diff --git a/.gitignore b/.gitignore new file mode 100644 index 0000000..89cc49c --- /dev/null +++ b/.gitignore @@ -0,0 +1,5 @@ +.pio +.vscode/.browse.c_cpp.db* +.vscode/c_cpp_properties.json +.vscode/launch.json +.vscode/ipch diff --git a/.vscode/extensions.json b/.vscode/extensions.json new file mode 100644 index 0000000..e80666b --- /dev/null +++ b/.vscode/extensions.json @@ -0,0 +1,7 @@ +{ + // See http://go.microsoft.com/fwlink/?LinkId=827846 + // for the documentation about the extensions.json format + "recommendations": [ + "platformio.platformio-ide" + ] +} diff --git a/include/README b/include/README new file mode 100644 index 0000000..194dcd4 --- /dev/null +++ b/include/README @@ -0,0 +1,39 @@ + +This directory is intended for project header files. + +A header file is a file containing C declarations and macro definitions +to be shared between several project source files. You request the use of a +header file in your project source file (C, C++, etc) located in `src` folder +by including it, with the C preprocessing directive `#include'. + +```src/main.c + +#include "header.h" + +int main (void) +{ + ... +} +``` + +Including a header file produces the same results as copying the header file +into each source file that needs it. Such copying would be time-consuming +and error-prone. With a header file, the related declarations appear +in only one place. If they need to be changed, they can be changed in one +place, and programs that include the header file will automatically use the +new version when next recompiled. The header file eliminates the labor of +finding and changing all the copies as well as the risk that a failure to +find one copy will result in inconsistencies within a program. + +In C, the usual convention is to give header files names that end with `.h'. +It is most portable to use only letters, digits, dashes, and underscores in +header file names, and at most one dot. + +Read more about using header files in official GCC documentation: + +* Include Syntax +* Include Operation +* Once-Only Headers +* Computed Includes + +https://gcc.gnu.org/onlinedocs/cpp/Header-Files.html diff --git a/lib/MQ135/MQ135.cpp b/lib/MQ135/MQ135.cpp new file mode 100644 index 0000000..676ed31 --- /dev/null +++ b/lib/MQ135/MQ135.cpp @@ -0,0 +1,123 @@ +/**************************************************************************/ +/*! +@file MQ135.cpp +@author G.Krocker (Mad Frog Labs) +@license GNU GPLv3 + +First version of an Arduino Library for the MQ135 gas sensor +TODO: Review the correction factor calculation. This currently relies on +the datasheet but the information there seems to be wrong. + +@section HISTORY + +v1.0 - First release +*/ +/**************************************************************************/ + +#include "MQ135.h" + +/**************************************************************************/ +/*! +@brief Default constructor + +@param[in] pin The analog input pin for the readout of the sensor +*/ +/**************************************************************************/ + +MQ135::MQ135(uint8_t pin) { + _pin = pin; +} + + +/**************************************************************************/ +/*! +@brief Get the correction factor to correct for temperature and humidity + +@param[in] t The ambient air temperature +@param[in] h The relative humidity + +@return The calculated correction factor +*/ +/**************************************************************************/ +float MQ135::getCorrectionFactor(float t, float h) { + return CORA * t * t - CORB * t + CORC - (h-33.)*CORD; +} + +/**************************************************************************/ +/*! +@brief Get the resistance of the sensor, ie. the measurement value + +@return The sensor resistance in kOhm +*/ +/**************************************************************************/ +float MQ135::getResistance() { + int val = analogRead(_pin); + return ((1023./(float)val) * 5. - 1.)*RLOAD; +} + +/**************************************************************************/ +/*! +@brief Get the resistance of the sensor, ie. the measurement value corrected + for temp/hum + +@param[in] t The ambient air temperature +@param[in] h The relative humidity + +@return The corrected sensor resistance kOhm +*/ +/**************************************************************************/ +float MQ135::getCorrectedResistance(float t, float h) { + return getResistance()/getCorrectionFactor(t, h); +} + +/**************************************************************************/ +/*! +@brief Get the ppm of CO2 sensed (assuming only CO2 in the air) + +@return The ppm of CO2 in the air +*/ +/**************************************************************************/ +float MQ135::getPPM() { + return PARA * pow((getResistance()/RZERO), -PARB); +} + +/**************************************************************************/ +/*! +@brief Get the ppm of CO2 sensed (assuming only CO2 in the air), corrected + for temp/hum + +@param[in] t The ambient air temperature +@param[in] h The relative humidity + +@return The ppm of CO2 in the air +*/ +/**************************************************************************/ +float MQ135::getCorrectedPPM(float t, float h) { + return PARA * pow((getCorrectedResistance(t, h)/RZERO), -PARB); +} + +/**************************************************************************/ +/*! +@brief Get the resistance RZero of the sensor for calibration purposes + +@return The sensor resistance RZero in kOhm +*/ +/**************************************************************************/ +float MQ135::getRZero() { + return getResistance() * pow((ATMOCO2/PARA), (1./PARB)); +} + +/**************************************************************************/ +/*! +@brief Get the corrected resistance RZero of the sensor for calibration + purposes + +@param[in] t The ambient air temperature +@param[in] h The relative humidity + +@return The corrected sensor resistance RZero in kOhm +*/ +/**************************************************************************/ +float MQ135::getCorrectedRZero(float t, float h) { + return getCorrectedResistance(t, h) * pow((ATMOCO2/PARA), (1./PARB)); +} diff --git a/lib/MQ135/MQ135.h b/lib/MQ135/MQ135.h new file mode 100644 index 0000000..7f13aaf --- /dev/null +++ b/lib/MQ135/MQ135.h @@ -0,0 +1,56 @@ +/**************************************************************************/ +/*! +@file MQ135.h +@author G.Krocker (Mad Frog Labs) +@license GNU GPLv3 + +First version of an Arduino Library for the MQ135 gas sensor +TODO: Review the correction factor calculation. This currently relies on +the datasheet but the information there seems to be wrong. + +@section HISTORY + +v1.0 - First release +*/ +/**************************************************************************/ +#ifndef MQ135_H +#define MQ135_H +#if ARDUINO >= 100 + #include "Arduino.h" +#else + #include "WProgram.h" +#endif + +/// The load resistance on the board +#define RLOAD 10.0 +/// Calibration resistance at atmospheric CO2 level +// #define RZERO 76.63 +#define RZERO 1 +/// Parameters for calculating ppm of CO2 from sensor resistance +#define PARA 116.6020682 +#define PARB 2.769034857 + +/// Parameters to model temperature and humidity dependence +#define CORA 0.00035 +#define CORB 0.02718 +#define CORC 1.39538 +#define CORD 0.0018 + +/// Atmospheric CO2 level for calibration purposes +#define ATMOCO2 397.13 + +class MQ135 { + private: + uint8_t _pin; + + public: + MQ135(uint8_t pin); + float getCorrectionFactor(float t, float h); + float getResistance(); + float getCorrectedResistance(float t, float h); + float getPPM(); + float getCorrectedPPM(float t, float h); + float getRZero(); + float getCorrectedRZero(float t, float h); +}; +#endif diff --git a/lib/README b/lib/README new file mode 100644 index 0000000..6debab1 --- /dev/null +++ b/lib/README @@ -0,0 +1,46 @@ + +This directory is intended for project specific (private) libraries. +PlatformIO will compile them to static libraries and link into executable file. + +The source code of each library should be placed in a an own separate directory +("lib/your_library_name/[here are source files]"). + +For example, see a structure of the following two libraries `Foo` and `Bar`: + +|--lib +| | +| |--Bar +| | |--docs +| | |--examples +| | |--src +| | |- Bar.c +| | |- Bar.h +| | |- library.json (optional, custom build options, etc) https://docs.platformio.org/page/librarymanager/config.html +| | +| |--Foo +| | |- Foo.c +| | |- Foo.h +| | +| |- README --> THIS FILE +| +|- platformio.ini +|--src + |- main.c + +and a contents of `src/main.c`: +``` +#include +#include + +int main (void) +{ + ... +} + +``` + +PlatformIO Library Dependency Finder will find automatically dependent +libraries scanning project source files. + +More information about PlatformIO Library Dependency Finder +- https://docs.platformio.org/page/librarymanager/ldf.html diff --git a/platformio.ini b/platformio.ini new file mode 100644 index 0000000..9128281 --- /dev/null +++ b/platformio.ini @@ -0,0 +1,16 @@ +; PlatformIO Project Configuration File +; +; Build options: build flags, source filter +; Upload options: custom upload port, speed and extra flags +; Library options: dependencies, extra library storages +; Advanced options: extra scripting +; +; Please visit documentation for the other options and examples +; https://docs.platformio.org/page/projectconf.html + +[env:uno] +platform = atmelavr +board = uno +framework = arduino +lib_deps = + MQ135 diff --git a/src/main.cpp b/src/main.cpp new file mode 100644 index 0000000..33c15f4 --- /dev/null +++ b/src/main.cpp @@ -0,0 +1,22 @@ +#include +#include + +#define PIN_MQ135 A0 +MQ135 mq135_sensor = MQ135(PIN_MQ135); + +void setup() { + Serial.begin(9600); +} + +void loop() { + float val = analogRead(A0); + Serial.print ("raw = "); + Serial.println (val); + float zero = mq135_sensor.getRZero(); + Serial.print ("rzero: "); + Serial.println (zero); + float ppm = mq135_sensor.getPPM(); + Serial.print ("ppm: "); + Serial.println (ppm); + delay(2000); +} \ No newline at end of file diff --git a/test/README b/test/README new file mode 100644 index 0000000..b94d089 --- /dev/null +++ b/test/README @@ -0,0 +1,11 @@ + +This directory is intended for PlatformIO Unit Testing and project tests. + +Unit Testing is a software testing method by which individual units of +source code, sets of one or more MCU program modules together with associated +control data, usage procedures, and operating procedures, are tested to +determine whether they are fit for use. Unit testing finds problems early +in the development cycle. + +More information about PlatformIO Unit Testing: +- https://docs.platformio.org/page/plus/unit-testing.html