Arduino Machine Control System

I need someone to turn a bare-bones Arduino setup into a reliable machine-control solution. The exact board is still open—Uno, Mega, or even a Nano could work—so I’m looking for guidance on the best fit along with the full implementation. My main objective is to switch and sequence external machinery safely and repeatably from a single Arduino, adding expandability for more I/O in the future.

Here’s what I’m expecting from you:
• Clean, well-commented sketch that handles start/stop logic, basic fault checking, and manual override
• Schematic or clear wiring diagram showing power, relays, and any protection components
• Quick read-me so I can upload, test, and troubleshoot on my own

If you have experience driving relays, solid-state switches, or industrial contactors with Arduino, let’s talk.