Diff: convertToBAC.cpp

Revision:

0:35f90b280233

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/convertToBAC.cpp	Mon Apr 23 22:18:27 2018 +0000
@@ -0,0 +1,11 @@
+//Written by Todd Clark
+#include "convertToBAC.h"
+
+float getBAC(float input){
+    float voltage = input * 3; //Conversion from input resistance to voltage.
+    float calibratedVoltage = voltage / 0.6; //Convert voltage to work with our 3 volt output signal.
+    float ppm = 1033.992 + (55.84479 - 1033.992)/(1 + pow((calibratedVoltage/4.540421), 8.423297)); //Calculate ppm from our voltage values based on specs for MQ-3 gas sensor.
+    float bac = (ppm * 0.21) / 100; //Calculate BAC from ppm. Formula taken from http://nootropicdesign.com/projectlab/2010/09/17/arduino-breathalyzer/
+    float calibratedBac = bac - 0.12; //Calibrate sensor based on value at 0% alcohol.
+    return (calibratedBac < 0.0) ? 0 : calibratedBac;
+}
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