Designing Carbon Monoxide Detector Circuit with MQ307A Sensor: Need Help!

[pouchito]

Hi All,

I m designing a carbon monoxide detector circuit, I bought the MQ307A carbon monoxide sensor but unfortunately i was not able to find on the net any useful documentaion related to it :(

Please I urgently need your help to solve this problem
All i found out is the datasheet but i was not able to understand 100/100 what s going on, All the other sensor i found contains 4 pins while mine contains 3 pins and i ve no time to import other sensors from outside my country

Thanks in advance

 

[berkeman]

I did a google search on MQ307A carbon monoxide sensor, which got me to the manufacturer, Hanwei:

http://sensor.diytrade.com/sdp/58594/4/cp-25284.html

Try clicking on the "Contact Us" button for their phone numbers. Give them a call and ask for Tech Support or some other resource that they may be able to provide you.

 

[wxrocks]

I would guess one pin is your supply, one your common, and one is your output voltage. Maybe post the datasheet in pdf form here and someone could help.

 

[pouchito]

Well, i emailed them No answer :(

 

[berkeman]

Well, i emailed them No answer :(

That's why I suggested that you call them.

 

[pouchito]

any other solution :(

there is a time delay between us around 8 hours , i called them in the morning but didn;t answer :(

 

[berkeman]

Well, you say you have the datasheet. Can you post a pointer to it or scan it and post it here for us to look at? The datasheet should be sufficient in most cases.

 

[pouchito]

The datasheet can be found in :

http://www.hwsensor.com/English/pro_info/PDF/MQ300/GAS%20SENSOR%20MQ307A.pdf

 

[NoTime]

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

pin 1 common ground.
Pin 3 heater +0.2v(+-5%) low +0.9v high(+-0.1v)@120ma
Vc +5v to RL (1K-10k) to pin 2.
Output signal acrost RL.

 

[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 --- 1.2at 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??

As i understood is when i apply the low voltage (0.6v in this case) i will be able to measure the CO
and when i apply the high voltage (3V in this case) i ll be able to measure the methane ,is this true ?

Thanks for all your help Dudes :)

 

[pouchito]

I used RL = 13K

 

[NoTime]

For the 306, apparently a 3v heater.
Low looks it might be 0.9v.

The data sheets arn't consistent between the 306 and 306a.
Looks like a translation error.

 

[pouchito]

I m using the MQ 307 and not 306

No there s no error
But they posted only the datasheet of the MQ307A and said that the differebce is in the heater voltage which is 3V instead of 0.9V but didn't specify what to use instead of 0.2V (low heater voltage ) ...:(
ANyone knows??

 

[dlgoff]

I would think that the sensor would be put in a stream of gas inorder to allow the temperature to stabalize. I've seen CO2 detectors that have a small pump to supply a constant gas flow. However they were IR devices.

 

[pouchito]

Thank you All...
still waiting for the company to answer my phone call :(