Thank you a lot. I am ordering the parts tomorrow 
Now I got it. The whole problem was that I thought the pins were digital and I imagined the voltage was changed by the MQ3 according to the amount of alcohol. And actually it produced only different Analog Waves that are related to the alcohol concentration.
Got my self cleared up, here is the last modification you actually proposed to make, and I still kept one of the pins connected to the Digital because I would need to transmit later directly digital information.
