Hi, I have a project to detect H2S or ppm gas levels. I'm using MQ-136 gas sensor module. I think this module doesn't have RL specifically. Does anyone have a code program for this module? Please help me. I'm so confused 
According to Google it is an analog device with falling resistance with increasing concentration. Put it in a circuit with another resistor in series and connect the mid point to an analogue input. Depending on which side of the set up you connect to 5v and which side to 0v, you can get the input to read high numbers for increasing H2S or lower numbers.
As an aside, as h2s is do toxic, where are you getting the h2s from to play with your sensor?
As I recall a few 100 ppm is hazardous to Heath. Good thing your nose will detect a few ppm!
I'm using MQ 136 sensor module. So its just have 5v, AO, DO and Ground. And I'll try this module in mountain. As a comparison, i'll use H2S detector.
Ok, have you hooked up the sensor to 5v, 0v and an analog input?
Did you try one of the example analog input programs?
What result did you get?
Unless you have a source of h2s, how are you going to test your sensor?
If you do have a source of h2s, how are you going to avoid poisoning yourself?
Probably enough questions for now 
I have connected to 5v. But not with 0v because I have not understood yet. and I do not have a sample program for MQ 136 and I ask that. For the results with the program I made showing the number 1-10 depending on the air. I plan to buy H2S liquid under 100 ppm for testing
Google the part number and the data sheet has the circuit diagram to hook it up.
Until you hook the circuit up correctly, the program is no use to you.
See the example codes for analogRead as I mentioned before.
I do not have a sample program for MQ 136 and I ask that
Google "arduino mq136 tutorial".
Hi,
Welcome to the forum.
Please read the first post in any forum entitled how to use this forum.
http://forum.arduino.cc/index.php/topic,148850.0.html
Have you googled MQ 136 sensor module arduino
Tom... 
It sounds like you don't have much chemistry lab experience. You will kill yourself and others around you. Stay away from H2S. If you need to test your mq136 once you have it running do so using flatus.
Hai, i have a problem with my project. I have a MQ-136 module sensors, but i don't know how to calibrate and get a right ppm to detect a H2S gas level. Please help me,please help my project. This is for my final project
bagas1717:
Hai, i have a problem with my project. I have a MQ-136 module sensors, but i don't know how to calibrate and get a right ppm to detect a H2S gas level. Please help me,please help my project. This is for my final project
Do you have that standard concentration of H2S gas to use? And do you have a vessel that can be filled with that gas? Can you put your sensor with the wire connections in that vessel?
Paul
Hi,
Do you have a specs/data sheet?
Please post a link to your data/specs please?
They usually give you a calibrated curve to show you how to interpret it output.
Tom...
how to find slope from that curve??
Hi,
Have you googled MQ-136 arduino ?
Tom...
@bagas1717, please do not cross-post. Threads merged.
bagas1717:
how to find slope from that curve??
Calibrate your sensors to a series of known H2S concentrations.
Did you notice the data sheet shows a double log scale?
"Fig.3 is shows the typical sensitivity characteristics of the MQ-136 for several gases. in their:
Temp: 20℃、
Humidity: 65%、
O2 concentration 21%
RL=20kΩ
Ro: sensor resistance at 10ppm of H2Sin the clean air.
Rs: sensor resistance at various concentrations of gases."
Unfortunately their description of Ro doesn't match the chart. The chart shows that Ro/Rs at 10ppm is no 1.0. Looks more like 1.3
The official way to measure Ro is to measure the sensor resistance in a 10ppm concentration of the gas in air at 65% humidity and 20°C. Fortunately they provide a level for clean air. Looks like Rs/Ro is about 3.4 for clear air so take Rs in clean air and multiply by 3.4 to get Ro. Then you can use Rs/Ro to get rough approximations of ppm:
3.4 = 0 ppm
1.3 = 10 ppm
0.6 = 110 ppm
Looks like linear interpolation would be close enough.
Please note the pre-heat time: 24 hours. The heater circuit must be running for a full day before you can expect to get accurate results. The heater circuit draws 160 mA (800 mW at 5.0 V).
To calculate Rs you can take an analog reading:
const float Rl = 20000.0; // Load resistor is 20k Ohms.
float Rs = Rl * ((1023.0 / analogRead(A0)) - 1.0);
const float Ro = <value you calculated based on Rs in clean air>;
float ratio = Rs/Ro;
Yes i have. And im not get an answer to get right ppm.
Unless you have access to reagents needed to produce H2S, as well as a glass gas mixing apparatus, you will not be able to do an accurate calibration. But what kind of accuracy do you need? Do you want to know if H2S is present, or are you doing some sort of measurements where you need the answer in fractional ppm?
If I were trying to calibrate a hydrogen sulfide sensor, I'd fart into a plastic bag and measure that. Human flatus contains about 0.1 ppm of H2S, give or take depending on diet. You don't really want to go messing with higher concentrations unless you are a professional, and have professional equipment for handling it.