Thank you for the reply MarkT, I just got the LM339 , the resistor, etc... and i'm trying to find out the connection diagram.
I have very basic knowledge on electronics and i'm prety lost trying to understand how to connect them.
I got the mainidea which i believe is to convert the analog signal to a square digital signal for the arduino digital port to be able to recognise it. I beleive we have to use one of the 4 inputs of LM339 and get an output for the arduino port. I its not to much trouble can you please upload a conection diagram?