Mini HVAC

1#include <AFMotor.h>
2#include <Wire.h>
3#include "Adafruit_MCP9808.h"
4
5Adafruit_MCP9808  tempsensor = Adafruit_MCP9808();
6AF_DCMotor fan(2);
7
8unsigned long currMillis;
9unsigned  long prevMillis = 0;
10double kp = 410;
11double ki = 2*kp/20; 
12double kd =  kp*20/8;
13double dt = 0.01;          // Specify sample time in seconds (fixed)
14double  dtmillis = dt*1000;  // Sample time in milliseconds
15int setpoint;
16float input;
17float  Output;
18float err;
19float pTerm;
20int IntThresh;
21float integrated_err;
22float  dTerm;
23float iTerm;
24float last_err;
25
26
27void setup(){
28  Serial.begin(9600);
29  
30  if (!tempsensor.begin()) {
31    Serial.println("Couldn't find MCP9808!");
32    while (1);
33  }
34  fan.run(RELEASE);
35  fan.setSpeed(0);
36}
37
38void  loop(){
39setpoint = 30;               // Specified by user, r(t)
40  float c  = tempsensor.readTempC();
41  Serial.print("Temp: "); 
42  Serial.println(c);  Serial.println("*C\	");
43input = (c);                 // Read by your sensor,  y(t) ... analogRead(...)
44err = (input - setpoint);    // Compute Error, e(t)  = r(t) - y(t)
45delay(200);
46// ====================== Compute Proportional term:  ========================
47pTerm = kp * (err);                 
48// ======================  Compute Integral term: ===========================
49IntThresh = .3;                      //  Set value for max intergral term
50if (abs(err) > IntThresh)            // Crude  way to prevent integrator 'windup'
51{                                    
52    integrated_err += err;           // Accumulate the error integral
53}
54else  
55{
56    integrated_err = 0;              // Zero it if out of bounds 
57}
58iTerm  = ki * integrated_err;         // Compute actual Integral term
59// ======================  Compute Derivative term: ===========================
60dTerm = kd * (err - last_err)*dt;  
61// ====================== Compute PID control command, u(t): =================
62Output  = constrain(pTerm + iTerm + dTerm, 0, 255);       
63fan.run(FORWARD);
64fan.setSpeed(Output);    // Use u(t) to drive the plant, i.e. analogWrite(Output), motor.run(Output),  etc...
65
66last_err = err;      // Set last_err to err for next time through  loop
67