Carbon monoxide Detector Help - Electronic Circuits Projects Diagrams Free

pouchito · 17th November 2006, 08:23 PM

Hi All,

I am designing a circuit that detects the CO in the air.
I bought the carbon monoxyde sensor called (MQ 307 hanwei manufacturer) but unfortunately i didn't find on the net any docs related to it.
i ve just found the datasheet which didn't help me too much analysing its operation sad.gif

All the docs i found are related to figaro sensor that have 4 pins while mine has 3 pins

Please can anyone help
Thanks in advance

audioguru · 17th November 2006, 08:44 PM

Gather all the information for a project first, design it then order its parts.

Are you going to learn how to speak Chinese then go to the manufacturer hoping that somebody there knows anything about your sensor?

fingaz · 18th November 2006, 09:26 AM

I assume this is the sensor you got.

Look here for the info on pins: http://www.hwsensor.com/English/pro_...nfo/Gassgm.htm
And example circuits

Your device actually has 4 pins (kind of) but either pin A or pin B is connected to one end of the heater coil (pin 3)

See the attatched images

Hope this is of some help to you

pouchito · 18th November 2006, 10:54 AM

I ve checked the datasheet
but i m not able to fully understand its operation
can you help ??
what i understood is either the heater gonna work or the sensor, am i right ?

fingaz · 18th November 2006, 11:24 AM

From what i can gather, you need to power the heater with 5V (either DC or AC) and the voltage between pins 2 and 3 will alter depending on the level of CO(carbon monoxide) in the air. Though I'm not 100% sure of this. The variable resistor it shows is used to adjust sensitivity.

The supply voltage needs to be accurate (to within 0.1V) I'd guess you'll be using DC power source because it's probably more convenient for this, and I'd recommend a voltage regulator (7805 or similar) in which case you need a supply voltage of at least 7V

pouchito · 18th November 2006, 11:28 AM

what i understood is that the heater voltage must be equal to 0.9v
the power supply =5-6V
either the heater or the sensor gonna work, they will not work together

Am i right ????

what do u think the value of the variable resistor must be ???

Hero999 · 18th November 2006, 11:44 AM

If you post the datasheet here and we might be able to help you.

pouchito · 18th November 2006, 11:46 AM

The datasheet is :
http://www.hwsensor.com/English/pro_...R%20MQ307A.pdf

Hero999 · 18th November 2006, 11:58 AM

That link doesn't work for me.

pouchito · 18th November 2006, 12:04 PM

pls check the attachement

fingaz · 18th November 2006, 12:51 PM

Ok, things look different on the datasheet.

So you need 'a low temerature' to detect CO and a 'high temerature' to detect methane. I guess you need to power the heater with 0.2V for the low temp.

Looking at the test circuit, pin 1 is common ground for both the test and heater voltage, pin 2 is the sensor output, and pin3 is the +v for the heater.
Test voltage=5v

If you take a 5v supply, connect the negative to pin 1. connect +0.2v to pin 3, and connect load resistance between pin 2 and +5V, the voltage across the load resistance will alter depending on the level of CO.

If you did the same, but with a supply of +0.9V to pin 3, then the voltage across the load would alter depending on the level of Methane.

I "THINK" that's how it would work, though It will only let me view part of the data sheet.

pouchito · 19th November 2006, 09:12 AM

Well I tested the MQ307 which requires a 3V instead for the 0.9V for the heater and i got these results :

in CO:
at t=0 and no heater voltage applied it was 1.74v

heater at 0.6v (for 120s) 1.84v ---- 1.82---- 1.81--- 1.8 ----- 1.73 ---- 1.57

heater at 3v (for 30 sec) 1.3v ---- 1.24 --- 1.22

again heater at 0.6 v 0.28 --- 0.24 ---0.22--- 0.16

again at 3v 1.18 --- 1.17 --- 1.2

at 0.6v 0.3 --- 0.1

I took 0.6V as the low voltage for the heater instead of 0.2V (MQ307A) since there is no datasheet for the MQ307 all we know it is the same exept for the heater voltage

Does the testings seems logical??
Do you think we can do the testings only once since we did not get the same results in the later case??

Thanks for helping Dudes

pouchito · 19th November 2006, 09:49 AM

Hello Fingaz,which pages you were not able to see?

pouchito · 19th November 2006, 09:53 AM

if you can't see page 2 of the pdf you need to allow the Chinese simplified update.

Hero999 · 19th November 2006, 10:26 AM

If you manage to get this working, how are you going to test it?

Do you have a bottle of CO handy or something?

Or you could burn some charcoal.

