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Carbon Monixide Sensor

  1. Nov 16, 2006 #1
    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
  2. jcsd
  3. Nov 16, 2006 #2


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    Staff: Mentor

    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 [Broken]

    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.
    Last edited by a moderator: May 2, 2017
  4. Nov 16, 2006 #3
    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.
  5. Nov 17, 2006 #4
    Well, i emailed them No answer :(
  6. Nov 17, 2006 #5


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    Staff: Mentor

    That's why I suggested that you call them.
  7. Nov 17, 2006 #6
    any other solution :(

    there is a time delay between us around 8 hours , i called them in the morning but didn;t answer :(
  8. Nov 17, 2006 #7


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    Staff: Mentor

    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.
  9. Nov 18, 2006 #8
    The datasheet can be found in :

    http://www.hwsensor.com/English/pro_info/PDF/MQ300/GAS%20SENSOR%20MQ307A.pdf [Broken]
    Last edited by a moderator: May 2, 2017
  10. Nov 18, 2006 #9


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    Science Advisor
    Homework Helper

    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.
  11. Nov 19, 2006 #10
    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??

    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 :)
  12. Nov 19, 2006 #11
    I used RL = 13K
  13. Nov 19, 2006 #12


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    Science Advisor
    Homework Helper

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

    The data sheets arn't consistant between the 306 and 306a.
    Looks like a translation error.
  14. Nov 19, 2006 #13
    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??
  15. Nov 19, 2006 #14


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    Gold Member

    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.
  16. Nov 22, 2006 #15
    Thank you All...
    still waiting for the company to answer my phone call :(
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