MQ2 Sensor w/AirQuality Sketch
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I'm using similar sensors, this test sketch works fine for me, but I'm using raw readings from this sensors.
8 sensors connected to A0-A7 pins on arduino nano directly to analog output pin on each sensor board.#include <SPI.h> #include <MySensor.h> unsigned long SLEEP_TIME = 10000; // Sleep time between reports (in milliseconds) #define NODE_ID 4 MySensor gw; MyMessage msg(0, V_VAR1); int lastLightLevel[8] = {0}; unsigned long lastRefreshTime = 0; void setup() { pinMode(13, OUTPUT); // warm up sensors (3 minutes) for (int i = 0; i < 180; i++) { digitalWrite(13, HIGH); delay(250); digitalWrite(13, LOW); delay(250); digitalWrite(13, HIGH); delay(250); digitalWrite(13, LOW); delay(250); } gw.begin(NULL, NODE_ID); gw.sendSketchInfo("GasSensors", "1.5"); gw.present(1, S_AIR_QUALITY, false, "MQ-2"); gw.present(2, S_AIR_QUALITY, false, "MQ-3"); gw.present(3, S_AIR_QUALITY, false, "MQ-4"); gw.present(4, S_AIR_QUALITY, false, "MQ-6"); gw.present(5, S_AIR_QUALITY, false, "MQ-7"); gw.present(6, S_AIR_QUALITY, false, "MQ-8"); gw.present(7, S_AIR_QUALITY, false, "MQ-9"); gw.present(8, S_AIR_QUALITY, false, "MQ-135"); } void loop() { gw.wait(100); boolean bNeedRefresh = (millis() - lastRefreshTime) > SLEEP_TIME; if (bNeedRefresh) { lastRefreshTime = millis(); } for (int i = 0; i < 8; i++) { int lightLevel = 0; for (int j = 0; j < 32; j++) lightLevel += analogRead(i); lightLevel = (lightLevel / 32); int nDifference = lastLightLevel[i] - lightLevel; if ((abs(nDifference) > 5) || bNeedRefresh) { gw.send(msg.setSensor(i + 1).set(lightLevel)); lastLightLevel[i] = lightLevel; } } }Raw ADC readings are 20-80 (differs from sensor to sensor) for fresh outdoor air.
@robosensor What is on pin 13? In the Setup() warmup part?
btw, I am getting a value of 1 or 2, after warmup. -
@robosensor What is on pin 13? In the Setup() warmup part?
btw, I am getting a value of 1 or 2, after warmup.@gigaguy pin 13 connected to board's led :)
Warm up is just 3-minute pause (with led blinking) between power up and start of main loop measurements transmission. Cold sensors shows very big measurements, so I heating them up for 3 minutes. -
@robosensor What is on pin 13? In the Setup() warmup part?
btw, I am getting a value of 1 or 2, after warmup.@gigaguy
example response of sensors for natural gas (left) and alcohol (right):
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@robosensor this graph shows well the limit ofg the MQ gas sensors, they somehow all react to the same gases, and thus are not one gas specific.
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@robosensor this graph shows well the limit ofg the MQ gas sensors, they somehow all react to the same gases, and thus are not one gas specific.
@epierre in general, you are right, but there are exceptions.
This measurements, but one sensor per graph:
And 6-day graph of all sensors:
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@robosensor sure, but people need to know not to rely for their life on these classes of sensors.
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is it normal that the reads of my MQ-2 sensor are 0ppm in fresh air?
If I use a lighter to throw some gas, the reads skyrocket and then without gas they go back to zero.
Should I adjust the sensitivity? -
@Viper_Scull If you follow my method, it considers clean air has no toxic gas so it should be 0.
If you are able to do a calibration, you could change that, but I would recommend to keep the straight lean air way if you cannot do that.
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@Viper_Scull If you follow my method, it considers clean air has no toxic gas so it should be 0.
If you are able to do a calibration, you could change that, but I would recommend to keep the straight lean air way if you cannot do that.
@epierre said:
@Viper_Scull If you follow my method, it considers clean air has no toxic gas so it should be 0.
If you are able to do a calibration, you could change that, but I would recommend to keep the straight lean air way if you cannot do that.
@epierre I use the AirQualitySensor example in the MySensors library that I believe is your work indeed. Happy now to know that it's ok 0ppm for clean air.
One thing I noticed on the sketch is that last_mq inital value is 0. If we are in clean air, no value is send to the gateway when connected because val_mq = last_mq, so the controller would have no data to display unless it sets it to zero by default or gas is present.
By the way, I can't get domoticz to recognize this sensor. It receives the name of the sketch and the version, but although I can see that the sensor sends the value, there's no sign of it in the log of domotic and no device is recognized.
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@Viper_Scull I have someone else reporting this, you should ask @GizMoCuz for him to support it
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@epierre, already asked. Turns out, domoticz doesn't support V_VARs. Changing V_VAR1 in the sketch for V_DUST_LEVEL works.
@Viper_Scull Domoticz supports V_VARs, just not as a viewable or modifiable value on the controller. It will store and return the V_VARs values for the sketch, nothing more.
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