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!!!
