Gas sensor
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sergey
Sep 21, 2019, 1:32:14 PM9/21/19
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Hi! Being concerned that my country house becomes older and older and little cracks along the masonry of wood burning stove has been appearing i decided to make gas analyser for CO detection. Initially i selected MQ series - quite cheap low selective gas sensors. They are able to detect wide spectre of different gases.
I bought:
After some time i figured out that both of them pointless for my goal and switched to more professional line of sesnors and eventually stopped at this one : https://www.ebay.com/itm/ZE07-CO-Carbon-Monoxide-Module-Electrochemical-Sensor-Of-Concentration/142765627442?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649
Turns out that MQ-9 shows very specific selectivity, like to react on gas from the lighter, but does not respond to bottled gas(LPG).
Opposit it MQ-2 reacts on anything - alcohol,LPG,bensin, acetone and even (peoples says) on a farting.
Based on these traits of MQ-2 i decided to make LPG leakage detector with this sensor. I have small room for bottled LPG and i placed the detector there.
I share code with you , and i hope Mike won't criticize my silly code on top of his magnificent system.
The sensor works simply under ESP Wemos D1. Led might be connected to suitable pin for visualisation of threshold trigger (don't forget for limiting resistor).
Initially you have to heat up the sensor for at least several hours. When figures calms down and you are pretty sure that the sensor situated properly and in a "clean air" press reset either on ESP board or on http of sensor. It give opportunity for the sensor remember "clean air" values. And further calculates air pollutions based this value.
More information inside the ino file. Criticism and any ideas about sensors are welcome.
Lone Surviver
Sep 21, 2019, 3:36:42 PM9/21/19
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Sergey,
It looks like you are starting another way-cool project. I can't help you with the programming or the hardware....but a couple of things about gasses might be useful.
You mentioned having a small room with LPG tanks in it. LPG has become a catch-all name for several gasses and some are a mix of flammable gas.
It is not usually a good idea to store tanks inside a closed room...here's why:
Natural gas is lighter than air...and it will rise into any rooms (spaces) above it...and if you are unlucky...something very bad might happen.
Propane is heavier than air...and will descend (settle) to the lowest part of a dwelling....and again...you gotta be lucky and hope you don't have a gas driven water heater in the basement as an ignition source.
If you must store them in a closed area....a gas detector is a wise move....very wise.....
You mention cracks in the masonry of your wood burning stove. Is this an entirely masonry fireplace? Or is there a metal insert that actually contains the fire?
You also challenge my memory on wood burning stoves generation CO.....That seems improbable ( no guarantees here) because of the enormous volume of air necessary to make them work...but you can never be over cautious.
I did some quick reading on fireplaces and CO............seems there is a way to screw that up too......It has never been reported in my area because it is rarely a primary heat source here.
My own home requires me to keep the furnace off when i have the fireplace going because they compete for the available air....then i have to open a window ....and there goes the heat......
I posted this just in case someone needs the info on flammable gas characteristics.
sergey
Sep 21, 2019, 5:36:32 PM9/21/19
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Thanks for your comment. Typically we use propane-butane mixture for the bottled gas, that has 28 gram/mol molar weight - almost equal to the air.. Due to my poor vocabulary i mentioned "room" , actually it's not the room it's a special box, situated on the outsides wall of the kitchen. I decided to exploit ability of this sensor fill even small concentration of stuff. Valves on ballones fails from time to time and starts leak the gas. The sensor is able to catch this even faster then humans nose.
Yes, it almost entirely masonry fireplace (from bricks) with big glass-made doors. It is quite common thing when people in a hurry to close the damper of the stove with incompletely burned wood....
And even small dose is enough for bad things...
Sure i'm trying to maintain my stove in good condition , but anyway it's big enought and small craks might appears in unpredictable places.
Poisoning by CO is very common thing.... unfortunately. Lucky it isn't my primary living place but all my family and my friends likes watching a fire.)))
sergey
Nov 2, 2019, 6:00:40 AM11/2/19
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Hi folks!
In continue my sensor's story i want to introduce one more sensor which is considered to be as more professional device.https://www.ebay.com/itm/ZE07-CO-Carbon-monoxide-module-electrochemical-sensor-of-gas-concentration/252562355641?hash=item3acde3b5b9:g:~gMAAOSwmfhX7RD4
The ZE07-CO sensor is intended for measurement of CO concentration in air. Everybody know that CO hasn't smell, invisible but poisoning gas. Being playing with cheap air sensors described above i noticed that any wooden stove emit harmful gases at particular circumstances ( end of burning , low atmosphere pressure and etc.) I have got wonderful and expensive german made wooden burning stove that works by the principle of slow burning Bullerjan that heats second floor bedroom. All such kind of stove works on principle slow burning in lack of air that allows them works for long time with minimal fuel consumption.It consider to be obvious (at least in our country) that if something was made in Germany it going to be extremely reliable and good working. Turns out that the stove emit quite big amount of CO especially during nasty weather when atmosphere pressure is low. The concentration has measured by this sensor reached up to 25 ppm in a peak whereas normal concentration floated about 0.5 ppm. The concentration gradient has reached their maximum close the ceiling (when CO climb toghether with hot air) then it delluted around room with average concentration about 10 ppm in their maximum. It is clear that all these concentration not considered to be a dangerous for health but anyway they are harmful and would be better to minimise the leakage somehow. Later i figured out from seller that asbestos sealing ring is needed to be serviced after a year of using... (i didn't know that and it wasn't printed anywhere)
I have the figures, that this sensor shows , checked by my acquaintance who has a car service and they has a lot of different industrial sensors. Datasheet says that the sensors goes factory calibrated and has their own internal autocalibration.
Due to inside organisation the sensor is quite slow it reacts on any changes averagely after a 15 sec.It has several outputs and i decided to use the digital one with UART interface. Due to code debugging necessity i need to move TX and RX on other GPIOs. There are several libraries in the internet dedicated to these sensors but all doesn't work or seems "underprepared" i decided to write down my own functions (frankly i don't know how to write the librarary :) )
I've added two LEDs to the circuit , one of them serviced "warning threshold" other one is for "dangerous threshold" both are tunable over standart Mpp's http interface. Initially i wanted to use a buzzer for "dangerous threshold", but unfortunately i didn't find any suitable (by current over GPIO) buzzer for this purpose, if someone can share any information about it with me i would appreciate it.
I would rather don't want to publish the code , you know ...all these stuff around human health is so complicated.... but if somebody interested in such project i ready to share.
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