I'm working on my capstone project for school, and I'm at a loss as to what to do. The PLCs we have only have AC inputs and outputs, but due to time and budget constraints, I am unable to source some relays in time to drive everything. I have the outputs wired through relays, but I'm stuck at the inputs. I understand the input modals rectify the AC signal before putting the result to and optical isolator. If so, then could it be possible to power the inputs directly with just a DC current? I don't have the part numbers for the input modules, but the PLCs are Allen Bradly PLC-5/2. Oh, and if it matters, the project parameters was to created something using a PLC and I decided to make a drag tree using LEDs and IR triggers.