Carbon monoxide Detector Help

[pouchito]

I used the graphs of the datasheet to compare my results.
Here are the results i got while testing the CO sensor in Air :

initially when no heater voltage applied,it was 1.78v
heater voltage at 0.6v ==>output voltage 1.83v ---- 1.82---- 1.81 1.8
at 3v at the first second 2.4v
then quickly 1.8 --- 1.74 ---1.73

at 0.6 v at the first second 4.2v
then quickly 3 --- 2.3 ---1.8--- 1.79 fixed at this value


Comparing it to the graph, i think it is ok, am i right ?

 

[fingaz]

ok,

at 3V, it looks loike it takes a couple of seconds to warm up to temp. the test in air look like pretty much like the graph on the data sheet.

The results from the test you did in CO vary a lot, so I would do more testing to get a better idea of what readings you can reliably expect. . . then you can design your circuit based on the 'likely' readings

 

[pouchito]

Exactly this is what i analysed too.
But don't you think i m on the right track ??
Because when explosed to the CO it varies==> sensor working ???
What i need to know is maybe we can do the readings only one and cannot do it twice , maybe we need to reset all the sustem and wait for the CO to evapor from the sensor and redo it .what do u think ??

do u think it s better to change the value of the RL ???

 

[fingaz]

I think you're certainly on the right track there. Exposing the sensor to CO causes the voltage across RL to vary, this would seem to indicate that the sensor is working. We don't know how long it will take for all traces of the CO to disperse, and the sensor to return to it's 'normal' readings, so maybe leave it while before repeating the test. See if you get similar readings then.

I would not alter the load resistance, this will affect the results you get on any further tests and you would not be able to compare them to the previous results.

 

[pouchito]

Thanks

Concerning the MQ307 i m using, i ve searched the net and was not able to find the datasheet :S
I found the datasheet of the MQ307A
They said that they are identical but the voltage heater differs
the MQ307A needs 0.9V while the MQ307 needs 3 V
But they didn't specify the low heater voltage
What i know the low heater volage for the MQ307A is 0.2 V
I ASSUMED the MQ307 low heater voltage 0.6 V
Do you think am i right in my assumptions ???

 

[fingaz]

That's the question?

We don't know, and we can only assume. I think the best way to find out the ideal voltage for the heater, to detect CO is to Try different voltages, and see the test results. we know it works with 0.6V, but maybe this is not the 'ideal' voltage. Maybe try 1.2V(or0.9V) and compare the results. see which gives you the 'most distinct' difference between tests 'in the presence of CO' and tests in 'clean air'
I would assume that whichever gives the greater difference is closer to the 'ideal' heater voltage.

I'm sure we'll get there in the end

 

[pouchito]

OH!!!!
You don't know how much is difficult the testings...
I told you i was poisoned the day before
Gold Loves me I didn't die :S
That's is why i m trying to collect as much data as i can and analyse it before performing another test

I was thinking since i m not interested in the methane and i don't care to test it , do you think i can apply directly the low assumed voltage and not enter a square wave (30sec for low voltage and 120sec for high voltage )

Any suggestions???

 

[audioguru]

You could just measure the amount of the colour blue of your skin to determine the amount of CO in the air.

Imagine trying to use an old sensor without having its datasheet. It is nearly impossible.

The readings are very different each time a measurement is made so who knows what is being measured???

 

[Hero999]

Hi Hero999,

Well I tested the CO and post the results, can u check them pls and tell me if it sounds logical ???

You r right the CO and his relatives (CO2....) are very toxic
I had an irresistable headache....vomitting....dizzyy....
Can you imagine that i m not able to analyze and interpret what i got from the testings ...still not able to fully concentrate :S

Bloodyhell it sounds like you're lucky to have survived.

Perhaps you should consider seeking medical attention, there may be long term effects, such as brain damage!

 

[audioguru]

You are very lucky to still be alive after playing with then breathing poison.

A doctor might tell you that you need a brain or head transplant because your original brain might be damaged too much and can't be repaired.

 

[Hero999]

Also is this device going to be safety critical?

If so be very careful, if you kill or injure yourself then fair enough but if someone else is relying on it then you might be sued (at the very least).

Either way, playing with poison gas without a gas mask is like playing with magnetrons and microwave transofmers - stupid.

 

[fingaz]

If you want to collect more data, email the manufacturer. . . In the mean time we are only guessing. We have no way of comparing the results to the concentration of CO in the air. Like I said before, much of this is guess work. The test results you got before would tend to indicate that the sensor is working, but you have no way of reliably calibrating it.

I would suggest that any further tesing is done at a distance (by using wires to extend the sensor?) and as I said twice before IN A WELL VENTILATED AREA!

I did not realise that the testing procedure had caused you such problems! That's my fault for not reading your thread fully.

 

[pouchito]

I soldered the sensor with a 2 m cable but did not put a mask....I was concentrating on the experiment and didnt take much precautions ...
Anyway I hope that it does not have a bad effect on my brain later on

TO Summarize what I m up to :

- sensor works fine in air ( comapring it to the datasheet's graph)
-when explosed to the CO it varies but yet we can't tell anything about the values because it needs to be calibrated and we don't know how
- we can't tell what must be the low heater voltage unless the company answers me (and it is not answering i need someone who is living in China to make them a call)

- Still confused if i must turn the heater ON or there is NO need

Am I right ???

 

[Hero999]

Wikipedia says "A concentration of as little as 0.04% (400 parts per million) carbon monoxide in the air can be fatal." which isn't much so testing in a well ventilated area won't give adequate protection against poisoning.

You should wear a mask connected to a supply of fresh air, perhapps wearing a nose clip and breathing through a piece of tube with the other end in fresh air might do the job.

Edit:
Testing from a safe distance would be just as safe and more convenient to.

 

[pouchito]

I will do all of that in my second testings
But i need your opinion and to collect as much information as i can so i won't need a third test....

 

[Hero999]

There's no way of calibrating it without a sample of carbon monoxide of a known concentration or a another calibrated instrument to compare it with.

 

[pouchito]

You are 100/100 right Hero
But pls can u tell me if what i understood is correct ? concerning the heater voltage ....Am i obliged to supplu the low then the high voltage even if i m not interested in measuring the methane???

 

[nisrine]

the RL value is important too, you said you took it to be 13 K . I think it will be better to make it smaller

 

[nisrine]

God Be With You in your second Testing ..........

 

[fingaz]

Wikipedia says "A concentration of as little as 0.04% (400 parts per million) carbon monoxide in the air can be fatal." which isn't much so testing in a well ventilated area won't give adequate protection against poisoning.

Edit:
Testing from a safe distance would be just as safe and more convenient to.

I 'assumed' that testing in a well ventilated area (eg OUTSIDE) would be just like standing next to a car while its engine is running (since he is using an engine exhaust to provide the CO)

But I think we all agree that the best, and safest option is to keep as much distance as possible between the 'experimenter' and the source of the gas.