MQ-131 for ozone does not work

Hi all,

I bought 2 mq131 sensor for ozone detection from different suppliers. First one was obtained from aliexpress, so i though the sensor was broken. Second one is from a spanish supplier.

I have the same problem with both sensors: no changes in analog output when they are exposured to ozone. Ozone is also measured with an industrial sensor for I+D so I am completely sure that it is correctly generated.

I know this kind of sensors are very difficult cause there are several models, etc. As consequence, before calibrating it, i just checked the analog response to ozono.

The serial monitor shows this all the time (with and without ozone 5ppm)

D0: 1 -- A0: 6
D0: 1 -- A0: 6
D0: 1 -- A0: 6
D0: 1 -- A0: 6
D0: 1 -- A0: 6
D0: 1 -- A0: 6

This is the sensor I have and my code

https://store.open-electronics.org/Gas-Sensor-MQ-131-Ozone-Module-ym315

wiring:

https://botland.com.pl/en/content/159-Arduino-and-Ozone-sensor

I'd appreciate any kind of help! Thanks in advance

int sensor_AOUT = A0; //connected from AOUT to the sensor to A1 on the Arduino 
int sensor_DOUT = 9; //connect DOUT from sensor to Arduino pin 2 
int wartosc_AOUT ; //variable for the value of AOUT 
int wartosc_DOUT ; //variable for the value of DOUT 
 
void setup() { 
 Serial.begin(9600); //start the monitor serial port 
 pinMode(9, INPUT); //set pin 2 as input 
 
} 
 
void loop() { 
 
 wartosc_AOUT = analogRead(sensor_AOUT); //load values from AOUT 
 wartosc_DOUT = digitalRead(sensor_DOUT); //load values DOUT 
 
 Serial.print("D0: "); //display on serial monitor 
 Serial.print(wartosc_DOUT); 
 Serial.print(" -- A0: "); 
 Serial.println(wartosc_AOUT); 
 delay(200); //delay between consecutive readings

Did you "burn in" the sensor for at least 24 hours, as required? See the data sheet (preheat time).

jremington:
Did you "burn in" the sensor for at least 24 hours, as required? See the data sheet (preheat time).

yes, I did.

Preheat for 48h, 6V from adapter, not USB

Where did you get the ozone you used to test with? How old was the source? Ozone is not a persistent gas, if I remember correctly.

Paul

Hello everyone,

I'm having the same issue, my analog output is always the same. First I read the sensor in a normal environment, then I took it to a sealed cabin where I have an ozone gerenator.

marcusvicentini:
Hello everyone,

I'm having the same issue, my analog output is always the same. First I read the sensor in a normal environment, then I took it to a sealed cabin where I have an ozone gerenator.

But, did the digital out ever go LOW? That is supposed to indicate ozone.

Paul

Today I ran a few more tests. The analog out is now varying to 3 or 4 when I place the sensor inside the cabin. The digital out is always the same. I regulated the Dout very close to 0 and yet it didn't change

marcusvicentini:
Today I ran a few more tests. The analog out is now varying to 3 or 4 when I place the sensor inside the cabin. The digital out is always the same. I regulated the Dout very close to 0 and yet it didn't change

That is good news, but what do you mean "regulated the Dout very close to 0"? Dout should be watched with an Arduino digital pin by doing a digital read on that pin.

Paul

Paul_KD7HB:
Where did you get the ozone you used to test with? How old was the source? Ozone is not a persistent gas, if I remember correctly.

Paul

the "good one" is an industrial ozone meter (8.000€) got from 2B technology. You are right, ozone is not persistent but, in my case, it is generated continuously.

Paul_KD7HB:
But, did the digital out ever go LOW? That is supposed to indicate ozone.

Paul

Generaly, not. It is always HIGH. Increasing sensivity to the maximum, DOUT is always LOW, even when there is no ozone.

I asked the seller and he said to me that he is going to sent me a new one, If it (the third sensor I test) shows same behaviour, It will mean Im doing something wrong