tims new code

open_incubator.ino

@@ -1,59 +1,118 @@
-#include <PID_v1.h>
-#define RelayPin 13
+/* FamiLAB incubator V0.2: Now with cooling capability!
+This project arose out of the need for a 37˚C incubator for E.coli culturing (Biohacking).  
+Additionally a peltier was used so that organisms that grow at lower temperature (20˚), could be cultured as well.
+A L6203 heavyduty H-bridge was used to achieve the PWM switching, and also the switch the peltier from heating mode to cooling mode
 
+PID code taken, with some modification, from "PID without a PhD" by Tim Wescott http://igor.chudov.com/manuals/Servo-Tuning/PID-without-a-PhD.pdf
 
-//Define Variables we'll be connecting to
-double Setpoint, Input, Output;
+TODO:
+7-segment display output!
+Verification of thermristor temp readings?
 
-//Specify the links and initial tuning parameters
-PID myPID(&Input, &Output, &Setpoint,2,5,1, DIRECT);
+*/
 
 
-int WindowSize = 5000;
-unsigned long windowStartTime;
+//Define our variables
+const int internalThermistor = 0; //Analog input attatched to the thermistor inside the incubator
+const int externalThermistor = 1; //Analog input attatched to the thermistor sampling the ambient air temperature outside the box
+const int inOne = 9; //Goes to logic input pin #1 for the L6203 H-bridge, if this is High and the inTwo is low, Out1 will source current and Out2 will sink it
+const int inTwo = 10; //Goes to logic input pin #2 for the L6203 H-bridge, if this is High and the inOne is low, Out2 will source current and Out1 will sink it
+const int enablePin = 11; //Goes to the enable pin, if this isn't brought high the chip won't do anything
+double setPoint = 37; //Temperature setpoint, in degrees celcius
+double error = 0;
+double feedback = 0;
+double tempReading = 0;
+double tempReadingExternal = 0;
+int sampleInverval = 1000; //Sampling interval in milliseconds
 
 
+struct SPid {
+double dState; // Last position input double 
+double iState; // Integrator state 
+double iMax; 
+double iMin;   // Maximum and minimum allowable integrator state
+double pGain;  // proportional gain
+double iGain;  // integral gain
+double dGain;  // derivative gain 
+
+};
+
+struct SPid thePID;
+
+double UpdatePID(struct SPid *pid, double error, double position) {
+double pTerm, dTerm, iTerm, feedback;
+pTerm = pid->pGain * error;
+// calculate the proportional term
+// calculate the integral state with appropriate limiting
+pid->iState += error;
+if (pid->iState > pid->iMax) pid->iState = pid->iMax; else if (pid->iState < pid->iMin) pid->iState = pid->iMin;
+iTerm = pid->iGain * pid->iState * double(sampleInverval/1000); // calculate the integral term 
+dTerm = pid->dGain * (position - pid->dState); pid->dState = position;
+
+feedback = pTerm + iTerm - dTerm;
+//Our analog write function only takes 0-255, so if the PID output is greater than 255 cap it.
+if (feedback > 255) feedback = 255; if (feedback < -255) feedback = -255;
+
+return feedback;
+
+}
 
 double thermistor_read(int RawADC) {
  double Temp;
  Temp = log(((10240000/RawADC) - 10000));
  Temp = 1 / (0.001129148 + (0.000234125 + (0.0000000876741 * Temp * Temp ))* Temp );
  Temp = Temp - 273.15;            // Convert Kelvin to Celcius
- Temp = (Temp * 9.0)/ 5.0 + 32.0; // Convert Celcius to Fahrenheit
  return Temp;
 }
 
-void setup()
-{
-  Setpoint = 130;
 
-  myPID.SetOutputLimits(0, WindowSize);
 
-  //turn the PID on
-  myPID.SetMode(AUTOMATIC); 
+void setup() {                
+ //Begin serial and initialize our data values for thePID struct.
+ Serial.begin(9600);
+ thePID.pGain = 15;
+ thePID.iGain = 1.5;
+ thePID.dGain = 1;
+ thePID.iMax = 160;
+ thePID.iMin = -160;
+ pinMode(inOne,OUTPUT);
+ pinMode(inTwo,OUTPUT);
+ pinMode(enablePin,OUTPUT);
+ digitalWrite(enablePin,HIGH);
+ digitalWrite(inOne,LOW);
+ digitalWrite(inTwo,LOW);
 
-  Serial.begin(9600);
+
+
 }
 
-void loop()
-{
-  Input = thermistor_read(analogRead(0));
-  myPID.Compute();
-
-  /************************************************
-   * turn the output pin on/off based on pid output
-   ************************************************/
-  unsigned long now = millis();
-  if(now - windowStartTime > WindowSize) { // time to shift the Relay Window
-    windowStartTime += WindowSize;
-  }
+void loop() {
+  //Internal Thermistor 
+  tempReading = thermistor_read(analogRead(0));
+  tempReadingExternal = thermistor_read(analogRead(5));
+  error = setPoint - tempReading;
+  feedback = UpdatePID(&thePID,error,tempReading);
+  //Serial.print("Interior Temp: ");
+  Serial.println(tempReading);
+  //Serial.print("Exterior Temp: ");
+  //Serial.println(tempReadingExternal);
+  //Serial.print("Feedback: ");
+  //Serial.println(feedback);
 
-  if(Output > now - windowStartTime) 
-    digitalWrite(RelayPin,HIGH);
+  //If feedback is >= 0, then heat the box by PWM switching the peltier
+  if (feedback >= 0)
+  {
+   analogWrite(inOne,feedback);
+   analogWrite(inTwo,0);
+  }
   else
-    digitalWrite(RelayPin,LOW);
+  //If feedback is < 0, flip the current through the peltier so that its now cooling and PWM it the same way.
+  {
+   analogWrite(inOne,0);
+   analogWrite(inTwo,-feedback); 
+  }
+
 
-  Serial.println(Input);
-  analogWrite(3,Output);
+  delay(sampleInverval);
+        
 }
-