I think outsourcing the “dangerous parts” i.e. buying a power supply instead of building one. Apart from that, most applications stay in the 5V range and few mA

I think outsourcing the “dangerous parts” i.e. buying a power supply instead of building one. Apart from that, most applications stay in the 5V range and few mA. If you are using something that requires more current then just over engineer. A motor that uses 0.5A? Buy a 3A mosfet, flipping 120v electricity? Buy a premade relay module that is already optically decoupled and just feed it 5V signals. When it comes to stuff failing in general at hobby level you either burn something instantly (plug the power to an IC backwards and see the magic smoke go away) or it just heats up VERY VERY FAST! I once plugged an external 5V power to a development board that was already USB powered but I didn’t know it… it started smelling like something was burning within a few seconds and I burned myself by touching it instead of pulling the heat camera :-)