Breaking gas leakage sensor

Dozens of explosions occur in Russia every year due to a gas leak. In particular, the sad record was noted in 2008, when only in January there were 7 powerful explosions in which people were injured and killed. On the destruction and loss, I do not say. And these are only cases that hit the federal news feed. In fact, gas leaks are much larger. Depreciation of equipment, carelessness and irresponsibility are the main causes of such tragedies. They may be less if more actively introduce gas leakage monitoring systems implemented on low-cost electrochemical sensors. One of these devices fell into my hands. The article is devoted to the analysis of the device and possible non-sports ways to use it. However, the main function of the device is entirely, therefore, after technical bullying, it will be further tested in a biogas laboratory, which can be read here , and then donated to Mother, who has gas all her life in the kitchen).

Attention! Age limit of article 18+

And we have gas in the apartment! And you?

In fact, gas is one of the most convenient things to use. Professional cooks prefer to cook it on gas stoves. It is fast, convenient, economical, and meat and good steaks, perhaps, can be cooked only on fire. Gas heats millions of people, and modern gas equipment is safe and secure, provided that you follow it closely and operate it correctly. Even with my not bad understanding of technology, I studied with interest the device of a gas boiler precisely from the point of view of safety. Yes, indeed, such devices are reliable.


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This simple picture shows the general principle of operation of the device, the construction is actually not quite simple. What is necessary in each such device is control of gas consumption and flame burning. To control it, use infrared sensors, and at the slightest interruptions in the gas supply, the automation reliably shuts off the device. Gas equipment must be installed only by gas service specialists and must be regularly checked.



With all the reliability of the equipment can not exclude the likelihood of gas leaks. To control such leaks in the gas add special odorous substances - odorants. Their task is to create a smell that is necessary to establish gas leaks mainly in household consumption. To give the required level of odor to the gas, the norms of odorants for ethyl mercaptan are set to not less than 16 g / 100 m3 of gas. These are extremely toxic and volatile substances with a disgusting smell. It is this smell that a person regards as a gas leak, while natural gas itself has no color or smell.

We control leaks

Gas leakage can occur for various reasons, but in most cases this is due to the negligence of a person. Milk ran away, gas was lowered on the stove and it went out, often small children play with gas. There may be jumps of the main pressure in the gas pipe due to the freezing of gas pipes in extreme cold, as condensate may accumulate in them. Therefore, it is useful to have a gas leak sensor that can alert people about the leak, for example, with an additional audible signal. One of these devices (link) I came across to study.



The device is externally made of good plastic, silk screen printing, but all the inscriptions are in English. Made, of course, in my beloved China. The device plugs directly into a power outlet and does not require batteries. Consumption is scanty (I think a few watts), so it is not able to wind a lot of electricity. The design is well thought out from the point of view of the gas cell. The device has special notches for air to penetrate more freely. However, to install the device, it is better to use a short extension cord and position it as stated in the instructions - for natural main gas closer to the ceiling (methane is lighter than air), and if you use liquefied gas or propane cylinders - to the floor, since this gas is heavier air and spreads down. When turned on, the device emits a short signal and begins to be calibrated. This process takes a few minutes. At this time, nothing happens and only a flashing dash on the digital indicator. When the device is calibrated, a zero appears on the screen. Calibration is an important point and the fact that it is very good. Since an integral sensor is used, the device takes the gas level at zero at the time of calibration, which reduces the likelihood of false alarms. This is convenient, for example, in the kitchen, when in any case, when a gas is set on fire, there is a short-term leak and it is better to calibrate the device with all the burners and the oven turned on and after a few minutes turn on the gas leak sensor for calibration, so that the device understands the “working” level of the air composition and did not pick when not needed. The device was tested in combat conditions in my biogas laboratory, which I told about in my post “Biogas from biomass” and at Mother’s house, which has gas all my life. By the way, these sensors are very useful in old houses, where prehistoric gas equipment is installed. Of course, I repeatedly tried to replace the stove, but this is not so easy. Mom, old school, small kitchen. Therefore, in the majority of old apartments there are such small slabs, although they were made very soundly. Even under Stalin)

Opening the device

Of course, I opened the device for its detailed study. It was not a lot of work, as there are no latches in it, everything is on screws.



