Added MQ2 Air quality sensor by epierre (converted to 1.4)

libraries/MySensors/MyMessage.h

@@ -48,7 +48,7 @@ typedef enum {
 typedef enum {
 	S_DOOR, S_MOTION, S_SMOKE, S_LIGHT, S_DIMMER, S_COVER, S_TEMP, S_HUM, S_BARO, S_WIND,
 	S_RAIN, S_UV, S_WEIGHT, S_POWER, S_HEATER, S_DISTANCE, S_LIGHT_LEVEL, S_ARDUINO_NODE,
-	S_ARDUINO_REPEATER_NODE, S_LOCK, S_IR, S_WATER
+	S_ARDUINO_REPEATER_NODE, S_LOCK, S_IR, S_WATER, S_AIR_QUALITY
 } sensor;
 
 // Type of data stream  (for streamed message)

libraries/MySensors/examples/AirQualitySensor/AirQualitySensor.ino

@@ -0,0 +1,196 @@
+/*
+  Vera Arduino MQ2
+
+  connect the MQ2 sensor as follows :
+
+  A H A   >>> 5V
+  B		  >>> A0
+  H       >>> GND
+  B       >>> 10K ohm >>> GND
+  
+  Contribution: epierre
+  Based on http://sandboxelectronics.com/?p=165
+  
+  License: Attribution-NonCommercial-ShareAlike 3.0 Unported (CC BY-NC-SA 3.0)
+ 
+  Modified by HEK to work in 1.4
+*/
+
+#include <SPI.h>
+#include <MySensor.h>  
+#include <Wire.h> 
+
+#define 	CHILD_ID_MQ                   0 
+/************************Hardware Related Macros************************************/
+#define 	MQ_SENSOR_ANALOG_PIN         (0)  //define which analog input channel you are going to use
+#define         RL_VALUE                     (5)     //define the load resistance on the board, in kilo ohms
+#define         RO_CLEAN_AIR_FACTOR          (9.83)  //RO_CLEAR_AIR_FACTOR=(Sensor resistance in clean air)/RO,
+                                                     //which is derived from the chart in datasheet
+/***********************Software Related Macros************************************/
+#define         CALIBARAION_SAMPLE_TIMES     (50)    //define how many samples you are going to take in the calibration phase
+#define         CALIBRATION_SAMPLE_INTERVAL  (500)   //define the time interal(in milisecond) between each samples in the
+                                                     //cablibration phase
+#define         READ_SAMPLE_INTERVAL         (50)    //define how many samples you are going to take in normal operation
+#define         READ_SAMPLE_TIMES            (5)     //define the time interal(in milisecond) between each samples in 
+                                                     //normal operation
+/**********************Application Related Macros**********************************/
+#define         GAS_LPG                      (0)
+#define         GAS_CO                       (1)
+#define         GAS_SMOKE                    (2)
+/*****************************Globals***********************************************/
+unsigned long SLEEP_TIME = 30000; // Sleep time between reads (in milliseconds)
+//VARIABLES
+float Ro = 10000.0;    // this has to be tuned 10K Ohm
+int val = 0;           // variable to store the value coming from the sensor
+float valMQ =0.0;
+float lastMQ =0.0;
+float           LPGCurve[3]  =  {2.3,0.21,-0.47};   //two points are taken from the curve. 
+                                                    //with these two points, a line is formed which is "approximately equivalent"
+                                                    //to the original curve. 
+                                                    //data format:{ x, y, slope}; point1: (lg200, 0.21), point2: (lg10000, -0.59) 
+float           COCurve[3]  =  {2.3,0.72,-0.34};    //two points are taken from the curve. 
+                                                    //with these two points, a line is formed which is "approximately equivalent" 
+                                                    //to the original curve.
+                                                    //data format:{ x, y, slope}; point1: (lg200, 0.72), point2: (lg10000,  0.15) 
+float           SmokeCurve[3] ={2.3,0.53,-0.44};    //two points are taken from the curve. 
+                                                    //with these two points, a line is formed which is "approximately equivalent" 
+                                                    //to the original curve.
+                                                    //data format:{ x, y, slope}; point1: (lg200, 0.53), point2:(lg10000,-0.22)                                                     
+
+
+MySensor gw;
+MyMessage msg(CHILD_ID_MQ, V_VAR1);
+
+
+void setup()  
+{ 
+  gw.begin();
+
+  // Send the sketch version information to the gateway and Controller
+  gw.sendSketchInfo("Air Quality Sensor", "1.0");
+
+  // Register all sensors to gateway (they will be created as child devices)
+  gw.present(CHILD_ID_MQ, S_AIR_QUALITY);  
+
+  Ro = MQCalibration(MQ_SENSOR_ANALOG_PIN);         //Calibrating the sensor. Please make sure the sensor is in clean air 
+                                                    //when you perform the calibration  
+}
+
+void loop()      