Anyway even though you know CO is highly toxic, I recommend you read the Wikipedia artical first before playing with the stuff. One breath of that stuff and you're history for sure!
http://en.wikipedia.org/wiki/Carbon_monoxide_poisoning

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17th November 2006, 08:23 PM	(permalink)
pouchito	Carbon monoxide Detector Help Hi All, I am designing a circuit that detects the CO in the air. I bought the carbon monoxyde sensor called (MQ 307 hanwei manufacturer) but unfortunately i didn't find on the net any docs related to it. i ve just found the datasheet which didn't help me too much analysing its operation sad.gif All the docs i found are related to figaro sensor that have 4 pins while mine has 3 pins Please can anyone help Thanks in advance

17th November 2006, 08:44 PM	(permalink)
audioguru	Gather all the information for a project first, design it then order its parts. Are you going to learn how to speak Chinese then go to the manufacturer hoping that somebody there knows anything about your sensor? __________________ Uncle $crooge

18th November 2006, 10:54 AM	(permalink)
pouchito	I ve checked the datasheet but i m not able to fully understand its operation can you help ?? what i understood is either the heater gonna work or the sensor, am i right ?

18th November 2006, 11:24 AM	(permalink)
fingaz	From what i can gather, you need to power the heater with 5V (either DC or AC) and the voltage between pins 2 and 3 will alter depending on the level of CO(carbon monoxide) in the air. Though I'm not 100% sure of this. The variable resistor it shows is used to adjust sensitivity. The supply voltage needs to be accurate (to within 0.1V) I'd guess you'll be using DC power source because it's probably more convenient for this, and I'd recommend a voltage regulator (7805 or similar) in which case you need a supply voltage of at least 7V __________________ 'Intellectuals solve problems. . . Geniuses prevent them.' . . . Albert Einstein

18th November 2006, 11:28 AM	(permalink)
pouchito	what i understood is that the heater voltage must be equal to 0.9v the power supply =5-6V either the heater or the sensor gonna work, they will not work together Am i right ???? what do u think the value of the variable resistor must be ???

18th November 2006, 11:44 AM	(permalink)
Hero999	If you post the datasheet here and we might be able to help you. __________________ I also post at the following sites: http://www.stop-microsoft.org http://www.heated-debates.com Screen name: Aloone_Jonez

18th November 2006, 11:46 AM	(permalink)
pouchito	The datasheet is : http://www.hwsensor.com/English/pro_...R%20MQ307A.pdf

18th November 2006, 11:58 AM	(permalink)
Hero999	That link doesn't work for me. __________________ I also post at the following sites: http://www.stop-microsoft.org http://www.heated-debates.com Screen name: Aloone_Jonez

18th November 2006, 12:51 PM	(permalink)
fingaz	Ok, things look different on the datasheet. So you need 'a low temerature' to detect CO and a 'high temerature' to detect methane. I guess you need to power the heater with 0.2V for the low temp. Looking at the test circuit, pin 1 is common ground for both the test and heater voltage, pin 2 is the sensor output, and pin3 is the +v for the heater. Test voltage=5v If you take a 5v supply, connect the negative to pin 1. connect +0.2v to pin 3, and connect load resistance between pin 2 and +5V, the voltage across the load resistance will alter depending on the level of CO. If you did the same, but with a supply of +0.9V to pin 3, then the voltage across the load would alter depending on the level of Methane. I "THINK" that's how it would work, though It will only let me view part of the data sheet. __________________ 'Intellectuals solve problems. . . Geniuses prevent them.' . . . Albert Einstein

19th November 2006, 09:12 AM	(permalink)
pouchito	Well I tested the MQ307 which requires a 3V instead for the 0.9V for the heater and i got these results : in CO: at t=0 and no heater voltage applied it was 1.74v heater at 0.6v (for 120s) 1.84v ---- 1.82---- 1.81--- 1.8 ----- 1.73 ---- 1.57 heater at 3v (for 30 sec) 1.3v ---- 1.24 --- 1.22 again heater at 0.6 v 0.28 --- 0.24 ---0.22--- 0.16 again at 3v 1.18 --- 1.17 --- 1.2 at 0.6v 0.3 --- 0.1 I took 0.6V as the low voltage for the heater instead of 0.2V (MQ307A) since there is no datasheet for the MQ307 all we know it is the same exept for the heater voltage Does the testings seems logical?? Do you think we can do the testings only once since we did not get the same results in the later case?? Thanks for helping Dudes

19th November 2006, 09:49 AM	(permalink)
pouchito	Hello Fingaz,which pages you were not able to see?

19th November 2006, 09:53 AM	(permalink)
pouchito	if you can't see page 2 of the pdf you need to allow the Chinese simplified update.

19th November 2006, 10:26 AM	(permalink)
Hero999	If you manage to get this working, how are you going to test it? Do you have a bottle of CO handy or something? Or you could burn some charcoal. Anyway even though you know CO is highly toxic, I recommend you read the Wikipedia artical first before playing with the stuff. One breath of that stuff and you're history for sure! http://en.wikipedia.org/wiki/Carbon_monoxide_poisoning __________________ I also post at the following sites: http://www.stop-microsoft.org http://www.heated-debates.com Screen name: Aloone_Jonez