simple oxygen sensor

Hi ,

I would like to install an oxygensensor in the engineroom of a boat. this room is closed, so it would be nice to see if its actually enough oxygen there. Now there is the question what kind of sensor I should use: http://playground.arduino.cc/Main/MQGasSensors

my first guess is to use MQ2 sensor for"flamable and combustible gasses." (what is the effect of the heater on flamable gases?)

but actually it is the amount of oxygen in the air, I am interested in. so what is the best sensor for this ? MQ135 can detect "air quality"(what does this mean?)

here i found a lot of different oxygen sensors: http://www.apollo-sensors.com/s04/apollo-sensors/yjml/20080923/2183375/3.html

and O2S-XX-T3( http://www.mcsensors.com/PDF/O2S-XX-T3%E8%BF%B7%E4%BD%A0%E5%9E%8B%E6%8E%A2%E5%A4%B4.pdf ) looks nice and operates at 4,5V. but the internal temperature is 700°C. what if there is a fuelleakage? :sweat_smile:

and here is one sensor, which operates without heater and only at roomtemp!(not really useful). and it costs 70bugs!(way to much) http://www.aliexpress.com/store/product/The-FIGARO-oxygen-sensor-KE-25-KE-50-KE-25F3-Original-and-Stock/614934_656857962.html

what do you think, any suggestion?:) thank you!

The heater inside the sensor is a real danger with combustable gasses. Don't even think about putting it in a closed engine room.

The 70 dollars seems a normal price, many cost more.

Could a lambda sensor for a car be used as oxygen sensor ? Used ones are less than 70 dollars. I don't know if they need heat.

Hi Erdin, :)

so most of the sensors from this list (http://playground.arduino.cc/Main/MQGasSensors) work with heating/oxidation.

in this sheet (http://www.pololu.com/file/download/MQ2.pdf?file_id=0J309) they write about portable applications in industry. Now I imagine a worker going into a tank and he gets an explosive warning. So I am going to check out the lambda sensor, thanks for that.

I would be very glad, if somebody can share some experience with this devices.

The MQ series use mostly 5V for the heater. Some use a lower voltage, but still the heater inside gets hot. That is the way these sensors work. http://en.wikipedia.org/wiki/Electrochemical_gas_sensor

I'm sure they write about industrial applications. But these cheap sensors are best used indoors in a house. Since they are sensitive, a little change of air compounds can be detected. A closed engine room on the other hand is something that could be filled with gasses if something went wrong. Someone going in a tank should not use these sensors. Professional gas sensors costs hundreds of dollars. Most of those devices combine a few sensors. I think the oxygen sensor and temperature sensor are used to correct the other sensors.

The best way to use the MQ sensors is for air quality. For example the MQ135 you mentioned. It can be used indoors and it is sensitive for a range of smelly and harmful gasses. If the results are printed over a long period it is possible to say when the air quality is good or not. So you could make something that shows the text "please open window".

the MQ-2 sensor is sensitive for flamable gases (http://playground.arduino.cc/Main/MQGasSensors).

the application i was thinking of was something like you sad: actually the arduino should warn me if there are gases or too little oxygen and that I should open the door.

a lambdasensor works grate if there is air to compair with. in this case i would not be happy to have one end of the sensor exposed to the outside of the room, because there is wind and rain and snow and the sensor would not stay functional for a long time.

The MQ-2 is the cheapest gas sensor I think. 3 dollars on Ebay.

I strongly suggest you don't use the MQ sensors, and use a sensor without a heater. That is going to cost money, there is no other way.