kegerator.c.ino

// Code accompanying my blog post on my kegerator setup, found here:
// http://www.dingostick.com/2018/12/kegerator-v10.html

// 1. https://www.pjrc.com/teensy/td_libs_OneWire.html
#include <OneWire.h>

// 2. https://github.com/milesburton/Arduino-Temperature-Control-Library
#include <DallasTemperature.h>

#define LOGGING

// INPUT
const int tempSensor = A3;
OneWire oneWire(tempSensor);
DallasTemperature sensors(&oneWire);

// OUTPUT
// PWM-capable pins for the LEDs 
const int blueLed = 8,
      greenLed = 9,
      redLed = 10;

const int relay = A0;

// SETTINGS
// Stout should be nearer 50°
const float targetTemperatureF = 48.0;

const float upperTempLimitF = targetTemperatureF + 3.0; // Above this temp, relay turns on -> start cooling
const float lowerTempLimitF = targetTemperatureF - 2.0; // Below this temp, relay turns off -> stop cooling

const int loopMsec = 1000 * 5;

// VARIABLES
int relayStatus = 0;


// All the important stuff
void setup() {
   pinMode(blueLed, OUTPUT);
   pinMode(greenLed, OUTPUT);
   pinMode(redLed, OUTPUT);
   pinMode(relay, OUTPUT);
   
   pinMode(tempSensor, INPUT);

   #ifdef LOGGING
     Serial.begin(9600);
     Serial.println("Initializing thermostat");
   #endif

   // start OneWire library
   sensors.begin();
}


void loop() {
   #ifdef LOGGING
     //Serial.println("Requesting temperatures...");
   #endif
   
   // read temperature
   sensors.requestTemperatures();
   float currentTemp = sensors.getTempFByIndex(0);

   #ifdef LOGGING
     Serial.print("Read currentTemp = ");
     Serial.println(currentTemp);
   #endif

   if (currentTemp < -150)
   {
      // The thermistor + OneWire will typically read about -196.60 if not properly wired up.
      // Instead of treating this as a "too cold" reading, give a visual indication that it's bad.
	    // Here, we'll still keep the same delay but will flash alternating red/blue.
      #ifdef LOGGING
        Serial.print("Bad temperature reading (");
        Serial.print(currentTemp);
        Serial.println(")");
      #endif
      for(int i = 0; i < loopMsec; i+= 1000)
      {
         digitalWrite(blueLed, HIGH);
         digitalWrite(redLed, LOW);
         delay(500);
         
         digitalWrite(blueLed, LOW);
         digitalWrite(redLed, HIGH);
         delay(500);
      }
      
      return;
   }
   else if (currentTemp < lowerTempLimitF)
   {
      // too cold. set the blue light
      digitalWrite(redLed, LOW);
      digitalWrite(greenLed, LOW);
      digitalWrite(blueLed, HIGH);

      // and turn off the relay if it's running
      if (relayStatus)
      {
        #ifdef LOGGING
          Serial.println("Turning off the relay");
        #endif
         digitalWrite(relay, LOW);
         relayStatus = 0;
      }
   }
   else if (upperTempLimitF < currentTemp)
   {
      // too warm
      digitalWrite(redLed, HIGH);
      digitalWrite(greenLed, LOW);
      digitalWrite(blueLed, LOW);

      if (!relayStatus)
      {
        #ifdef LOGGING
          Serial.println("Turning on the relay");
        #endif
         digitalWrite(relay, HIGH);
         relayStatus = 1;
      }
   }
   else
   {
      // goldilocks zone. let the relay keep (not) doing its thing for now, but set the LEDs
      digitalWrite(redLed, LOW);
      digitalWrite(greenLed, HIGH);
      digitalWrite(blueLed, LOW);
   }

   delay(loopMsec);
}