Diff: main.cpp

Revision:

3:00a491d8ed0c

Parent:

2:6e731a17523c

--- a/main.cpp	Sun Feb 07 19:08:57 2016 +0000
+++ b/main.cpp	Fri Jun 23 14:53:24 2017 +0000
@@ -1,39 +1,16 @@
-/** A demo application to show how to mangage and control a heater element 
- * through a PID loop using a Thermistor input and PWM output
- * for the @NXP (@freescale) FRDM-K64F demo board.
- *
- * This particular example drives the heater element for a 3d Printer Extruder.
- *
- * For more information on PID control check out Brett Beauregard's Arduino PID library:
- *
- *  https://github.com/br3ttb/Arduino-PID-Library
- *
- * The wikipedia article on PID controllers is a good place to start on
- * understanding how they work:
- *
- *  http://en.wikipedia.org/wiki/PID_controller
- *
- * The Thermistor value to Temerature routine uses the Steinhart-Hart equation.
- This is a Thermistor to Temerature conversion demo 
-
-Much thanks to @Adafruit for this tutorial:
-https://learn.adafruit.com/thermistor/using-a-thermistor
-
-The 100K Thermistor is configured with a 4.7k series resistor 
-tied to vcc (3.3v)  like this:
-
+/*
     +3.3v
       |
       \
-      /  4.7k series resistor
+      /  10k Résistance série
       \
       /
       |
-      .-----------O To Anlog pin on FRDM board
+      .-----------O Vers Anolog 0 de la carte
       |
       \
       /
-  Thermistor  100k Nominal
+  Thermistance  10k Nominal
       \
       /
       |
@@ -54,25 +31,25 @@
 Ticker PrintTicker;                     // Send process results to Console once per second       
 Ticker ticker;                          // Set up the millis() ticker.
                                        
-#define  DEFAULT_Kp 1
-#define  DEFAULT_Ki 0.002
-#define  DEFAULT_Kd 20
+#define  DEFAULT_Kp 100
+#define  DEFAULT_Ki 0
+#define  DEFAULT_Kd 0
 
 #define AUTOMATIC 1
 #define MANUAL    0
 #define DIRECT  0
 #define REVERSE  1
-#define thermistor A3                       // FRDM-K64F Analog input pin A3   - Adjust to your particular board
-#define driver PTC3                         // FRDM-K64F PWM output pin PTC3   - Adjust to your particular board
-
-AnalogIn Thermistor(thermistor);            // Read temperature value from thermistor on A3
-PwmOut Driver(driver);                      // PWM drive FET heater on PTC3  values are 0-1.0 
+#define thermistor A0                       // Analog input pin A0 
+#define driver PB_3                         // PWM output pin PB_3
+#define PERIOD 2.0
+AnalogIn Thermistor(thermistor);            // Read temperature value from thermistor on A0
+PwmOut Driver(PB_3);                      // PWM drive values are 0-1.0 
                                             // For 0-100% 
-             
+float temp;             
 float Input, Output, Setpoint; 
 PID controller(&Input, &Output, &Setpoint, DEFAULT_Kp , DEFAULT_Ki , DEFAULT_Kd , DIRECT);
 
-#define RATE 1.0                            // Print rate  Once per second
+#define RATE 2.0                            // Print rate  once every two seconds
   
 void PrintValues() {                        // Routine to print out results to console
     pc.printf("Input      Output     Setpoint   Kp        Ki        Kd        time\r\n");
@@ -86,14 +63,13 @@
  
   startMillis();                            // Initialize timer.
  
-  pc.baud(115200);    
-  pc.printf("\r\nThermistor PID Test - Build " __DATE__ " " __TIME__ "\r\n");
+  pc.baud(9600);    
+  //pc.printf("\r\nThermistor PID Test - Build " __DATE__ " " __TIME__ "\r\n");
   
-  PrintTicker.attach(&PrintValues,RATE);    // Start PID process running at 100ms rate.
-
-  Setpoint = 80;                            // Set target temperature in degrees Celcius.
+  PrintTicker.attach(&PrintValues,RATE);    // Start PID process running at 2s rate.
+  controller.SetSampleTime(2000);
+  Setpoint = 24;                            // Set target temperature in degrees Celcius.
   controller.SetMode(AUTOMATIC);            // Turn PID controller on.
-  
 
   while(1){
    
@@ -102,50 +78,20 @@
      controller.Compute();                  // Process PID loop. 
 
      Driver = Output/1000;                  // Sent PWM value scaled 0 - 1.0 as mbed requires 
-
+    
   }
  
 }
 
 
-// This is the workhorse routine that calculates the temperature
-// using the Steinhart-Hart equation for thermistors
-// https://en.wikipedia.org/wiki/Steinhart%E2%80%93Hart_equation
-
 float getTemperature() {
-#define THERMISTORNOMINAL 100000      // 100k 
-// temp. for nominal resistance (almost always 25 C)
-#define TEMPERATURENOMINAL 25   
-// The beta coefficient of the thermistor (usually 3000-4000)
-#define BCOEFFICIENT 3950
-// the value of the 'other' resistor
-#define SERIESRESISTOR 4700    
-
-// This is the workhorse routine that calculates the temperature
-// using the Steinhart-Hart equation for thermistors
-// https://en.wikipedia.org/wiki/Steinhart%E2%80%93Hart_equation
-
-    float temperature, resistance;
-    float steinhart;
-    int a;
-    
-    a = Thermistor.read_u16();       // Read 16bit Analog value
-//    pc.printf("Raw Analog Value for Thermistor = %d\r\n",a);
-  
-    /* Calculate the resistance of the thermistor from analog votage read. */
-    resistance = (float) SERIESRESISTOR / ((65536.0 / a) - 1);
-//    pc.printf("Resistance for Thermistor = %f\r\n",resistance);
-   
-    steinhart = resistance / THERMISTORNOMINAL;         // (R/Ro)
-    steinhart = log(steinhart);                         // ln(R/Ro)
-    steinhart /= BCOEFFICIENT;                          // 1/B * ln(R/Ro)
-    steinhart += 1.0 / (TEMPERATURENOMINAL + 273.15);   // + (1/To)
-    steinhart = 1.0 / steinhart;                        // Invert
-    temperature = steinhart - 273.15;                   // convert to C
-
-//    pc.printf("Extruder Temperature is %f\r\n", temperature);
+float h = Thermistor.read_u16();
+    h = (h/65536)*3.3;                      //Conversion Bit to Voltage
+    pc.printf("voltage %f\r\n", h);
+    temp = -30.705*h+91.788;                //Converson Voltage to °C
+    pc.printf("temp = %f\r\n",temp);
  
-    return temperature;    
+    return temp;    
 
 }
- 
+