 50,000-100,000 SHU in comparison.)
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DAB 6 days ago in reply to beacon_dave

When it comes to peppers I want flavor, not suicide.

I used to work with some pepper heads who tried to show how manly they were.

I may be crazy, but I am not that stupid.
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robogary 6 days ago in reply to DAB

Aji Charapitas have a solid but not overwhelming kick (about 50,000 scoville heat units, similar to Cayenne or Aji Amarillo), along with a fruity, citrusy flavor.

I also started red marconis which are sweet ish peppers used in Italian dishes.

These are not anywhere near the Carolina Reaper pepper, measures between 1.4–2.2 million Scoville Heat Units (SHU), with the hottest reaching over 2.2 million.

I love thai peppers taste and have even ground them up into ham salad for a kick.
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