Revision 0:59f09202ccbb, committed 2017-10-05

Comitter:

rossatmsoe

Date:

Thu Oct 05 20:02:27 2017 +0000

Commit message:

Thermometer (using thermistor) that creates beeps of increasing pitch and pulse rate as temperature rises above nominal. Demonstrates use of #include for your own header files, and #define for constants.

Changed in this revision

diff -r 000000000000 -r 59f09202ccbb main.cpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/main.cpp	Thu Oct 05 20:02:27 2017 +0000
@@ -0,0 +1,57 @@
+/*  Audible Thermometer
+
+Creates beeps of increasing pitch and pulse rate as the temperature
+rises above the nominal value.
+
+Hardware:   10k resistor from A0 to ground
+            10k nominal thermistor from A0 to 3V3
+            Speaker from D9 to ground
+
+*/
+
+#include "mbed.h"
+#include "thermistor.h"   // This file contains the temperature calculation
+
+#define  NOMINAL_TEMP  75  // Change the nominal temperature here
+
+AnalogIn therm(A0);
+PwmOut speaker(D9);
+Serial pc(USBTX,USBRX);
+
+// This function will be defined in this file, main.cpp
+void beep(float freq, float duration);
+
+int main()
+{
+    while(1) {
+        
+        // Calculate Temperature
+        int tempF = temp_calc(therm);  // This function is in thermistor.h
+        
+        // Calculate difference from nominal
+        int difference = tempF-NOMINAL_TEMP;
+        
+        // If I have a fever...
+        if (difference >= 1) {
+            
+            // Create a warning beep that gets higher in pitch and
+            // more rapid as temperature increases
+            float frequency = difference*100;
+            float duration = .5/difference;
+            
+            // Call beeping function defined below
+            beep(frequency,duration);
+            
+            wait(duration);
+        }
+    }
+}
+
+void beep(float freq, float duration)   // Note that one of the variables
+{                                       // in the note() function has the same
+    speaker.period(1/freq);             // as a variable in main().
+    speaker=.5;                         // That's ok, since they are local
+    wait(duration);                     // to their respective functions.
+    speaker=0;                          // This function also uses a global
+}                                       // variable, speaker.
+

diff -r 000000000000 -r 59f09202ccbb mbed.bld
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/mbed.bld	Thu Oct 05 20:02:27 2017 +0000
@@ -0,0 +1,1 @@
+http://mbed.org/users/mbed_official/code/mbed/builds/235179ab3f27
\ No newline at end of file

diff -r 000000000000 -r 59f09202ccbb thermistor.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/thermistor.h	Thu Oct 05 20:02:27 2017 +0000
@@ -0,0 +1,16 @@
+/* thermistor.h
+
+   Contains the definition for the Fahrenheit temperature calculation
+   
+   The input is the analog reading, and the returned float value is the
+   temperature in degrees Fahrenheit.
+
+*/
+
+float temp_calc(float analog_value) {
+        double R_ratio = (1/analog_value - 1);
+        double logR_ratio=log(R_ratio);
+        double T_kelvin=1/(.003354016+.000256985*logR_ratio+.000002620131*logR_ratio*logR_ratio);
+        float T = 1.8*(T_kelvin - 273) + 32;
+        return T;
+}
\ No newline at end of file