+{     
+  uint16_t valMQ = MQGetGasPercentage(MQRead(MQ_SENSOR_ANALOG_PIN)/Ro,GAS_CO);
+  Serial.println(val);
+  
+   Serial.print("LPG:"); 
+   Serial.print(MQGetGasPercentage(MQRead(MQ_SENSOR_ANALOG_PIN)/Ro,GAS_LPG) );
+   Serial.print( "ppm" );
+   Serial.print("    ");   
+   Serial.print("CO:"); 
+   Serial.print(MQGetGasPercentage(MQRead(MQ_SENSOR_ANALOG_PIN)/Ro,GAS_CO) );
+   Serial.print( "ppm" );
+   Serial.print("    ");   
+   Serial.print("SMOKE:"); 
+   Serial.print(MQGetGasPercentage(MQRead(MQ_SENSOR_ANALOG_PIN)/Ro,GAS_SMOKE) );
+   Serial.print( "ppm" );
+   Serial.print("\n");
+     
+  if (valMQ != lastMQ) {
+      gw.send(msg.set((int)ceil(valMQ)));
+      lastMQ = ceil(valMQ);
+  }
+  
+  gw.sleep(SLEEP_TIME); //sleep for: sleepTime 
+}
+
+/****************** MQResistanceCalculation ****************************************
+Input:   raw_adc - raw value read from adc, which represents the voltage
+Output:  the calculated sensor resistance
+Remarks: The sensor and the load resistor forms a voltage divider. Given the voltage
+         across the load resistor and its resistance, the resistance of the sensor
+         could be derived.
+************************************************************************************/ 
+float MQResistanceCalculation(int raw_adc)
+{
+  return ( ((float)RL_VALUE*(1023-raw_adc)/raw_adc));
+}
+ 
+/***************************** MQCalibration ****************************************
+Input:   mq_pin - analog channel
+Output:  Ro of the sensor
+Remarks: This function assumes that the sensor is in clean air. It use  
+         MQResistanceCalculation to calculates the sensor resistance in clean air 
+         and then divides it with RO_CLEAN_AIR_FACTOR. RO_CLEAN_AIR_FACTOR is about 
+         10, which differs slightly between different sensors.
+************************************************************************************/ 
+float MQCalibration(int mq_pin)
+{
+  int i;
+  float val=0;
+ 
+  for (i=0;i<CALIBARAION_SAMPLE_TIMES;i++) {            //take multiple samples
+    val += MQResistanceCalculation(analogRead(mq_pin));
+    delay(CALIBRATION_SAMPLE_INTERVAL);
+  }
+  val = val/CALIBARAION_SAMPLE_TIMES;                   //calculate the average value
+ 
+  val = val/RO_CLEAN_AIR_FACTOR;                        //divided by RO_CLEAN_AIR_FACTOR yields the Ro 
+                                                        //according to the chart in the datasheet 
+ 
+  return val; 
+}
+/*****************************  MQRead *********************************************
+Input:   mq_pin - analog channel
+Output:  Rs of the sensor
+Remarks: This function use MQResistanceCalculation to caculate the sensor resistenc (Rs).
+         The Rs changes as the sensor is in the different consentration of the target
+         gas. The sample times and the time interval between samples could be configured
+         by changing the definition of the macros.
+************************************************************************************/ 
+float MQRead(int mq_pin)
+{
+  int i;
+  float rs=0;
+ 
+  for (i=0;i<READ_SAMPLE_TIMES;i++) {
+    rs += MQResistanceCalculation(analogRead(mq_pin));
+    delay(READ_SAMPLE_INTERVAL);
+  }
+ 
+  rs = rs/READ_SAMPLE_TIMES;
+ 
+  return rs;  
+}
+ 
+/*****************************  MQGetGasPercentage **********************************
+Input:   rs_ro_ratio - Rs divided by Ro
+         gas_id      - target gas type
+Output:  ppm of the target gas
+Remarks: This function passes different curves to the MQGetPercentage function which 
+         calculates the ppm (parts per million) of the target gas.
+************************************************************************************/ 
+int MQGetGasPercentage(float rs_ro_ratio, int gas_id)
+{
+  if ( gas_id == GAS_LPG ) {
+     return MQGetPercentage(rs_ro_ratio,LPGCurve);
+  } else if ( gas_id == GAS_CO ) {
+     return MQGetPercentage(rs_ro_ratio,COCurve);
+  } else if ( gas_id == GAS_SMOKE ) {
+     return MQGetPercentage(rs_ro_ratio,SmokeCurve);
+  }    
+ 
+  return 0;
+}
+ 
+/*****************************  MQGetPercentage **********************************
+Input:   rs_ro_ratio - Rs divided by Ro
+         pcurve      - pointer to the curve of the target gas
+Output:  ppm of the target gas
+Remarks: By using the slope and a point of the line. The x(logarithmic value of ppm) 
+         of the line could be derived if y(rs_ro_ratio) is provided. As it is a 
+         logarithmic coordinate, power of 10 is used to convert the result to non-logarithmic 
+         value.
+************************************************************************************/ 
+int  MQGetPercentage(float rs_ro_ratio, float *pcurve)
+{
+  return (pow(10,( ((log(rs_ro_ratio)-pcurve[1])/pcurve[2]) + pcurve[0])));
+}