This my first take on an Arduino Nano PLC(ish) device. It uses standard discrete components and thus is rather cheap to build. But discrete components do take up a bit more space. The inputs can accept up to 24v and are connected to the analoge pins, using optocouplers the inputs are electrically isolated from the Arduino. The outputs uses relays, the outputs from the relay uses an external source, that can be, with current relays, up to 250VAC or 30VDC. Outputs are grouped with 3,3,2 relays per group, 8 in total. This version only has 8 relays, and an extra port added (P9) this is specifically ment to be used with an ethernet adaptor (ENC28J60)