Reply To: Single layer PCB design Forum › Get Help › Electronics › Single layer PCB design May 12, 2022 at 3:13 pm #1946 Quote Angel LMAdmin Hi Mohamed! I actually designed it to be a Shield for an Arduino Mega… The PDIG1 Connector is supposed to connect the shield to the Arduino Mega. Also, there are inputs for the opto sensors, labeled as P1, P2, P3, P4, P5, P6 and P7.