Diff: thermistor.cpp

Revision:

0:5459d9074b70

diff -r 000000000000 -r 5459d9074b70 thermistor.cpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/thermistor.cpp	Sun May 17 18:10:37 2020 +0000
@@ -0,0 +1,34 @@
+#include "mbed.h"
+#include "thermistor.h"
+ 
+Thermistor::Thermistor(PinName ThermistorPin, int NominalRes, int Beta, int SeriesResistor) : thermistorpin(ThermistorPin), nominalres(NominalRes), beta(Beta), seriesresistor(SeriesResistor) {
+    init();
+}
+ 
+void Thermistor::init() {
+    //defaults:
+    //beta = 3950 // The beta coefficient of the thermistor (usually 3000-4000)
+    //seriesresistor = 4700 //value of the second resistor - seriesresistor
+}
+ 
+void Thermistor::get_temperature() {
+    int temperaturenominal = 25; //temperature when the resistance is measured
+    a = thermistorpin.read_u16(); // Read 16bit Analog value
+    res = (float) seriesresistor / ((65536.0 / a) - 1); // get resistance of the thermistor
+    steinhart = res / nominalres;  // (R/Ro)
+    steinhart = log(steinhart);                 // ln(R/Ro)
+    steinhart /= beta;                  // 1/B * ln(R/Ro)
+    steinhart += 1.0 / (temperaturenominal + 273.15);   // + (1/To)
+    steinhart = 1.0 / steinhart; //invert
+    temp = steinhart - 273.15;           // to celsius
+}
+ 
+float Thermistor::temperature() {
+    get_temperature();
+    return temp;
+}
+
+float Thermistor::resistance() {
+    get_temperature();
+    return res;
+}
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