Hello, I purchased an MQ-3 gas sensor from aliexpress. I tried to make it work, but every analogRead gives value of 1023. It's all hooked up properly (vcc, ground, A0 to A0). I tried using external analogReference and hooking aref up to 5V, didn't help. The A0 value shows 0 when connected to ground and 660 when to 3.3V. Seems like the problem isn't in the board, pin's voltage is read properly. Even funnier thing happens to soil humidity sensor. It shows 1023 when dry, submerged in water reads ~100. I don't think the code is the problem so no need to post it. The board used is arduino uno. Do you know what I can do to fix it? Thank you all in advance! Take care.
Don't know what you're using for the humidity sensor but in regards to the MQ-3, look at Fig. 2 in the spec sheet and notice the response curse has a negative slope. Also note the load resistor value. It may create a problem with the ADC input impedance.
The problem is that even after heating up and being exposed to alcohol, smoke and benzine it doesn't change the 1023 reading. The sensor came soldered to a circuit board - I can always unsolder it and hook it up the jumper way :) I'm upset because after doing everything like on tutorials it just doesn't cooperate. Hope you will help me solve the problem, I'll keep thinking and tomorrow update what I've discovered. My timezone is different and it's late.
You would get a high reading if the load resistor was missing or very high in value.