Revision 0:8b77aea74642, committed 2016-01-25

Comitter:

unix_guru

Date:

Mon Jan 25 22:38:30 2016 +0000

Child:

1:b852d582ad0e

Commit message:

Extruder/Heated Bed controller for the FRDM-K64F

Changed in this revision

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/PID.lib	Mon Jan 25 22:38:30 2016 +0000
@@ -0,0 +1,1 @@
+https://developer.mbed.org/teams/FRDM-K64F-Code-Share/code/PID/#117e0c36eb22

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/PIDHeater.cpp	Mon Jan 25 22:38:30 2016 +0000
@@ -0,0 +1,75 @@
+#include "PIDHeater.h"
+
+PID controller(DEFAULT_Kp , DEFAULT_Ki , DEFAULT_Kd , 0.1);       // Initialize PID controller  -- Kc, Ti, Td, interval
+ 
+ 
+PIDHeater::PIDHeater(PinName sensorPin, PinName pwmoutPin): thermistor(sensorPin), driver(pwmoutPin) {
+
+    heaterOn = false;
+    controller.setInputLimits(0, 250);      // MIN/MAX Temperature values 
+    controller.setOutputLimits(0.0, 1.0);   // Pwm output from 0.0 to 1.0
+//  controller.setMode(AUTO);
+    controller.setSetPoint(22);             // Set initial Temperature to 22 degrees celcius
+ }
+ 
+void PIDHeater::configureRange(float minTemperature, float maxTemperature) {
+    if (minTemperature < maxTemperature) {
+        minTemp = minTemperature;
+        maxTemp = maxTemperature;
+        controller.setInputLimits(minTemperature, maxTemperature);      // MIN/MAX Temperature values    
+    }
+}
+ 
+float PIDHeater::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
+
+    return temperature;    
+
+}
+ 
+bool PIDHeater::isHeaterOn() {
+    return heaterOn;
+}
+ 
+void PIDHeater::run() {
+    getTemperature();
+    driver = controller.compute(currentTemp, desiredTemp);
+}
+  
+ 
+void PIDHeater::setTemperature(float temp) {
+    if (temp >= minTemp && temp <= maxTemp) {
+        desiredTemp = temp;
+        controller.setSetPoint(desiredTemp);             // Set desired temperature in celcius
+    }
+}
+ 
+           
\ No newline at end of file

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/PIDHeater.h	Mon Jan 25 22:38:30 2016 +0000
@@ -0,0 +1,43 @@
+#ifndef PID_HEATER_H
+#define PID_HEATER_H
+ 
+#include "mbed.h"
+ 
+#include "PID.h"
+// These values were borrowed from Marlin Firmware defaults
+#define  DEFAULT_Kp 17.52
+#define  DEFAULT_Ki 0.62
+#define  DEFAULT_Kd 123.43
+
+  
+/** A simple class for temperature control of a heater element using PID
+ * a heater driven via PWM digital output and one analog temperature sensor.
+ *
+ * Author(s): Michael Ball  unix_guru@hotmail.com
+ *
+ */
+class PIDHeater{
+    public:
+        /** Constructor receives pin names of the temperature sensor and
+         * the DigitalOut pin to which the heater driver is connected. */
+        PIDHeater(PinName sensorPin, PinName digitalOutPin);
+        /** Set the temperature range of the sensor. */
+        void configureRange(float minTemperature, float maxTemperature);
+        /** Read the current room temperature from the sensor. */
+        float getTemperature();
+        /** Test if the heater in turned ON. */
+        bool isHeaterOn();
+        /** Set the desired room temperature. */
+        void setTemperature(float temp);
+        /** Attach run process to a timer */
+        void run();
+        
+    private:
+        AnalogIn thermistor;
+        DigitalOut driver;
+        Ticker ticker;
+        bool heaterOn;
+        float currentTemp, desiredTemp, minTemp, maxTemp, hysteresis, pwmValue;
+};
+ 
+#endif // HEATER_H
\ No newline at end of file

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/main.cpp	Mon Jan 25 22:38:30 2016 +0000
@@ -0,0 +1,39 @@
+/** 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 more information on PID control 
+ *
+ * Author(s): Michael Ball  unix_guru@hotmail.com
+ *
+ */
+
+#include "mbed.h"
+
+#include "PIDHeater.h"                  // PIDHeater simply takes two variables
+                                        // The Thermistor input and the Heater output.
+                                        // 
+Serial pc(USBTX, USBRX);
+Ticker ticker;                        
+
+#define RATE 0.1                        // Check temp every 100ms
+PIDHeater extruder(A3, PTC3);           // Thermistor on A3 heater on PTC3
+
+void run_PID_loop() {                        // Periodically test temperature and set output
+    extruder.run();
+}    
+
+int main(){
+ 
+  extruder.configureRange(0,250);       // Set MIN/MAX temperature in degrees Celcius.
+  extruder.setTemperature(25);         // Set target temperature to 25 degrees Celcius.
+  
+  ticker.attach(&run_PID_loop,RATE);    // Start PID process running at 100ms rate.
+
+  while(1){
+   
+     pc.printf("Extruder Temperature is %f\r\n", extruder.getTemperature());
+     
+     wait(1);  
+
+  }
+ 
+}
\ No newline at end of file

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/mbed.bld	Mon Jan 25 22:38:30 2016 +0000
@@ -0,0 +1,1 @@
+http://mbed.org/users/mbed_official/code/mbed/builds/6f327212ef96
\ No newline at end of file