MQ135 with RS485

[qobouky]

Hello,

I try to get working my MQ135 on RS485 but I cannot manage to make it working.

I use UNO as Gateway + 2 separate sensors (DHT on UNO and MQ135 on pro mini 5V)
DHT works correctly but MQ135 does not work.

For testing purpose I disconnected DHT.

I wanted to be sure that MQ135 is connected correctly so I uploaded another code and everything works correctly, But with code below I cannot send data to gateway. I used as a source of code following MySensor forum code

Connection

MQ135 - arduino pro mini 5V
Vcc - Vcc 5V
GND - GND
AO - A1

RS485 - arduino pro mini 5V
DI - D9
R0 - D8
DE/RE - D2
GND - GND
Vcc - Vcc 5V
A - A(gateway RS485)
A - A(gateway RS485)

CODE

/*
  Arduino MQ135
  connect the sensor as follows :
  A H A   >>> 5V
  B       >>> A0
  H       >>> GND
  B       >>> 10K ohm >>> GND
 
  Contribution: epierre
  Based on David Gironi http://davidegironi.blogspot.fr/2014/01/cheap-co2-meter-using-mq135-sensor-with.html
  http://skylink.dl.sourceforge.net/project/davidegironi/avr-lib/avr_lib_mq135_01.zip
 
*/

// Enable debug prints
#define MY_DEBUG


// Enable RS485 transport layer
#define MY_RS485

// Define this to enables DE-pin management on defined pin
#define MY_RS485_DE_PIN 2

// Set RS485 baud rate to use
#define MY_RS485_BAUD_RATE 9600

// Enable this if RS485 is connected to a hardware serial port
//#define MY_RS485_HWSERIAL Serial1

// #include <SPI.h>    
//#include <MySensor.h>
#include <MySensors.h>
#include <Wire.h> 

#define CHILD_ID_AIQ 0
#define AIQ_SENSOR_ANALOG_PIN 1

#define MQ135_DEFAULTPPM 399 //default ppm of CO2 for calibration
#define MQ135_DEFAULTRO 68550 //default Ro for MQ135_DEFAULTPPM ppm of CO2
#define MQ135_SCALINGFACTOR 116.6020682 //CO2 gas value
#define MQ135_EXPONENT -2.769034857 //CO2 gas value
#define MQ135_MAXRSRO 2.428 //for CO2
#define MQ135_MINRSRO 0.358 //for CO2

unsigned long SLEEP_TIME = 30000; // Sleep time between reads (in seconds)
//VARIABLES
float mq135_ro = 10000.0;    // this has to be tuned 10K Ohm
int val = 0;                 // variable to store the value coming from the sensor
float valAIQ =0.0;
float lastAIQ =0.0;

// MySensor gw;
MyMessage msg(CHILD_ID_AIQ, V_LEVEL);

void setup()  
{
//  gw.begin();

  // Send the sketch version information to the gateway and Controller
 // gw.sendSketchInfo("AIQ Sensor MQ135", "1.0");

  // Register all sensors to gateway (they will be created as child devices)
//  gw.present(CHILD_ID_AIQ, S_AIR_QUALITY);  
   
}

void presentation()
{
  // Send the sketch version information to the gateway and Controller
  sendSketchInfo("AIQ Sensor MQ135", "1.0");
 
  // Register all sensors to gw (they will be created as child devices)
  present(CHILD_ID_AIQ, S_AIR_QUALITY);  
}

/*
 * get the calibrated ro based upon read resistance, and a know ppm
 */
long mq135_getro(long resvalue, double ppm) {
return (long)(resvalue * exp( log(MQ135_SCALINGFACTOR/ppm) / MQ135_EXPONENT ));
}

/*
 * get the ppm concentration
 */
double mq135_getppm(long resvalue, long ro) {
double ret = 0;
double validinterval = 0;
validinterval = resvalue/(double)ro;
if(validinterval<MQ135_MAXRSRO && validinterval>MQ135_MINRSRO) {
ret = (double)MQ135_SCALINGFACTOR * pow( ((double)resvalue/ro), MQ135_EXPONENT);
}
return ret;
}

void loop()      
{    
  uint16_t valr = analogRead(AIQ_SENSOR_ANALOG_PIN);// Get AIQ value
  Serial.println(val);
  uint16_t val =  ((float)22000*(1023-valr)/valr); 
  //during clean air calibration, read the Ro value and replace MQ135_DEFAULTRO value with it, you can even deactivate following function call.
  mq135_ro = mq135_getro(val, MQ135_DEFAULTPPM);
  //convert to ppm (using default ro)
  valAIQ = mq135_getppm(val, MQ135_DEFAULTRO);

