The PCB from OSHPark arrived some days ago and I finished the solder. I used a conventional solder iron, so it takes some time! :)
I did some tests and the electronics works fine! I will post more details in the next few days.
But, bad luck! The x-axis stepper motor drive from the 3D printer (I'm using a printrboard) bugged few minutes before the first print, so, I need to wait a replacement from ebay. A RAMPS 1.4 board with extra Pololu.
Since the reproductibility of measurement is very important, I will wait for a proper diode and led support for the real tests