updated code and hardware for clog detection and defrost

AulaStud_fridge_compressor_timer_controller.ino

@@ -1,24 +1,45 @@
 // Hi! Barb here: this is a quick and dirty implementation of a refrigeration compressor + evaporator fan(s) controller.
-// I wrote this code to run it on an attiny45 that I was able to solder on the back of a 5V relay inside the refrigerator's
+// I wrote this code to run it on an arduino nano 168 (previously: attiny45) that I was able to solder on the back of a 5V relay inside the refrigerator's
 // control panel. This code relies on an external thermostat already doing its work and is not meant to manage internal
 // temperature. It is written to make sure the compressor can get a minimum rest-time between cycles as to not overheat.
-// This relay and attiny are connected in series with the main thermost's relay, so that they only function when it's calling.
-// With this in mind, we assume the thermostat has just called for cooling every time the attiny is booted and leave the
+// This relay and microcontroller are connected in series with the main thermost's relay, so that they only function when it's calling.
+// With this in mind, we assume the thermostat has just called for cooling every time the arduino is booted and leave the
 // compressor running. After a set period of s (timerMAX) the compressor is switched off.
 // In order to aid thermal transfer and maximize COP while using butane as refrigerant, the system needs to have a higher
 // average temperature. Due to this reason, a fan is fitted between the fridge and freezer compartments to move air between
 // the two. The fan is turned on after fanStartDelay to prevent rapid heating of the freezer and turned back on when the
 // timer hits fanStopAdvance to allow for further freezer sub-cooling.
 
-// Last updated: 05/03/24
+// updated: 05/03/24
+// notes: tweaked timing and added fan startup delay + anticipated shut-off
+
+// updated: 02/07/24
+// notes: added temperature-based clog detection and provision for reversing valve
+
+// updated: 04/07/24
+// notes: moved from attiny45 to arduino nano to increase memory and serial port
+
+#include <OneWire.h>
+#include <DallasTemperature.h>
 
 bool disable = 0;               // bool to store compressor disable status
 int timer = 0;                  // active countdown timer, between timerMax and 0
 const int timerMAX = 1500;      // (countdown in seconds)
-int relayPin = 0;               // compressor relay output pin (active LOW)
-int fanPin = 1;                 // fan MOSFET output pin (active HIGH)
+const int relayPin = 3;         // compressor relay output pin (active LOW)
+const int fanPin = 2;           // fan MOSFET output pin (active HIGH)
+const int alertLED = 4;         // Defrost ongoing warning LED
+const int SENSOR = 5;           // digital Input connected to DS18B20 sensor's DQ pin, used to detect clogs in refrigeration cycle
+//const int RValve = 3;           // Reversing Valve relay output (relay N.O.; valve normally not reversed)
 const int fanStartDelay = 60;   // fan turn-on delay in seconds
 const int fanStopAdvance = 30;  // fan turn-off advance in seconds (before the compressor stops, allows to sub-cool the freezer)
+const int checkTimeDelay = 300; // after this amount of seconds we start checking condenser temperature
+const int delayTime = 750;      // cycle delay in ms (should be 1s, but we need to correct for computing time)
+
+OneWire oneWire(SENSOR);              // setup a oneWire instance
+DallasTemperature sensors(&oneWire);  // pass oneWire to DallasTemperature library
+
+float temperature = 0;          // var to store temperature in Celsius
+int minTemp = 35;               // hot gas low-temp limit in celcius (indicative of clog!) usually 40 to 45C when actively running
 
 void setup() {
   // put your setup code here, to run once:
@@ -26,53 +47,108 @@ void setup() {
   // firstly, we initialize the needed outputs
   pinMode(relayPin, OUTPUT);
   pinMode(fanPin, OUTPUT);
+  pinMode(alertLED, OUTPUT);
+  //pinMode(RValve, OUTPUT);
   // then we set them low to keep the compressor on and the fans off at boot
+  // the reversing valve is in the non-reversed position by default
   digitalWrite(relayPin, LOW);
   digitalWrite(fanPin, LOW);
+  digitalWrite(alertLED, LOW);
+  //digitalWrite(RValve, LOW);
+
+  // initialize serial
+  Serial.begin(9600);
+  Serial.println("serial initialized");
+  
+  // initialize the dallas temperature sensor
+  sensors.begin();
+  Serial.println("condenser temperature sensor initialized");
+  Serial.println("minimum condenser temperature:");
+  Serial.println(minTemp);
+
   // lastly, we set the timer at maximum so that the loop starts counting down
   timer = timerMAX;
 }
 
