MQ7 - sensor CO

My name is Thomas. I’m writing because I have seen on product list a gas sensor MQ7. I would like to make a CO detector using MQ7. Could You tell me if my connections are good? And is it dummy if I use pins number 2,4,6 for VCC or pins 1,3,5? (connect them conversely - at my wire).

At link below is my wire:

Sorry for my English and thanks for response.

Hi, Thomas.

Your schematic looks correct. The MQ gas sensors have light to no polarity, so it should not matter which side you choose to connect to VCC.

- Ryan

Thanks for the anwer :slight_smile:

But I have another one: I have read in datasheet that the MQ7 need two kind of heather voltage (V and 1,4V), so can I just connect heather pin (pin 4 in my wire) to VDC = 5V? Or I should connect it somewhere where I could change the voltage (for exaple using PWM from microprocessor) ?

For sure: :slight_smile:


I don’t know where you see 1.4V. You should be able to connect Vc and Vh if you keep the voltage below 5V. I have connected them and seen it responding to gases. It certainly doesn’t break it.

- Ryan

In table position: Heating Voltage (low) is 1,4V and at Figure 5 - there is also 1,4V. … c/MQ-7.pdf

But if you say that I can connect Vc and Vh to 5V (DC) and it should work so I will do that.

Thanks for help.