Multiple MQ Sensors - Arduino doesn't switch on while wired to computer

Hello everyone,

I have an issue with my MQ sensors. When I use each one separately (with analog pin), it perfectly works. When I try to use two or more at the same time, my arduino UNO board doesn't switch on when I wired it to my computer by USB. The computer doesn't recognize the board, so I assume this is not a coding issue.

Can someone have an idea why my arduino board doesn't switch on?

I use MQ2, MQ3, MQ5, MQ7 and MQ135. I try to add a power supply 7,5V - 1,5A. I also try to use the 2 GND pins for 2 sensors, but nothing works.

Those sensors have heaters which draw large currents (900 mA or more), you cannot power them from the Arduino's 5V pin, you need a separate 5V supply large enough for all your sensors combined.

Hello,

The sensor's heater have a resistor = 33Ohms and it's powered in 5V. So it should have a 150mA, not 950mA. Am I wrong ?

You are right, I misread 900 mW as mA, still, if all 5 heaters are on that is 750 mA, that might pull your 5V USB down enough to cause a reset. I believe USB is rated to supply 500 mA per port.
Even with power through the barrel jack, that current is still coming through the UNO's 5V regulator and causing it to overheat and cut out.

Yeah you're right! Plus there is a current peak when the arduino is switch on so with only two sensors the current is up to 800mA when it's switched on. With a power supply and coils it should work.

Thanks! :slight_smile:

Hey. I have the same project on working multiple mq sensors. How did you power up yours? Did your project works? Im considering to use arduino uno sensor shield. Thank you

I have been working 3 of those MQ sensors (together with an UNO) for a few years now. Power for those is supply with a separate power supply at approx 4 volts and they work nicely. They are not calibrated in PPM value but I can follow the different readings on a 24 hrs graphic and I can see that they react very fast with presence of substance that the can detect.