 void loop() {
   // put your main code here, to run repeatedly:
-
+  Serial.print("timer: ");
+  Serial.println(timer);
+  Serial.print("compressor status: ");
+  if (disable == 0){
+    Serial.println("ON");
+  }
+  else {
+    Serial.println("OFF");
+  }
+  sensors.requestTemperatures();                      // send command to get temperatures
+  temperature = sensors.getTempCByIndex(0);           // read temperature in Celsius
+  Serial.print("condenser temperature: ");
+  Serial.println(temperature);
+  
   // fan control logic:
   // only enable fans after the compressor has been running for a while
   if (timer == (timerMAX - fanStartDelay) && disable == 0) {
     // enable fan(s) after set delay if the compressor is not disabled
     digitalWrite(fanPin, HIGH);
+    Serial.println("fans enabled");
   }
   else if (timer == fanStopAdvance && disable == 0) {
     // disable when we are about to stop the compressor
     digitalWrite(fanPin, LOW);
+    Serial.println("fans disabled");
   }
   else {
     // do nothing
   }
 
+  // detect clogs by reading condenser temperature and automatically defrost to fix them
+  if (timer < (timerMAX - checkTimeDelay) && temperature < minTemp && disable == 0) {
+    digitalWrite(fanPin, HIGH); // keep fans on to defrost and prevent thermostat from satsfying
+    digitalWrite(alertLED, HIGH); // turn on an LED on front panel to warn of current defrost
+    digitalWrite(relayPin, HIGH); // compressor off
+    Serial.println("clog detected! requesting defrost...");
+    Serial.println("compressor off, fans on");
+    timer = timerMAX;
+    while (timer > 0) {
+      timer = timer - 5;
+      Serial.println("counting down, defrost");
+      Serial.print("timer: ");
+      Serial.println(timer);
+      delay (1000);
+    }
+    timer = 0; // zero the timer so that we immediately go into an off cycle
+  }
+
   // compressor control logic
   if (timer > 0 && disable == 0) {
     // when compressor is active, countdown moves at 1s/cycle
     timer--;
+    digitalWrite(relayPin, LOW);
   }
   
   else if (timer > 0 && disable == 1) {
     // when compressor is off, countdown moves at (1/5)s/cycle (5 times faster!)
     timer = timer - 5;
+    digitalWrite(relayPin, HIGH);
   }
   
   else if (timer == 0) {
     // reset countdown timer to max once 0 is reached
+    Serial.println("countdown complete, resetting timer");
     timer = timerMAX;
     
     // relay control logic: warning! LOW = active!
     if (disable == 0) {
       disable = 1;
+      Serial.println("disabled");
       digitalWrite(relayPin, HIGH);
     }
     else if (disable == 1) {
       disable = 0;
-      digitalWrite(relayPin, LOW);
+      Serial.println("enabled");
+      digitalWrite(relayPin, LOW);  // turn compressor on at end of off cycle
+      digitalWrite(fanPin, LOW);    // turn fans off at end of off cycle (in case defrost was triggered)
     }
   }
   
@@ -81,9 +157,10 @@ void loop() {
     timer = 0;
     disable = 0;
     digitalWrite(fanPin, LOW);
+    Serial.println("error detected, fans & compressor disabled");
   }
   
   // now wait 1s so that we can roughly count time using the timer variable
   // this is a stopping delay, kinda bad, but we don't have any inputs, hence it shouldn't matter!
-  delay(1000);
+  delay(delayTime);
 }

README.md

@@ -4,4 +4,13 @@ Questo controller è montato DOPO il termostato, in modo da impostare dei limiti
 
 UPDATE 03/'24:
 Ho aggiunto un delay di 60s all'accensione delle ventole per permettere al freezer di pre-raffreddarsi e poi uno spegnimento delle stesse 30s prima del compressore per far calare ulteriormente la temperatura nel comparto freezer.
-Ho aumentato il tempo totale di accensione a 1500s (25'), portando il tempo di spegnimento forzato a 1/5 (5' con l'impostazione corrente)
+Ho aumentato il tempo totale di accensione a 1500s (25'), portando il tempo di spegnimento forzato a 1/5 (5' con l'impostazione corrente)
+
+// updated: 05/03/24
+// notes: tweaked timing and added fan startup delay + anticipated shut-off
+
+// updated: 02/07/24
+// notes: added temperature-based clog detection and provision for reversing valve
+
+// updated: 04/07/24
+// notes: moved from attiny45 to arduino nano 168 to increase memory and serial port