  Serial.print ( "Val / Ro / value:");
  Serial.print ( val);
  Serial.print ( " / ");
  Serial.print ( mq135_ro);
  Serial.print ( " / ");
  Serial.print ( valAIQ);

 
  if (valAIQ != lastAIQ) {
    //  gw.send(msg.set(MQ135_DEFAULTPPM+(int)ceil(valAIQ)));
       send(msg.set(MQ135_DEFAULTPPM+(int)ceil(valAIQ)));
      lastAIQ = ceil(valAIQ);
  }
 
  // Power down the radio.  Note that the radio will get powered back up
  // on the next write() call.
  //gw.sleep(SLEEP_TIME); //sleep for: sleepTime
  sleep(SLEEP_TIME); //sleep for: sleepTime
}

 
/*****************************  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 ro, float *pcurve)
{
  return (double)(pcurve[0] * pow(((double)rs_ro_ratio/ro), pcurve[1]));
}

SENSOR LOG

16 MCO:BGN:INIT NODE,CP=RSNNA---,REL=255,VER=2.3.1
26 TSM:INIT
27 TSF:WUR:MS=0
28 TSM:INIT:TSP OK
30 TSM:FPAR
49 TSF:MSG:SEND,255-255-255-255,s=255,c=3,t=7,pt=0,l=0,sg=0,ft=0,st=OK:
2056 !TSM:FPAR:NO REPLY
2058 TSM:FPAR
2075 TSF:MSG:SEND,255-255-255-255,s=255,c=3,t=7,pt=0,l=0,sg=0,ft=0,st=OK:
4083 !TSM:FPAR:NO REPLY
4085 TSM:FPAR
4103 TSF:MSG:SEND,255-255-255-255,s=255,c=3,t=7,pt=0,l=0,sg=0,ft=0,st=OK:
6111 !TSM:FPAR:NO REPLY
6113 TSM:FPAR
6130 TSF:MSG:SEND,255-255-255-255,s=255,c=3,t=7,pt=0,l=0,sg=0,ft=0,st=OK:
8138 !TSM:FPAR:FAIL
8139 TSM:FAIL:CNT=1
8141 TSM:FAIL:DIS
8143 TSF:TDI:TSL

GATEWAY LOG

0;255;3;0;9;0 MCO:BGN:INIT GW,CP=RSNGA---,REL=255,VER=2.3.1
0;255;3;0;9;5 TSM:INIT
0;255;3;0;9;7 TSF:WUR:MS=0
0;255;3;0;9;9 TSM:INIT:TSP OK
0;255;3;0;9;12 TSM:INIT:GW MODE
0;255;3;0;9;15 TSM:READY:ID=0,PAR=0,DIS=0
0;255;3;0;9;18 MCO:REG:NOT NEEDED
0;255;3;0;14;Gateway startup complete.
0;255;0;0;18;2.3.1
0;255;3;0;9;23 MCO:BGN:STP
0;255;3;0;9;29 MCO:BGN:INIT OK,TSP=1
0;255;3;0;9;32 TSM:READY:NWD REQ
0;255;3;0;9;52 TSF:MSG:SEND,0-0-255-255,s=255,c=3,t=20,pt=0,l=0,sg=0,ft=0,st=OK:

Thank you very much for any help!!!

[qobouky]

Now I replaced mini pro and used nano instead. Data were send successfully.

Do you have any idea what can be wrong with mini pro?

[rejoe2]

@qobouky said in MQ135 with RS485:

!TSM:FPAR:FAIL

This basically means there's no communication between the node and GW.
Note: at RS485 transport layer, automatic NodeID assigning methods for the nodes will not work, so you have to do it manually.
Just saw this even isn't mentionned in the RS485 motion sketch example.

[qobouky]

@rejoe2 said in MQ135 with RS485:

NodeID

Hmm, I tried to define sensor as 30 but still the same result. In log of sensor I can see

114875 !TSM:FPAR:NO REPLY
114877 TSM:FPAR
114895 TSF:MSG:SEND,30-30-255-255,s=255,c=3,t=7,pt=0,l=0,sg=0,ft=0,st=OK:

I think that it is not a case. As I told everything works with arduino nano.

How I can check if data from sensor are reading?
It seems that code does not continue if sensor is not connected to gateway.

[qobouky]

I found an root cause.

In pin definition was

#define AIQ_SENSOR_ANALOG_PIN 1

but should be

#define AIQ_SENSOR_ANALOG_PIN A1

I do not know why with first definition it worked with nano but did not work with mini.