9 in 1 MQ Sensor Modules Kit Project Super Starter Kits for Gas Detection

This is a nice array of gas sensors. It's a shame they included no documentation whatsoever, but on the plus side, they're extremely easy to use and set up. Connect the 5V and ground pins. Then, you have the option of using the analog or digital out for readings. I prefer to use the analog output when feasible. An LM393 comparator is used to convert the analog signal to digital logic for the digital output and this can be adjusted with the potentiometer. I hope these hold up over time, I'll be using them in some outdoor projects.

I did not test the Sensors yet so the quality is unknown. I am in the process of building a PM2.5 Particulate Matter Sensor. My problem is the poor shipping, they were all jammed in this little box. Most of the sensor metal screens were all bent up. Two of the sensors were not labeled. Now I have to guess at the sensor type. One has a housing that is not even in the Amazon picture. What kind of Rinky Dink outfit is this. Kind of disappointed

Poor soldering is visible. Tried to fix, but only 4 out of 9 working.

Husband is planning to use these for a prototype for an unmanned robotic leak detection system to test for gas leaks. He wants to create something that can gather information on leaks in places it isn't safe for a person to enter.

All are calibrated the same so, you are buying 6 of the exact same sensor. Any adjustments are slight and it doesn’t have much of an impact so, you still have 6 identical sensors.

Adjusting my review as I only just opened them. All the silver can ones have a label on the side of the can. It's not written on the board anywhere. 3 and 7 don't have labels so just going to have to assume based on the the color. EDIT: upon doing some more research I think the Carbon Monoxide sensor may be useless and I'm not sure what that means for other sensors. Apparently, this type of sensor needs to be 'burned in' at 5V for 60s and then switched down to a lower voltage for readings. With a fairly generic board under each one fo these sensors, I highly doubt that is happening automatically for you or whether you can work around it by PWMing the power pin. God knows the digital output pin is probably useless in this case. I did try hooking it up normally with the provided pins and the thing just got very warm with constant 'high' readings regardless of how you adjust the pot. The lack of documentation for these sensors really kills any sort of hope of development.

The sensors are not labelled. There is no way to tell which is which. Completely worthless.