Made the device by hardworking Chinese girls (boys), soldered by hand and not even laundered from rosin. However, everything is done soundly and even verified by the Chinese Quality Department). Of course, it was interesting for me on which sensor the device was made and how it was recorded according to the scheme. A priori, I thought that the device uses an MQ series sensor and was not mistaken. I did not find any more familiar parts (I'm talking about controllers, of course). The device put mysterious Chinese chips, and the device itself is designed with obvious redundancy. After all, the MQ series sensor can be run on a penny Attiny or ATmega in a few microseconds. And if Arduinka was lying around, then even faster. We connect the signal output of the sensor to any analog port, for example A0, supply power and after a minute we receive data):

int sensorValue; void setup() { Serial.begin(9600); //    } void loop() { sensorValue = analogRead(0); //      ? Serial.println(sensorValue, DEC); //     ,  ! delay(1000); //  1 ,    } 

This is not even a code to call. By the way, arduinschiki good fellows, the site is very faithful to all about these sensors collected. Link

But back to our device under investigation. Most likely, the circuit is designed to be used in various sensors and devices by replacing the sensor and flashing. Fine! Everything else is standard. Of course, I would add an additional fuse in the power supply circuit, but this is more likely for cowards than for brave Chinese engineers. Even in the device I was surprised by the signaling device at 85 dB. Gently spill liquid nails at the gas sensor.



Maybe 85 dB is not there, but it beeps loudly and rather nasty. Thus, the notification in the device is implemented soundly. By the way, the loud siren does not turn on immediately. The device first begins to pick, when the reading on the screen becomes more than three units, and if more than 9, a loud siren is activated. By type of car. Perhaps her neighbors can even hear.

A little about the gas sensor. The same was in my collection. This is the MQ series sensor from Henan Hanwei Electronics. A popular sensor from a series of electrochemical sensors, whose manufacturing technology is well developed. The principle of operation of the gas detection sensor is based on the property of changing the conductivity of a thin film layer of tin dioxide SnO2 when it comes into contact with the gas to be detected. Sensitivity to various gases is achieved by doping various impurities in the sensitive layer of the sensor. The sensor element itself consists of a ceramic microtuba with Al2O3 coating and a sensitive layer of tin dioxide deposited on it. A heating element passes inside the tube, which heats the sensitive layer to the temperature at which it begins to react to the gas being detected. When gas enters the sensor, gas is absorbed and, as a result, the sensor resistance drops. For a couple of hundred rubles, you can buy a choice from the MQ series sensors you need.



Heating is required for sensor operation. However, this is all miniature, so you will not feel any sensible heating of the sensor. The signal is, of course, analog. Sensors are reliable and quite durable if they are not used in aggressive conditions. Good speed, short recovery time. However, these sensors do not have very good selectivity, and also require calibration. But it gives the opportunity to have fun with him is not standard!

Not sports use. 18+

Such use happened due to the birthday of one of the employees, which we decided to slightly celebrate in a narrow circle. Gathered in a small meeting room by the end of the working day. A company of four drank brandy. About an hour later, in the room, where at that moment alcohol had already been drunk decently, the signals of the device, which was plugged in, began to be heard. It cheered those present. However, any approaching drunk person with the desire to blow on the device instantly caused a siren and a violent laugh. Thus, the device can be made and breathalyzer. No wonder. MQ sensors are more or less sensitive to different gases. This is well illustrated by the sensitivity graph for various gases.



Later it was found that 50 grams of strong alcohol (brandy) for 3-4 hours causes a siren when you exhale for 5 seconds to the sensor device.

Now about smoking. Since the concentration of CO in the smoke is already exorbitant, the device responds instantly to tobacco smoke. Therefore, in the smoking room, literally in a minute the siren turns on. An experiment was also conducted with smokers and non-smokers. Purging through the tube for 10 seconds.



The standard for a non-smoking person was chosen a wonderful girl with a beautiful name Lucien, who could not blow out more than 2 units on the device. Smoker blows 8-9 units. Literally dragon exhaust.

findings

The device is working. From good - great design, reliability. I think, having bought such a device, you can make an original non-standard gift for someone who uses gas in the kitchen or heats the house for them. Low energy consumption. Very high sensitivity. The siren is turned on for the entire coil at concentrations of more than 0.2% of explosive. There is plenty of time to respond to a gas leak. On the other hand, weak selectivity. The device may give false positives. It is also necessary to carefully consider the installation site. Of course, I would like to have a wireless data transfer protocol from the device, it would be much more interesting. Well, in general, the device is definitely useful.

Didn't you forget to turn off the gas when leaving home?

Have a nice day, everyone!

PS - And the iron?