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Description: Simple breakout board for the MQ - 3, MQ - 4 and MQ - 6 gas sensors.  All you need is VCC at 5V, GND, and a resistor to an ADC, that is it.

Note: This is the PCB only. Sensors listed below.

Dimensions: 16.8mm diameter

Documents:


 

Comments 26 comments

  • Hi everyone. Just managed to get a proper connection scheme for this thing. So here you go: (GND TO Ground), (A1 TO +5V), (H1 TO +5V) and [B1 TO (10kohm to ground) AND TO (Analog pin)]. Works for me. Tried it with…perfume :D

  • I tested the board with a multimeter’s buzzer and found that both As are connected together and both Bs are connected together (see the datasheet for As and Bs). So all you need is:

    H1 -> 5V, A1 -> 5V, GND -> GND, B1 -> Microcontroller’s input

  • It would be great if you guys could carry a gas sensor socket, like this one.

  • i am trying to use this with the MQ-7 and can’t figure out the orientation. does the side with Mq-7 sticker align with the “Gas Sensor” print on the breakout board? I tried looking for a wiring diagram on the MQ-7 but couldn’t find a good response

  • Has anyone figured out this breakout board wiring? All the comments below seem to be contradicting one another at various points.

    My guess so far is this:

    • GND = Ground
    • H1 = Ground with 10k resistor
    • A1 =5v
    • B1 = 5v

    I purchased two and have not soldered the second to the breakout board as I am stil unsure as to how the four pins should be hooked up. Any and all assistance is appreciated.

  • So whats the wiring diagram for this?!? Theres a wiring diagram for the sensor, but this thing has only 4 pins…

  • Quick question to SF or anyone who has one of these:
    What is the pin spacing of the 4 holes? (where the wires attach in the picture) Is it a standard .1", able to be mounted on a circuit board? Also, what is the diameter of the hole in the center?
    To SparkFun:
    A dimensional drawing would help tremendously. (IMHO)
    –Ian

  • There is 6 pin in but just 4 pin out. I just tought that 3 of the sensor pin are connected together at pin output H1 but the internal connection like as below
    H one to GND
    H other to H1
    A one to A1
    A second not connected
    B one to B1
    B second not connected
    But other A should be at 5V
    and other B should be at GND with 10K by the wiring refer.
    http://wiring.org.co/learning/basics/airqualitymq135.html
    could some one tell me the solution? The sensor should be hot for having efficient data. and the best wiring connection was given at above.
    The connection on below should be pulled down at B to GND?
    http://img55.imageshack.us/img55/6237/alchoolau5.jpg

  • Could definitely use a schematic of this breakout board in use. I tried a lot of diff possible ways and while I got one to show me something in the serial output the sensor was getting hot and I am sure that is wrong.

  • Hi - I am still a little confused by this. I gather H1 should be connected to +5v, and that GND goes to ground.
    What do A1 and A2 connect to? I assume one to a ADC pin, and the other through a resistor to GND, but can’t seem to get it to work.
    It would be helpful if the diagram/schematic showed a sample connection.

  • Three days later:
    Now that I’ve actually received them, however, the boards are not the same as imaged - but are correctly labeled and wired. The terminals are, on the boards I’ve received, labeled B1 and A1 and are properly connected to the sensor pins.
    The photos here are of an incorrectly wired board, surely an earlier version. The original poster was correct, but the shipped boards are fine.
    What confuses this matter is the document, which shows the part in three drawings of two orientations; only one of the three drawings, the top one with the heater pins horizontal, is electrically and physically correct. I think the original board layout fell victim to misleading documentation.

    • This is indeed the case, as I pointed this issue out in Dec ‘08 and had the boards I purchased refunded. They scrapped their remaining stock and ordered new ones, but it would seem that they never updated the pictures.

  • Actually, the board appears to be fine. The silkscreening is just misleading; A1/A2 should be A/B.
    The photos show both sides, flipped vertically. I believe you’ll see that the connections are correct.

  • I think this is wired incorrectly- the datasheet for the alcohol sensors states that you need to measure between one of the ‘B’ terminals, and one of the ‘A’ terminals. On the board, it looks like you are bringing out the connections for A1 and A2, which is reasonably usesless, as they are connected together in the part.


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