how to use mq7 sensor

good day everyone, I got a mq7 sensor with a breakout board online and I am using it to test for carbon monoxide, whenever I run the code, i get the values from the serial monitor but the values I am getting seem to just be the analog values and not ppm values, please how can I get the ppm values thanks.

IF there was no calibration chart with the sensor and you are unable to calibrate it your self, then you can only guess at the ppm values.

Paul

whenever I run the code, i get the values from the serial monitor but the values I am getting seem to just be the analog values

Yes that is correct.

The mq7 sensor just returns a voltage. It needs to be on for 48 hours, then you need to put it in an atmosphere of known concentration of carbon monoxide. Then make a note of the reading you get, do this for a few concentrations and plot a graph of voltage out for PPM values. This will need to be repeated every few months.

The sensor, while widely used in amateur circles, is almost useless for serious measurement.

If you want to do the calibration yourself, the gasses are available from many sources, Grainger being one. Google for calibration gasses.

Paul

okay so @grumpy_mike, after leaving it on for 48hrs, i need to put it in an environment with known CO level and read the reading from the serial monitor,.. plot the graph afterwards.. so that means the mq7 will never give out output in ppm. , @paul, is the concentration of CO known in grainger

aycoolt: okay so @grumpy_mike, after leaving it on for 48hrs, i need to put it in an environment with known CO level and read the reading from the serial monitor,.. plot the graph afterwards.. so that means the mq7 will never give out output in ppm. , @paul, is the concentration of CO known in grainger

Yes, the concentration is known. If you go that way, be sure you get enough cans for the test. A couple of years ago we tried to get a nitrogen generation system to work as was sold to us. Tech came with cans of O2 with known concentration. The O2 sensor value was subtracted from the N2 gas, giving the N2 concentration. The calibration for the O2 sensor specified a specific flow of O2. The tech did not bring enough cans of O2 so could not complete the calibration run. We returned the N2 system.

Paul

How we can connect a LCD display to get the readings ?

Hi, Where did you get the MQ7 breakout board from?

This link to a Sparkfun project may help. they use the sensors characteristic curve to do basic calibration. Have you looked at the MQ7 data sheet?

https://learn.sparkfun.com/tutorials/hazardous-gas-monitor?_ga=2.37547813.420330226.1558685202-68910915.1549292048

Datasheet;

https://cdn.sparkfun.com/datasheets/Sensors/Biometric/MQ-7%20Ver1.3%20-%20Manual.pdf

Tom... :)