Thermistor.h

00001 #ifndef THERMISTOR_H
00002 #define THERMISTOR_H
00003 ///
00004 /// @mainpage Thermistor Temperature library
00005 ///
00006 /// This is a Thermistor to Temerature conversion library 
00007 ///
00008 /// Much thanks to @Adafruit for this tutorial:
00009 /// https://learn.adafruit.com/thermistor/using-a-thermistor
00010 ///
00011 /// The 100K Thermistor is configured with a 4.7k series resistor 
00012 /// tied to vcc (3.3v)  like this:
00013 ///
00014 ///    +3.3v
00015 ///      |
00016 ///      \
00017 ///      /  4.7k series resistor
00018 ///      \
00019 ///      /
00020 ///      |
00021 ///      .-----------O To Anlog pin on FRDM board
00022 ///      |
00023 ///      \
00024 ///      /
00025 ///  Thermistor  100k Nominal
00026 ///      \
00027 ///      /
00028 ///      |
00029 ///     ---
00030 ///     GND
00031 ///  
00032 ///
00033 /// @author Michael J. Ball
00034 ///  unix_guru at hotmail.com
00035 ///  @unix_guru on Twitter
00036 ///  March 2016
00037 /// 
00038 /// @code 
00039 /// #include "mbed.h"
00040 /// #include "Thermistor.h"
00041 ///    
00042 /// Serial pc(USBTX, USBRX);
00043 /// 
00044 /// Thermistor bed(PTB10);
00045 /// Thermistor extruder(PTB11);
00046 /// 
00047 /// int main()
00048 /// {
00049 ///     pc.baud(115200);    
00050 ///     pc.printf("\r\nThermistor Test - Build " __DATE__ " " __TIME__ "\r\n");
00051 ///   
00052 ///     while(1) {  
00053 ///        pc.printf("Bed Temperature %f *C\r\n",bed.get_temperature()); 
00054 ///        wait(.5); 
00055 ///        pc.printf("Extruder Temperature %f *C\r\n",extruder.get_temperature()); 
00056 ///       wait(.5); 
00057 ///     }
00058 /// }
00059 
00060 /// ...
00061 /// @endcode
00062 ///
00063 /// @license
00064 /// Licensed under the Apache License, Version 2.0 (the "License");
00065 /// you may not use this file except in compliance with the License.
00066 /// You may obtain a copy of the License at
00067 ///
00068 ///    http://www.apache.org/licenses/LICENSE-2.0
00069 ///
00070 /// Unless required by applicable law or agreed to in writing, software
00071 /// distributed under the License is distributed on an "AS IS" BASIS,
00072 /// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
00073 /// See the License for the specific language governing permissions and
00074 /// limitations under the License.
00075 ///
00076 
00077 
00078 #include "mbed.h"
00079 
00080 
00081 #define THERMISTORNOMINAL 10000      // 100k default 
00082 // temp. for nominal resistance (almost always 25 C)
00083 #define TEMPERATURENOMINAL 25   
00084 // The beta coefficient of the thermistor (usually 3000-4000)
00085 #define BCOEFFICIENT 3950
00086 // the value of the 'other' resistor
00087 #define SERIESRESISTOR 4700    
00088   
00089 
00090 class Thermistor {
00091 public:
00092     Thermistor(PinName pin);  
00093     /** Receives a PinName variable.
00094      * @param pin mbed pin to which the thermistor is connected
00095      */
00096  
00097 
00098     float get_temperature();
00099     /**  This is the workhorse routine that calculates the temperature
00100      *   using the Steinhart-Hart equation for thermistors
00101      *   https://en.wikipedia.org/wiki/Steinhart%E2%80%93Hart_equation
00102      */
00103     void init();                                    // Set default Steinhart-Hart values
00104     void set_ThermistorNominal(float thermnom);     // Change the thermistors nominal resistance
00105     void set_TemperatureNominal(float tempnom);     // Change the thermistors nominal temperature
00106     void set_BCoefficient(float bcoefficient);      // Change the thermistors BCoefficient
00107     void set_SeriesResistor(float resistor);        // Change the value of the series resistor
00108  
00109 private:
00110     AnalogIn _pin;
00111     double ThermistorNominal;
00112     double TemperatureNominal;
00113     double BCoefficient;
00114     double SeriesResistor;
00115 };
00116  
00117 #endif