temperature control improvements

PyCoffeeNano/PyCoffeeNano.ino

@@ -27,6 +27,7 @@ const int milliseconds = 10;
 int timeratio = 1;
 // pumpRatio is = seconds to pump water for and will be updated over serial
 int pumpRatio = 15; // warning: there is usually ~5s dead time from pump startup to water flowing out of nozzle
+int pumpStatus = 0; // support variable to enable pumping while heating, added feb 24
 // This next variable is used to get current "time" in ms and break out of while cycles that need a time limit safeguard
 unsigned long startTime;
 unsigned long pMillis;
@@ -257,6 +258,7 @@ void Heat() {
   delay(100);
   Serial.print(desiredTemp);
   delay(100);
+  // initialize variables at safe values
   Tc = 0; // current temperature
   Tp = -10; // temperature at previous cycle
   Tstart = - 100; // temperature at start of Heat() function
@@ -268,38 +270,38 @@ void Heat() {
     Vo = analogRead(tempSensorPin);
     R2 = R1 * (1023.0 / (float)Vo - 1.0);
     logR2 = log(R2);
-    T = (1.0 / (c1 + c2*logR2 + c3*logR2*logR2*logR2));
-    Tc = (T - 273.15);
+    T = (1.0 / (c1 + c2*logR2 + c3*logR2*logR2*logR2)); // compute temperature from NTC
+    Tc = (T - 273.15); // convert from Kelvin to Celsius for readability
     
-    if (millis() - startTime == 1000) {
+    if (millis() - startTime > 500 && millis() - startTime < 1500) {
       Tstart = Tc; // support variable to store temp at beginning, so that we can be sure it's increasing
+      delay(1001); // make sure we only set startTime once!
     }
 
     // check if temperature is within the acceptable range and break out of the loop without error if done heating:
-    if (Tc > desiredTemp) {
-      // temperature is within range, so break out of the loop:
+    if (Tc > desiredTemp && pumpStatus == 0) {
       delay(100);
       Serial.write("reached desired temp\n");
       delay(100);
       Serial.print(Tc);
-      break;
+      break; // temperature is within range, break out of the loop:
     }
 
-    if (Tc < -100) {
+    if (Tc < -100) { // break the loop if temperature < -100, can only happen if cable gets unplugged
       delay(100);
       Serial.write("u-Thermocouple: unplugged or failed\n");
       unrecoverableErr = 1;
       break;
     }
 
-    if (millis() - startTime > 20000 && Tc - Tstart < 1) {
+    if (millis() - startTime > 20000 && Tc - Tstart < 1 && pumpStatus == 0) { // break the loop if temperature is not increasing
       delay(100);
-      Serial.write("p-Thermocouple: positioning or relay fault\n");
+      Serial.write("p-Thermocouple: not detecting heating, positioning or relay fault\n");
       unrecoverableErr = 1;
       break;
     }
 
-    if (millis() - startTime > 60000) {
+    if (millis() - startTime > 90000 && pumpStatus == 0) { // break out of the loop after 60s if the boiler is not yet hot
       delay(100);
       Serial.write("h-taking too long, continuing...\n");
       break;
@@ -309,12 +311,19 @@ void Heat() {
     // check aprox. derivative every second and shut off heater if temperature is increasing too quickly!
     // conversely, heater is turned on if temperature is not incresing quickly enough
     if (millis() > (pMillis + 1000)){
-      
-      if (Tc < (desiredTemp - 20)) {
+
+      // initially run the heater on fully. eg: if we set the number to 30 and start with
+      // Tambient = 20C and desiredTemp = 90 the heater will stay fully on until 90-30 = 60C
+      //if (Tc < (desiredTemp - 30)) { // old if with variable temp
+
+      // new if with hard-coded minimum pulsing enable temperature of 70C
+      if (Tc < 70 || Tc < (desiredTemp - 20)) {
         digitalWrite(boilerPin, HIGH);
       }
-      
-      else if ((Tc - Tp) < 0.5) {
+
+      // change this value for proportional behaviour: lower values will cycle the relay more often.
+      // Cycling often reduces temperature undershoot, but will shorten contact lifespan
+      else if ((Tc - Tp) < 0.6) {
         digitalWrite(boilerPin, HIGH);
       }
 
@@ -324,6 +333,20 @@ void Heat() {
       
       else {
         digitalWrite(boilerPin, LOW);
+        // delay(1000); // extra 1s delay to keep boiler off for 2s total (delay + millis())
+      }
+
+      // this next if lets us call us for pumping while still monitoring heat
+      if (pumpStatus == 1 && ((millis() - startTime)/1000) < pumpRatio) {
+        digitalWrite(pumpPin, HIGH);
+      }
+      else if (pumpStatus == 1 && ((millis() - startTime)/1000) > pumpRatio) {
+        digitalWrite(pumpPin, LOW);
+        break;
+      }
+      else {
+        //digitalWrite(pumpPin, LOW);
+        //pumpStatus = 0;
       }
       
       Tp = Tc;
@@ -414,12 +437,15 @@ void Pump() {
   digitalWrite(greenLED, LOW);
   delay(100);
   Serial.write("pumping Water...\n");
-  digitalWrite(pumpPin, HIGH);
-  while (pumpRatio > 1) {
-    pumpRatio--;
-    delay(1000);
-  }
-  digitalWrite(pumpPin, LOW);
+  pumpStatus = 1; // set pumpStatus variable to 1 to tell Heat() function to pump
+  Heat(); // call Heat function with current parameters
+  pumpStatus = 0; // set pumpStatus variable to 0
+  //digitalWrite(pumpPin, HIGH);
+  //while (pumpRatio > 1) {
+  //  pumpRatio--;
+  //  delay(1000);
+  //}
+  //digitalWrite(pumpPin, LOW);
   delay(100);
   Serial.write("Pumping water done\n");
   digitalWrite(greenLED, HIGH);
@@ -434,7 +460,7 @@ void makeCoffee() {
   // care must be taken to place these functions earlier in the code, or the compiler will rightfully freak out
   while (true) {
   
-  desiredTemp = 85;
+  desiredTemp = 80;
   Heat(); // First we pre-heat the boiler
   if (unrecoverableErr == 1) {
     break;
@@ -491,7 +517,7 @@ void makeCoffee() {
     break;
   }
 
-  desiredTemp = 95;
+  desiredTemp = 90;
   Heat(); // First we pre-heat the boiler
   if (unrecoverableErr == 1) {
     break;
@@ -500,6 +526,7 @@ void makeCoffee() {
   if (dry == 0) {
     //digitalWrite(boilerPin, HIGH);
     delay(100);
+    desiredTemp = 95; // temperature to try and maintain while making coffee
     Pump(); // Pump ratio (in seconds) will be read from serial input in final release
     digitalWrite(boilerPin, LOW);
   }