would you please explain which pins are the input and output in the breathalizer sensor? the sensor did not come with schematics to explain which pin is which. I think that's our problem why our project doesn't work. thank you for your time.

Could you please provide a product code or URL for the specific sensor you have? You won't get much help unless you can identify the sensor.

Jon Freetronics: Practical Arduino:

thank you for replying. We already figured it out, thanks. We have another doubt, the breathalizer circuit has a 100 K ohm potentiometer which is used to adjust the leds sentivity, but it seems to be very sensitive and sometimes is very difficult to give it a fine adjustment. could we change the value on the pot? and what value would that be? thanks again for your help.

We still don't know what you are talking about. As already requested, do you have a link to this sensor?

If you’re using the MQ-3 its really hard to get it the same, since it heats up and the output changes based on that.

We’re thinking about making some sort of “sensor” setup that only turns it on when someone is blowing towards it. Still a work in progress though.