Todd Clark
Breathalyzer running on the MBED 1768 Platform; EE4427 Group 3 Spring 2018
Dependencies: 4DGL-uLCD-SE mbed
convertToBAC.cpp@0:35f90b280233, 2018-04-23 (annotated)
- Committer:
- phred754
- Date:
- Mon Apr 23 22:18:27 2018 +0000
- Revision:
- 0:35f90b280233
EE4427 Final Project Group 3
Who changed what in which revision?
| User | Revision | Line number | New contents of line |
|---|---|---|---|
| phred754 | 0:35f90b280233 | 1 | //Written by Todd Clark |
| phred754 | 0:35f90b280233 | 2 | #include "convertToBAC.h" |
| phred754 | 0:35f90b280233 | 3 | |
| phred754 | 0:35f90b280233 | 4 | float getBAC(float input){ |
| phred754 | 0:35f90b280233 | 5 | float voltage = input * 3; //Conversion from input resistance to voltage. |
| phred754 | 0:35f90b280233 | 6 | float calibratedVoltage = voltage / 0.6; //Convert voltage to work with our 3 volt output signal. |
| phred754 | 0:35f90b280233 | 7 | 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. |
| phred754 | 0:35f90b280233 | 8 | float bac = (ppm * 0.21) / 100; //Calculate BAC from ppm. Formula taken from http://nootropicdesign.com/projectlab/2010/09/17/arduino-breathalyzer/ |
| phred754 | 0:35f90b280233 | 9 | float calibratedBac = bac - 0.12; //Calibrate sensor based on value at 0% alcohol. |
| phred754 | 0:35f90b280233 | 10 | return (calibratedBac < 0.0) ? 0 : calibratedBac; |
| phred754 | 0:35f90b280233 | 11 | } |